//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11823 SUBJECT: GRB 110328A: Swift detection of a burst DATE: 11/03/28 13:32:29 GMT FROM: Scott Barthelmy at NASA/GSFC J. R. Cummings (NASA/UMBC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), S. Campana (INAF-OAB), V. D'Elia (ASDC), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), O. M. Littlejohns (U Leicester), R. Margutti (INAF-OAB), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), C. Pagani (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), M. H. Siegel (PSU), E. Sonbas (GSFC/USRA/Adiyaman Univ.), R. L. C. Starling (U Leicester), G. Stratta (ASDC), G. Tagliaferri (INAF-OAB) and E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift Team: At 12:57:45 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110328A (trigger=450158). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 251.233, +57.590 which is RA(J2000) = 16h 44m 56s Dec(J2000) = +57d 35' 25" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for 20-min long image triggers, the BAT lightcurve does not show anything significant. The XRT began observing the field at 13:22:19.8 UT, 1474.6 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 251.2054, +57.5808 which is equivalent to: RA(J2000) = 16h 44m 49.29s Dec(J2000) = +57d 34' 50.8" with an uncertainty of 6.3 arcseconds (radius, 90% containment). This location is 62 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. UVOT took a finding chart exposure of 150 seconds with the White filter starting 1482 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is J. R. Cummings (jayc AT milkyway.gsfc.nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11824 SUBJECT: GRB 110328A: a second trigger, probably a hard X-ray transient (Swift J164449.3+573451) DATE: 11/03/28 14:33:10 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), H. A. Krimm (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC), C. Pagani (U Leicester), K. L. Page (U Leicester), T. Sakamoto (NASA/UMBC), C. J. Saxton (UCL-MSSL), E. Sonbas (GSFC/USRA/Adiyaman Univ.), R. L. C. Starling (U Leicester), M. C. Stroh (PSU) and C. A. Swenson (PSU) report on behalf of the Swift Team: At 13:40:41 UT, the Swift Burst Alert Telescope (BAT) re-triggered on what we are tentatively calling GRB 110328A (trigger=450161). The BAT on-board calculated location is consistent with the coordinates reported for GRB 110328A (GCN Circ 11823; Cummings et al). Both this trigger and the earlier trigger (450158) were image triggers, so the light curves do not show any significant features. The current trigger was on the rise to the SAA. The source is brightening. It is quite rare for BAT to trigger a second time on a GRB, so this is either an unusually long GRB, GRB 110328A, or a new galactic transient, Swift J164449.3+573451. The galactic coordinates are longitude=86.71, latitude=+39.44. We note that the XRT was in Windowed Timing mode during the entire previous observing window, indicating that the X-ray counterpart was quite bright (> 10 cps). This also suggests either a very long-lived GRB or a galactic transient. We encourage observations at other wavelengths to help determine the nature of this object. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11825 SUBJECT: GRB / X-ray transient 110328A: Gemini optical observations DATE: 11/03/28 16:24:06 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick) and N.R. Tanvir (U. Leicester) report for a larger collaboration: "We observed the localization of the GRB / X-ray transient GRB 110328A (BAT trigger ID 450158/450161) with Gemini-N/GMOS on 28 March 2011, starting at 15:02 UT, two hours after the initial trigger, and 1.3 hours after the second trigger from the same source. Observations were obtained in very poor conditions, with substantial extinction due to cloud. At the X-ray localisation of GRB 110328A we do not find any evidence for a source down to a limiting magnitude of R>22.2, calibrated against USNO stars." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11826 SUBJECT: GRB 110328A: Enhanced Swift-XRT position DATE: 11/03/28 18:31:56 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 2353 s of XRT Photon Counting mode data and 5 UVOT images for GRB 110328A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 251.20787, +57.58334 which is equivalent to: RA (J2000): 16h 44m 49.89s Dec (J2000): +57d 35' 00.0" with an uncertainty of 1.7 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// ATEL #3242 ATEL #3242 Title: Swift J164449.3+573451 (AKA GRB110328A): A new candidate SFXT? Author: J. A. Kennea (PSU), P. Romano (INAF-IASF Palermo), H. A. Krimm (CRESST/GSFC/NASA), J. Cummings (NASA/UMBC), D. N. Burrows (PSU), G. Tagliaferri (INAF-OAB), P. A. Evans (U Leicester), S. D. Barthelmy (NASA/GSFC), A. A. Breeveld (UCL-MSSL), J. M. Gelbord (PSU) Queries: kennea@astro.psu.edu Posted: 28 Mar 2011; 21:12 UT Subjects:X-ray, Transient At 12:57 UT on 2011-Mar-28 Swift/BAT triggered on a newly discovered transient source, initially thought to be a new GRB, GRB110328A (Cummings et al., GCN #11823). A second BAT trigger on this source at 13:40UT on 2011-Mar-28, cast doubt on the GRB nature of this source (Barthelmy et al., GCN #11824), and it is likely that the triggering source is a hard galactic X-ray transient, which was named Swift J164449.3+573451. The most accurate position for this transient is RA, Dec = 251.20787, +57.58334 which is equivalent to: RA (J2000): 16h 44m 49.89s Dec (J2000): +57d 35' 00.0" with an uncertainty of 1.7 arcsec (radius, 90% confidence), reported by Osborne et al., GCN #11826. This location does not correspond with any known cataloged object, and examination of a 6.5ks ROSAT PSPC observation taken on 1990-Jun-01 shows no detection of the source, from which we extrapolate an 3-sigma upper limit of 2.5 x 10^-13 erg/s/cm-2 in the XRT 0.3-10 keV band. Examining the first two orbits of Swift/XRT data, we observe the following. In the first orbit the source is initially detected at a rate of ~10 XRT count/s, rising to ~50 c/s at the end of the first orbit. During this period the spectrum can be fit by an absorbed power-law model with a photon index of 1.66 +/- 0.04. The source also showed enhanced absorption over the expected galactic value of 1.7x10^20 cm^-2, with an additional absorption component of 7.4 +/- 0.4 x 10^21 cm^-2. The average flux, uncorrected for absorption, was 9.5 x 10^-10 erg/s/cm^2 (0.3-10 keV). In the second orbit the source had become much fainter (~1 c/s), and much softer, with a photon index of 2.97 +/- 0.35. The average flux in the 2nd orbit, uncorrected for absorption, was 3.3 x 10^-11 erg/s/cm^2 (0.3-10 keV). We searched for emission at the outburst location in the BAT hard X-ray transient monitor in the 15-50 keV band. During the first trigger interval (1208s from 2011-Mar-28 12:57:50 UT), the source was detected at 0.022 +/- 0.004 ct/s/cm^2 (100 mCrab), fading somewhat by the second interval (1134s from 13:22 UT) to 0.019 +/- 0.002 ct/s/cm^2. The source was not in the BAT field of view for roughly 21 hours before the trigger, last appearing in the BAT FOV at 2011-Mar-27 16:05:28 UT. The source was not detected in this pointing. When integrating the four days prior to the trigger (Mar 24-27) we see a 4.2-sigma excess (0.0028 +/- 0.0007 ct/s/cm2 or 13 mCrab) and the light curve on shorter time scales shows variation. There was no detection before Mar 24. This suggests that the source was active in hard X rays for several days before the trigger. We note that the overall behavior is not consistent with a GRB nature. However, there are striking similarities with what was observed during the 2008 March 19 outburst of the supergiant fast X-ray transient (SFXT) IGR J16479-4514 (Romano et al 2008, ApJ, 680, L137) starting from the double triggering of the BAT. The shape of the IGR J16479-4514 light curve was also rising to a peak that reached about 60 c/s at the end of the first orbit followed by a much dimmer, 0.5 c/s, second orbit. The photon index was 0.98+/-0.07 and 2.6+/-0.7 in the first and second orbit, respectively, with absorption in excess of the expected Galactic value. Given these similarities, the large dynamic range of ~50 shown in the light curve of Swift J164449.3+573451, and a record of hard X-ray activity preceding the BAT triggers, we suggest that this may be a new SFXT candidate, despite the location off the Galactic plane. We also note that despite the low extinction towards this object (E(B-V) = 0.019, Schlegel et al., 1998), there is no detection of an optical counterpart by UVOT with an 3 sigma upper limit of v>20. Levan et al. (GCN #11825) also report an upper limit of r>22.2. Further observations at all wavelengths are strongly encouraged. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11827 SUBJECT: GRB 110328A / Swift J164449.3+573451: PTF Quiescent Optical Counterpart DATE: 11/03/28 21:23:00 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko (UC Berkeley), P. E. Nugent (LBNL / UC Berkeley), Derek B. Fox (Penn State), E. O. Ofek and M. M. Kasliwal (Caltech) report on behalf of a larger collaboration: As part of the Palomar Transient Factory, we have obtained pre-outburst optical (R-band) imaging of the field of the high-energy transient source GRB 110328A / Swift J164449.3+573451 (GCNs 11823, 11824) with the Palomar 48-inch Oschin Schmidt telescope over the time period from 2009 May to 2010 October. In a stacked frame of all available data, we find a faint, unresolved source at location (J2000.0): RA: 16:44:49.97 Dec: +57:34:59.7 The astrometric uncertainty associated with this position is ~ 150 mas in each coordinate (based on the USNO-B1 catalog). This is consistent with the enhanced XRT position (GCN 11826), and is therefore likely to be associated with the high-energy transient. The detection of such a relatively bright optical counterpart strongly disfavors a cosmological long-duration GRB, and instead suggests that Swift J164449.3+573451 is more likely a new Galactic transient source (GCN 11824, ATEL 3242). In attempting to estimate the brightness of this object, we find that nearby calibration stars from the USNO-B catalog are likely to be inaccurate (resulting in limits significantly deeper than our system can achieve). Based on past observations of other fields, we estimate the brightness of the counterpart to be R ~ 22, although we caution that this estimate may suffer from significant uncertainty. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11828 SUBJECT: GRB / X-ray transient 110328A: MITSuME OkayamaOptical upper limits DATE: 11/03/29 01:34:43 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB / X-ray transient 110328A (Cummings et al., GCN 11823) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2011-03-28 13:21:15 UT (~24 min after the burst). We did not find any new point source within the XRT circle (Cummings et al., GCNC 11823) in all the three bands. Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration. T0+[day] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------ 0.04784 14:06:38 4740.0 >19.5 >19.7 >19.0 0.11100 15:37:35 4740.0 >20.4 >20.2 >19.6 0.24717 18:53:40 4440.0 >20.7 >20.4 >19.7 ------------------------------------------------------ T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11829 SUBJECT: GRB 110328A/ Swift J164449.3+573451 : Xinglong TNT Upper limit DATE: 11/03/29 01:44:00 GMT FROM: L.P. Xin at NAOC L.P. Xin, Y.L. Qiu, J.Y. Wei, J. Wang, J.S. Deng, C. Wu, X. H. Han, M, Zhai on behalf of EAFON report: We observed GRB 110328A (Cummings et al. GCN 11823) with Xinglong TNT telescope at 14:13:22 UT on March 28, 2011, 1.26 hour after the first burst trigger, 33 min after the second trigger. A series of R-band images were obtained with an exposure time of 300 sec for each frame. At the X-ray location of GRB 110328A, and the likely optical counterpart position (Cenko et al. GCN 11827) , we do not find any new source down to the limit of 20 mag in R band relatively to USNO B1.0 R2 mag at the mean time of 1.75 hour after the first trigger . Further observations from larger telescopes are encouraged. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11830 SUBJECT: GRB 110328A / Swift J164449.3+573451: NOT optical observations. DATE: 11/03/29 06:55:40 GMT FROM: Giorgos Leloudas at Dark Cosmology Centre G. Leloudas, D. Malesani (DARK/NBI), N.R. Tanvir (U. Leicester), Dong Xu (WIS), A.J. Levan (U. Warwick), P. Jakobsson (U. Iceland), T. Pursimo (NOT), report on behalf of a larger collaboration. We used the Nordic Optical Telescope (La Palma, Spain) equipped with ALFOSC to observe the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al., GCN 11823; Barthelmy et al., GCN 11824). Observations started at 01:47 UT (12.8 and 12.1 hr after the first and second trigger, respectively). We obtained 2x600 s in BVR and 4x300 s in z. In all filters we detect an object at the coordinates (J2000): RA: 16:44:50.0 DEC: +57:34:59.13 with an astrometric calibration error of approximately 0.3 arcsec. This position is within the enhanced XRT error circle (Osborne et al., GCN 11826) and is consistent with the coordinates of the object reported by Cenko et al. (GCN 11827) from pre-outburst images. At the moment we have no good photometric calibration of the field so photometry should be considered preliminary (see also GCN 11827). Assuming R = R1 = 19.40 and B = B2 = 21.30 for the USNO B1.0 star 1475-0312998, we estimate for the counterpart B = 24.0 +- 0.2 and R = 22.6 +- 0.05 (statistical errors only). At this stage it is not possible to verify whether the source is variable. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11833 SUBJECT: GRB 110328A: Gemini spectroscopic observations DATE: 11/03/29 16:13:27 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick), N.R. Tanvir, K. Wiersema (U. Leicester), D. Perley (U.C. Berkeley) report for a larger collaboration: "We obtained spectroscopic observations of the optical source associated with GRB 110328A with Gemini/GMOS on 29th March 2011. A preliminary reduction shows emission lines associated with Hbeta, and OIII (4959, 5007) at a common redshift of z~0.35. This suggests either a chance alignment of a soft X-ray transient with a external galaxy (although the lack of an optical counterpart within our Galaxy would be puzzling), or, more likely, that GRB 110328A is an extragalactic object, with properties unlike any previously observed GRB We thank the staff of Gemini, in particular Richard McDermid, for the execution of these observations" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11834 SUBJECT: GRB 110328A / Swift J164449.3+573451: optical spectroscopy from GTC DATE: 11/03/29 16:28:48 GMT FROM: Antonio Deugarte at IAA-CSIC C.C. Thoene, J. Gorosabel (IAA-CSIC), A. de Ugarte Postigo (DARK/NBI), R. Sanchez-Ramirez (IAA-CSIC), T. Muñoz-Darías (OAB-INAF), S. Guziy and A.J. Castro-Tirado (IAA-CSIC) report on behalf of a larger collaboration: We observed the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al. GCNC 11823) using the 10.4m GTC telescope in Roque de los Muchachos Observatory (La Palma, Spain). We identified the optical counterpart (Cenko et al. GCNC 11827, Leloudas et al. GCNC 11830) and obtained low-resolution spectroscopy of the source. The observations consisted in 3x1200s exposures with the R300B grating starting at 4:40 UT of the 29th March, 15.7h after the first BAT trigger). In the spectrum we detect a good signal continuum from 4000 to 10000 A with several emission lines superposed, which we identify as [OII], [OIII], Hbeta and Halpha at a common redshift of 0.354, consistent with the value reported by Levan et al. (GCNC 11833). We acknowledge the excellent support from the GTC staff. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11836 SUBJECT: GRB 110328A / Swift J164449.3+573451: EVLA Detection DATE: 11/03/29 21:50:24 GMT FROM: Ashley Zauderer at CfA Ashley Zauderer, Edo Berger (Harvard), Dale A. Frail (NRAO) and Alicia Soderberg (Harvard) report on behalf of a larger collaboration: We observed the peculiar Swift event GRB110328A / Swift J164449.3+573451 (GCNs 11823, 11824) with the EVLA on March 29.37 UT at two frequencies (1 GHz bandwidth each) centered at 4.94 and 6.69 GHz. We find a single, unresolved >10 sigma radio source within the Swift-XRT error circle (GCN 11826) at the following position (J2000): RA = 16:44:49.93, DEC = +57:34:59.7 coincident with the PTF and NOT optical source (GCNs 11827 and 11830). The optical source showed no clear variability in brightness and is thus most likely the host galaxy of this event, with a redshift of z=0.35 (GCNs 11833, 11834). The EVLA source is most likely the radio afterglow of this peculiar burst. Further observations are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11837 SUBJECT: GRB 110328A / Swift J164449.3+573451: optical observations DATE: 11/03/30 01:45:38 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (SAI MSU), A. Pozanenko (IKI), E. Klunko (ISTP) on behalf of larger GRB follow up collaboration report: We observed the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823) with AZT-33IK telescope of Sayan observatory (Mondy) starting on March 28 (UT) 13:46:35, i.e. 6 minutes after second trigger (Barthelmy et al. GCNC 11824). We identified the optical counterpart (Cenko et al. GCN 11827, Leloudas et al. GCN 11830) in the combined image of a total exposure of 67 min. The photometry of the optical counterpart in the combined image is R=21.50 +/- 0.10 and based on the USNO-A2.0 star 1425-08596694 assuming R=16.6. The photometry is still preliminary and calibration of field stars is necessary (Cenko et al. GCN 11827) to confirm the variable nature of the optical counterpart. [GCN OPS NOTE(30apr11): Per author's request, Elunko was changed to Klunko.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11838 SUBJECT: GRB 110328A / Swift J164449.3+573451: PAIRITEL NIR Upper Limits DATE: 11/03/30 03:07:14 GMT FROM: Adam Morgan at U.C. Berkeley A. N. Morgan, C.R. Klein, A. A. Miller, and J. S. Bloom (UC Berkeley) report: We observed the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al., GCN 11823, Barthelmy et al., GCN 11824) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at 2011-03-29 08:32:46 UT, ~19.6 hours after the first Swift Trigger. In mosaics (effective exposure time of 0.39 hours) taken simultaneously in the J, H, and Ks filters, we do not detect any source at the optical/radio position (Cenko et al., GCN 11827, Leloudas et al., GCN 11830, Zauderer et al., GCN 11836, Volnova et al. GCN 11837). The preliminary photometry yields: post burst t_mid (hr) exp.(hr) filt U. Limit (3 sig) 19.9 0.39 J > 19.1 19.9 0.39 H > 18.2 19.9 0.39 Ks > 16.9 Further observations will be performed tonight. All magnitudes are given in the Vega system, calibrated to 2MASS. No correction for Galactic extinction has been made to the above reported values. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11839 SUBJECT: GRB 110328A / Swift J164449.3+573451: LOAO R-band Observation DATE: 11/03/30 06:13:19 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im (CEOU/SNU), Yuji Urata (NCU), and Kuiyun Huang (ASIAA) on behalf of EAFON Starting at 2011 March 29,10:53:45 UT (roughly 22 hrs after the 1st burst alert), we obtained a series of R-band images of the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823) using the 1.0m telescope at Mt. Lemmon, AZ, USA. We identify the optical counterpart (Volonva et al. GCN 11837, Cenko et al. GCN 11827, Leloudas et al. GCN 11830, Degarte et al. GCN 11834) in a stacked image with the total integration time of 2500 secs. A preliminary analysis shows that the brightness of the counterpart is R = 22.1 +- 0.4 mag, where the photometry calibration is based on the USNO B-1 star 1475-0312998. We thank the LOAO operator, I. Baek for her assistance of this observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1840 SUBJECT: GRB030131: Optical limit DATE: 03/01/31 14:53:46 GMT FROM: Derek Fox at CIT P.A. Price (RSAA/ANU) and D.W. Fox (Caltech) report on behalf of a larger collaboration: "We have imaged the full localization region of GRB030131 (GCN 1838) with the Palomar 48-inch Oschin Telescope + NEAT camera, in six 120s exposures over 10:42 UT to 11:31 UT. The summed image from these unfiltered exposures reaches a limiting magnitude of R~21 mag as estimated from the magnitude of several USNO-A2.0 stars in the image. We identify no new sources by reference to images from the Second Digitized Sky Survey. We estimate the magnitude of any new source to be R>20 mag at the mean epoch of our observations, 11:16 UT, which is 3.62 hours after the burst." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11841 SUBJECT: GRB 110328A / Swift J164449.3+573451: CARMA mm detection DATE: 11/03/30 14:49:44 GMT FROM: Ashley Zauderer at CfA Ashley Zauderer, Edo Berger (Harvard), Dale A. Frail (NRAO), Alicia Soderberg (Harvard), Shri Kulkarni (Caltech), Shaye Storm (UMD) and Chat Hull (UC Berkeley) report: "We observed the peculiar Swift event GRB110328A / Swift J164449.3+573451 (GCNs 11823, 11824) with CARMA beginning on March 30.39 UT at 98 GHz. We find a bright, unresolved source coincident with our EVLA detection (GCN 11836) with a preliminary flux density of about 15 mJy. Additional analysis is on-going and further observations are planned. We thank the CARMA observatory personnel for their support of these observations." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11842 SUBJECT: GRB 110328A / Swift J164449.3+573451: BAT refined analysis DATE: 11/03/30 17:06:00 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), A. Melandri (INAF-OAB), D. M. Palmer (LANL), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) The source originally identified as GRB 110328A (Cummings et al. GCN Circ. #11823 and Barthelmy et al. GCN Circ. #11824) has triggered BAT several times. It is a highly unusual object. It is coincident with an optical source at redshift z = 0.35 (Levan et al., GCN Circ #11833), as well as a radio source (Zauderer et al., GCN Circ #11836). The source continues to be detectable and variable in BAT more than 40 hours after the initial trigger, with peak brightness on the order of 200 mCrab. The source is at high galactic latitude, 39.4 degrees. The summary of BAT triggers so far is: TrigNum Date Time TrigDur Intensity UT [sec] [c/sec] 450158 28 Mar 12:57:45 1208 6.1 450161 28 Mar 13:40:41 64 19.4 450257 29 Mar 18:26:25 320 15.6 450258 29 Mar 19:57:45 64 38.2 This table does not represent all the possible triggers, because the on- board triggering algorithm requires the intensity of the any following event to be slightly more than twice the previous intensity. Also note that the on-board threshold was commanded to zero between the 2nd and 3rd triggers in order to enhance future triggers, and that it was later commanded to be 4 times the 4th trigger's intensity after the 4th trigger to suppress further triggers. The observation of the source including the discovery image was T-4 sec to T+1211 sec. A fit to a power law spectrum from BAT survey data on this interval has a photon index of 1.72 ± 0.18. The fluence from 15 to 150 keV using this model was (3.0 ± 0.3) x 10^-6 ergs/cm^2. The first followup observation, during which the second trigger occurred, was T+1465 sec to T+2348 sec. The photon index from that observation was 1.37 ± 0.11. The fluence was (2.7 ± 0.2) x 10^-6 ergs/cm^2. The light curve from the BAT transient monitor (15-50 keV): http://swift.gsfc.nasa.gov/docs/swift/results/transients/weak/SwiftJ164449.3p573451/ shows variability, but that the source was first detectable on 25-March-2011 and has, on average, continued to brighten since the trigger. Please see also Kennea et al., ATel#3242 for more information: http://www.astronomerstelegram.org/?read=3242 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11843 SUBJECT: GRB 110328A / Swift J164449.3+573451: beamed emission DATE: 11/03/30 17:23:02 GMT FROM: Sergio Campana at INAF-OAB S. Campana (INAF-OAB), S. Covino (INAF-OAB), G. Tagliaferri (INAF-OAB), V. D'Elia (ASI-ASDC), L. Stella (INAF-OAR), R. Salvaterra (Insubria University): GRB 110328A/ Swift J164449.3+573451 is characterized by a very fast variability. A doubling time less than 500 s can be easily recovered from the Swift X-ray data. Assuming that the entire source is varying, this poses a limit on the mass of the varying object of M1<5x10^5 solar masses, based on the arguments of Cavallo & Rees (1978) and assuming a conversion efficiency of ~10%, typical of accretion onto a black hole. On the other side if this source is really at z=0.354 (Levan et al. GCN 11833; Thoene et al. GCN 11834), as confirmed by the radio position of the counterpart (Zauderer et al. GCN 11836), its peak flux of ~10^-8 erg/cm2/s (0.3-10 keV based on the Swift Burst analyser, Evans et al. 2010, A&A 509 A102) implies a luminosity of ~5x10^48 erg/s. In order not to overcome the Eddington limit a mass of M2>3x10^10 solar masses is needed. The two mass estimates strongly disagree providing clear evidence for a highly beamed emission. //////////////////////////////////////////////////////////////////////// ATEL #3250 ATEL #3250 Title: Swift J164449.3+573451/GRB 110328A: Continued Swift Monitoring Author: J. A. Kennea (PSU), P. Romano (INAF-IASF Palermo), H. A. Krimm (CRESST/GSFC/NASA), J. Cummings (NASA/UMBC), D. N. Burrows (PSU), G. Tagliaferri (INAF-OAB), P. A. Evans (U Leicester), S. D. Barthelmy (NASA/GSFC), A. A. Breeveld (UCL-MSSL), J. M. Gelbord (PSU), G. Israel (INAF-OAR), P. Esposito (INAF-OAC), T. Sakamoto (GSFC/UMBC), M. M. Chester (PSU), S. T. Holland (CRESST/USRA/GSFC), C. Wolf (PSU), N. Gehrels (NASA/GSFC) Queries: kennea@astro.psu.edu Posted: 30 Mar 2011; 19:25 UT Subjects:X-ray, Transient We report on continued monitoring of the new X-ray transient Swift J164449.3+573451/GRB 110328A (e.g. Kennea et al, ATEL #3242) by Swift. During 2011-Mar-29, Swift J164449.3+573451/GRB 110328A brightened significantly, triggering the Swift/BAT twice, at 18:26:25.19UT and 19:57:45.19UT respectively (see Sakamoto et al., GCN Circ #11842 for more details on the BAT characteristics). The XRT light-curve shows significant variability, and is characterized by periods of bright flares, with the XRT measured brightness varying with a dynamic range of ~400 (~0.2 XRT c/s to ~80 XRT c/s). These flaring episodes last of the order of 2-3 x 10^4 seconds, with many flares occurring within these time periods. In the XRT light-curve, which currently covers from 2011-Mar-28 12:57UT to 2011-Mar-30 13:46UT, ~2 days, we see evidence for 5 major flaring outbursts, the timing of these outbursts does not appear to be periodic. These outburst events are seen in both XRT and BAT light-curves, which are well correlated. The underlying light-curve shows no evidence for a fading trend. The source shows hardness changes that are correlated with the source brightness, with a correlation coefficient of r=0.71 when comparing the XRT count rate to the ratio of the 1.5-10 keV and 0.3-1.5 keV bands. A Fourier analysis of the first set of WT data (1.3 ks, MJD 55648.559-55648.946) was performed and no significant periodicity was found. The 3-sigma upper limits on the pulsed fraction, defined as semi-amplitude of the modulation divided by the mean source count rate, computed according to Israel & Stella 1996,ApJ, 468, 369 for a sinusoidal signal is 12% for periods between 3.5ms to 3s (we could not set meaningful upper limits on the pulsed fraction above 3s because of substantial red noise). Further timing analysis is ongoing. Summed UVOT observations of the source reveal no detection of an optical counterpart in any filter. The deepest images obtained are in the UVOT white and u filters; co-added images give the following upper limits: white (11.3ks) > 23.4 mag; u (23.6ks) > 22.9 mag. Photometry was performed using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627). The source has a very atypical light-curve if it is a GRB. MAXI reports detection of this transient ~4 hours before the initial BAT trigger (Kimura et al., ATEL #3244), suggesting that the source was rising from quiescence at the time of the initial BAT trigger. This behavior is much more typical of a Galactic X-ray transient or some AGN flares. For example in the case of MAXI J1659-152, MAXI detected the rising flux ~5.5 hours before the source had reached sufficient brightness to trigger BAT (Negoro et al., ATEL #2873), although we note that an apparent associated optical counterpart with a measured redshift of z=0.35 (Levan et al., GCN Circ #11833, Thoene et al., GCN Circ #11834), and the detection of a bright radio source at a location consistent with this optical afterglow, are consistent with the transient being extragalactic in origin. We also note that the properties of the X-ray light-curve are becoming less consistent with those of an SFXT, which this source was previously suggested to be (Kennea et al., ATEL #3242), and this combined with the lack of a bright optical companion and the high galactic latitude, make the SFXT hypothesis less likely. Monitoring observations of this source by Swift are on-going. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11844 SUBJECT: GRB 110328A / Swift J164449.3+573451: No optical variability of the optical counterpart DATE: 11/03/30 20:49:44 GMT FROM: Giorgos Leloudas at Dark Cosmology Centre G. Leloudas, D. Malesani (DARK/NBI), D. Xu (WIS), P. Jakobsson (U. Iceland), J. Telting (NOT), report on behalf of a larger collaboration. We observed again the field of the peculiar source GRB 110328A / Swift J164449.3+573451 (Cummings et al., GCN 11823; Kennea et al., ATel 3242) with the NOT equipped with ALFOSC, using the same instrument setup adopted in our first observation (Leloudas et al. GCN 11830). Observations were carried in the R and z filters with exposures of 3x600 and 8x300 s, respectively. The observations were carried out starting on 04:10 UT, roughly 26 hr after our first observations and 39 hr after the first Swift trigger. The reported galaxy at z=0.35 (Cenko et al., GCN 11827; Levan et al., GCN 11833; Thoene et al., GCN 11834), which is consistent with the position of the X-ray and radio emission (Osborne et al., GCN 11826; Zauderer et al., GCN 11836), does not show measurable variability over this time range. Its R-flux has remained constant to within 0.02 +- 0.07 mag, relative to several stars in the field. Image subtraction using ISIS (Alard 2000, A&AS 144, 363) also does not reveal any variable source on the potential host galaxy or nearby. Similarly, no variability is observed in the z-band up to 0.02 +- 0.15 mag. Given the strong variability of the X-ray counterpart over the same time span, this suggests that the optical emission is dominated by the host galaxy contribution. Preliminary photometric calibration using the Landolt standard field SA 107 yields R = 19.35 for the USNO star 1475-0312998, close to its archival value (R=19.4) that was used in GCN 11830. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11845 SUBJECT: GRB 110328A / Swift J164449.3+573451: PAIRITEL NIR Detection in 2nd Epoch DATE: 11/03/30 21:28:44 GMT FROM: Adam Morgan at U.C. Berkeley A. N. Morgan, J. S. Bloom (UC Berkeley), A.J. Levan (U. Warwick), and N.R. Tanvir (U. Leicester), report: We continued to observe the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al., GCN 11823, Barthelmy et al., GCN 11824) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona for a second epoch beginning at 2011-03-30 08:22:23 UT, ~43.4 hours after the first Swift Trigger. In mosaics (effective exposure time of 1.9 hours) taken simultaneously in the J, H, and Ks filters, we detect a source in all 3 filters at the optical/radio position (Cenko et al., GCN 11827, Leloudas et al., GCN 11830, Zauderer et al., GCN 11836, Volnova et al., GCN 11837, Im et al. GCN 11839, Kelemen et al. 11840, Zauderer et al. GCN 11841). The preliminary photometry yields: post burst t_mid (hr) exp.(hr) filt mag m_err 44.9 1.90 J 19.1 0.3 44.9 1.90 H 18.9 0.5 44.9 1.90 Ks 17.3 0.4 Compared to our first epoch upper limits at ~20 hours post-burst (Morgan et al., GCN 11838), these values suggest either a constant source or re-brightening in J. All magnitudes are given in the Vega system, calibrated to 2MASS. No correction for Galactic extinction has been made to the above reported values. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11846 SUBJECT: GRB 110328A / Swift J164449.3+573451: Gemini and UKIRT IR observations DATE: 11/03/30 21:38:38 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester), A. Morgan, J. Bloom, S.B. Cenko (U.C. Berkeley) report for a larger collaboration: "We obtained IR observations of GRB 110328A using both UKIRT/WFCAM and Gemini-N/NIRI on 30 March 2011, beginning at ~13:00 UT. Observations were obtained in J and H with UKIRT and in K with NIRI. The source is detected in all filters, and confirms the very red colour of the counterpart suggested by Morgan et al (GCN 11845). Comparison of these images with those taken with PAIRITEL provides maginal evidence for brightening between the PAIRITEL observations and those obtained with UKIRT and Gemini. Formally Delta_K = 0.52 +/- 0.21 and Delta_H = 0.73 +/- 0.35 mag. However, we caution that the difference between instruments, coupled with slightly different filter responses, may impact these results, and hence at present we cannot establish variability with high confidence. Further observations are planned" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11847 SUBJECT: GRB 110328A / Swift J164449.3+573451: X-ray analysis and a mini-blazar analogy DATE: 11/03/30 23:02:09 GMT FROM: Josh Bloom at UC Berkeley J. S. Bloom, N. R. Butler, S. B. Cenko, D. A. Perley (UC Berkeley) report: "We perform a time-resolved X-ray spectral analysis of the Swit XRT data for GRB1103028A / Swift J164449.3+573451 (Cummings et al., GCN 11823; Kennea et al., ATel 3242). As reported by Kennea et al. (ATel 3250), the X-ray hardness correlates with the X-ray flux. We find that, in the low-flux state, the spectrum is well-fit by an aborbed powerlaw; while a blackbody model is preferred for the high-flux state. For a reference time t0 of 2011/03/28 12:57:45.2 UT, the (PC mode) spectrum in the time regions: t-t0 = (6.08, 100.87 ksec): NH_excess= (0.61+/-0.03) x 10^22 cm^-2 (z=0) (NH_Galactic= 0.017 x 10^22 cm^-2) Gamma = 1.97+/-0.06 Flux= (5.99+/-0.21) x 10^-11 erg cm^-2 s^-1 [0.3-10 keV] chi^2/nu= 312.50/254 t-t0 = (116.89, 176.05 ksec): NH_excess= (0.60+/-0.05) x 10^22 cm^-2 (z=0) Gamma= 1.98+/-0.05 Flux= (1.09+/-0.05) x 10^-10 erg cm^-2 s^-1 [0.3-10 keV] chi^2/nu= 253.06/224 are well-fit by absorbed powerlaw models. In both of these regions, an absorbed blackbody fit has a significantly lower fit quality (chi^2/nu= 845.01/254, and 609.46/224, respectively). In contrast, in times of high flux, the WT and PC mode spectra are soft: t-t0 = (1.49, 6.08 ksec; WT): NH_excess = (0.61+/-0.03) x 10^22 cm^-2 (z=0) Gamma= 1.63+/-0.04 Flux= (1.21+/-0.03) x 10^-9 erg cm^-2 s^-1 [0.3-10 keV] chi^2/nu= 840.42/449 t-t0 = (111.35, 111.49 ksec; WT): NH_excess= (0.66+/-0.02) x 10^22 cm^-2 (z=0) Gamma= 1.64+/-0.03 Flux= (2.02+/-0.03) x 10^-9 erg cm^-2 s^-1 [0.3-10 keV] chi^2/nu= 1339.16/583 t-t0= (116.00, 116.46 ksec; PC): NH_excess= (0.3+/-0.3) x 10^22 cm^-2 (z=0) Gamma= 1.4+/-0.4 Flux= (1.3+/-0.2) x 10^-9 erg cm^-2 s^-1 [0.3-10 keV] chi^2/nu= 9.16/10 In each of these 3 high flux time regions, a blackbody fit is preferred relative to the quoted powerlaw fits above (chi^2/nu= 762.17/449, 1235.52/583, and 7.82/11, respectively). In these regions, the best-fit temperature is kT ~ 1 keV. The fact that none of the fits in these regions exhibits chi^2/nu ~ 1 may suggest a superposition of thermal and non-thermal components is required. We note that the BAT photon indices (Sakamoto et al.; GCN #11842) are comparable to the hard photon indices here, possibly indicating a continuation of these spectra to higher energies. The energetics of the continuing event are intriguing, with an average luminosity in the X-rays of L_X ~ 2.5 x 10^47 erg/s continuing for T~10^5 sec implying a total energy output of E_X,tot ~ 2.5x10^52 erg. Assuming this energy is liberated in an accretion process at 10% efficiency, the total mass involved in accretion over the first day is ~0.1 M_sun. If the source of this accreted mass is a tidal disruption of a main sequence star (M_* ~ 0.5 M_sun; R_* ~ 10^10 cm), then this implies a black hole mass of ~few x 10^6 M_sun assuming the disruption radius at the size scale implied by the X-ray variability timescale (500 s; Campana et al. [GCN 11843]), l=1.5x10^12 cm. This disruption radius would be several times the innermost stable orbit of a 10^6 M_sun BH. We also note an analogy of the reported behavior to blazar activity, in that highly variable gamma-ray and (non-thermal) X-ray emission is accompanied by (presumably) non-thermal long-wavelength emission (radio and sub-mm). The compressed timescales of variability from ordinary blazars (~10 minutes vs ~1 day) could be attributable to a smaller mass BH (~10^6 instead of 10^8 - 10^9 M_sun). Taken together, this suggests that GRB 110328A / Swift J164449.3+57345 may be the result of tidal disruption event viewed (nearly) face on to a newly formed jet. Note if this is the case--and the evidence for beamed emission has been suggested elsewhere by Campana et al. [GCN 11843]--then the energetics and accretion-mass inferences would be relaxed by an unknown Gamma factor. Hence, the inferred BH mass of few x 10^6 M_sun might be considered an upper limit. With this interpretation, we would expect the emission to be astrometrically coincident with the nucelus of the host galaxy (something not observed with GRBs in general), exhibit time-variable behavior at radio wavebands (including short timescale flickering), and a rising OIR event over the next few weeks (to an unobscured absolute magnitude of M_V ~ -18 to -21 mag)." We thank Eliot Quataert for helpful discussions. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11848 SUBJECT: GRB 110328A / Swift J164449.3+573451: EVLA observations of a brightening radio source DATE: 11/03/30 23:07:49 GMT FROM: Edo Berger at Harvard Ashley Zauderer, Edo Berger (Harvard), Dale A. Frail (NRAO) and Alicia Soderberg (Harvard) report: "We re-observed the peculiar Swift event GRB110328A / Swift J164449.3+573451 (GCNs 11823, 11824) with the EVLA on March 30.49 UT. At the two frequenciescentered at 4.94 and 6.69 GHz we find that the previously-detected radio source (GCN 11836) has significantly brightened (~10-sigma confidence level). This provides the first clear evidence connecting the quiescent optical source at z=0.35 (GCNs 11827, 11830, 11833, 11834), which is positionally coincident with the brightening radio source, and the transient X-ray/gamma-ray source (which is localized to only 1.7" radius accuracy; GCN 11826)." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11849 SUBJECT: GRB 110328A / Swift J164449.3+573451 DATE: 11/03/31 11:03:35 GMT FROM: Guy Pooley at MRAO, Cambridge, UK Guy Pooley (University of Cambridge) reports: The unusual source GRB 110328A / Swift J164449.3+573451 (GCNs 11823, 11824) was observed with the AMI large array at MRAO, Cambridge (UK) on 2011 Mar 31 over a frequency band from 13.5 to 17.25 GHz. The first observation ran from 02h07m to 08h06m UT; the weather conditions were poor. This observation started 2d13h after the first BAT trigger. The source reported in GCNs 11836, 11848 was detected with a mean flux density of 2.95 +- 0.30 mJy. Analysis of the data in 4 equal time divisions shows a steady increase (2.25, 2.48, 2.56, 3.46 mJy), and a spectral analysis shows a rising spectrum. A second observation from 09h01m to 10h17m UT gives a mean flux density of 2.75 +- 0.30 mJy and also suggests a rising spectrum. This message is quotable in publications. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11850 SUBJECT: GRB 110328A / Swift J164449.3+573451: KASINICS K-band Observation DATE: 11/03/31 14:14:56 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Won-Kee Park (CEOU/SNU), Hyun-Il Sung, Yeong-Beom Jeon (KASI), Yuji Urata (NCU), and Kuiyun Huang (ASIAA) on behalf of EAFON Starting at 2011 March 31,07:04 UT, we performed K-band observation of the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823) using the KASINICS instrument on the 1.8m telescope at Mt. Bohyun Observatory in Korea. We clearly detect the NIR counterpart in K (Morgan et al. 11845; Levan et al. GCN 11846). Using 2MASS stars in the vicinity, we obtain K ~ 16.86 +- 0.02 mag (statistical error only) for the NIR counterpart. The brightness of the object is consistent with the value reported in Levan et al. (GCN 11846), implying no significant brightening over about 18 hrs time span. Further NIR observations are being carried out. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11851 SUBJECT: GRB 110328/Swift J164449.3+573451: Fermi observations DATE: 11/03/31 14:47:15 GMT FROM: Sergio Campana at INAF-OAB S. Campana, L. Foschini, G. Tagliaferri, G. Ghisellini, S. Covino (INAF-OAB) report: We retrieved Fermi LAT publicly available data in near-real time from http://fermi.gsfc.nasa.gov/cgi-bin/ssc/LAT/LATDataQuery.cgi to search for high energy emission from GRB 110328 / Swift J164449.3+573451 within the time interval: 2011-03-27 00:00:00 UTC 2011-03-31 00:00:00 UTC We used LAT Science Tools 9.18.6 and the corresponding calibration files to perform the analysis. We analyzed data for each of the four days and in none of the corresponding datasets we detect the source. Following Foschini et al. (2011, http://arxiv.org/abs/1101.1085), we derived a 3 sigma upper limit of ~3x10^-7 ph/cm2/s in the 0.1-100 GeV energy band in each exposure (lasting 4-5 ks). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11852 SUBJECT: GRB 110328A / Swift J164449.3+573451: Mondy optical observations DATE: 11/03/31 16:37:26 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Pozanenko (IKI), A. Volnova (SAI MSU), E. Klunko (ISTP) on behalf of larger GRB follow up collaboration report: We continue observation (Volnova et al. GCN 11837) of the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823) with AZT-33IK telescope of Sayan observatory (Mondy). Several series of images in R- band were taken on March 28 an 29. In the first epoch we clearly detect the optical counterpart (Cenko et al. GCN 11827, Leloudas et al. GCN 11830), while we do not detect it in the second epoch. The photometry below is based on the USNO-A2.0 star 1425-08596694 assuming R=16.6. The first column represents the time since first Swift trigger (Cummings et al. GCN 11823). T0+ Filter, Exposure, OT mag., UpperLimit (3 sigma) (mid, d) (s) 0.08944 R 6420 21.50 +/- 0.11 23.7 1.25258 R 870 n/d 22.9 Based on the above photometry we tentatively suggest the variability of the optical counterpart between the two epochs. However the more precise calibration of the field stars are necessary to make a definite conclusion about variability. [GCN OPS NOTE(30apr11): Per author's request, Elunko was changed to Klunko.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11853 SUBJECT: GRB 110328A / Swift J164449.3+573451: Infrared transient DATE: 11/03/31 18:19:39 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick), D. Perley (U.C. Berkeley), N.R. Tanvir (U. Leicester), J. Bloom, S.B. Cenko (U.C. Berkeley) report for a larger collaboration: "We re-observed the localization of GRB 110328A with Gemini-N/NIRI on 31 March 2011. Observations were taken in the K-band, and began at 13:15UT, roughly 24 hours after our previous observation (Levan et al. GCN 11846). We find that the IR source, coincident with the X-ray (Osborne et al. GCN 11826) and radio (Zauderer et al. GCN 11848) localisations has faded by 0.25 +/- 0.03 magnitudes over this time frame. Hence we conclude that the IR light does contain a substantial contribution from transient emission. We note that the apparent brightening of the source in a few hours between the observations of Morgan et al. (GCN 11845) and Gemini (GCN 11846), coupled with the fading over the subsequent 24 hours, suggests that the behaviour of the system is complex, and as in the X-ray, is not simply modelled by either a rising, or decaying lightcurve. The location of the source is consistent with the galaxy observed in the optical with a measured redshift z=0.351, (Levan et al. GCN 11833, Thoene et al. GCN 11834) hence increasing the confidence in a true association. Further observations are planned." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11854 SUBJECT: GRB 110328A / Swift J164449.3+573451: Radio-optical/NIR Astrometry DATE: 11/03/31 18:47:00 GMT FROM: Edo Berger at Harvard E. Berger (Harvard), A. Levan (U. Warwick), N. R. Tanvir (U. Leicester), A. Zauderer, A. M. Soderberg (Harvard), and D. A. Frail (NRAO) report: "We performed absolute and relative astrometry on radio and optical images of GRB 110328A / Swift J164449.3+573451 (GCNs 11823, 11824) in an atempt to locate the radio transient (GCNs 11836, 11848) relative to the quiescent optical source at z=0.35 (GCNs 11827, 11830, 11833, 11834). We used EVLA observations at a mean frequency of 5.8 GHz (GCNs 11836, 11848), a Gemini-N/GMOS r-band image, and a UKIRT/WFCAM J-band image (GCN 11846). The Gemini and UKIRT images were astrometrically aligned relative to 2MASS using 20 and 55 objects in common, respectively, leading to an rms scatter of 0.14" and 0.10" in each coordinate, respectively. For the EVLA image we used the native astrometric solution relative to the ICRS. The accuracy of the astrometry is verified by imaging and measuring the position of the phase calibrator, which agrees with the ICRS position to better than 0.4 mas. We note that the 2MASS point-source-catalog positions used to align the Gemini and UKIRT images are reconstructed onto the ICRS. We find the following coordinates for the optical source in the Gemini image (J2000): RA = 16:44:49.939 DEC = +57:34:59.64 with an uncertainty of 0.14" in each coordinate, dominated by the astrometric solution uncertainty. The position of the faint NIR counterpart in the UKIRT image is: RA = 16:44:49.958 DEC = +57:35:00.00 with an uncertainty of about 0.3" in the source centroid, and an additional 0.1" due to astrometric solution uncertainty. Finally, the ICRS position of the radio transient is: RA = 16:44:49.925 DEC = +57:34:59.68 with negligible centroid uncertainty of about 0.01". The relative offset between the radio and optical positions is therefore 0.12+/-0.20", or about 0.6+/-1.0 kpc (at z=0.35). The offset relative to the NIR position is 0.42+/-0.42". Thus, the radio transient position is consistent with arising in the nucleus of the host galaxy (GCN 11847). We find an additional common source between the radio, optical, and NIR images with the following positions: optical: RA = 16:44:48.047 DEC = +57:32:16.83 near-IR: RA = 16:44:48.093 DEC = +57:32:17.03 radio: RA = 16:44:48.139 DEC = +57:32:16.74 This source is a galaxy with extended structure in the optical/NIR images, but it is unresolved in the radio. We therefore associate the radio position with the nucleus of the galaxy (positions given above). The resulting positional offsets are 0.75+/-0.20" (radio-to-optical) and 0.47+/-0.15" (radio-to-NIR). We caution that the error bars do not include a systematic uncertainty in centroiding on the galaxy nucleus (~0.1"), and do not account for potential distortions due to the location of the object near the edge of the Gemini image. Taken at face value, the offset between these positions potentially reflects a relative shift between the optical/NIR and radio astrometric systems. If applied to the radio counterpart of GRB 110328A / Swift J164449.3+573451, this shift would lead to a significant offset (~3-sigma confidence level) between the radio position and the center of the host galaxy. To conclude, absolute astrometry indicates that the radio transient is consistent with arising in the nucleus of the host galaxy (0.6+/-1.0 kpc); the relative radio-optical/NIR positions of an additional common source allow for an offset of up to ~3 kpc. Additional wide-field (~10') deep NIR imaging may provide a larger number of common objects with the EVLA images, thereby impoving the relative astrometric solution. //////////////////////////////////////////////////////////////////////// ATEL #3252 ATEL #3252 Title: GRB 110328A / Swift J164449.3+573451: Followup at 15 GHz Author: Kunal Mooley, Joseph Richards, Walter Max-Moerbeck, Martin Shepherd (Caltech), Dale Frail (NRAO), Shri Kulkarni, and Anthony Readhead (Caltech) Queries: mansi@astro.caltech.edu Posted: 1 Apr 2011; 06:46 UT Subjects:Radio, Millimeter, Infra-Red, Optical, X-ray, Gamma Ray, Gamma-Ray Burst, Transient GRB 110328A / Swift J164449.3+573451 (GCNs #11823, #11824) was observed on 31 March 2011 (UT) with the Owens Valley Radio Observatory (OVRO) 40-meter radio telescope (15 GHz center frequency; 3.0 GHz bandwidth; 2.5 GHz noise-equivalent reception bandwidth), at the location of the EVLA counterpart (GCNs #11836, #11848). Two observations were carried out: (1) UT 08:48 to 09:10 hours, mean flux density: 2.45 +/- 1.14 mJy (2) UT 16:02 to 16:59 hours, mean flux density: 5.14 +/- 0.84 mJy. The 40-meter telescope at OVRO has a Dicke switched receiver; two beams (primary and reference) are used to reduce atmospheric and ground pickup. Possible sources of error are: (i) contaminating radio emission in the reference beam; this will reduce the observed flux density, and (ii) atmospheric transparency variations. Note that during the observations, the weather conditions were favorable. More observations of this source with the 40-meter telescope are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11855 SUBJECT: GRB 110328A / Swift J164449.3+57345: Correction to GCN 11850 DATE: 11/04/01 12:57:45 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Won-Kee Park (CEOU/SNU), Hyun-Il Sung, Yeong-Beom Jeon (KASI), Yuji Urata (NCU), and Kuiyun Huang (ASIAA) on behalf of EAFON It was reported earlier in Im et al. (GCN 11850) that KASINICS K-band imaging started at 2011 March 31, 07:04 UT. The starting time needs to be corrected to March 30, 14:43 UT, which is only 1:43 behind the observation time of Levan et al. (GCN 11846). Considering the proximity of the observation times, the no detection in the variability (GCN 11850) is not surprising. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11856 SUBJECT: GRB 110328A / Swift J164449.3+573451: KASINICS NIR Observation DATE: 11/04/01 13:04:13 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Won-Kee Park (CEOU/SNU), Hyun-Il Sung, Yeong-Beom Jeon (KASI), Yuji Urata (NCU), and Kuiyun Huang (ASIAA) on behalf of EAFON We continued NIR observation of GRB 110328A / Swift J164449.3+573451 using the KASINICS on the 1.8m telescope at Mt. Bohyun Observatory in Korea. The observation started at 2011 March 31, 14:45:20 UT, and we obtained a series of images in H and K. The NIR counterpart is clearly detected in both bands, with the K-band magnitude at 17.29 +- 0.03. Comparison with the K-band magnitude of the same object from the previous night data (Im et al. GCN 11850) shows the dimming of the object by 0.43 mag over one day. The H-band data also show variability, confirming the variability of the source reported earlier (Leval et al. GCN 11854) More NIR imaging is planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11862 SUBJECT: GRB110328A/Swift J164449.3+573451: Fermi LAT Observations DATE: 11/04/02 06:06:13 GMT FROM: Nicola Omodei at Stanford U. N. Omodei (Stanford), E. Troja (NASA/GSFC/ORAU), R. Corbet (CRESST/UMBC/GSFC), J. S. Perkins (CRESST/UMBC/GSFC), J. L. Racusin (NASA/GSFC), J. E. McEnery (NASA/GSFC) on behalf of the Fermi Large Area Telescope collaboration. At the time of the first Swift trigger (Cummings et al., GCN 11823) the Fermi spacecraft was operating in pointing mode observing the region of Cyg X-3. The ToO was terminated at 15:13 UT (2.25 hours on target after the initial Swift trigger) and the Fermi spacecraft continued in normal rocking mode. During the time of Cyg X-3 pointed mode observation the GRB110328A/Swift J164449.3+573451 was at 47 degrees from the LAT boresight. We report here the 95% confidence upper limits on the flux for different exposures spanning the time period of the bright activity of the source. Upper limits (in units of ph/cm^2/s) have been computed between 100 MeV and 10 GeV using the standard likelihood tool, publicly available at the Fermi Science Support Center Web site (http://fermi.gsfc.nasa.gov/ssc/data/analysis/software/). The model assumed in the fit for the source is a power law. The two sets of ULs were derived by fixing the spectral index to 2 and 2.5, respectively. We report upper limits on day-long time scales: | Date | Flux (Index = 2) | Flux (Index = 2.5) | | 2011-03-26 | <3.3e-07 | <6.0e-07 | | 2011-03-27 | <2.9e-07 | <5.2e-07 | | 2011-03-28 | <1.8e-07 | <2.8e-07 | | 2011-03-29 | <1.7e-07 | <2.6e-07 | | 2011-03-30 | <2.3e-07 | <3.9e-07 | | 2011-03-31 | <2.2e-07 | <3.4e-07 | We also searched over a shorter time window around the time of the first three Swift triggers (during the hour following each trigger). For the last Swift trigger (Sakamoto et al., GCN 11842) the source was never in the LAT field of view, therefore we omit it in the following table: | Date | Flux (Index = 2) | Flux (Index = 2.5) | | 2011-03-28 12:57:45.2 | <1.5e-06 | <9.1e-07 | | 2011-03-28 13:40:41.2 | <3.0e-06 | <4.7e-06 | | 2011-03-29 18:26:25.1 | <2.1e-06 | <2.6e-06 | No significant gamma-ray emission is seen from the direction of GRB110328A/Swift J164449.3+573451 in the full 27 months of Fermi LAT data. We report an upper limit of 1.7e-8 ph/cm^2/s (from 100 MeV to 10 GeV) and an upper limit of 1.5e-10 ph/cm^2/s (from 1 GeV to 300 GeV). Knowing that this object could be highly variable, we investigated possible emission on timescales of 5 and 2 days over the lifetime of the Fermi mission. No significant emission was seen in any of the time bins in this light curve. We also report that no significant sources are detected within three degrees from the position of GRB110328A/Swift J164449.3+573451 are present integrating the data over 27 months. The Fermi LAT point of contact for this source is Nicola Omodei (nicola.omodei@slac.stanford.edu). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11867 SUBJECT: GRB 110328A: Konkoly observations. DATE: 11/04/02 14:58:11 GMT FROM: Janos Kelemen at Konkoly Obs/Hungary J. Kelemen, K. Sarneczky (Konkoly Obs.) on behalf of the GRB OT observing program at the Konkoly Observatory. During the period 30/03/2011 - 31/03/2011 we observed the field of GRB 110328A / Swift J164449.3+573451 detected by Swift (Cummings et al., GCN 11823; Barthelmy et al., GCN 11824) with a 60/90 cm Schmidt telescope located at the Mountain Station of the Konkoly Observatory. For the photometry of the OT reported by Cenko et al., (GCN 11827); G. Leloudas et. al., (GCN11830) nearby stars of the UCAC3 catalogue was used. Summary of our results: J.D. magnitude Band 2455650.58459 21.8 +/- 0.2 R 2455651.56924 21.5 +/- 0.2 R 2455652.41122 21.6 +/- 0.2 R //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11872 SUBJECT: GRB 110328A/Swift J164449.3+573451: SARA-N detection DATE: 11/04/03 03:37:13 GMT FROM: Adria C. Updike at Clemson U William C. Keel, Erin Darnell (U Alabama), Adria C. Updike (NASA/GSFC), D. Alexander Kann (TLS Tautenburg), and Dieter H. Hartmann (Clemson University) report: We observed the field of GRB 110328A/Swift J164449.3+573451 (Cummings et al., GCN 11823) on April 1 at 11:50 UT (3.96 days after the trigger) for 20 minutes in the R band with the SARA North telescope at KPNO. At the location of the optical counterpart (Cenko et al., GCN 11827; Volnova et al., GCN 11837) we marginally detect the transient at R = 21.7 +/- 0.3 as compared to the USNO B1.0 catalog and the comparison star given by Leloudas et al. (GCN 11844), in good agreement with the earlier observations of Kelemen et al. (GCN 11867). This GCN resulted from a collaboration initiated by the BAUTforum. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11874 SUBJECT: GRB 110328A / Swift J164449.3+573451: Keck/DEIMOS Optical Spectroscopy DATE: 11/04/04 04:27:16 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko, D. A. Perley, J. S. Bloom (UC Berkeley), K. Hurley (SSL), J. X. Prochaska, J. Brodie, N. Singh, J. Arnold, A. Romanowsky, J. C. Forbes (UCO/Lick), and D. Forbes (Swinburne) report on behalf of a larger collaboration: We have obtained medium-resolution optical spectroscopy of the optical counterpart (Cenko et al., GCN 11827) of the high-energy transient GRB 110328A / Swift J164449.3+573451 (Cummings et al., GCN 11823) with the DEIMOS spectrograph mounted on the Keck II telescope. Observations began at 14:55 UT on 2011 Mar 31 and cover the wavelength range from 4500-9500 A. We identify strong nebular emission features associated with [O II], [O III], H-beta, H-alpha, [N II], and [S II] at a redshift consistent with that reported by Levan et al. (GCN 11833) and Thoene et al. (GCN 11834). Using a preliminary flux calibration, we find that the Balmer decrement (H-alpha / H-beta) is only marginally larger than the value expected for Case B recombination (consistent at the 2 sigma level). This would suggest that the observed red colors of the optical / NIR counterpart (e.g., Morgan et al., GCN 11845; Levan et al., GCN 11846) are either due to 1) an intrinsically red transient source, or 2) dust localized to the source of the transient emission (which does not affect the bulk of the ongoing star formation in the galaxy). Constructing a diagnostic diagram (e.g., Baldwin, Phillips, and Terlevich 1981, PASP, 93, 5) based on the observed ratio of the narrow emission lines, we find the source falls within the locus of star-forming galaxies, and thus does not appear to exhibit any evidence for past nuclear activity. A plot of the diagnostic diagram of the host, showing the empirical dividing line between star-forming galaxies and AGNs from Kauffmann et al (2003, MNRAS, 341, 33- solid line), the theoretical dividing lines from Kewley and Dopita (2002, ApJS, 142, 35 - dashed lines), and the empirical dividing lines from Ho, Filippenko, and Sargent (1997, ApJS, 112, 315), along with analogous measurements from the MPA-JHU value-added SDSS database, can be found at: http://astro.berkeley.edu/~cenko/public/grb/GRB110328A/bpt.png //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11880 SUBJECT: GRB 110328A / Swift J164449.3+573451: millimeter detection at PdBI DATE: 11/04/04 18:14:26 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia A. J. Castro-Tirado (IAA-CSIC), M. Bremer, J.-M. Winters and P. Cox (IRAM), J. Gorosabel, S. Guziy (IAA-CSIC), J. M. Castro Cerón (ESA/ESAC) and A. de Ugarte Postigo (DARK/NBI), on behalf of a larger collaboration, report: "Following the detection by Swift of GRB 110328A / Swift J164449.3+573451 (Sbarufatti et al. GCNC 11798), millimeter observations were conducted on Mar 31 at the Plateau de Bure Interferometer. Consistent with the EVLA radio counterpart (Zauderer et al. GCNC 11836) we clearly detect a source at 3-mm with a flux density of ~20 mJy (200 sigma), confirming a 30% increase in flux density with respect to a previous mm observation on Mar 30 (Zauderer et al. GCN 11841). Further observations are scheduled. We acknowledge the Bure staff for its excellent support." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11881 SUBJECT: GRB 110328A / Swift J164449.3+573451, HST Observations DATE: 11/04/04 18:46:17 GMT FROM: Andrew S. Fruchter at STScI Andrew Fruchter, Kuntal Misra, John Graham (STScI), Andrew Levan (U. Warwick), Nial Tanvir (U. Leicester) and Joshua Bloom (UC Berkeley) report for a larger collaboration: We have observed the field of GRB 110328A / Swift J164449.3+573451 using the WFC3 on the Hubble Space Telescope. We observed in both the near-IR (F160W) and optical (F606W). The observations were performed between 03:00 and 04:00 UT on 4 April 2011. We obtained four dithered exposures of 250s each in F160W. The combined drizzled image has a FWHM of 0.16 arcsec. At the location of the transient we find a nearly pointlike source. Using the two stars in the field which are in both the UCAC3 and 2MASS catalogs for astrometric alignment, we find that the position of this source agrees with that of EVLA (GCN 11854) to within our estimated astrometric error of 0.07 arcsec (340 pc at the distance of the source). In the optical F606W filter we obtained three dithered exposures of 420s each. This combined optical image shows a clearly resolved but compact host galaxy. The nucleus of the galaxy is coincident with the position of the IR source. Using an aperture with a radius of of one arcsecond, we obtain AB magnitudes of 20.75 +/- 0.04 (F160W) and 22.82 +/- 0.02 (F606W) for the central source plus surrounding host galaxy. The astrometric agreement between the HST images and the radio, as well as the observed near-IR variability (GCN 11853) suggest that the transient is associated with the nucleus of this galaxy. Future HST observations should be able to place good constraints on the nuclear variability in both the optical and near-IR, and thus perhaps on the interesting proposal that we are seeing a mini-blazar powered by a tidal disruption event (GCN 11847). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11882 SUBJECT: GRB 110328A / Swift J164449.3+573451: Keck LRIS R-band photometry DATE: 11/04/05 06:24:09 GMT FROM: Michitoshi Yoshida at HASC,Hiroshima U M. Yoshida (HASC, Hiroshima Univ.), M. Yagi and Y. Komiyama (NAOJ) We performed R band imaging observation of the optical counterpart of GRB 110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823) with LRIS attached to Keck-I telescope. The observation was made at 2011-04-01 15:22 UT. We obtained two 30 sec exposure frames and clearly detected the source (Cenko et al. GCN 11827; Leloudas et al. GCN 11830; Volnova et al. GCN 11837; Im et al. GCN 11839) in both frames. Using GSC2.3: N4JF005367 and N4JF005228 (F-magnitude = 15.90 and 17.13, respectively) for flux calibration, we obtained R-band AB magnitude of 22.61 +- 0.09. Taking into account photometric error of the GSC catalog, we consider that this result is consistent with the HST photometry done on 2011-04-04 (Fruchter et al. GCN 11881) and the OT shows no significant variation between our observation and the HST observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11886 SUBJECT: GRB 110328/Swift J164449.3+573451: Chandra observations DATE: 11/04/06 00:20:06 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick), N. Butler, J. Bloom (U.C. Berkeley), N.R. Tanvir (U. Leicester), A.S. Fruchter (STScI) report for a larger collaboration: "We observed GRB 110328/Swift J164449.3+573451 (Cummings et al. GCN 11823) with the Chandra X-ray Observatory on 4 April 2011, beginning at 02:30UT. A total of 15 ks of observation were obtained with the High Resolution Camera (HRC-I). The X-ray counterpart is strongly detected at a mean observed flux of ~5e-11 ergs/s/cm^2, and continues to show strong variability, with flaring of a factor two in flux over the duration of the observations. Utilizing three additional point sources in common to both our Chandra observations, and those taken with Gemini and UKIRT (e.g. Levan et al. GCN 11846) we performed relative astrometry between the optical/IR and X-ray sources. Preliminary analysis suggests the location of the X-ray counterpart is offset 0.07 +/- 0.25 arcseconds from the optical/IR counterpart in our Gemini images. We thank the staff of CXC, in particular Harvey Tannenbaum and Ping Zhao, for their assistance in obtaining this data" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11891 SUBJECT: GRB 110328A/Swift J164449.3+573451: BAT recent rate increase and pre-outburst,light curve DATE: 11/04/06 21:40:50 GMT FROM: Hans Krimm at NASA-GSFC H. A. Krimm (CRESST/GSFC/USRA) and S. D. Barthelmy (GSFC) report on behalf of the Swift/BAT team: We report on the time history of the discovery outburst of Swift J164449.3+573451 and archival searches for past emission. The current outburst started on 2011-Mar-25 (MJD 55645) with a detection of 0.0059 ± 0.0016 ct/s/cm2 (~25 mCrab). BAT first triggered on the source on 2011-Mar-28 (Cummings et al, GCN 11823). There were numerous flares as high as 220 mCrab over the next three days, then the count rate dropped to an average level of 0.0009 ct/s/cm2 and the flares stopped. For the past three days the rate shown a slight increase to 0.0015 ± 0.0005 ct/s/cm2 (~7 mCrab) on 2001-Apr-05, although no flares above 40 mCrab have been seen. For a detailed time history of the early part of the outburst see Sakamoto et al, GCN 11842. The Swift/BAT transient monitor archival data were searched back to February 12, 2005 for previous detections of Swift J164449.3+573451. These searches were made on three different time scales with the following results: On a 16-day timescale (the longest available), we set a 3-sigma upper limit of 0.0011 ct/s/cm2 (~5 mCrab). On a 1-day timescale, there were three isolated days before the outburst when the source was found at above the 3-sigma level: 2009-Mar-31 (MJD 54921) 0.0036 ± 0.0011 ct/s/cm2 2009-Sep-14 (MJD 55088) 0.0036 ± 0.0010 ct/s/cm2 2011-Mar-14 (MJD 55634) 0.0035 ± 0.0011 ct/s/cm2 All three episodes correspond to approximately 15 mCrab. However, given 1866 independent days examined, three 3-sigma points is consistent with statistics. For all other 1-day images, we can set a 3-sigma upper limit. This limit varies depending on the exposure of the source, with 90% of the daily limits within the range of 0.0015 ct/s/cm2 to 0.010 ct/s/cm2. On shorter time scales, we are unable to set a limit below the 6-sigma level for a previously unknown source. Before March 2011 there was no interval when Swift J164449.3+573451 was seen above 6-sigma on any time scale from 64 seconds to a full Swift pointing (nominally 1200 seconds). Corresponding count rate limits cannot be specified since they depend critically on the time scale and location of the source in the BAT field of view. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11910 SUBJECT: GRB 110328A/Swift J164449.3+573451 UVOT Upper Limits DATE: 11/04/08 18:38:46 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (MSSL/UCL), M. M. Chester (PSU), S. T. Holland (CRESST/USRA/GSFC) , F.E. Marshall (NASA/GSFC) and J. R. Cummings (NASA/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT has been observing the field of GRB110328A/Swift J164449.3+573451 since 1483s after the initial trigger (Cummings et al., GCN Circ. 11823). We have found no source in any filter at the position of the afterglow (Cenko et al., GCN Circ. 11827), using individual exposures or summed exposures. Summing up all the data in each filter, beginning with the first BAT trigger on 28th March through 7th April, we have obtained the following 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627): Filter Exp(s) Mag --------------------------------------------------------------------- white 29579 >23.9 v 2541 >21.1 b 1493 >21.5 u 58559 >23.5 w1 59906 >23.4 m2 29000 >23.0 w2 15547 >22.9 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11911 SUBJECT: GRB 110328A / Swift J164449.3+573451: VLBA Observations DATE: 11/04/08 19:41:35 GMT FROM: Edo Berger at Harvard Andreas Brunthaler (MPIfR), Alicia Soderberg (Harvard), Michael Rupen (NRAO), Ashley Zauderer, Edo Berger (Harvard), Dale Frail (NRAO), and Michael Bietenholz (York U.) report: "We observed the variable radio counterpart (GCNs 11836, 11848) of GRB 110328A / Swift J164449.3+573451 (GCNs 11823, 11824) with the Very Long Baseline Array (VLBA) and Effelsberg Radio Telescope for 7 hours beginning on April 2 at 6:00 UT. Observations at both telescopes were carried out at a central frequency of 8.46 GHz. Based on a preliminary analysis of the VLBA baselines alone, we report a significant detection (SNR=29) of the source at position: RA: 16 44 49.9313 DEC: 57 34 59.6895 with a conservative error estimate of 0.5 mas dominated by the positional uncertainty of the phase calibrator, J1638+5720. This is the most precise position available for the transient. It is coincident with the measured positions for the variable radio, NIR, and X-ray counterparts (GCNs 11836, 11848, 11853, 11854, 11886) and the host galaxy nucleus (GCN 11881). The source is not resolved in our VLBA observation; this constrains the size to be smaller than that of the beam: 1.9 x 0.7 mas at a position angle of 18 deg. Further VLBI observations are planned to set limits on the proper motion and source structure. We thank the NRAO and Effelsberg scheduling staff for enabling these rapid response observations. " //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11913 SUBJECT: GRB 110328A / Swift J164449.3+573451: optical observations DATE: 11/04/09 12:36:58 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Rumyantsev (CrAO), A. Volnova (SAI MSU), E. Klunko (ISTP), A. Pozanenko (IKI), on behalf of larger GRB follow up collaboration report: We observed the 110328A / Swift J164449.3+573451 (Cummings et al., GCN 11823) with Shajn telescope of CrAO observatory and AZT-33IK telescope of Sayan observatory (Mondy) . Several series were taken on March 31, April 1 and 3. In each epoch of our observations we clearly observed the optical counterpart (Cenko et al., GCN 11827, Leloudas et al., GCN 11830, Volnova et al., GCN 11837). The photometry is based on the USNO B1.0 star 1476-0321081 (16 45 07.13 +57 36 03.4) assuming R=19.38. The first column represents the time since first Swift trigger (Cummings et al., GCN 11823). #, T0+ Filter Exposure OT telescope 4. 3.28240 R 10230 22.44 +/-0.14 AZT-33IK 5. 4.35111 R 69x60 22.45 +/-0.12 ZTSh 6. 6.44459 R 96x60 22.68 +/-0.05 ZTSh Some details of our observations can be found at http://grb.rssi.ru/GRB110328A/ [GCN OPS NOTE(30apr11): Per author's request, Elunko was changed to Klunko.