GRB 211025A

J.D. Gropp (PSU), D. M. Palmer (LANL), B. Sbarufatti (PSU) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 05:10:20 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 211025A (trigger=1081113).  Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 162.377, +31.557 which is
   RA(J2000) = 10h 49m 30s
   Dec(J2000) = +31d 33' 26"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty).  As is usual for an image trigger, the
immediately available BAT lightcurve is unclear, but there does
appear to be a peak between T+30 and T+64, with a peak count rate
of ~300 counts/s (15-350 kev) at ~38 s after the nominal trigger time.

The XRT began observing the field at 05:12:23.2 UT, 123.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 162.38427, 31.51343 which
is equivalent to:
   RA(J2000)  = 10h 49m 32.22s
   Dec(J2000) = +31d 30' 48.3"
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This
location is 158 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.  We cannot determine whether the source
is fading at the present time. No spectrum from the promptly downlinked
event data is yet available to determine the column density.

The initial flux in the 2.5 s image was 5.36e-09 erg cm^-2 s^-1 (0.2-10
keV).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 131 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image processing
FAILED because of no aspect solution. Results from the list of sources
generated on-board are not available at this time. No correction has been made
for the expected extinction corresponding to E(B-V) of 0.027.

Burst Advocate for this burst is J.D. Gropp (jdg44 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/)

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2418 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 211025A, 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 = 162.38304, +31.51233 which is equivalent
to:

RA (J2000): 10h 49m 31.93s
Dec (J2000): +31d 30' 44.4"

with an uncertainty of 2.1 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.

S. R. Oates (U.Birmingham) and J. D. Gropp (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 211025A
131 s after the BAT trigger (Gropp et al., GCN Circ. 30986
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 ).
A source consistent with the XRT position (Evans et al. GCN Circ. 30987
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 )
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
 RA  (J2000) =  10:49:31.93 = 162.38304 (deg.)
 Dec (J2000) = +31:30:44.3  =  31.51231 (deg.)
with an estimated uncertainty of 0.9 arc sec. (radius, 90% confidence).

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_FC           131          281          147       > 20.2
white              131          943          220       19.90 +/- 0.25
white             5965         6164          197       > 20.4
v                 4940         6509          329       > 19.0
b                 5760         5960          197       > 19.8 
uvw1               669          688           19       > 17.5
uvw1              5350         5550          197       > 19.5
uvm2              5145         5345          197       > 19.4
uvw2              4735         6370          393       > 20.0  

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.027 in the direction of the burst
(Schlegel et al. 1998).

J.P. Osborne (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC &
INAF-OAR), V. D'Elia (SSDC & INAF-OAR), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), K.L. Page (U. Leicester),
A.P. Beardmore (U. Leicester) and J.D. Gropp report on behalf of the
Swift-XRT team:

We have analysed 4.0 ks of XRT data for GRB 211025A (Gropp et al. GCN
Circ. 30986
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 ), from 115 s to 28.0 ks after the  BAT trigger. The data
comprise 203 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 enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 30987
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 ).

The late-time light curve (from T0+4.7 ks) can be modelled with a
power-law decay with a decay index of alpha=1.3 (+0.6, -0.4).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.91 (+/-0.06). The
best-fitting absorption column is  7.1 (+/-1.4) x 10^20 cm^-2, in
excess of the Galactic value of 2.4 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.33 (+0.22, -0.12)
and a best-fitting absorption column consistent with the Galactic
value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 2.8 x 10^-11 (3.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.4 (+3.5, -0.0) x 10^20 cm^-2
Galactic foreground: 2.4 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.33 (+0.22, -0.12)

If the light curve continues to decay with a power-law decay index of
1.3, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x
10^-14 (6.4 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01081113.

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

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

Using the data set from T-239 to T+844 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 211025A (trigger #1081113)
(Gropp, et al., GCN Circ. 30986
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 ).  The BAT ground-calculated position is
RA, Dec = 162.407, 31.506 deg which is 
  RA(J2000)  =  10h 49m 37.8s 
  Dec(J2000) = +31d 30' 20.8" 
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a single broad pulse beginning at T+0,
peaking around T+50 sec and declining to background by T+150 sec. 
T90 (15-350 keV) is 103.5 +- 27.6 sec (estimated error including systematics).
 
The time-averaged spectrum from T+12.32 to T+128.5 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.96 +- 0.28.  The fluence in the 15-150 keV band is 7.7 +- 1.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+51.66 sec in the 15-150 keV band
is 0.5 +- 0.1 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/1081113/BA/

V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, 
D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, T.Pogrosheva, E.Minkina,
A.Chasovnikov, V.Topolev, V.Grinshpun, 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
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

A. Gabovich, V.Yurkov 
(Blagoveschensk Educational State University)


MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 211025A ( J.D. Gropp et al., GCN 30986
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 ) errorbox  63953 sec after notice time and 64035 sec after trigger time at 2021-10-25 22:57:35 UT, with upper limit up to  17.5 mag. The observations began at zenith distance = 76 deg. The sun  altitude  is -49.5 deg. 

The galactic latitude b = 64 deg., longitude l = 197 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1764428

We obtain a following upper limits.  

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

   64126 |   MASTER-Kislovodsk |   C |   180 | 17.5 |        
Filter C is a clear (unfiltred) band. 


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

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 211025A (Gropp, et al., GCN 30986
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 ) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on October 25, from 11:27 to 11:49 UT (corresponding to 6.28 to 6.82 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 4x160s exposures in R and I bands. We detect a source consistent with the Swift UVOT detection coordinates (Oates, et al., GCN 30991
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 ) in R-band, but not in I-band. The following magnitudes and upper limits are calculated using the USNO-B.1 catalog as reference:

R=20.51+/-0.27
I>18.04

These magnitudes are not corrected for galactic extinction.

R.S. is funded by NSF AST grant #1831682