GRB 200109A

S. Xiao, Y. F. Du, Y. G. Zheng, C. Cai, Q. Luo, 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 2020-01-09T01:45:51.89 (T0), Insight-HXMT/HE detected 
GRB 200109A (trigger ID: HEB200109073) in a routine search of the data, 
which also triggered Fermi/GBM (GCN #26689
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 ), and Swift (GCN #26678
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 ).

The Insight-HXMT/HE light curve mainly consists of multiple 
pulses with a duration (T90) of 36.405 s measured from T0-0.650 s. 
The 1-ms peak rate, measured from T0+ 9.281 s, is 595 cnts/sec. 
The total counts from this burst is 6014 counts. 
URL_LC: http://www.hxmt.org/images/GRB/HEB200109073_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.

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
A. Melandri (INAF-OAB), 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 200109A (trigger #948361)
(Melandri et al., GCN Circ. 26678
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 ).  The BAT ground-calculated position is
RA, Dec = 307.116, 52.988 deg which is
   RA(J2000)  =  20h 28m 27.7s
   Dec(J2000) = +52d 59' 17.7"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a weak structure with several
overlapping
pulses that start at ~T-30 s to ~T+20 s, followed by a weaker tail
emission that lasts till ~T+100 s. T90 (15-350 keV) is 112.0 +- 32.0 sec
(estimated error including systematics).

The time-averaged spectrum from T-31.45 to T+112.55 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.31 +- 0.14.  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+8.05 sec in the 15-150 keV band
is 0.7 +- 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/948361/BA/

GRB 200109A: Swift/UVOT Upper Limits

K. K. Simpson (PSU) and A. Melandri (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200109A
110 s after the BAT trigger (Melandri et al., GCN Circ. 26678
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 ).
No optical afterglow consistent with the XRT position
(Melandri et al. GCN Circ. 26678
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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           110          259          147         >20.5
u_FC               268          518          246         >19.0
white              110         1023          295         >20.9
u                  268          518          246         >19.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.29 in the direction of the burst
(Schlegel et al. 1998).

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

"At 01:45:51.89 UT on 9 January 2020, the Fermi Gamma-Ray Burst Monitor
(GBM) triggered and located GRB 200109A (trigger 600227156 / 200109074),
which also triggered the Swift/BAT approximately 25 s later
(Melandri et al. 2019, GCN 26678
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 ). The Fermi GBM Final Real-time
Localization (GCN 26677
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 ) is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 57
degrees.

The GBM light curve shows a complex structure with a duration (T90) of
about 41 s (50-300 keV). The time-averaged spectrum from T0-0.8 s to
T0+41.2 s is best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.98 +/- 0.08 and the
cutoff energy, parameterized as Epeak, is 449 +/- 109 keV.

The event fluence (10-1000 keV) in this time interval is
(6.9 +/- 0.6)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.7 s in the 10-1000 keV band
is 2.3 +/- 0.2 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/"

V. D'Elia (ASDC), D.N. Burrows (PSU), J. D. Gropp (PSU), A. Tohuvavohu
(U. Toronto), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester),
J.P. Osborne (U. Leicester), A. D'Ai (INAF-IASFPA) and A. Melandri
report on behalf of the Swift-XRT team:

We have analysed 6.3 ks of XRT data for GRB 200109A (Melandri et al.
GCN Circ. 26678
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 ), from 91 s to 24.1 ks after the  BAT trigger. The data
comprise 48 s in Windowed Timing (WT) mode (the first 7 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. 26681
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 ).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.9 (+/-0.3). At T+216 s  the decay
steepens to an alpha of 8.0 (+0.0, -3.2) before breaking again at T+262
s to a final decay with index alpha=1.50 (+0.28, -0.38).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.70 (+0.32, -0.30). The
best-fitting absorption column is  6.9 (+2.7, -2.2) x 10^21 cm^-2, in
excess of the Galactic value of 4.0 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 5.2 x 10^-11 (7.6 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.9 (+2.7, -2.2) x 10^21 cm^-2
Galactic foreground: 4.0 x 10^21 cm^-2
Excess significance: 2.2 sigma
Photon index:	     1.70 (+0.32, -0.30)

If the light curve continues to decay with a power-law decay index of
1.50, the count rate at T+24 hours will be 1.3 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.0 x
10^-15 (1.0 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/00948361.

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 406 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 200109A, 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 = 307.12462, +52.99363 which is equivalent
to:

RA (J2000): 20h 28m 29.91s
Dec (J2000): +52d 59' 37.1"

with an uncertainty of 1.7 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. Melandri (INAF-OAB), M. G. Bernardini (INAF-OAB),
P. D'Avanzo (INAF-OAB), J.D. Gropp (PSU), N. J. Klingler (PSU),
S Laha (GSFC/UMBC/CRESST), D. M. Palmer (LANL), M. H. Siegel (PSU),
K. K. Simpson (PSU) and A. Tohuvavohu (U Toronto) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 01:46:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200109A (trigger=948361).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 307.171, +53.003 which is 
   RA(J2000) = 20h 28m 41s
   Dec(J2000) = +53d 00' 12"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of 70 sec.  The peak count rate
was ~1600 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 01:47:59.1 UT, 102.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
307.1258, 52.9932 which is equivalent to:
   RA(J2000)  = 20h 28m 30.19s
   Dec(J2000) = +52d 59' 35.5"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 104 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 3.98
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 1.12e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 109 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. Because of the density of catalogued stars, further
analysis is required to report an upper limit for any afterglow in the
sub-image. 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 0.29. 

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 01:45:51 UT on 9 Jan 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 200109A (trigger 600227156.894404 / 200109074).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 284.7, Dec = 68.9 (J2000 degrees, equivalent to J2000 18h 58m, 68d 54'), with a statistical uncertainty of 10.4 degrees.

The angle from the Fermi LAT boresight is 40.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200109074/quicklook/glg_skymap_all_bn200109074.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200109074/quicklook/glg_healpix_all_bn200109074.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200109074/quicklook/glg_lc_medres34_bn200109074.gif