Gamma-ray Burst 250605A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:52:47 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  GRB_RA:          166.977d {+11h 07m 54s} (J2000),
                   167.291d {+11h 09m 10s} (current),
                   166.359d {+11h 05m 26s} (1950)
  GRB_DEC:         -19.795d {-19d 47' 40"} (J2000),
                   -19.933d {-19d 55' 57"} (current),
                   -19.524d {-19d 31' 25"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       4722 [cnts]    Image_Peak=420 [image_cnts]
  TRIGGER_DUR:     1.024 [sec] 
  TRIGGER_INDEX:   147     E_range: 25-100 keV
  BKG_INTEN:       17399 [cnts]
  BKG_TIME:        67932.26 SOD {18:52:12.26} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        20831 TJD;   156 DOY;   25/06/05
  GRB_TIME:        67951.27 SOD {18:52:31.27} UT
  GRB_PHI:          49.14 [deg]
  GRB_THETA:        33.04 [deg]
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     53.50 [sigma]
  IMAGE_SIGNIF:    15.53 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +0  +2  +4  +0  +0 +17  +0 
  SUN_POSTN:        74.11d {+04h 56m 26s}  +22.63d {+22d 37' 52"}
  SUN_DIST:        100.33 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.69d {+12h 50m 46s}   -7.32d {-07d 19' 12"}
  MOON_DIST:        27.66 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.07, 36.80 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      176.27,-23.27 [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:        This is a GRB.  
  COMMENTS:        This trigger occurred at longitude,latitude = 336.71,7.35 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:54:40 UT
  NOTICE_TYPE:     Swift-XRT Image
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  GRB_RA:          166.9571d {+11h 07m 49.7s} (J2000),
                   167.2715d {+11h 09m 05.1s} (current),
                   166.3395d {+11h 05m 21.4s} (1950)
  GRB_DEC:         -19.7882d {-19d 47' 17.5"} (J2000),
                   -19.9262d {-19d 55' 34.2"} (current),
                   -19.5173d {-19d 31' 02.3"} (1950)
  GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
  GRB_INTEN:       41 [cnts]
  IMG_START_DATE:  20831 TJD;   156 DOY;   25/06/05
  IMG_START_TIME:  68049.26 SOD {18:54:09.26} UT,   98.0 [sec] since BAT Trigger T
  ime
  CENTROID_X:      268.42,  raw= 268  [pixels]
  CENTROID_Y:      293.29,  raw= 293  [pixels]
  ROLL:            290.60 [deg]
  GAIN:            1
  MODE:            2, Short Image mode
  WAVEFORM:        134
  EXPO_TIME:       0.10 [sec]
  GRB_POS_XRT_Y:   -12.73
  GRB_POS_XRT_Z:   -101.78
  IMAGE_URL:       sw01321323000msxps_rw.img
  SUN_POSTN:        74.11d {+04h 56m 26s}  +22.63d {+22d 37' 53"}
  SUN_DIST:        100.31 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.70d {+12h 50m 49s}   -7.33d {-07d 19' 38"}
  MOON_DIST:        27.68 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.05, 36.79 [deg] galactic lon,lat of the burst
  ECL_COORDS:      176.24,-23.27 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Image.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:54:30 UT
  NOTICE_TYPE:     Swift-XRT Position
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  GRB_RA:          166.9571d {+11h 07m 49.70s} (J2000),
                   167.2715d {+11h 09m 05.16s} (current),
                   166.3395d {+11h 05m 21.48s} (1950)
  GRB_DEC:         -19.7882d {-19d 47' 17.5"} (J2000),
                   -19.9262d {-19d 55' 34.2"} (current),
                   -19.5173d {-19d 31' 02.3"} (1950)
  GRB_ERROR:       5.5 [arcsec radius, statistical plus systematic, 90% containment]
