Gamma-ray Burst 210708A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 08 Jul 21 02:25:58 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     1059460,   Seg_Num: 0
  GRB_RA:          173.699d {+11h 34m 48s} (J2000),
                   173.960d {+11h 35m 50s} (current),
                   173.095d {+11h 32m 23s} (1950)
  GRB_DEC:         -49.187d {-49d 11' 11"} (J2000),
                   -49.306d {-49d 18' 20"} (current),
                   -48.910d {-48d 54' 36"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       2438 [cnts]    Image_Peak=131 [image_cnts]
  TRIGGER_DUR:     1.024 [sec] 
  TRIGGER_INDEX:   146     E_range: 25-100 keV
  BKG_INTEN:       15895 [cnts]
  BKG_TIME:        8724.66 SOD {02:25:24.66} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        19403 TJD;   189 DOY;   21/07/08
  GRB_TIME:        8737.08 SOD {02:25:37.08} UT
  GRB_PHI:         129.38 [deg]
  GRB_THETA:        12.98 [deg]
  SOLN_STATUS:     0x2083
  RATE_SIGNIF:     8.42 [sigma]
  IMAGE_SIGNIF:    6.82 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +0  +2  -3  +0  +0  +4  +0 
  SUN_POSTN:       107.54d {+07h 10m 09s}  +22.46d {+22d 27' 24"}
  SUN_DIST:         92.78 [deg]   Sun_angle= -4.4 [hr] (East of Sun)
  MOON_POSTN:       83.77d {+05h 35m 06s}  +24.47d {+24d 28' 14"}
  MOON_DIST:       108.42 [deg]
  MOON_ILLUM:      4 [%]
  GAL_COORDS:      290.27, 11.79 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      199.91,-46.30 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        SWIFT-BAT GRB Coordinates.  
  COMMENTS:        This is a rate trigger.  
  COMMENTS:        A point_source was found.  
  COMMENTS:        This does not match any source in the on-board catalog.  
  COMMENTS:        This does not match any source in the ground catalog.  
  COMMENTS:        There is a bright star (mag=5.50) 3.34 arcmin from this position.  
  COMMENTS:        This is a GRB.  
  COMMENTS:        Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.  
  COMMENTS:        This trigger occurred at longitude,latitude = 234.30,-2.56 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 08 Jul 21 02:26:46 UT
  NOTICE_TYPE:     Swift-XRT Nack-Position
  TRIGGER_NUM:     1059460,   Seg_Num: 0
  POINT_RA:        173.679d {+11h 34m 43s} (J2000)
  POINT_DEC:       -49.173d {-49d 10' 22"} (J2000)
  IMG_START_DATE:  19403 TJD;   189 DOY;   21/07/08
  IMG_START_TIME:  8797.54 SOD {02:26:37.54} UT,   60.5 [sec] since BAT Trigger Time
  COUNTS:          2    Min_needed= 20
  STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
  PH2_ITER:        1    Max_iter_allowed= 4
  ERROR_CODE:      1
  COMMENTS:        SWIFT-XRT Nack Position.  
  COMMENTS:        No source found in the image.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 08 Jul 21 02:29:39 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     1059460,   Seg_Num: 0
  GRB_RA:          173.699d {+11h 34m 48s} (J2000),
                   173.960d {+11h 35m 50s} (current),
                   173.095d {+11h 32m 23s} (1950)
  GRB_DEC:         -49.187d {-49d 11' 11"} (J2000),
                   -49.306d {-49d 18' 20"} (current),
                   -48.910d {-48d 54' 36"} (1950)
  GRB_DATE:        19403 TJD;   189 DOY;   21/07/08
