GRB150821A

This page lists all entries on GRB150821A in GRBweb

Summary Fermi GBM IPN Swift GCN 18186 GCN 18187 GCN 18190 GCN 18191 GCN 18192 GCN 18194 GCN 18195 GCN 18196 GCN 18197 GCN 18199 GCN 18200 GCN 18224

Summary table
Variable Value Source
GRB_name_Fermi GRB150821406
T0 9:44:00 UTC GCN_circulars,Swift Det
ra 341.9132° Swift
decl -57.8939° Swift
pos_error 7.90e-05° Swift
T90 103.426 s Fermi_GBM
T90_error 5.753 s Fermi_GBM
T90_start 9:44:24.428 UTC Fermi_GBM
fluence 5.21e-05 erg/cm² Fermi_GBM
fluence_error 2.84e-07 erg/cm² Fermi_GBM
redshift 0.7550
T100 172.1 s
GBM_located False
mjd 57255.40555555555 GCN_circulars,Swift Det
Fermi GBM table
GRB_name_Fermi GRB150821406
trigger_name bn150821406
ra 341.9129°
decl -57.8942°
pos_error 2.41e+00°
datum 2015-08-21
t_trigger 9:44:20.332 UTC
T90 103.426 s
T90_error 5.753 s
T90_start 9:44:24.428 UTC
fluence 5.21e-05 erg/cm²
fluence_error 2.84e-07 erg/cm²
flux_1024 1.11e+01 erg/cm²/s
flux_1024_error 3.32e-01 erg/cm²/s
flux_1024_time 1.71e+01 erg/cm²/s
flux_64 1.36e+01 erg/cm²/s
flux_64_error 1.41e+00 erg/cm²/s
IPN table
GRB_name GRB150821A
ra 341.9042°
decl -57.8667°
pos_error 5.00e-02°
redshift 0.7550
Swift table
GRB_name GRB150821A
t_trigger 9:44:00 UTC
ra 341.9132°
decl -57.8939°
pos_error 7.90e-05°
T90 172.1 s
fluence 7.90e-07 erg/cm²
redshift 0.7550
GCN 18186 table
GRB_name GRB150821A
GCN_number 18186
Detection_method Swift Det
t_trigger 9:44:00 UTC
ra 341.9060°
decl -57.8750°
Circular_text TITLE: GCN CIRCULAR NUMBER: 18186 SUBJECT: GRB 150821A: Swift detection of a burst with an optical afterglow DATE: 15/08/21 09:59:12 GMT FROM: Kim Page at U.of Leicester E. Troja (NASA/GSFC/UMCP), M. G. Bernardini (INAF-OAB), S. B. Cenko (GSFC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), P. A. Evans (U Leicester), A. Melandri (INAF-OAB) and K. L. Page (U Leicester) report on behalf of the Swift Team: At 09:44:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150821A (trigger=652847). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 341.906, -57.875 which is RA(J2000) = 22h 47m 37s Dec(J2000) = -57d 52' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of at least 100 sec. The peak count rate was ~2840 counts/sec (15-350 keV), at ~35 sec after the trigger. The XRT began observing the field at 09:48:04.2 UT, 243.3 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 341.9129, -57.8941 which is equivalent to: RA(J2000) = +22h 47m 39.10s Dec(J2000) = -57d 53' 38.8" with an uncertainty of 4.9 arcseconds (radius, 90% containment). This location is 70 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 251 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 22:47:39.18 = 341.91326 DEC(J2000) = -57:53:38.1 = -57.89393 with a 90%-confidence error radius of about 0.61 arc sec. This position is 0.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 16.48 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is E. Troja (eleonora.troja AT 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.)