  GRB_INTEN:       2.80e-08 [erg/cm2/sec]
  GRB_SIGNIF:      6.40 [sigma]
  IMG_START_DATE:  20831 TJD;   156 DOY;   25/06/05
  IMG_START_TIME:  68049.26 SOD {18:54:09.26} UT,   98.0 [sec] since BAT Trigger Time
  TAM[0-3]:        327.70 237.13 261.57 243.67
  AMPLIFIER:       2
  WAVEFORM:        134
  SUN_POSTN:        74.11d {+04h 56m 26s}  +22.63d {+22d 37' 53"}
  SUN_DIST:        100.31 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.70d {+12h 50m 49s}   -7.33d {-07d 19' 36"}
  MOON_DIST:        27.68 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.05, 36.79 [deg] galactic lon,lat of the burst
  ECL_COORDS:      176.24,-23.27 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Coordinates.  
  COMMENTS:        The XRT position is 1.18 arcmin from the BAT position.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:54:42 UT
  NOTICE_TYPE:     Swift-XRT Processed Image
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  GRB_RA:          166.9571d {+11h 07m 49.7s} (J2000),
                   167.2715d {+11h 09m 05.1s} (current),
                   166.3395d {+11h 05m 21.4s} (1950)
  GRB_DEC:         -19.7882d {-19d 47' 17.5"} (J2000),
                   -19.9262d {-19d 55' 34.2"} (current),
                   -19.5173d {-19d 31' 02.3"} (1950)
  GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
  GRB_INTEN:       41 [cnts]
  IMG_START_DATE:  20831 TJD;   156 DOY;   25/06/05
  IMG_START_TIME:  68049.26 SOD {18:54:09.26} UT,   98.0 [sec] since BAT Trigger Time
  CENTROID_X:      268.42,  raw= 268  [pixels]
  CENTROID_Y:      293.29,  raw= 293  [pixels]
  ROLL:            290.60 [deg]
  GAIN:            1
  MODE:            2, Short Image mode
  WAVEFORM:        134
  EXPO_TIME:       0.10 [sec]
  GRB_POS_XRT_Y:   -12.73
  GRB_POS_XRT_Z:   -101.78
  IMAGE_URL:       sw01321323000msxps_rw.img
  SUN_POSTN:        74.11d {+04h 56m 26s}  +22.63d {+22d 37' 53"}
  SUN_DIST:        100.31 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.71d {+12h 50m 49s}   -7.33d {-07d 19' 38"}
  MOON_DIST:        27.68 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.05, 36.79 [deg] galactic lon,lat of the burst
  ECL_COORDS:      176.24,-23.27 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Processed Image.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:56:09 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  GRB_RA:          166.977d {+11h 07m 54s} (J2000),
                   167.291d {+11h 09m 10s} (current),
                   166.359d {+11h 05m 26s} (1950)
  GRB_DEC:         -19.795d {-19d 47' 40"} (J2000),
                   -19.933d {-19d 55' 57"} (current),
                   -19.524d {-19d 31' 25"} (1950)
  GRB_DATE:        20831 TJD;   156 DOY;   25/06/05
  GRB_TIME:        67951.27 SOD {18:52:31.27} UT
  TRIGGER_INDEX:   147
  GRB_PHI:          49.14 [deg]
  GRB_THETA:        33.04 [deg]
  DELTA_TIME:      19.00 [sec]
  TRIGGER_DUR:     1.024 [sec] 
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     53.50 [sigma]
  IMAGE_SIGNIF:    15.53 [sigma]
  LC_URL:          sw01321323000msb.lc
  SUN_POSTN:        74.11d {+04h 56m 26s}  +22.63d {+22d 37' 53"}
  SUN_DIST:        100.33 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.72d {+12h 50m 52s}   -7.33d {-07d 19' 58"}
  MOON_DIST:        27.67 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.07, 36.80 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      176.27,-23.27 [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:        This is a GRB.  
  COMMENTS:        This trigger occurred at longitude,latitude = 336.71,7.35 [deg].  
  