  GRB_TIME:        8737.08 SOD {02:25:37.08} UT
  TRIGGER_INDEX:   146
  GRB_PHI:         129.38 [deg]
  GRB_THETA:        12.98 [deg]
  DELTA_TIME:      38.00 [sec]
  TRIGGER_DUR:     1.024 [sec] 
  SOLN_STATUS:     0x2083
  RATE_SIGNIF:     8.42 [sigma]
  IMAGE_SIGNIF:    6.82 [sigma]
  LC_URL:          sw01059460000msb.lc
  SUN_POSTN:       107.54d {+07h 10m 10s}  +22.46d {+22d 27' 23"}
  SUN_DIST:         92.78 [deg]   Sun_angle= -4.4 [hr] (East of Sun)
  MOON_POSTN:       83.81d {+05h 35m 14s}  +24.47d {+24d 28' 28"}
  MOON_DIST:       108.40 [deg]
  MOON_ILLUM:      4 [%]
  GAL_COORDS:      290.27, 11.79 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      199.91,-46.30 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        SWIFT-BAT GRB Lightcurve.  
  COMMENTS:           
  COMMENTS:        The next comments were copied from the BAT_POS Notice:  
  COMMENTS:        This is a rate trigger.  
  COMMENTS:        A point_source was found.  
  COMMENTS:        This does not match any source in the on-board catalog.  
  COMMENTS:        This does not match any source in the ground catalog.  
  COMMENTS:        There is a bright star (mag=5.50) 3.34 arcmin from this position.  
  COMMENTS:        This is a GRB.  
  COMMENTS:        Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.  
  COMMENTS:        This trigger occurred at longitude,latitude = 234.30,-2.56 [deg].  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 08 Jul 21 02:30:19 UT
  NOTICE_TYPE:     Swift-XRT Position
  TRIGGER_NUM:     1059460,   Seg_Num: 0
  GRB_RA:          173.7372d {+11h 34m 56.92s} (J2000),
                   173.9981d {+11h 36m 00.46s} (current),
                   173.1333d {+11h 32m 31.99s} (1950)
  GRB_DEC:         -49.1512d {-49d 09' 04.3"} (J2000),
                   -49.2703d {-49d 16' 13.0"} (current),
                   -48.8746d {-48d 52' 28.6"} (1950)
  GRB_ERROR:       7.2 [arcsec radius, statistical plus systematic, 90% containment]
  GRB_INTEN:       1.00e-10 [erg/cm2/sec]
  GRB_SIGNIF:      10.00 [sigma]
  IMG_START_DATE:  19403 TJD;   189 DOY;   21/07/08
  IMG_START_TIME:  8804.00 SOD {02:26:44.00} UT,   66.9 [sec] since BAT Trigger Time
  TAM[0-3]:        100.00 100.00 100.00 100.00
  AMPLIFIER:       1
  WAVEFORM:        31
  SUN_POSTN:       107.54d {+07h 10m 10s}  +22.46d {+22d 27' 22"}
  SUN_DIST:         92.78 [deg]   Sun_angle= -4.4 [hr] (East of Sun)
  MOON_POSTN:       83.81d {+05h 35m 15s}  +24.48d {+24d 28' 31"}
  MOON_DIST:       108.41 [deg]
  MOON_ILLUM:      4 [%]
  GAL_COORDS:      290.29, 11.83 [deg] galactic lon,lat of the burst
  ECL_COORDS:      199.91,-46.25 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Coordinates.  
  COMMENTS:        There is a bright star (mag=5.50) 0.87 arcmin from the XRT position.  
  COMMENTS:        This Notice was ground-generated -- not flight-generated.  
  COMMENTS:        TAM values, flux and significance fields are not valid.  
  COMMENTS:        This position was automatically generated on the ground using  
  COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
  COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
  COMMENTS:        The probability that this is a serendipitous source in the  
  COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.  
  

