GRB 191213A

S. B. Cenko (GSFC), A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC),
J.D. Gropp (PSU), N. J. Klingler (PSU), H. A. Krimm (NSF),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 04:06:23 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 191213A (trigger=944091).  Due to a Sun constraint,
Swift did not slew to this burst. 
The BAT on-board calculated location is 
RA, Dec 224.507, -9.726 which is 
   RA(J2000) = 14h 58m 02s
   Dec(J2000) = -09d 43' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for an image trigger, there is
no obvious variation in the immediately-available lightcurve. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 16:25 UT on 2019 December 23. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). 
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/)

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
S. B. Cenko (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 191213A (trigger #944091)
(Cenko et al., GCN Circ. 26398
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 ).  The BAT ground-calculated position is
RA, Dec = 224.530, -9.745 deg which is
   RA(J2000)  =  14h 58m 07.2s
   Dec(J2000) = -09d 44' 41.9"
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 56%.

The mask-weighted light curve shows some weak emission that starts at ~T-30
s
and remains detectable until the burst went out of the BAT FOV at T+139 s.
It is likely that the emission continues beyond T+139 s. The burst did not
come
back into the BAT FOV within the next ~ 2 hours.

The time-averaged spectrum from T-33.52 to T+104.01 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.49 +- 0.16.  The fluence in the 15-150 keV band is 2.1 +- 0.2 x 10^-6
erg/cm2.
The 1-sec peak photon flux measured from T+99.95 sec in the 15-150 keV band
is 0.5 +- 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/944091/BA/

I. Carrasco (UMA), Y.-D. Hu, E. Fernandez-Garcia, M. A. Castro Tirado 
and A. J. Castro-Tirado (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), S. 
Jeong and I. H. Park (SKKU) and M. D. Caballero-Garcia (ASU-CAS, CZ) on 
behalf of a larger collaboration, report:

The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico 
Nacional in San Pedro Martir (Mexico) observed GRB 191213A ( Cenko et 
al., GCNC 26398 ) starting at 13:16 UT (~9.17 hr after trigger) at high 
airmass. Within the refined Swift/BAT error position ( Lien et al., GCNC 
26418 ), no optical afterglow is found down to 18.6 mag in the clear 
filter on the co-added 15 images (60s each).

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

A. Ridnaia, S. Golenetskii, R.Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko,
and T. Cline on behalf of the Konus-Wind team, report:

The ultra-long GRB 191213A (Swift-BAT trigger #944091:
Cenko et al., GCN 26398
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 ; Lien et al., GCN 26418
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 )
was detected by Konus-Wind (KW) in the waiting mode.

The burst light curve shows the main multipeaked episode of emission
started at ~T0(BAT)-25 s and lasted until ~T0(BAT)+1815 s (the
duration is ~1790 s; T0(BAT)=14781.499 s UT (04:06:21.499)).
There is also a weaker broad pulse of emission seen before the main
pulse from ~T0(BAT)-834 s to ~T0(BAT)-772 s. It might be related to
GRB 191213A (it was detected by the same KW detector, and the KW
ecliptic latitude response for it is consistent with the common
origin with the main episode).

As observed by KW, the burst (main episode) had a fluence of
1.12(-0.06,+0.07)x10^-4 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(BAT)+676.012s, of 2.5(-0.41,+0.41)x10^-7 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The emission shows no signs of strong spectral variability.
Modeling the KW 3-channel time-integrated spectrum
(from ~T0(BAT)-24.660 s to ~T0(BAT)+1815.340 s)
by a power law with exponential cutoff model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.16 (-0.12,+0.14), and Ep = 409 (-71,+110) keV.

Thus, the prompt gamma-ray emission properties of this GRB:
fluence, peak flux, Ep, and duration are similar to those
observed in other ultra-long GRBs.

The KW light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB191213A/

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.