GRB 230802A

C. de Barra (UCD), J.Mangan (CNRS/IJCLab) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 06:50:22.23 UT on 2 August 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230802A (trigger 712651827 / 230802285),
which was also detected by Swift BAT (N. J. Klingler et al. 2023, GCN 34313
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 ).
The Fermi GBM on-ground location is consistent with the Swift BAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 107 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 38 s (50-300 keV)The time-averaged spectrum from -14.3s to 26.6 s is
best fit by a simple power law function with index -1.7 +/- 0.02.

The event fluence (10-1000 keV) in this time interval is
(1.3 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.4 s in the 10-1000 keV band
is 5.6 +/- 0.4 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC),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-240 to T+962 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 230802A (trigger #1182085)
(Klingler et al., GCN Circ. 34313
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 ).  The BAT ground-calculated position is
RA, Dec = 76.232, 19.552 deg which is
   RA(J2000)  =  05h 04m 55.6s
   Dec(J2000) = +19d 33' 06.3"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 99%.

The BAT  light curve shows a complex structure with a duration of ~ 200 sec.
T90 (15-350 keV) is 175.62 +- 18.26 sec (estimated error including
systematics).

The time-averaged spectrum from T-6.04 to T+230.70 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.60 +- 0.07.  The fluence in the 15-150 keV band is 5.0 +- 0.2 x 10^-06
erg/cm2.
The 1-sec peak photon flux measured from T+0.60 sec in the 15-150 keV band
is 2.3 +- 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/1182085/BA/

GRB 230802A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and N. J. Klingler (GSFC/UMBC/CRESSTII)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230802A
73 s after the BAT trigger (Klingler et al., GCN Circ. 34313
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 ).
No optical afterglow consistent with the XRT position
(Evans et al., GCN Circ. 34317
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 )
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            73          223          147         >20.0
u_FC               286          535          246         >19.5
white               73         1186          353         >20.5
v                  615         1581          117         >18.4
b                  541         1506           97         >19.2
u                  286         5048          492         >19.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.614 in the direction of the burst
(Schlegel et al. 1998).

V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, 
G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov,  D.Cheryasov, Ya.Kechin
(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),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez 
(INAOE, Guillermo Haro Astrophysics Observatory),

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

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


MASTER-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 230802A ( N. J. Klingler et al., GCN 34313
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 ) errorbox  65651 sec after notice time and 65669 sec after trigger time at 2023-08-03 01:04:55 UT, with upper limit up to  15.3 mag. Observations started at twilight.  The observations began at zenith distance = 65 deg. The sun  altitude  is -13.8 deg. 

The galactic latitude b = -12 deg., longitude l = 183 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2248891

We obtain a following upper limits.  

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

   65759 |      MASTER-Tavrida |   C |   180 | 15.3 |        
Filter C is a clear (unfiltred) band. 


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

E. Fernandez-Garcia, Y.-D. Hu, A. J. Castro-Tirado, I. Perez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar (UMA) and I. M. Carrasco-Garcia (SMA) and I. H. Park (SKKU), on behalf of a larger collaboration, report:

Following the detection of GRB 230802A by Swift (Klingler et al. GCNC 34313), the BOOTES-5/JGT 0.6m robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically observed the GRB location starting on Aug. 02, 11:41 UT (~ 4.9 h after trigger). No new optical source is detected on the co-added image (13 x 60 s, clear filter) within the enhanced Swift/XRT error region (Goad et al. GCNC 34317) down to 19.7 mag, which is consistent with the limit reported by UVOT (Klingler et al. GCNC 34313).

We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for their excellent support.

A.P. Beardmore (U. Leicester), B. Sbarufatti (INAF-OAB), A. D'Ai
(INAF-IASFPA), A. Melandri (INAF-OAR), J. D. Gropp (PSU), S. Dichiara
(PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester) and P.A. Evans
report on behalf of the Swift-XRT team:

We have analysed 7.9 ks of XRT data for GRB 230802A, from 52 s to 40.1
ks after the  BAT trigger. The data comprise 386 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 light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=0.4 (+/-0.4). At T+345 s  the decay
steepens to an alpha of 2.5 (+0.4, -0.3) before breaking again at
T+1364 s to a final decay with index alpha=1.26 (+0.16, -0.30).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.02 (+/-0.04). The
best-fitting absorption column is  6.5 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 3.4 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.66 (+0.22, -0.21)
and a best-fitting absorption column of 4.5 (+1.5, -1.1) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.9 x 10^-11 (6.5 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     4.5 (+1.5, -1.1) x 10^21 cm^-2
Galactic foreground: 3.4 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.66 (+0.22, -0.21)

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 1.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.2 x
10^-14 (9.7 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/01182085.

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

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

Using 1180 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 230802A, 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 = 76.23985, +19.56066 which is equivalent
to:

RA (J2000): 05h 04m 57.56s
Dec (J2000): +19d 33' 38.4"

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.

N. J. Klingler (GSFC/UMBC/CRESSTII), V. D'Elia (SSDC & INAF-OAR),
P. A. Evans (U Leicester), J. A. Kennea (PSU), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), A. Melandri (INAF-OAR),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 06:50:26 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 230802A (trigger=1182085).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 76.221, +19.570 which is 
   RA(J2000) = 05h 04m 53s
   Dec(J2000) = +19d 34' 10"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a wide pulse
structure with a duration of about 60 sec.  The peak count rate
was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 06:51:30.3 UT, 64.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 76.23952, 19.56147
which is equivalent to:
   RA(J2000)  = 05h 04m 57.48s
   Dec(J2000) = +19d 33' 41.3"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 69 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. 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 1.25e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 73 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
0.614. 

Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.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/)