  
• GCN Circular #40632
  V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
  MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB250605.79 (trigger No 1321323,11h 07m 54.48s , -19d 47m 42.0s, R=0.05) errorbox 16 sec after notice time and 37 sec after trigger time at 2025-06-05 18:53:08 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 31 deg. The sun altitude is -39.9 deg.
  The galactic latitude b = 37 deg., longitude l = 273 deg.
  Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2893644
  We obtain a following upper limits.

  Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
  _________|_____________________|_____|_______|______|________
  
        43 |         MASTER-SAAO |   C |    10 | 17.9 |        
  

  Filter C is a clear (unfiltred) band.
  The observation and reduction will continue. The message may be cited.
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:57:12 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  POINT_RA:        166.985d {+11h 07m 56s} (J2000)
  POINT_DEC:       -19.801d {-19d 48' 02"} (J2000)
  POINT_ROLL:      290.599d
  IMG_START_DATE:  20831 TJD;   156 DOY;   25/06/05
  IMG_START_TIME:  68058.26 SOD {18:54:18.26} UT,   107.0 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        2.344
  N_STARS:         36
  X_OFFSET:        544 [pixels]
  Y_OFFSET:        544 [pixels]
  X_MAX:           1503 [pixels]
  Y_MAX:           1503 [pixels]
  DET_THRESH:      13
  PHOTO_THRESH:    7
  SL_URL:          sw01321323000msufc0106.fits
  SUN_POSTN:        74.11d {+04h 56m 27s}  +22.63d {+22d 37' 54"}
  SUN_DIST:        100.34 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.72d {+12h 50m 54s}   -7.34d {-07d 20' 13"}
  MOON_DIST:        27.67 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.09, 36.80 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      176.28,-23.27 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:57:28 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  POINT_RA:        166.985d {+11h 07m 56s} (J2000)
  POINT_DEC:       -19.801d {-19d 48' 02"} (J2000)
  POINT_ROLL:      290.599d
  IMG_START_DATE:  20831 TJD;   156 DOY;   25/06/05
  IMG_START_TIME:  68058.26 SOD {18:54:18.26} UT,   107.0 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        2.344
  N_STARS:         36
  X_OFFSET:        544 [pixels]
  Y_OFFSET:        544 [pixels]
  X_MAX:           1503 [pixels]
  Y_MAX:           1503 [pixels]
  DET_THRESH:      13
  PHOTO_THRESH:    7
  SL_URL:          sw01321323000msufc0106.fits
  SUN_POSTN:        74.11d {+04h 56m 27s}  +22.63d {+22d 37' 54"}
  SUN_DIST:        100.34 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.73d {+12h 50m 54s}   -7.34d {-07d 20' 16"}
  MOON_DIST:        27.67 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.09, 36.80 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      176.28,-23.27 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Source List.  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:58:33 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  POINT_RA:        166.985d {+11h 07m 56s} (J2000)
  POINT_DEC:       -19.801d {-19d 48' 02"} (J2000)
  ROLL:            290.599d
  IMG_START_DATE:  20831 TJD;   156 DOY;   25/06/05
  IMG_START_TIME:  68058.26 SOD {18:54:18.26} UT,   107.0 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     770842493
  X_OFFSET:        987 [pixels]
  Y_OFFSET:        799 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1147
  Y_GRB_POS:       959
  BINNING_INDEX:   1
  IM_URL:          sw01321323000msuni0142.fits
  SUN_POSTN:        74.11d {+04h 56m 27s}  +22.63d {+22d 37' 54"}
  SUN_DIST:        100.34 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.73d {+12h 50m 56s}   -7.34d {-07d 20' 31"}
  MOON_DIST:        27.68 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.09, 36.80 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      176.28,-23.27 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Image.  
  COMMENTS:        The GRB Position came from the XRT Position Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 05 Jun 25 18:58:46 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     1321323,   Seg_Num: 0
  POINT_RA:        166.985d {+11h 07m 56s} (J2000)
  POINT_DEC:       -19.801d {-19d 48' 02"} (J2000)
  ROLL:            290.599d
  IMG_START_DATE:  20831 TJD;   156 DOY;   25/06/05
  IMG_START_TIME:  68058.26 SOD {18:54:18.26} UT,   107.0 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     770842493
  X_OFFSET:        987 [pixels]
  Y_OFFSET:        799 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1147
  Y_GRB_POS:       959
  BINNING_INDEX:   1
  IM_URL:          sw01321323000msuni0142.fits
  SUN_POSTN:        74.11d {+04h 56m 27s}  +22.63d {+22d 37' 54"}
  SUN_DIST:        100.34 [deg]   Sun_angle= -6.2 [hr] (East of Sun)
  MOON_POSTN:      192.73d {+12h 50m 56s}   -7.34d {-07d 20' 34"}
  MOON_DIST:        27.68 [deg]
  MOON_ILLUM:      74 [%]
  GAL_COORDS:      272.09, 36.80 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      176.28,-23.27 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Image.  
  COMMENTS:        The GRB Position came from the XRT Position Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN Circular #40633
  R. Gupta (NASA GSFC), J. J. DeLaunay (PSU), S. Dichiara (PSU), C. Gronwall (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), H. A. Krimm (NSF), M. J. Moss (GSFC), K. L. Page (U Leicester), T. M. Parsotan (GSFC), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
  At 18:52:31.27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250605A (trigger=1321323). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 166.977, -19.795 which is