GCN 18187 table
GRB_name GRB150821A
GCN_number 18187
Detection_method Swift-BAT Det
redshift 0.7550
Circular_text TITLE: GCN CIRCULAR NUMBER: 18187 SUBJECT: GRB 150821A: VLT/X-shooter redshift DATE: 15/08/21 11:30:04 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst V. D'Elia (ASI/ASDC and INAF-OAR), T. Kruehler (ESO), K. Wiersema (U. Leicester), N. R. Tanvir (U. Leicester), J. Japelj (U. Ljubljana), G. Pugliese (API/UvA), D. Malesani (DARK/NBI), B. Milvang-Jensen (DARK/NBI), J. P. U. Fynbo (DARK/NBI), report on behalf of a larger collaboration: We observed the optical counterpart of GRB 150821A (Troja et al., GCN 18186) with the ESO VLT equipped with the X-shooter spectrograph. Four spectra with individual exposure time of 600 s were secured covering the wavelength range 3,000-25,000 AA. Observations were carried out in robotic "rapid response mode" (RRM) and spectroscopy began 12.4 min after the BAT trigger (7.7 min after the XRT position, at which point the VLT was triggered). The afterglow is well detected in our acquisition image, with a magnitude of R ~ 16 (11.1 min after the GRB), calibrated to one nearby USNO star. We detect a number of absorption features at a common redshift of z = 0.755, including Mg II, Mg I, Fe II, Zn II. We also detect fine-structure lines at the same redshift (e.g. FeII* 2396 / 2389, and Ni II** 2166 / 2217 / 2223), confirming that the absorption system is local to the GRB and not intervening. We thank the kind assistence of the observing staff at Paranal, in particular Claudia Cid and Marcela Espinoza.
GCN 18190 table
GRB_name GRB150821A
GCN_number 18190
Detection_method Fermi GBM Det
t_trigger 9:44:20.330 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 18190 SUBJECT: GRB 150821A: Fermi GBM detection DATE: 15/08/21 15:43:49 GMT FROM: Oliver Roberts at UCD/Fermi O.J. Roberts (UCD) reports on behalf of the Fermi GBM team: "At 09:44:20.33 UT on August 21st 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150821A (trigger 461843064/150821406), which was also detected by Swift (Troja et al. 2015, GCN 18186). The trigger resulted in an Autonomous Repoint Request (ARR) due to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. Both the GBM in-flight and on-ground locations are consistent with the Swift position. The angle of the burst direction to the Fermi LAT boresight is 57 degrees. The GBM light curve consists of a FRED-like burst, with two unresolved peaks and a duration of about 103 s (50-300 keV). The time-averaged spectrum from T0-2.0s to T0+101.4s is well fit by a Band function with Epeak = 322 +/- 18 keV, Alpha =-1.21 +/- 0.01 and Beta = -2.27 +/- 0.10. The event fluence (10-1000 keV) in this time interval is (6.87 +/- 0.08)E-05 erg/cm^2. The 1.024 s peak photon flux measured starting from T0+17.1s in the 10-1000 keV band is 11.1 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN 18191 table
GRB_name GRB150821A
GCN_number 18191
Detection_method Swift-XRT Det
ra 341.9133°
decl -57.8938°
Circular_text TITLE: GCN CIRCULAR NUMBER: 18191 SUBJECT: GRB 150821A: Enhanced Swift-XRT position DATE: 15/08/21 16:45:25 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 910 s of XRT Photon Counting mode data and 2 UVOT images for GRB 150821A, 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 = 341.91332, -57.89384 which is equivalent to: RA (J2000): 22h 47m 39.20s Dec (J2000): -57d 53' 37.8" with an uncertainty of 1.8 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.
GCN 18192 table
GRB_name GRB150821A
GCN_number 18192
Detection_method Swift-UVOT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 18192 SUBJECT: GRB 150821A: Swift/UVOT Detection DATE: 15/08/21 19:28:53 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150821A 251 s after the BAT trigger (Troja et al., GCN Circ. 18186). We use the UVOT position as reported there which is consistent with the enhanced XRT position (Goad et al. GCN Circ. 18191). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 251 401 147 16.59 +/- 0.03 v 560 580 20 17.21 +/- 0.18 b 484 504 19 17.48 +/- 0.12 u 460 479 19 16.70 +/- 0.11 w1 435 629 39 17.62 +/- 0.18 m2 410 7287 372 >19.8 w2 535 1904 156 19.85 +/- 0.28 The magnitudes in the table 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).
