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GRB 250706A

GCN Circular 41083

Subject

GRB 250706A: Swift-BAT refined analysis

Date

2025-07-13T21:01:31Z (a year ago)

From

Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>

Via

Web form

D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Gupta (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), M. J. Moss (GSFC), T. Parsotan (GSFC),
D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250706A (trigger #1330958)
(Moss, et al., GCN Circ. 40988Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 284.011, 32.327 deg which is
   RA(J2000)  =  18h 56m 02.7s
   Dec(J2000) = +32d 19' 36.8"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 26%.

The mask-weighted light curve shows a single-peak structure that starts at
~T-1 s, peaks at ~T+2 s, and ends at ~T+40 s.
T90 (15-350 keV) is 31.9 +- 7.2 sec (estimated error including systematics).

The time-averaged spectrum from T0 to T+40 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.34 +- 0.17.  The fluence in the 15-150 keV band is 1.6 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.93 sec in the 15-150 keV band
is 1.3 +- 0.3 ph/cm2/sec.  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/1330958

GCN Circular 41010

Subject

GRB 250706A: Swift-XRT refined Analysis

Date

2025-07-07T16:05:07Z (a year ago)

From

Phil Evans at U of Leicester <pae9@star.le.ac.uk>

Via

R. Brivio (INAF-OAB), D.N. Burrows (PSU), M.A. Williams (PSU), S.
Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB) and P.A. Evans report on
behalf of the Swift-XRT team:

We have analysed 5.7 ks of XRT data for GRB 250706A, from 131 s to 55.6
ks after the   trigger. The data comprise 285 s in Windowed Timing (WT)
mode (the first 10 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. The refined XRT position is RA,
Dec = 284.0176, +32.3216 which is equivalent to:

RA (J2000): 18 56 04.22
Dec(J2000): +32 19 17.6

with an uncertainty of 3.5 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.76 (+0.12, -0.13), followed by a break at T+427 s to
an alpha of 2.27 (+0.18, -0.14).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.87 (+/-0.09). The
best-fitting absorption column is  2.6 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 1.2 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 3.8 x 10^-11 (5.2 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     2.6 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: 6.4 sigma
Photon index:	     1.87 (+/-0.09)

If the light curve continues to decay with a power-law decay index of
2.27, the count rate at T+24 hours will be 3.3 x 10^-5 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x
10^-15 (1.7 x 10^-15) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01330958.

This circular is an official product of the Swift-XRT team.

GCN Circular 41008

Subject

GRB 250706A: Swift/UVOT Upper Limits

Date

2025-07-07T12:51:03Z (a year ago)

From

Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

Via

Web form

M. H. Siegel (PSU) and M. J. Moss (GSFC) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250706A
147 s after the BAT trigger (Moss et al., GCN Circ. 40988Loading...
 
 ).
No optical afterglow consistent with the XRT position 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

u_FC               147          397          246         >19.5
v                  453          473           19         >16.8
b                  403          423           19         >18.0
u                  147          397          246         >19.5
w1                 502          509            6         >18.2
m2                 477          497           19         >17.9
w2                 429          449           19         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.093 in the direction of the burst
(Schlegel et al. 1998).

GCN Circular 41006

Subject

GRB 250706A: REM optical/NIR observations

Date

2025-07-07T10:22:00Z (a year ago)

From

Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>

Via

Web form

R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:

We observed the field of GRB 250706A detected by Swift/BAT (Moss et al., GCN 40988Loading...
 
 ) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, and H bands, started on 2025 July 07 at 06:21:07 UT (i.e. 14.5 hr after the burst), and lasted for about 1 hour.

From preliminary inspection, we do not detect any optical/NIR counterpart within the Swift/XRT error region down to the following 3sigma limits:

r > 19.8 (AB; calibrated against the Pan-STARRS catalogue),
at a mid-time of 15.1 hr after the trigger;

H > 15.3 (Vega; calibrated against the 2MASS catalogue),
at a mid-time of 14.6 hr after the trigger.

GCN Circular 41002

Subject

Swift GRB 250706A: Global MASTER-Net observations report

Date

2025-07-07T08:24:35Z (a year ago)

From

Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

Via

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-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 GRB 250706A ( M. J. Moss et al., GCN 40988Loading...
 