     RA(J2000) = 11h 07m 54s
     Dec(J2000) = -19d 47' 42"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a complex light curve with one strong pulse between T0-2 sec to T0+10 sec and a second dimmer but broad pulse between T0+40 sec to T0+100 sec. The peak count rate was 4,000 counts/sec (15-350 keV), at ~2 sec after the trigger.
  The XRT began observing the field at 18:54:09.2 UT, 98.0 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 166.9571, -19.7882 which is equivalent to:

     RA(J2000)  = 11h 07m 49.70s
     Dec(J2000) = -19d 47' 17.5"
  

  with an uncertainty of 5.5 arcseconds (radius, 90% containment). This location is 71 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 144 seconds with the White filter starting 106 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 0.039.
  Burst Advocate for this burst is R. Gupta (rahulbhu.c157 AT gmail.com). 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 #40634
  B. P. Gompertz (U. Birmingham), Dimple (U. Birmingham), A. Martin-Carrillo (UCD), G. Corcoran (UCD) and D. B. Malesani (DAWN/NBI and Radboud), report on behalf of a larger collaboration:
  We initiated follow-up observations of GRB 250605A (Gupta et al., GCN 40633) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 20:48:52.89 UT, ~2 hours after the Swift/BAT trigger, and consisted of 10x60 s exposures in the SDSS i filter. Observations were taken close to twilight, at high airmass, and the target was 28 deg from the moon at 77% illumination.
  Within the Swift/XRT error box, we detect a possible optical counterpart, not present in archival imaging, with an AB magnitude of i ~ 21.1 at RA = 11:07:49.7, Dec = -19:47:15.4. However, this detection is only significant at the 2-sigma level and further, deeper observations are required to confirm its reality. Formally, we measure a 3-sigma upper limit of i > 20.6 within the XRT localisation region.
  We also note the presence of a faint source visible in the Legacy Survey archival imaging with an AB magnitude of i = 23.54. The source position is consistent with the possible optical counterpart, and may be the host galaxy of GRB 250605A.
  Magnitudes are calibrated against nearby Pan-STARRS stars and not corrected for galactic extinction.
• GCN Circular #40642
  P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
  Using 3740 s of XRT Photon Counting mode data and 7 UVOT images for GRB 250605A, 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 = 166.95715, -19.78841 which is equivalent to:

  RA (J2000): 11h 07m 49.72s
  Dec (J2000): -19d 47' 18.3"
  

  with an uncertainty of 2.0 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 Circular #40644
  A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
  We have analysed 7.0 ks of XRT data for GRB 250605A, from 90 s to 50.2 ks after the trigger. The data comprise 149 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
  The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=4.36 (+0.19, -0.15). At T+164 s the decay flattens to an alpha of 3.19 (+0.29, -0.32) before breaking again at T+326 s to a final decay with index alpha=0.79 (+/-0.07).
  A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.12 (+0.06, -0.05). The best-fitting absorption column is 2.59 (+0.20, -0.19) x 10^21 cm^-2, in excess of the Galactic value of 4.3 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.10 (+0.13, -0.12) and a best-fitting absorption column of 2.9 (+/-0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (5.5 x 10^-11) erg cm^-2 count^-1.
  A summary of the PC-mode spectrum is thus:

  Total column:	     2.9 (+/-0.5) x 10^21 cm^-2
  Galactic foreground: 4.3 x 10^20 cm^-2
  Excess significance: 8.7 sigma
  Photon index:	     2.10 (+0.13, -0.12)
  

  If the light curve continues to decay with a power-law decay index of 0.79, the count rate at T+24 hours will be 0.085 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x 10^-12 (4.7 x 10^-12) erg cm^-2 s^-1.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01321323.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #40645
  L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Z. H. Yao, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team.
  SVOM/VT conducted ToO follow-up observations of the GRB 250605A (Gupta et al., GCN 40633, Melandri et al., GCN 40644). The observation started on 2025-06-06T05:02:39 UT in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. 
  No uncatalogued sources are detected in single or stacked images within the Swift/XRT error box (Evans et al., GCN 40642) and the possible optical candidate reported by Gompertz et al. (GCN 40634). The 3 sigma limit magnitudes are derived as below:

  Mid time    | Band | Exposure Time | 3 sigma limit magnitude
  11.28 hour    VT_B      59*70 sec         >23.6 mag    
  11.28 hour    VT_R      59*70 sec         >23.6 mag
  

  The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
• GCN Circular #40657
  M. H. Siegel (PSU) and R. Gupta (NASA GSFC) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 250605A 107 s after the BAT trigger (Gupta et al., GCN Circ. 40633). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 40642) is detected in the initial UVOT exposures. 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
  
  white_FC           107          251          141            >20.9
  white             5225        11166          933            >21.41
  v                16403        17310          885            >20.07
  b                 5020         5220          196            >19.83
  u                 4815        22332          204            >19.32
  uvw1             21418        22318          885            >20.16
  uvm2             17315        18088          761            >20.44
  uvw2             11173        11858          674            >20.47
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.039 in the direction of the burst (Schlegel et al. 1998).
• GCN Circular #40667
  R. Gupta (GSFC), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (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 250605A (trigger #1321323) (Gupta, et al., GCN Circ. 40633). The BAT ground-calculated position is RA, Dec = 166.963, -19.786 deg which is

     RA(J2000)  =  11h 07m 51.1s 
     Dec(J2000) = -19d 47' 10.5" 
  

  with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 35%.
  The BAT light curve shows a complex light curve with multiple emission episodes: a period of very dim extended emission between ~T0-100 sec to T0-10 leading up to one strong pulse between T0-10 sec to T0+10 sec and followed by a dim broad pulse between T0+40 sec to ~T0+125 sec. T90 (15-350 keV) is 176.05 +- 5.15 sec (estimated error including systematics).
  The time-averaged spectrum from T-100.30 to T+126.69 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.50 +- 0.22, and Epeak of 76.7 +- 27.6 keV (chi squared 71.54 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.0 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T-0.00 sec in the 15-150 keV band is 6.1 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.83 +- 0.05 (chi squared 79.05 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
  The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1321323