//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3161 SUBJECT: GRB 050401: Prompt XRT position DATE: 05/04/01 15:09:18 GMT FROM: David Burrows at PSU/Swift L. Angelini (GSFC), J. L. Racusin, S. Hunsberger, D. N. Burrows, J. E. Hill, J. A. Kennea, D. C. Morris, D. Grupe, J. A. Nousek (PSU), J. P. Osborne, K. L. Page, M. R. Goad, A. P. Beardmore, O. Godet, A. F. Abbey, A. A. Wells (U. Leicester), S. Campana, A. Moretti, C. Pagani, P. Romano, G. Tagliaferri, G. Chincarini (INAF-OAB), G. Cusumano, V. La Parola, V. Mangano, T. Mineo (INAF-IASF/Palermo), P. Giommi, M. Capalbi, M. Perri, F. Tamburelli (ASDC), F. Marshall, N. White, N. Gehrels (GSFC), P. Roming, P. Meszaros (PSU), P. Schady (MSSL), report on behalf of the Swift XRT team: The Swift BAT instrument triggered on GRB050401 at 14:20:15 UT and Swift executed a prompt slew (delayed by 9 seconds due to an Earth constraint) . The XRT found a bright source located at the following position (based on 38 counts in 2.5 seconds): RA(J2000) = +16h 31m 29s, Dec(J2000) = +02d 11' 14" We estimate an uncertainty of about 6 arcseconds. This source is located 42 arcseconds from the BAT position. We note that Swift had a solid attitude solution during this observation. The XRT reported a prompt raw spectrum that peaks at about 1 keV with a roughly power-law shape (based on 328 s of data in Windowed Timing mode). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3162 SUBJECT: Swift-BAT detection of GRB 050401 DATE: 05/04/01 15:25:21 GMT FROM: Louis M Barbier at NASA/GSFC/Swift L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), J. Norris (GSFC), J. Nousek (PSU), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Suzuki (Saitama), J. Tueller (GSFC) on behalf of the Swift team: At 14:20:15 UT Swift-BAT triggered on burst GRB 050401 (trigger=113120). The BAT-derived position is RA,Dec=247.880,+2.184 (J2000). We note this is 42 arcsec from the XRT Position GCN Notice. The lightcurve shows 5 main peaks with a total burst duration of 38 sec. The first peak started about 9 sec before the trigger, and the fifth peak started at T+23 sec. The peak count rate was 5000 cnts/sec. This burst was 56 deg of the BAT bore sight (<10% coding). We note that the Swift Star Trackers were locked at the time of the trigger and all initial inspections indicate that the attitude solution for the s/c is normal (unlike yesterday's episode). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3163 SUBJECT: GRB 050401: Optical afterglow candidate DATE: 05/04/01 15:48:05 GMT FROM: Paul Price at IfA,UH R. McNaught (RSAA, ANU) and P.A. Price (IfA, Hawaii) report on behalf of a larger collaboration: We have observed the XRT position of GRB 050401 (Swift trigger 113120) with the 40-inch telescope at Siding Spring Observatory starting at April 1.637 UTC. In an unfiltered exposure of 120 sec, we identify a source near the limiting magnitude of our observations, at approximate coordinates: 16:31:28.81 +02:11:14.2 J2000 This source is within the XRT error circle, and not present in the DSS. The source is about R ~ 20.3 mag. A subsequent image reveals that the source is stationary. Further observations are planned. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3164 SUBJECT: GRB 050401: Optical afterglow confirmed DATE: 05/04/01 16:34:27 GMT FROM: Paul Price at IfA,UH P.A. Price (IfA, Hawaii) and R. McNaught (RSAA, ANU) report on behalf of a larger collaboration: Continued observations of the field of GRB 050401 (GCN ##3161,3162) with the 40-inch telescope at Siding Spring Observatory reveals that the optical afterglow candidate (GCN #3163) is variable. In particular, in the course of two unfiltered and four R-band images, the source appears to have brightened and then faded. This source is therefore likely to be the optical afterglow of GRB 050401. Observations are ongoing at Siding Spring Observatory. A rough finding chart showing the afterglow is available from: http://www.ifa.hawaii.edu/~price/grb050401finder.ps This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3165 SUBJECT: GRB050401: ROTSE-III Detection of Prompt Optical Counterpart DATE: 05/04/01 18:49:02 GMT FROM: Eli Rykoff at U of Michigan/ROTSE E. S. Rykoff, S. A. Yost, D. A. Smith (Umich) report on behalf of the ROTSE