• GCN Circular #30412
  V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
  R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
  R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
  D. Buckley (South African Astronomical Observatory),
  O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
  A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
  V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
  MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB210708.10 (trigger No 1059460,11h 34m 47.76s , -49d 11m 13.2s, R=0.05) errorbox 63 sec after notice time and 90 sec after trigger time at 2021-07-08 02:27:07 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 62 deg. The sun altitude is -59.3 deg.
  The galactic latitude b = 12 deg., longitude l = 291 deg.
  Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1655482
  We obtain a following upper limits.

  Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
  _________|_____________________|_____|_______|______|________
  
        96 |         MASTER-OAFA |   C |    10 | 17.2 |        
       125 |         MASTER-OAFA |   C |    10 | 17.1 |        
       179 |         MASTER-OAFA |   C |    30 | 17.8 |        
       229 |         MASTER-OAFA |   C |    30 | 17.8 |        
  

  Filter C is a clear (unfiltred) band.
  The observation and reduction will continue. The message may be cited.
• GCN Circular #30413
  B. Sbarufatti (PSU), H. A. Krimm (NSF), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
  At 02:25:37 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210708A (trigger=1059460). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 173.699, -49.187 which is

     RA(J2000) = 11h 34m 48s
     Dec(J2000) = -49d 11' 11"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 10 sec. The peak count rate was ~1300 counts/sec (15-350 keV), at ~0 sec after the trigger.
  The XRT began observing the field at 02:26:37.5 UT, 60.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 173.73706, -49.15179 which is equivalent to:

     RA(J2000)  = 11h 34m 56.89s
     Dec(J2000) = -49d 09' 06.4"
  

  with an uncertainty of 12.2 arcseconds (radius, 90% containment). This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
  A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.58 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.5 (+3.01/-2.55) x 10^21 cm^-2 (90% confidence).
  UVOT data is not immediately available, possibly due to a bright star (mag=5.5) within 1 arcminute of the XRT location.
  Burst Advocate for this burst is B. Sbarufatti (bxs60 AT psu.edu). 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/)
• GCN Circular #30416
  D.N. Burrows (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), J. D. Gropp (PSU) and B. Sbarufatti report on behalf of the Swift-XRT team:
  We have analysed 6.8 ks of XRT data for GRB 210708A (Sbarufatti et al. GCN Circ. 30413), from 85 s to 22.8 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 173.7372, -49.1515 which is equivalent to:

  RA (J2000): 11 34 56.92
  Dec(J2000): -49 09 05.4
  

  with an uncertainty of 7.0 arcsec (radius, 90% confidence).
  The light curve can be modelled with a power-law decay with a decay index of alpha=1.76 (+0.30, -0.65).
  A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.5 (+0.4, -0.3). The best-fitting absorption column is 3.0 (+1.2, -1.0) x 10^21 cm^-2, in excess of the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.0 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1.
  A summary of the PC-mode spectrum is thus:

  Total column:	     3.0 (+1.2, -1.0) x 10^21 cm^-2
  Galactic foreground: 1.6 x 10^21 cm^-2
  Excess significance: 2.2 sigma
  Photon index:	     2.5 (+0.4, -0.3)
  

  If the light curve continues to decay with a power-law decay index of 1.76, the count rate at T+24 hours will be 8.8 x 10^-6 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x 10^-16 (5.1 x 10^-16) erg cm^-2 s^-1.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01059460.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #30421
  C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team:
  Swift-BAT detected GRB 210708A at 02:25:37 UT (GCN 30413). There was no Fermi-GBM onboard trigger around the event.
  An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified no counterparts.
  The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals identified a transient most significantly on the 4.096 s timescale, with a false alarm rate of 1.7e-04 Hz and a location consistent with the Swift-BAT event, using the standard search protocol with a S/N of 6. The GBM targeted search event was found with the highest significance with a "soft" spectrum (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB.
  [1] Goldstein et al. 2019 arXiv:1903.12597
• GCN Circular #30422
  T. Sakamoto (AGU), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), B. Sbarufatti (PSU), M. Stamatikos (OSU), 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 210708A (trigger #1059460) (Sbarufatti, et al., GCN Circ. 30413). The BAT ground-calculated position is RA, Dec = 173.759, -49.164 deg which is

    RA(J2000)  =  11h 35m 02.3s 
    Dec(J2000) = -49d 09' 50.2" 
  

  with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 94%.
  The mask-weighted light curve shows a single peak of duration about 3 seconds, starting just before T0. T90 (15-350 keV) is 2.77 +- 0.70 sec (estimated error including systematics).
  The time-averaged spectrum from T-0.69 to T+2.44 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.05 +- 0.29. The fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.14 sec in the 15-150 keV band is 0.8 +- 0.2 ph/cm2/sec. 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/1059460/BA/
• GCN Circular #30425
  M. H. Siegel (PSU) and B. Sbarufatti (PSU) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 210708A 121 s after the BAT trigger (Sbarufatti et al., GCN Circ. 30413). No optical afterglow consistent with the XRT position (Sbarufatti et al. GCN Circ. 30413) is detected in the initial UVOT exposures. We note that the XRT position is close to the bright star HD 100708, the brightness of which may obscure a faint afterglow. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:

  Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
  
  u_FC               121          370          246         >19.4
  v                  427         4406          236         >19.6
  b                  377         5077          108         >19.3
  u                  121         5021          481         >19.4
  w1                 476         4816          236         >18.9
  m2                 452         4611          236         >19.4
  w2                 403         4201          236         >19.5
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.160 in the direction of the burst (Schlegel et al. 1998).