GRB 191227A

Y. F. Du, Y. G. Zheng, C. Cai, Q. Luo, S. Xiao, Q. B. Yi, 
Y. Huang, C. K. Li, G. Li, X. B. Li, J. Y. Liao, S. L. Xiong,
C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, 
Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, 
Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team:

At 2019-12-27T01:39:34.400 (T0), Insight-HXMT/HE detected 
GRB 191227A (trigger ID: HEB191227069) in a routine search of the data, 
which was also triggered by Fermi/GBM, Swift/BAT and Konus-Wind (GCN #26593
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 ).

The Insight-HXMT/HE light curve mainly consists of multiple 
pulses with a duration (T90) of 20.65 s measured from T0+0.40 s. 
The 1-ms peak rate, measured from T0+6.72 s, is 18,542 cnts/sec. 
The total counts from this burst is 118,722 counts. 
URL_LC: http://www.hxmt.org/images/GRB/HEB191227069_lc.jpg 

All measurements above are made with the CsI detectors operating in the 
regular mode with the energy range of about 80-800 keV (deposited energy). 
Only gamma-rays with energy greater than about 200 keV can penetrate 
the spacecraft and leave signals in the CsI detectors installed inside 
of the telescope. 

Insight-HXMT is the first Chinese space X-ray telescope, which was 
funded jointly by the China National Space Administration (CNSA) and 
the Chinese Academy of Sciences (CAS). 
More information about it could be found at: 
http://www.hxmt.org.

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

The long-duration GRB 191227A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 26593
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 ;
Swift-BAT detection: Melandri et al., GCN Circ. 26595
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 ;
Stamatikos et al., GCN Circ. 26608
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 ;
Fermi-LAT detection: Fana Dirirsa et al., GCN Circ. 26598
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 )
triggered Konus-Wind at T0=5970.414 s UT (01:39:30.414).

The burst light curve shows a multi-peaked structure
which starts at ~T0-27 s and has a total duration of ~52 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB191227_T05970/

As observed by Konus-Wind, the burst
had a fluence of 1.02(-0.08,+0.09)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+8.096 s,
of 1.86(-0.35,+0.36)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+29.440 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.70(-0.12,+0.13),
the high energy photon index beta = -2.28(-0.16,+0.12),
the peak energy Ep = 275(-26,+30) keV
(chi2 = 102/97 dof).

The spectrum near the maximum count rate
(measured from T0+6.400 to T0+13.056 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.65(-0.18,+0.22),
the high energy photon index beta = -2.25(-0.22,+0.15),
the peak energy Ep = 266(-40,+46) keV
(chi2 = 82/97 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.

M. Stamatikos (OSU), 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), A. Melandri (INAF-OAB),
D. M. Palmer (LANL), T. Sakamoto (AGU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-61 to T+242 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 191227A (trigger #946344)
(Melandri et al., GCN Circ. 26595
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 ).  The BAT ground-calculated position is
RA, Dec = 319.172, -16.717 deg which is
   RA(J2000)  =  21h 16m 41.4s
   Dec(J2000) = -16d 43' 02.5"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 13%.

The mask-weighted light curve shows many overlapping pulses
that starts from ~T-30 s and ends at ~T+105 s. Several obvious peaks
can be seen at ~T0, ~T+3 s, ~T+5 s, and ~T+11 s, respectively.
T90 (15-350 keV) is 58.5 +- 14.4 sec (estimated error including
systematics).

The time-averaged spectrum from T-30.55 to T+105.93 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.30 +- 0.05.  The fluence in the 15-150 keV band is 2.5 +- 0.1 x 10^-5
erg/cm2.
The 1-sec peak photon flux measured from T+5.28 sec in the 15-150 keV band
is 21.8 +- 1.3 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/946344/BA/

S.Poolakkil(UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 01:39:24.72 UT on 27 December 2019, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 191227A(trigger 599103569 / 191227069),
which was also detected by the Swift/BAT (Melandri et al. 2019, GCN 26595
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 )
and Fermi LAT (Fana Dirirsa et al. 2019, GCN 26598
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 ).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 96
degrees.

The GBM light curve consists of multiple overlapping pulses
with a duration (T90) of about 25 s (50-300 keV).
The time-averaged spectrum from T0+8.19 s to T0+37.88 s is
best fit by a Band function with Epeak = 362 +/- 10 keV,
alpha = -0.93 +/- 0.01 and beta = -2.36 +/- 0.07.

The event fluence (10-1000 keV) in this time interval is
(7.30 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux
measured starting from T0+15.8 s in the 10-1000 keV band
is 38.0 +/- 0.5 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/"

F. Fana Dirirsa (Univ. of Johannesburg), F. Longo (University & INFN,
Trieste), M. Axelsson (KTH & Stockholm Univ.),
D. Kocevski (NASA/MSFC) and J. Racusin (NASA/GSFC) report on behalf of
the Fermi-LAT team:

On December 27, 2019, Fermi-LAT marginally detected high-energy emission from
GRB 191227A, which was also detected by Fermi-GBM (GCN 26593
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 ) and
Swift/BAT (Melandri et al, GCN 26595
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 ).
The best LAT on-ground location is found to be

RA, Dec 318.0, -16.9 (degrees, J2000)

with an error radius of 0.33 deg (90% containment, statistical error only).