GCN 18194 table
GRB_name GRB150821A
GCN_number 18194
Detection_method Swift-XRT Other
redshift 0.7550
Circular_text TITLE: GCN CIRCULAR NUMBER: 18194 SUBJECT: GRB 150821A: Swift-XRT refined Analysis DATE: 15/08/21 23:59:03 GMT FROM: Phil Evans at U of Leicester A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester) and E. Troja report on behalf of the Swift-XRT team: We have analysed 7.7 ks of XRT data for GRB 150821A (Troja et al. GCN Circ. 18186), from 233 s to 40.6 ks after the BAT trigger. The data comprise 1.1 ks in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 18191). The late-time light curve (from T0+5.9 ks) can be modelled with a power-law decay with a decay index of alpha=1.26 (+0.15, -0.13). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.85 (+/-0.03). The best-fitting absorption column is 1.66 (+0.09, -0.08) x 10^22 cm^-2, at a redshift of 0.755, in addition to the Galactic value of 1.8 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.21 (+/-0.15) and a best-fitting absorption column of 2.2 (+0.4, -0.3) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (7.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 1.8 x 10^20 cm^-2 Intrinsic column: 2.2 (+0.4, -0.3) x 10^22 cm^-2 at z=0.755 Photon index: 2.21 (+/-0.15) If the light curve continues to decay with a power-law decay index of 1.26, the count rate at T+24 hours will be 8.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.1 x 10^-13 (6.0 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00652847. This circular is an official product of the Swift-XRT team.
GCN 18195 table
GRB_name GRB150821A
GCN_number 18195
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 18195 SUBJECT: GRB 150821A: GROND afterglow observations DATE: 15/08/22 04:11:28 GMT FROM: Thomas Kruehler at MPE Garching T. Kruehler (ESO), F. Schrey, W. Bornemann, A. Rau and J. Greiner (all MPE) report on behalf of a larger collaboration: We observed the field of GRB 150821A (Swift trigger 652847; Troja et al., GCN 18186) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 02:02 UT on 2015-08-22, 16.3 hours after the GRB trigger. For the optical afterglow (Troja et al., GCN 18186, D'Elia et al. GCN 18187, Kuin & Troja, GCN 18192) we derive magnitudes of: g = 23.2 +- 0.1 r = 22.6 +- 0.1 i = 22.3 +- 0.1 z = 22.0 +- 0.2 at a midtime of 17.0 hours after the trigger. This photometry is in the AB system and calibrated against GROND zeropoints. Because GROND is presently being recommissioned, our measurements are preliminary.
GCN 18196 table
GRB_name GRB150821A
GCN_number 18196
Detection_method Swift-BAT Det
ra 341.9130°
decl -57.8830°
Circular_text TITLE: GCN CIRCULAR NUMBER: 18196 SUBJECT: GRB 150821A, Swift-BAT refined analysis DATE: 15/08/22 15:32:50 GMT FROM: Amy Lien at GSFC M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150821A (trigger #652847) (Troja, et al., GCN Circ. 18186). The BAT ground-calculated position is RA, Dec = 341.913, -57.883 deg which is RA(J2000) = 22h 47m 39.0s Dec(J2000) = -57d -52' -58.7" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 1.5%. Due to the low partial coding fraction of this burst, the light curves and burst durations are created using the special DETECTION mask aperture. However, the spectral analysis are done using the default FLUX aperture for more accurate results, and thus the spectral analysis is only available after T0+174.24 s, when the burst came into the BAT calibrated field of view. Note that the interval used for the spectral analysis included < 1% of the total fluence. The mask-weighted light curve starts at ~T0+20 s and contains several overlapping pulses. The main structure ends at ~T0+70 s, with a long-lasting tail until ~T0+330 s. T90 (15-350 keV) is 172.1 +- 99.0 sec (estimated error including systematics). The time-averaged spectrum from T+174.2 to T+330.7 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.10 +- 0.37. The fluence in the 15-150 keV band is 7.9 +- 1.9 x 10^-7 erg/cm2. The 1-s peak spectral analysis is unavailable because the 1-s peak duration happens before the burst came into the BAT calibrated field of view. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/652847/BA/
GCN 18197 table
GRB_name GRB150821A
GCN_number 18197
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 18197 SUBJECT: GRB 150821A: LCOGT Sutherland observations DATE: 15/08/23 11:56:57 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana), C. Mundell (U. Bath) on behalf of a larger collaboration report: The 1-m LCOGT telescopes in Sutherland (South Africa) began observing Swift GRB 150821A (Troja et al. GCN 18186) on August 21, 19:39 UT (~9.9 hours after the burst trigger) with SDSS r and i filters. At the position of the optical afterglow (Troja et al. GCN 18186; D'Elia et al. GCN 18187; Kuin et al. GCN 18192; Kruehler et al. GCN 18195) we do not detect any source down to the following limits: Mid Time Exposure Filter Magnitude (hrs) (s) --------------------------------------------------- 10.4 2880 r' > 20.4 10.6 2880 i' > 21.0 --------------------------------------------------- Calibration is done against R2 and I values of USNOB-1 nearby stars.