collaboration: ROTSE-IIIa, located at Siding Spring Observatory, Australia responded to Swift GRB050401 (Trigger #113120). An automated response produced images beginning 6.2 seconds after the GCN trigger under good conditions. The first image was taken at 01 Apr 14:20:39.2 UT, 33 seconds after the updated burst time as reported by Barbier et al (GCN 3162). We took ten 5 second, ten 20 second and sixty 60 s exposures, and imaging is ongoing. The images are unfiltered and were calibrated relative to USNO A2.0. Individual images have limiting magnitudes ranging from 16.0-17.3. We compared sets of 10 co-added frames to the DSS (second epoch). In our first co-added set of images we have a marginal detection of a source consistent with the XRT position (GCN 3161) and the candidate reported by McNaught & Price (GCN 3163). The source is at 17.0+/-0.2 for a 151 second co-add starting at 14:20:39.2 UT, with a limiting magnitude of 17.4. We do not detect any significant flux in our following images, to a limiting magnitude of 17.9/18.4 for sets of images beginning at 14:28:22.3 UT/14:39:57 UT. We also note that our first 5-s image was taken coincidentally with the end of the gamma-ray emission detected by Swift (GCN 3162). We do not detect significant flux to a limiting magnitude of 16.0. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3171 SUBJECT: GRB050401: TNG R-band observation DATE: 05/04/02 11:36:52 GMT FROM: Nicola Masetti at IASF,CNR,Bologna P. D'Avanzo, D. Fugazza (INAF-OAB), N. Masetti (INAF-IASF, Bologna) and M. Pedani (TNG), on behalf of a larger collaboration, report: "We have obtained R-band photometry of the optical afterglow (McNaught & Price, GCN #3163; Rykoff et al., GCN #3165) of GRB050401 (Angelini et al., GCN #3161; Barbier et al., GCN #3162) using DOLoRes at TNG. The observations, for a total exposure time of 30 minutes, were performed under moderate seeing conditions (around 1.2 arcsec). A preliminary analysis of the images allowed us to derive the following photometry for the OT, calibrated after observing the SA104 Landolt standard field: R = 23.18 +/- 0.10 on 2005 April 2.072 UT, 11.39 hours after the burst Using this OT magnitude and those reported in GCNs #3163 and #3165, and assuming a canonical power-law decay, we obtain for the OT a decay index alpha ~ 1, quite typical of GRB optical afterglows. We are particularly grateful to the TNG staff for their remarkable support to these observations." This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3173 SUBJECT: GRB 050401 BAT refined analysis DATE: 05/04/02 20:14:18 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (GSFC/NRC), S. Barthelmy, L. Barbier (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), M. Suzuki (Saitama), M. Tashiro (Saitama U.), J. Tueller (GSFC), on behalf of the Swift/BAT team: At 14:20:15 UT Swift-BAT detected GRB 050401 (trigger=113120) (GCN Circ 3162, Barbier et al.). The refined BAT ground position is (RA,Dec) = 247.880, +2.191, [deg; J2000] +- 3 arcmin, (95% containment). This is 38 arcseconds from the XRT (GCN Circ 3161, Angelini et al.) and confirmed optical afterglow (GCN Circ 3163, McNaught et al.) positions. The burst had 4 distinct peaks. There were three initial peaks of roughly comparable intensity, at times T-6, T-1 and T+3. These peaks all had durations of between 1 and 2 seconds. These peaks were followed by a stronger peak beginning at T+23 and lasting ~6 seconds. The total burst duration T90 is estimated at 33 seconds +/- 2 s (including systematics) The fluence derived from the event data is 1.4 X 10^-5 erg/cm^2 in the 15-350 keV band. The 1-s peak flux (T+24.6 s) is 14 ph/cm^2/s (also 15-350 keV). The photon index of the 1-s peak spectrum (T+0 s) is 1.17 +/- 0.12 (90% confidence). The time-averaged spectrum yields a photon index of 1.50 +/- 0.06 (90% confidence). Both the 1-s and time-averaged spectra are well fit by a simple power-law. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3174 SUBJECT: GRB050401: Maidanak optical observation DATE: 05/04/02 22:10:22 GMT FROM: Alexei Pozanenko at IKI, Moscow B. Kahharov, M. Ibrahimov, D. Sharapov (MAO), A.Pozanenko (IKI), V.Rumyantsev (CrAO), G.Beskin (SAO) report: We observed the afterglow (McNaught and Price, GCN 3163; Rykoff et al., GCN 3165) of the Swift GRB050401 (Angelini et al., GCN 3161; Barbier et al., GCN 3162) with 1.5m telescope of Maidanak Astronomical Observatory (MAO), Uzbekistan under good weather conditions (seeing is 1.0 arcsec). Preliminary R-photometry against of USNO-B1.0 Catalog is following: Mean time Exposure Mag. (UT) (s) Apr. 1.988 8x300 22.2 +/- 0.2 This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3175 SUBJECT: GRB 050401 Optical Observations DATE: 05/04/03 08:33:13 GMT FROM: Kuntal Mishra at ARIES,Nainital,India Kuntal Misra ((ARIES Naini Tal), Atish P. Kamble (Raman Reserach Institute, Bangalore) and S. B. Pandey (ARIES Naini Tal), on behalf of larger Indian GRB collaboration The Swift GRB 050401 (trigger = 113120) was monitored from 1.04-m reflector at ARIES, Naini Tal in V, R and I bands. The OT candidate reported by McNaught and Price (GCN 3163), seen in our R band (900 sec exp) frame taken on April 01.8359 UT was at 21.5 +/- 0.2 mag. Using this magnitude of the optical afterglow and those reported in GCN 3163 and GCN 3171, we derive a flux temporal decay index of ~ 1.0, consistent to D'Avanzo et al. 2005 (GCN 3171). This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3176 SUBJECT: GRB 050401: VLT spectroscopic redshift DATE: 05/04/03 19:59:02 GMT FROM: Jens Hjorth at U.Copenhagen Johan P. U. Fynbo, Brian L. Jensen, Jens Hjorth (Niels Bohr Institute), Klaas Wiersema, Rhaana Starling (U. Amsterdam), Paul Vreeswijk (ESO), Evert Rol, Andrew Levan (U. Leicester), Sara Ellison (U. Victoria), Nicola Masetti (IASF-Bologna) report on behalf of a larger collaboration: "Using FORS2 on the Very Large Telescope we have obtained spectra of the afterglow of GRB 050401 (GCN 3161, 3162, 3163) on 2005, April 2. We detect several absorption lines consistent with two absorption systems at redshifts z = 2.50 and z = 2.90. The likely redshift of GRB 050401 is hence z = 2.90. For a standard cosmology (H_0 = 70 km/s/Mpc, Omega_m = 0.3, Omega_w = 0.7, w = -1) the Swift fluence (GCN 3173) corresponds to an isotropic energy release of 2.6 x 10^53 erg. We thank Paul Price for providing a finding chart for the optical afterglow and the ESO staff for excellent support." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3177 SUBJECT: GRB050401, radio observation at 4.8 GHz and 8.64 GHz DATE: 05/04/04 12:21:42 GMT FROM: Kinwah Wu at MSSL-UCL L. Saripalli (ATNF, CSIRO), K. Wu (MSSL, UCL), K. K. Ghosh (NASA-NSSTC), D. A. Swartz (NASA-NSSTC) and A. F. Tennant (NASA-MSFC) report of radio observations of GRB050401. We observed the field of the GRB050401 using ATCA (6 km configuration) at Narrarbri, Australia on 2005 April 02 15.02 UT and April 03 14.22 UT. The duration of each observation was 1 hour. We do not detect signals above rms of 0.5 (4.8 GHz) and 0.6 mJy (8.64 GHz) in the field in each individual data set for the two observations. We also do not find significant signal above an rms of 0.4 mJy for the combined data set at 8.64 GHz. There appears to be a 2.5-sigma feature (rms of 0.3 mJy) at the position of the source (ref GCN 3163) in the combined data set at 4.8 GHz. The feature could be spurious given that the uv coverage was poor and the observation duration was short. The observations were granted as ToO (April 02) and discretion observation (April 03) by the ATNF director. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3178 SUBJECT: GRB050401: Radio observation at 610 MHz with GMRT DATE: 05/04/05 06:45:08 GMT FROM: Poonam Chandra at Tata Inst. Fund.Res. GRB050401: Radio observation at 610 MHz with GMRT Poonam Chandra and Alak Ray (Tata Institute of Fundamental Research (TIFR), Mumbai) report the observation of GRB 050401 with the Giant Metrewave Radio Telescope (GMRT) on 2005 April 2.77 (UT) at 617 MHz frequency with a bandwidth of 32 MHz. No radio emission is seen either at the Optical Transient afterglow position (GCN 3163) or the revised Swift BAT position (GCN 3173). The map rms is 0.23 mJy and 2-Sigma upper limit to the GRB flux density is 0.46 mJy. We thank the GMRT staff, in particular the National Centre for Radio Astrophysics (NCRA) Director Dr. Rajaram Nityananda for making the observations possible, and Dr. Paolo Freire, Yashwant Gupta and collaborators for allowing a part of their time to be used for this observation. GMRT is run by NCRA-TIFR. This observation was Target of Opportunity observation and the observing time was granted as discretionary time at the GMRT. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3179 SUBJECT: Konus-Wind observation of GRB 050401 DATE: 05/04/05 14:16:26 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report: A long multipeak GRB 050401 (Swift-BAT trigger 113120, GCN 3162,3173) triggered Konus-Wind at 51611.344 s UT (14:20:11.344). As observed by Konus-Wind, it had a duration of ~36 s, fluence (1.93 +/- 0.04)10-5 erg/cm2, peak flux (2.45 +/- 0.12)10-6 erg/cm2 s (both in the 20 keV - 2 MeV energy range). We derived two spectra: the first one integrated over three initial peaks (0 - 16.6 s) and the second integrated over the last, strongest peak (24.8 - 32 s). Both spectra are well fitted by a GRB (Band) model. For the 1st spectrum: the low-energy photon index is alpha = -1.15 +/- 0.16, the high energy photon index beta = -2.65 +/- 0.31, the break energy E0 = 156 +/- 45 keV, and the peak energy Ep = 132 +/- 16 keV. For the 2nd spectrum: the low-energy photon index is alpha = -0.83 +/- 0.21, the high energy photon index beta = -2.37 +/- 0.14, the break energy E0 = 102 +/- 30 keV, and the peak energy Ep = 119 +/- 26 keV. Assuming z = 2.90 (GCN 3176) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.3, Omega_\Lambda = 0.7, the isotropic energy release is E_iso = (3.53 +/- 0.07)1053 erg, the maximum luminosity is (L_iso)_max = (1.75 +/- 0.09)1053 ers/s, and the rest-frame peak energies are Ep_rest = (515 +/- 62) keV and Ep_rest = (464 +/- 101) keV correspondingly for the first and second spectrum. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3187 SUBJECT: GRB050401: Radio Detection DATE: 05/04/07 16:37:38 GMT FROM: Alicia Soderberg at Caltech A. M. Soderberg (Caltech) reports on behalf of the Caltech-NRAO-Carnegie GRB collaboration: "Using the Very Large Array at 8.5 GHz, we observed the field of GRB050401 (GCN 3162) on 2005 Apr 7.29 UT. We detect a radio source at our detection threshold at the following position: RA(J2000) = +16h 31m 28.82s, Dec(J2000) = +02d 11' 14.83" with an estimated uncertainty of 0.5 arcsec in each coordinate. This source is within the XRT error circle (GCN 3161) and consistent with the optical afterglow position (GCN 3163). The flux density of the source is 122 +- 33 uJy. Further observations are planned." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3233 SUBJECT: GRB 050401: Optical limit DATE: 05/04/11 11:57:48 GMT FROM: Ken ichi Torii at RIKEN K. Torii (Osaka U.) reports "The error region of GRB 050401 (Angelini, et al. GCN 3161; Barbier, et al. GCN 3162) was observed with the ART 14-inch telescope. BVRcIc imaging started at 2005 April 1, 14:22:23 UT (128-s after trigger) and 60-s exposure in each filter was repeated. The optical afterglow (McNaught & Price GCN 3163) is not detected in our frames and the following 3-sigma upper limits are derived relative to USNO-B1.0 magnitudes. MeanEpoch(UT) Magnitude Exposure 14:22:53 >12.8Rc 60s 14:24:02 >13.2Ic 60s 14:27:27 >13.4Rc 60s 14:28:34 >13.4Ic 60s 14:32:00 >13.7Rc 60s 14:33:07 >14.0Ic 60s " //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3319 SUBJECT: GRB 050401: Rc observation DATE: 05/04/27 15:23:16 GMT FROM: Corrado Bartolini at Universita di Bologna G. Greco, C. Bartolini, A. Guarnieri, A. Piccioni (Bologna University), G. Pizzichini (IASF-CNR, Sezione di Bologna), S. Bernabei and S. Marinoni (Osservatorio di Bologna) report: "We observed the optical afterglow (Mc Naught and Price, GCN 3163) of the Swift GRB050401 (Angelini et al. GCN 3161) with the 152-cm G. D. Cassini telescope of Bologna University equipped with the BFOSC CCD imager. We obtained 2x1800s Rc images on 2005 April 2.056 and April 2.092 UT. From the first image, in good sky conditions (seeing about 2"), we find Rc =3D 22.7 +- 0.4, using the calibration kindly provided to us by P. D'Avanzo and N. Masetti, performed at TNG telescope. In the second image, less deep, the object is hardly visible. The first image of the OT is posted into a public directory from where it can be retrieved by sftp using hostname: ermione.bo.astro.it username: publicGRB password: GRB_bo directory: GRB050401".