GRB 200512A

K. K. Simpson (PSU), V. D'Elia (SSDC), C. Gronwall (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), B. Sbarufatti (PSU), M. H. Siegel (PSU) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 20:33:15 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200512A (trigger=971846).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 7.396, -2.199 which is 
   RA(J2000) = 00h 29m 35s
   Dec(J2000) = -02d 11' 54"
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 20 sec.  The peak count rate
was ~600 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 20:34:25.5 UT, 69.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 7.41520, -2.21052
which is equivalent to:
   RA(J2000)  = 00h 29m 39.65s
   Dec(J2000) = -02d 12' 37.9"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 80 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 2.94
x 10^20 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 7.60e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
235 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
0.03. 

Burst Advocate for this burst is K. K. Simpson (kira.simpson1984 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/)

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

Using 744 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 200512A, 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 = 7.41477, -2.21036 which is equivalent
to:

RA (J2000): 00h 29m 39.54s
Dec (J2000): -02d 12' 37.3"

with an uncertainty of 1.4 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.

A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU),
A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne
(U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), P.
D'Avanzo (INAF-OAB) and K.K. Simpson report on behalf of the Swift-XRT
team:

We have analysed 7.4 ks of XRT data for GRB 200512A (Simpson et al. GCN
Circ. 27726
Loading...
 
 ), from 63 s to 58.1 ks after the  BAT trigger. The data
comprise 153 s in Windowed Timing (WT) mode (the first 5 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 Goad et al.
(GCN Circ. 27728
Loading...
 
 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.42 (+0.20, -0.37), followed by a break at T+161 s to
an alpha of 1.93 (+/-0.10).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.49 (+/-0.13). The
best-fitting absorption column is  2.6 (+0.7, -0.6) x 10^21 cm^-2, in
excess of the Galactic value of 2.9 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.20 (+0.23, -0.22)
and a best-fitting absorption column of 2.4 (+1.4, -1.2) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 6.1 x 10^-11 (6.7 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.4 (+1.4, -1.2) x 10^21 cm^-2
Galactic foreground: 2.9 x 10^20 cm^-2
Excess significance: 3.0 sigma
Photon index:	     1.20 (+0.23, -0.22)

If the light curve continues to decay with a power-law decay index of
1.93, the count rate at T+24 hours will be 6.7 x 10^-5 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.1 x
10^-15 (4.5 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/00971846.

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

F. E. Marshall (NASA/GSFC) and K. K. Simpson (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200512A
78 s after the BAT trigger (Simpson et al., GCN Circ. 27726
Loading...
 
 ).
No optical afterglow consistent with the enhanced XRT position
(Goad et al., GCN Circ. 27728
Loading...
 
 ) 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            78          228          147         >19.9
u_FC               236          486          246         >19.8
v                  567          760           39         >17.1
b                  493          858           58         >19.0
u                  236          833          285         >19.7
w1                 617          809           39         >17.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).

P. Veres (UAH) reports on behalf of the Fermi-GBM Team:


Swift-BAT detected GRB 200512A at 20:33:15 UT (GCN 27726
Loading...
 
 ). 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 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
search is 8.192 s, with a log likelihood ratio of 23. It has consistent
location, and it is consistent with a "normal" spectrum (Band function with
Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB.


[1] Goldstein et al. 2019 arXiv:1903.12597
Loading...
 
 

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

We observed Swift GRB 200512A (Simpson et al., GCN 27726
Loading...
 
 ) with the LCO 1-m Sinistro instrument at the Siding Spring Observatory, Australia site, on May 13, from 19:03 to 19:25 UT (corresponding to 23.50 to 23.87 hours from the GRB trigger time) with the Bessel I and R filters.

We performed a series of 5x120s exposures in R and I. We do not detect any fading sources in the individual frames (or in stacked images).  Using the USNO-B.1 catalog as reference, we obtain the following 3-sigma upper limits:

R > 20.90

I > 20.29

These magnitudes are not corrected for galactic extinction.

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

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
K. K. Simpson (PSU), 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 200512A (trigger #971846)
(Simpson et al., GCN Circ. 27726
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 7.417, -2.217 deg which is
   RA(J2000)  =  00h 29m 40.2s
   Dec(J2000) = -02d 13' 01.1"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a single-pulse structure.
The main emission starts at ~T-3 s, peaks at ~T+3 s, and ends at
~T+40 s. In addition, there are some weak emission that lasts
until ~T+80 s. T90 (15-350 keV) is 74.0 +- 14.3 sec (estimated
error including systematics).

The time-averaged spectrum from T-2.86 to T+78.14 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.68 +- 0.18.  The fluence in the 15-150 keV band is 8.1 +- 1.0 x 10^-7
erg/cm2.
The 1-sec peak photon flux measured from T+3.14 sec in the 15-150 keV band
is 0.4 +- 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/971846/BA/