//////////////////////////////////////////////////////////////////////// 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: 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. //////////////////////////////////////////////////////////////////////// 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: 11831 SUBJECT: GRB 110328B: Fermi GBM detection DATE: 11/03/29 12:02:10 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 12:29:19.19 UT on 28 March 2011, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 110328B (trigger 323008161 / 110328520). The on-ground calculated location, using the GBM trigger data, is RA = 121.1, DEC = 45.8 (J2000 degrees, equivalent to 8h 4m, 45d 48'), with an uncertainty of 1.2 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 31 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of a single pulse with a duration (T90) of about 120 s (50-300 keV). The time-averaged spectrum from T0+0.003 s to T0+122.882 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -1.17 (+0.04/-0.04) and the cutoff energy, parameterized as Epeak, is 538 (+96/-70) keV. The event fluence (10-1000 keV) in this time interval is (2.6 +/- 0.1)E-05 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+4.93 s in the 10-1000 keV band is 5.8 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 369 (+115/-69) keV, alpha = -1.11 +/-0.06 and beta = -1.94 (+0.10/-0.22). The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// 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: 11835 SUBJECT: GRB 110328B: Fermi-LAT Detection DATE: 11/03/29 16:58:08 GMT FROM: Vlasios Vasileiou at LUPM/Fermi-LAT V. Vasileiou (CNRS/IN2P3/LUPM), N. Omodei (Stanford), J. Chiang (SLAC), G. Vianello (SLAC), D. Kocevski (SLAC), and J. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT collaboration. The Fermi-Large Area Telescope (LAT) detected GRB 110328B on 28 March 2011 at 12:29:31 UT, using an automated on-ground analysis. This GRB was also independently detected by the GBM (von Kienlin, GCN 11831) and INTEGRAL SPI-ACS. The source is not detectable using our standard 0.1 - 300 GeV dataset. However, it is detectable if the lower energy threshold is reduced to 50 MeV. Using this dataset, we obtain a localization of RA, DEC (J2000 deg) = 117.6, 43.2 (07h 50m 24s, 43d 12' 00"), with an error of 1.7 deg (68% CL; statistical), compatible with the GBM localization. At the trigger time, the localization was at angle of ~33 degrees from the LAT boresight and ~45 degrees from the Earth's limb. Using a non-standard data selection that increases the low energy tens-of-MeV acceptance at the expense of a greater background, we find that the detected emission consists of a single pulse starting approximately at the time of the GBM trigger and lasting ~40 sec. According to preliminary spectral fits using this non-standard dataset, the spectral index of the detected emission is -3.31 +- 0.21 (68% CL), steeper than the Band-function beta reported by the GBM (-1.94 (+0.10/-0.22)). This suggests the presence of a spectral break between few MeV and few tens-of-MeV energies. Further analysis is ongoing. The Fermi LAT point of contact for this burst is Vlasios Vasileiou (vlasios.vasileiou@lupm.in2p3.fr). 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: 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.