 ) errorbox  46980 sec after notice time and 47035 sec after trigger time at 2025-07-07 04:52:26 UT, with upper limit up to  18.0 mag. The observations began at zenith distance = 64 deg. The sun  altitude  is -81.1 deg. 

The galactic latitude b = 13 deg., longitude l = 63 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2927564

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   47126 |         MASTER-OAFA |   C |   180 | 17.7 |        
   47319 |         MASTER-OAFA |   C |   180 | 17.8 |        
   49913 |         MASTER-OAFA |   C |   180 | 18.0 |        
   50108 |         MASTER-OAFA |   C |   180 | 18.0 |        
   51188 |         MASTER-OAFA |   C |   180 | 17.8 |        
   51392 |         MASTER-OAFA |   C |   180 | 17.9 |        
   52485 |         MASTER-OAFA |   C |   180 | 17.8 |        
   52679 |         MASTER-OAFA |   C |   180 | 17.6 |        
   53664 |         MASTER-OAFA |   C |   180 | 17.6 |        
   53965 |         MASTER-OAFA |   C |   180 | 17.7 |        
   54883 |         MASTER-OAFA |   C |   180 | 17.7 |        
   55239 |         MASTER-OAFA |   C |   180 | 17.7 |        
   56730 |         MASTER-OAFA |   C |   180 | 17.4 |        
   56924 |         MASTER-OAFA |   C |   180 | 17.2 |        
   57911 |         MASTER-OAFA |   C |   180 | 17.4 |        
   58211 |         MASTER-OAFA |   C |   180 | 17.1 |        
   59205 |         MASTER-OAFA |   C |   180 | 16.4 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

GCN Circular 41001

Subject

GRB 250706A: JinShan optical upper limits

Date

2025-07-07T07:17:13Z (a year ago)

From

Zipei Zhu at NAOC <zpzhu@nao.cas.cn>

Via

Web form

Z.P. Zhu, S.Q. Jiang, X. Liu, J. An, L.B. He, D. Xu (NAOC), S.Y. Fu(HUST), J.Z. Liu (XAO) report on behalf of a large collaboration:

We observed the field of GRB250706A detected by Swift/BAT (Moss et al., GCN 40988Loading...
 
 ), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations began at 15:55:19 UT on 2025-07-06, i.e., 6.8 minutes after the BAT trigger, and a series of frames were obtained in the Sloan r- and z-band.

No new optical source is detected within the XRT error circle (Moss et al., GCN 40988Loading...
 
 ), consistent with the reported results (Mohan et al., GCN 40990Loading...
 
 ; Wu et al., GCN 40998Loading...
 
 ), down to 5-sigma upper limits of r ~ 21.4 and z ~21.1, calibrated with nearby Pan-STARRS stars and not corrected for Galactic extinction.

We acknowledge the excellent support from T.Q. Chen for enabling these observations.

GCN Circular 41000

Subject

GRB 250706A: SAO RAS optical observations

Date

2025-07-07T03:57:27Z (a year ago)

From

Alexander Moskvitin at SAO RAS <mosk@sao.ru>

Via

Web form

A. Moskvitin and O. Spiridonova (SAO RAS),  
report on behalf of a GRB follow-up collaboration.

We observed the field of the GRB 250706A (Moss et al., GCN 40988Loading...
 
 )
with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer. 
We obtained 20 x 300 sec. images in Rc band on July 6, 
20:04:37--22:41:35 UT (t_mid - T0 = 5.5764 hours) under a good weather 
conditions and the seeing of 1".6.

In the XRT error circle (Moss et al., GCN 40988Loading...
 
 ) we detected a bright 
stellar-like source with the coordinates R.A. = 18:56:04.3, 
Dec. = +32:19:13.5 (J2000.0) also presented in the archival images.