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11915 SUBJECT: GRB 110328A / Swift J164449.3+573451: MASTER pre, prompt and follow-up observations DATE: 11/04/10 15:58:42 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zimnukhov, M. Kornilov, A.Kuznetsov, D.Zimnukhov, M. Kornilov, D.Gareeva, A.Sankovich Sternberg Astronomical Institute, Moscow State University V.Yurkov, Yu.Sergienko, D.Varda, I.Kudelina Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalozhnich, T.Kopytova, A. Popov Ural State University, Kourovka K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University MASTER II robotic telescope (MASTER-Net: http://87.226.242.22/all-new.php) located in Tunka(Siberia) was pointed to the GRB 110328A (Cummings et al., GCN Circ 11823) 23 sec s after notice time and 1257 sec after GRB time at 2011-03-28 13:18:42.285 UT. On our first (180s exposure) set we haven`t found optical transient within SWIFT error-box. The 3-sigma upper limit has been about 17.7mag The second Swift trigger (Number 450161, 11/03/28, 13:40:41.20) has been received during this follow-up observations. So we have synhronous prompt observatios of the GRB 110328A / Swift J164449.3+573451: Time start exp mlim T_mean (s) unfiltered (if needed) 2011-03-28 13:38:20 180 19.1 2011-03-28 13:38:21 180 19.1 2011-03-28 13:41:56 180 18.9 2011-03-28 13:41:56 180 18.9 2011-03-28 13:45:41 180 18.5 2011-03-28 13:45:41 180 18.7 2011-03-28 13:49:17 180 18.2 2011-03-28 13:49:17 180 18.2 .................................... 2011-03-28 13:38:20 2520 20.8 (T_mean = 2011-03-28 14:13:54.50) MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in MASTER-Amur was pointed to the GRB 110328A 16 sec s after notice time and 365 sec after GRB time at 2011-03-29 18:32:30.586 UT. On our first (70s exposure) set we haven`t found optical transient within SWIFT error-box. The beginning results: Time start exp mlim T_mean (s) unfiltered (if needed) 2011-03-29 18:32:30 70 19.1 2011-03-29 18:33:51 90 19.3 2011-03-29 18:35:32 110 19.5 2011-03-29 18:37:32 130 19.7 2011-03-29 18:39:52 160 19.8 2011-03-29 18:42:42 180 19.6 2011-03-29 18:46:04 180 19.5 2011-03-29 18:49:26 180 19.6 2011-03-29 18:52:48 180 19.6 .................................... 2011-03-29 18:37:32 3530 22.0 2011-03-29 19:10:15 MASTER II robotic telescope located in Kislovodsk was pointed to the GRB 110328A 28 sec s after notice time and 105 sec after GRB time at 2011-03-29 19:59:30.376 UT. On our first (20s exposure) set we haven`t found optical transient within SWIFT error-box. The 3-sigma upper limit has been about 18.8 mag Time start exp mlim T_mean (s) unfiltered (if needed) 2011-03-29 19:59:30 20 18.5 2011-03-29 20:00:18 30 19.1 2011-03-29 20:19:48 180 19.9 2011-03-29 20:23:17 180 19.9 2011-03-29 20:26:42 180 19.9 2011-03-29 20:30:07 180 19.8 2011-03-29 20:33:32 180 19.9 2011-03-29 20:36:58 180 19.9 2011-03-29 20:40:24 180 19.9 2011-03-29 20:43:52 180 19.8 2011-03-29 20:47:25 180 19.9 2011-03-29 20:50:50 180 19.9 2011-03-29 20:54:15 180 19.9 2011-03-29 20:57:40 180 19.9 2011-03-29 21:01:06 180 19.9 2011-03-29 21:04:31 180 20.0 .................................... 2011-03-29 20:19:48 10800 23.0 (T_mean=2011-03-29 22:54:51) There are 2 preburst images 1 month before the GRB 110328A / Swift J164449.3+573451 tregger in MASTER Tunka DataBase. Time start exp mlim T_mean UT (s) unfiltered (if needed) 2011-02-27 21:31:05 180 19.6 2011-02-27 22:21:49 180 20.3 There is no OT on our images. Our unfiltered magnitude is determined as m = 0.8R+0.2B. The photometry of the coadded images are based on the USNO B1.0 star 1475-0312998 (16 45 07.13 +57 36 03.4) assuming R=19.35, B=21.3 . Our results in agreement with Swift UVOT White limit (Breeveld et al., GCN Circ 11910). The summary diagramm of our observations is available at http://observ.pereplet.ru/images/GRB110328A/limit.gif The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11917 SUBJECT: GRB 110328A / Swift J164449.3+573451: R-band Monitoring DATE: 11/04/11 08:32:16 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Yiseul Jeon (CEOU/SNU), Hyun-Il Sung (KASI), Yuji Urata (NCU), and Kuiyun Huang (ASIAA) on behalf of EAFON We are conducting R-band monitoring of GRB 110328A, using the 1.0m telescope at the Mt. Lemmon (LOAO), AZ, USA. In the images taken during April 4, 5, and 7 (UT), we clearly identify the optical counterpart (Cenko et al. GCN 11827; Leloudas et al. GCN 11830; Volnova et al. GCN 11837; Im et al. GCN 11839; Yoshida et al. GCN 11882). The derived R-band magnitudes range from 22.3 to 22.6 mag, but uncertainties in the current photometry make it difficult to assess its variability at < ~0.3 mag. Further analysis of the data, as well as the continued monitoring of the object is planned. We thank the LOAO operator, I. Baek and J. Yoon for their assistance of these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11933 SUBJECT: GRB 110328A / Swift J164449.3+573451: WISE quiescent source upper limit DATE: 11/04/14 16:26:40 GMT FROM: Douglas Hoffman at IPAC/Caltech D. I. Hoffman (IPAC/Caltech), J. S. Bloom (UC Berkeley), R. M. Cutri (IPAC/Caltech), D. Perley (UC Berkeley), B. Cenko (UC Berkeley), N. Tanvir (Leicester), and A. Levan (Leicester) report: The Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010 AJ 140, 1868) scanned the location of GRB 110328A / Swift J164449.3+573451 from January 25, 2010 to January 28, 2010 in the four WISE bands. The coadded frames, each consisting of 39 individual images, do not reveal a detection of the quiescent source. Using a 15 arcsec aperture, we obtained the following 3-sigma upper limit estimates: Band U. Limit (mag) U. Limit (uJy) W1 (3.4 um) > 18.0 > 19 W2 (4.6 um) > 16.2 > 57 W3 (12 um) > 12.8 > 240 W4 (24 um) > 9.55 > 1270 WISE is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. [GCN OPS NOTE(14apr11): Per author's request, the greek-font mu characters were replaced with 'u's.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11956 SUBJECT: GRB 110328A/Swift J164449.3+573451: Maidanak Optical Observation DATE: 11/04/22 12:27:55 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Yiseul Jeon (CEOU/SNU), Mansur Ibrahimov (UBAI) On 2011 April 12 22:49 (UT), we observed GRB 110328A using SNUCAM on the 1.5m telescope at the Maidanak observatory, Uzbekistan. The optical counterpart is clearly detected at S/N > 10 in the R-band image, without exhibiting no strong flux variability. We thanks the staffs of the Maidanak observatory for carrying out this observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12041 SUBJECT: Swift J1644+57/GRB 110328A, Additional HST Observations DATE: 11/05/26 19:51:14 GMT FROM: Kuntal Misra at STScI Andrew Fruchter, Kuntal Misra, John Graham (STScI), Andrew Levan (U. Warwick), Nial Tanvir (U. Leicester) and Joshua Bloom (UC Berkeley) report for a larger collaboration: We have re-observed the field of Swift J1644+57/GRB 110328A using the WFC3 on the Hubble Space Telescope. The observations were performed between approximately 13:30 and 14:30 UT on 20 April 2011 using the F160W filter in the IR and the F606W filter in the optical. As in our previous HST observations (GCN 11881), we obtained four dithered exposures of 250s each in F160W. We find that the source, as measured in a one arcsecond aperture, faded in F160W to an AB magnitude of 20.84. This is a reduction of about 0.09 mag since the previous observation of 4 April 2011. In the optical F606W filter we again obtained three dithered exposures of 420s each. There is no significant change in total flux in a one-arcsecond aperture. However, subtraction of the F606W images from the two different epochs shows a small (27th mag) residual which lies about 0."05 north of the center of the host. This residual is at the detection limit of the image, due to the increased statistical noise under the host, and in fact lies about 0."06 from the location of the much brighter and more clearly detected IR residual (which is more closely aligned to the center of the host.). Given the astrometric difference between the IR and the optical, we believe it probable that the optical residual is noise; however, we plan to obtain further HST observations which may be able to resolve this issue. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12060 SUBJECT: GMRT detection of GRB 110328A DATE: 11/06/02 19:14:01 GMT FROM: Sayan Chakraborti at TIFR,Mumbai,India Naveen Yadav, Sayan Chakraborti, Alak Ray (TIFR, Mumbai, India) and Alicia Soderberg (Harvard University, Cambridge, MA) report: The field of GRB 110328A was observed with the Giant Metrewave Radio Telescope (GMRT) for 8 hours centred on May 28.8 UT at an effective frequency of 1264 MHz with a bandwidth of 32 MHz. We detect a point source consistent with the position of the transient with a flux of 0.431 +/- 0.049 mJy. The rms noise in the synthesized image is 0.023 mJy. We thank the Director GMRT for granting this DDT observation and the staff of the GMRT that made this observation possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12214 SUBJECT: Sw J1644+57 (GRB 110328A): Continued VLBA Observations DATE: 11/07/30 19:22:46 GMT FROM: S. Bradley Cenko at Caltech G. Bower, S. B. Cenko, J. S. Bloom (UC Berkeley) and B. D. Metzger (Princeton) report on behalf of a larger collaboration: We have obtained a second epoch of long-baseline interferometry with the VLBA of the unusual high-energy transient Sw J1644+57 (GRB 110328A; Levan et al, Science, 333, 199, 2011; Bloom et al, Science, 333, 203, 2011; Burrows et al., astro-ph/1104.4787; Zauderer et al., astro-ph/1106.3568). Observations were obtained on 2011 July 17 at 8.4 and 22 GHz with recording bandwidth of 512 Mbps. Preliminary analysis of images at both frequencies reveals a compact (i.e., unresolved) source with flux densities of 15 and 12 mJy, respectively. Errors in the flux density are set by the amplitude scale and are estimated at 10%. The 8.4 GHz localization is consistent with the position obtained from our previous epoch of VLBA observations on 2011 April 1 and 3 (Levan et al., Science 333, 199, 2011; see also Zauderer et al., astro-ph/1106.3568) at the level of ~ 300 uas. If we assume expansion with a constant speed from the time of the initial high-energy detections of this source, this places an upper limit on the average outflow Lorentz factor of Gamma <~ 5.