This was 96 deg from the LAT boresight at the time of the GBM trigger
and entered in the LAT field of view around
1 ks later. The localisation is consistent with the Swift/BAT position.

The detection significance lies just below the 5-sigma threshold, but
more than 3 photons with >90% probability to
be associated with the GRB are found in the time interval up to 10ks
after the GBM trigger. The photon flux above
100 MeV in this time interval is (9 +/- 4) e-7 ph/cm2/s.

The estimated photon index above 100 MeV is -2.0 +/- 0.3.

Further analysis is ongoing.

The Fermi-LAT point of contact for this burst is Feraol Fana Dirirsa
(fdirirsa@uj.ac.za)

The Fermi-LAT is a pair conversion telescope designed to cover the
energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration between NASA and
DOE in the U.S. and many scientific institutions
across France, Italy, Japan and Sweden.

R. Adachi, K. L. Murata, M. Oeda, K.Shiraishi, K. Iida, M. Niwano, F.
Ogawa, R. Hosokawa, S. Toma, N. Nakamura, Y. Yatsu, and N. Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of the optical counterpart (V. Lipunov et al.
#26596) of GRB 191227A (The Fermi GBM team #26593, A. Melandri et al.
#26595) with the optical three color (g���, Rc, and Ic) CCD cameras
attached to the MITSuME 50 cm telescope of Akeno Observatory,
Yamanashi, Japan.

The observation started on 19/12/27 08:08:42.73 UT. We did not detect
the optical counterpart in all three bands. We obtained the following
5-sigma limits for the magnitudes.

T0+[hour]    MID-UT T-EXP[sec]   5-sigma limits
-----------------------------------------------------------------------------------------------------
~6.75        08:57:46.67 3360         g���>17.4, Rc>16.9, Ic>16.2
-----------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used UCAC4 catalog for flux calibration.
The magnitudes are expressed in the AB system.

V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa,
A.Kuznetsov, D. Vlasenko, F. Balakin
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

R. Podesta, Carlos Lopez and F. Podesta
Observatorio Astronomico Felix Aguilar (OAFA)

D. Buckley, S. Potter, A. Kniazev, M. Kotze
South African Astronomical Observatory

K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk
Irkutsk State University

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory

V. Yurkov, A. Gabovich, Yu. Sergienko
Blagoveschensk Educational State University, Blagoveschensk

Hugo Levato
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

MASTER-OAFA robotic telescope (Global MASTER-Net: 
http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, 
vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan 
National University) was pointed to the  GRB191227.07 31 sec after notice 
time and 51 sec after trigger time at 2019-12-27 01:40:28 UT. On our first 
(10s exposure)  set we  found 1 optical transient within Swift error-box 
(ra=319.167 dec=-16.7033 r=0.05) brighter than  15.3.


  T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
---------|---------------------|-------|-----------------|-----------------|-------
       56   2019-12-27 01:40:28      10   (21h 16m 37.28s , -16d 43m 33.5s)     14.4

The 5-sigma upper limit has been about  15.3mag
The message may be cited.



The OT has irregular early time  behaviour since 51.1 till 501.5 seconds 
after the trigger.


The galactic latitude b = -40 deg., longitude l = 34 deg.
The observations made on zenith distance = 83 deg.The moon ( 1 % bright 
part) below the horizon (The altitude of the Moon is -14 deg. ).
The sun  altitude  is -20.6 deg.

A. Melandri (INAF-OAB), S. D. Barthelmy (GSFC),
M. G. Bernardini (INAF-OAB), N. J. Klingler (PSU),
S Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC) and M. J. Moss (GWU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 01:39:37 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 191227A (trigger=946344).  Swift did not slew immediately
due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 319.170, -16.704 which is 
   RA(J2000) = 21h 16m 41s
   Dec(J2000) = -16d 42' 15"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 30 sec.  The peak count rate
was ~12000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 15:10 UT on 2020 March 23. There will thus be no XRT or
UVOT data for this trigger before this time. 

Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.it). 
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/)

The Fermi GBM team reports the detection of a likely LONG GRB

At 01:39:24 UT on 27 Dec 2019, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 191227A (trigger 599103569.720864 / 191227069).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 319.7, Dec = -13.2 (J2000 degrees, equivalent to J2000 21h 18m, -13d 11'), with a statistical uncertainty of 1.0 degrees.

The angle from the Fermi LAT boresight is 93.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn191227069/quicklook/glg_skymap_all_bn191227069.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn191227069/quicklook/glg_healpix_all_bn191227069.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn191227069/quicklook/glg_lc_medres34_bn191227069.gif