After the PSF subtraction of this bright star we did not detect any 
significant sources down to the limiting magnitude of R_lim = 23.0.
(based on the nearby USNO-B1.0 stars and not corrected 
for the Galactic extinction)

Additionaly we divided whole set into two 10 x 300 sec. subsets
(1st: t_mid - T0 = 4.9217 hours, 2nd: t_mid - T0 = 6.2393 hours)
and found no significant residuals between two stacked images
and no variability of the mentioned bright star within 0.01 mag.
between two epochs.

This results are in agreement with OT non-detection by Moss et al. 
(GCN 40988Loading...
 
 ); Mohan et al. (GCN 40990Loading...
 
 ) and Wu et al. (GCN 40998Loading...
 
 ).

GCN Circular 40998

Subject

GRB 250706A: SVOM/C-GFT upper limit in eary phase

Date

2025-07-07T01:42:18Z (a year ago)

From

SVOM_group <svomgroup@bao.ac.cn>

Via

Web form

Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei, Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC) report on behalf of the SVOM/C-GFT team:

We observed the field of GRB250706A detected by Swift/BAT (GCN 40988

) with LATIOS on SVOM/C-GFT. Observations started at 2025-07-06T15:49:56 UTC, ~85 seconds after the trigger.

A series of g, r, and i band images were obtained. No credible candidate was detected within the error box provided by XRT (GCN 40988

) in our images after preliminary processing, the three sigma upper limits are:

Date-Obs (mid-time)	Mid_t - T0 (s)	Exposure Time (s)	Band	Upper Limit (AB)
2025-07-06T15:50:35	124	5×10	i	19.31
2025-07-06T16:00:55	744	6×30	g	20.66
2025-07-06T16:04:30	949	6×30	r	20.37

The photometry was calibrated with nearby Pan-STARRS1 stars.

We thank the observation assistants Bowen Li & Yinhuai Hao at Jilin observatory for their excellent support.

The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching.

GCN Circular 40990

Subject

GRB 250706A: GROWTH-India Telescope optical upper limit

Date

2025-07-06T18:21:04Z (a year ago)

From

Varun Bhalerao at IIT Bombay <varunb@iitb.ac.in>

Via

Web form

T. Mohan, A.P. Saikia, A. Salgundi, V. Swain, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and R. Norbu (IAO) report on behalf of the GIT team:

We observed the field of Swift GRB 250706A (Moss et al., GCN 40988

), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-07-06 16:04:55 UT, i.e., 16.4 min after the GRB trigger. We obtained multiple exposures each in r' and g' filters. After performing image subtraction using PanSTARRS reference images, we do not detect any afterglow candidates at the XRT localization. The photometric upper limits are as follows:

MJD (mid)	Filter	tmid-t0 (min)	Exposure Time (sec)	Upper limit (AB)
60862.670081	r'	18.9	300	20.0
60862.682546	g'	34.4	300	20.3
60862.699537	r'	61.3	300	20.5

The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.

The result is consistent with Swift UVOT upper limit (Moss et al., GCN 40988

The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.

GCN Circular 40988

Subject

GRB 250706A: Swift detection of a burst

Date

2025-07-06T16:05:46Z (a year ago)

From

Mike Moss at NASA GSFC <mikejmoss3@gmail.com>

Via

M. J. Moss (GSFC), E. Ambrosi (INAF-IASFPA), R. Gupta (NASA GSFC),
J. A. Kennea (PSU), A. Melandri (INAF-OAR), K. L. Page (U Leicester)
and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 15:48:30.96 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 250706A (trigger=1330958).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 284.007, +32.287 which is 
   RA(J2000) = 18h 56m 1.6s
   Dec(J2000) = +32d 17' 13"
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 35 sec.  The peak count rate
was ~750 counts/sec (15-350 keV), at ~7 sec after the trigger.

The XRT began observing the field at 15:50:53.1 UT, 142.2 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 284.01755, 32.32120 which
is equivalent to:
   RA(J2000)  = 18h 56m 04.21s
   Dec(J2000) = +32d 19' 16.3"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 127 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.20
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 5.25e-10 erg cm^-2 s^-1 (0.2-10
keV).

UVOT took a finding chart exposure of 250 seconds with the U filter starting
147 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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.093.

Burst Advocate for this burst is M. J. Moss (mikejmoss3 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/)