GRB 200917A

E. Sonbas (Adiyaman Univ.), E. Ambrosi (INAF-IASFPA),
S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), N. J. Klingler (PSU),
D. M. Palmer (LANL), B. Sbarufatti (PSU) and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 03:52:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200917A (trigger=996184).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 235.753, -4.695 which is 
   RA(J2000)  =  15h 43m 01s
   Dec(J2000) = -04d 41' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak
with a duration of about 15 sec.  The peak count rate
was ~1200 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 03:54:09.0 UT, 100.8 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 235.7247, -4.7011 which
is equivalent to:
   RA(J2000)  = 15h 42m 53.93s
   Dec(J2000) = -04d 42' 04.0"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 103 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.49 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 5.6
(+5.36/-4.35) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 104 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
0.19. 

Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.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/)

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

Using 1697 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 200917A, 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 = 235.72435, -4.70058 which is equivalent
to:

RA (J2000): 15h 42m 53.84s
Dec (J2000): -04d 42' 02.1"

with an uncertainty of 1.9 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.

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-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 200917A ( E. Sonbas et al., GCN 28435
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 ) errorbox  46136 sec after notice time and 46245 sec after trigger time at 2020-09-17 16:43:13 UT, with upper limit up to  15.9 mag. Observations started at twilight.  The observations began at zenith distance = 64 deg. The sun  altitude  is -10.4 deg. 

The galactic latitude b = 37 deg., longitude l =  2 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1443272

We obtain a following upper limits.  

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

   46335 |      MASTER-Tavrida |   C |   180 | 15.9 |        
Filter C is a clear (unfiltred) band. 


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

V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A.
Melandri (INAF-OAB) and E. Sonbas report on behalf of the Swift-XRT
team:

We have analysed 7.1 ks of XRT data for GRB 200917A (Sonbas et al. GCN
Circ. 28435
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 ), from 112 s to 34.8 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Goad et al. (GCN Circ. 28436
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 ).

The late-time light curve (from T0+5.1 ks) can be modelled with a
power-law decay with a decay index of alpha=1.31 (+0.17, -0.16).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.34 (+0.28, -0.26). The
best-fitting absorption column is  1.08 (+0.25, -0.22) x 10^22 cm^-2,
in excess of the Galactic value of 1.5 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 4.1 x 10^-11 (1.1 x 10^-10) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.08 (+0.25, -0.22) x 10^22 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 7.0 sigma
Photon index:	     2.34 (+0.28, -0.26)

If the light curve continues to decay with a power-law decay index of
1.31, the count rate at T+24 hours will be 5.2 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.1 x
10^-13 (5.5 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00996184.

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

J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM Team:



Swift-BAT detected GRB 200917A at 03:52:28 UT (Sonbas et al. 2020, GCN 28435
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 ).

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 also identified no counterparts.



The GBM targeted search [1], the most sensitive, coherent search for GRB-like

signals, was run from +/-30 s around BAT trigger time.

A transient source was identified whose most significant timescale according to

the automated search is 4.096 s, with a log likelihood ratio of 21. This timescale

corresponds to the first peak in the lightcurve, occurring -11 seconds before the

BAT trigger time. The full light curve consists of multiple peaks spanning from

approximately 11 seconds before to 10 seconds after the BAT trigger time.



The location is consistent with that from Swift-BAT.

The spectrum is consistent with a "normal" GRB template

(Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3).



[1] Goldstein et al. 2019 arXiv:1903.12597
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C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI),  H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
E. Sonbas (Adiyaman Univ.), M. Stamatikos (OSU),
T. N. Ukwatta (LANL)
(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 200917A (trigger #996184)
(Sonbas, et al., GCN Circ. 28435
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 ).  The BAT ground-calculated
position is RA, Dec = 235.742, -4.695 deg which is
   RA(J2000)  =  15h 42m 58.0s
   Dec(J2000) = -04d 41' 41.4"
with an uncertainty of 2.0 arcmin, (radius, sys+stat,
90% containment). The partial coding was 96%.

The mask-weighted light curve shows two peaks, a weak peak
at ~T-10 s and a stronger peak at ~T+5 s. T90 (15-350 keV) is
19.4 +- 2.9 sec (estimated error including systematics).

The time-averaged spectrum from T-15.76 to T+6.18 sec is best
fit by a simple power-law model.  The power law index of the
time-averaged spectrum is 2.24 +- 0.31.  The fluence in the
15-150 keV band is 3.0 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak
photon flux measured from T+5.04 sec in the 15-150 keV band
is 0.6 +- 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/996184/BA/

H. Kumar (IITB), K. Sharma(IITB), U. Stanzin (IAO), V. Bhalerao(IITB), G.
C. Anupama(IIA), S. Barway(IIA), report on behalf of the GROWTH-India
collaboration:

We observed GRB 200917A reported by Swift-BAT (E. Sonbas et al., GCN 28435
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 ,
M.R. Goad et al., GCN 28436
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 ) with 0.7m GROWTH-India Telescope (GIT). The
field was observed in the SDSS r��� filter starting at 2020-09-17T14:15:12.96 UT
i.e. ~10.37 hrs after the event detection by Swift-BAT. We obtained 6
exposures of 300 sec each, at an airmass of ~2.5. We did not find any
source in the stacked image within the uncertainty region of 1.9 arcsec
around the Swift-XRT position of RA(J2000): 15h 42m 53.84s, Dec(J2000):
-04d 42' 02.1" (GCN  28436
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 ). We obtained an upper limit of r > 20.23
mag (5-sigma),
calibrated against PanSTARRs PS1 data release (Flewelling et al., 2018).

The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree
field of view, set up by the Indian Institute of Astrophysics and the
Indian Institute of Technology Bombay with support from the Indo-US Science
and Technology Forum (IUSSTF) and the Science and Engineering Research
Board (SERB) of the Department of Science and Technology (DST), Government
of India (https://sites.google.com/view/growthindia/). It is located at the
Indian Astronomical Observatory (Hanle), operated by the Indian Institute
of Astrophysics (IIA).

GRB 200917A: Swift/UVOT Upper Limits

K. K. Simpson (PSU) and E. Sonbas (Adiyaman Univ.)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200917A
104 s after the BAT trigger (Sonbas et al., GCN Circ. 28435
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 ).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 28436
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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           104          254          147         >19.9
u_FC               262          512          246         >20.1
white              104         1708          412         >20.5
v                  592         1758          136         >18.9
b                  518         1684          117         >19.5
u                  262         1832          382         >20.2
w1                 641         1807          136         >18.7
m2                1762         1782           19         >18.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.19 in the direction of the burst
(Schlegel et al. 1998).