GCN 18199 table
GRB_name GRB150821A
GCN_number 18199
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 18199 SUBJECT: GRB 150821A: LCOGT Siding Springs early observations DATE: 15/08/24 15:29:32 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana), C. Mundell (U. Bath) on behalf of a larger collaboration report: The 1-m LCOGT telescopes in Siding Springs (Australia) began observing Swift GRB 150821A (Troja et al. GCN 18186) on August 21, 10:22 UT (38 minutes after the burst trigger) with SDSS r and i filters under initially poor sky conditions. We detect the optical afterglow (Troja et al. GCN 18186; D'Elia et al. GCN 18187; Kuin et al. GCN 18192; Kruehler et al. GCN 18195) with the following magnitudes: Mid Time Exposure Filter Magnitude (min) (s) ----------------------------------------------------- 135 1680 r' 19.1 +- 0.4 233 480 r' 19.7 +- 0.3 398 720 r' 20.3 +- 0.2 ----------------------------------------------------- Calibration is done against R2 and I values of USNOB-1 nearby stars.
GCN 18200 table
GRB_name GRB150821A
GCN_number 18200
Detection_method Konus-Wind Det
t_trigger 9:44:34.166 UTC
redshift 0.7550
Circular_text TITLE: GCN CIRCULAR NUMBER: 18200 SUBJECT: Konus-Wind observation of GRB 150821A DATE: 15/08/24 15:32:49 GMT FROM: Anna Kozlova at Ioffe Institute S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 150821A (Swift-BAT trigger #652847: Troja et al., GCN 18186; Stamatikos et al., GCN 18196; Fermi GBM detection: Roberts, GCN 18190) triggered Konus-Wind at T0=35074.166 s UT (09:44:34.166). The burst light curve shows a single multi-peaked pulse which started at ~T0-1.4 s and had a total duration of ~161.6 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of 9.16(-2.22,+2.38)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+4.768 s, of 3.68(-1.02,+1.27)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+164.096 s) is best fit in the 20 keV - 18 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.47 (-0.09,+0.15), the high energy photon index beta = -2.21 (-7.79,+0.29), the peak energy 350 (-125,+202) keV (chi2 = 129/97 dof) The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 18 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.07 (-0.10,+0.15), the high energy photon index beta = -3.13 (-6.87,+0.80), the peak energy 327 (-66,+58) keV (chi2 = 91/91 dof) The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150821_T35074/ The background variations in the soft KW band are due to solar activity. Assuming the redshift z=0.755 (D'Elia et al., GCN 18187) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, and Omega_Lambda = 0.73, we estimate the following rest-frame parameters: the isotropic energy release E_iso is ~1.4x10^53 erg, the peak luminosity L_iso is ~1.0x10^52 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,i, is ~614 keV. All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN 18224 table
GRB_name GRB150821A
GCN_number 18224
Detection_method Swift-UVOT Other
redshift 0.7550
Circular_text TITLE: GCN CIRCULAR NUMBER: 18224 SUBJECT: GRB 150821A: Flattening in the UVOT light curve DATE: 15/09/01 15:33:59 GMT FROM: Paul Kuin at MSSL Paul Kuin, Massimiliano de Pasquale (UCL/MSSL), Daniele Malesani (DARK/NBI) and Peter Brown (TAMU) report on behalf of the Swift UVOT team: The light curve from GRB 150821A as observed by Swift/UVOT has been monitored continuously since its discovery, up to about 300 ks in all seven filters, and in u, v and white since. The GRB brightness decreased as a straight power law with index -1.32 (+0.06/-0.05) until about 10 ks. At 100 ks there was a clear flattening in the light curve, and around 250 ks a slight brightening may have taken place, but the brightness could also be flat within our observational errors. Data taken at 835 ks are consistent with a flat or slightly decreasing brightness. The summed 5 ks image in the white band from 300 - 800 ks shows a nearby extended object to the north-west with white = 22.01 +/- 0.17 mag, slightly brighter than the GRB at about 10" distance which currently is at white=23.2 +/- 0.7 magnitudes, and is located about 5" from the edge of the nearby object. At this time it is unclear whether the observed flattening is due to the host galaxy (hosts at this distance have typically a size of 1" only) or are the emergence of a supernova contribution to the afterglow. At the redshift of z = 0.755 (D'Elia et al., GCN Circ. 18187), the observed brightness would imply a SN significantly brighter than those typically associated with GRBs. Further ground observations are encouraged.