GRB 190727B

A. Y. Lien (GSFC/UMBC), M. G. Bernardini (INAF-OAB),
P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU), N. J. Klingler (PSU),
A. Melandri (INAF-OAB), M. J. Moss (GWU), K. L. Page (U Leicester),
D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 20:18:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190727B (trigger=916733).  Swift could not slew to the location
due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 126.481, -13.268 which is 
   RA(J2000) = 08h 25m 55s
   Dec(J2000) = -13d 16' 03"
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 50 sec.  The peak count rate
was ~20,000 counts/sec (15-350 keV), at ~1 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 16:42 UT on 2019 September 12. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is A. Y. Lien (amy.y.lien 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/)

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

At 20:17:56 UT on 27 Jul 2019, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 190727B (trigger 585951481.447196 / 190727846).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 130.6, Dec = -15.7 (J2000 degrees, equivalent to J2000 08h 42m, -15d 41'), with a statistical uncertainty of 1.0 degrees.

The angle from the Fermi LAT boresight is 44.0 degrees.

The skymap can be found here:
http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190727846/quicklook/glg_skymap_all_bn190727846.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190727846/quicklook/glg_healpix_all_bn190727846.fit

The GBM light curve can be found here:
http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190727846/quicklook/glg_lc_medres34_bn190727846.gif

B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
585951481 at 20:17:56 on 27 July 2019 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 128.2+/-0.3 deg
Decl.(2000.0) = -12.2+/-0.5 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB190727846/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB190727846/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB190727846/json

P. Veres and C. Meegan (both UAH) report on behalf of the Fermi GBM Team:

At 20:17:56.45 UT on 27 July 2019, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 190727B (trigger 585951481/190727846), which was
also detected by the Swift/BAT (Lien et al., GCN 25176
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 ). The GBM on-ground
location is consistent with the Swift position.

The angle from the Fermi LAT boresight is 46 degrees.

The GBM light curve consists of multiple overlapping pulses with a duration
(T90) of about 35 s (50-300 keV). The time-averaged spectrum from T0 to
T0+44 s is adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.26 +/- 0.01 and the cutoff
energy, parameterized as Epeak, is 621 +/- 26 keV.

The event fluence (10-1000 keV) in this time interval is (7.02 +/-
0.05)E-05 erg/cm^2. The 1-second peak photon flux measured starting from
T0+21.8 s in the 10-1000 keV band is 43.0 +/- 0.4 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 information, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/

M. Kovacevic (INFN Perugia), D. Tak (Univ. of Maryland & NASA/GSFC),
F. Longo (University and INFN, Trieste),
M. Arimoto (Kanazawa Univ.), and M. Axelsson (KTH and Stockholm Univ.)
report on behalf of the Fermi-LAT team:

On July 27, 2019, Fermi-LAT detected high-energy emission from
GRB 190727B, which was also detected by Fermi-GBM (Veres et al., GCN
25180
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 ) and Swift-BAT (Lien et al., GCN 25176
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 ).

The best LAT on-ground location is found to be

RA, Dec 126.19, -13.34 (degrees, J2000)

with an error radius of 0.28 deg (90% containment, statistical error only).
This was 46 deg from the LAT boresight at the time of the GBM trigger:

T0 =  20:17:56.45 UT.

The data from the Fermi-LAT show a significant increase
in the event rate after the GBM trigger that is spatially correlated with the
GBM emission with high significance.
The photon flux above 100 MeV in the time interval 0-1500 s after the
GBM trigger is (3.15 +/- 1.25)E-6 ph/cm2/s.
The highest-energy photon in this interval is a 2.2 GeV event observed
at T0 + 345 s.
The estimated photon index above 100 MeV is -2.3 +/- 0.4.

The Fermi-LAT point of contact for this burst is Milos Kovacevic
(milos.kovacevic@pg.infn.it).

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.

M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
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 190727B (trigger #916733)
(Lien et al., GCN Circ. 25176
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 ).  The BAT ground-calculated position is
RA, Dec = 126.500, -13.272 deg which is
   RA(J2000)  =  08h 25m 59.9s
   Dec(J2000) = -13d 16' 18.9"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 70%.

The mask-weighted light curve shows a structure with multiple bright pulses
that starts at ~T-20 s and ends at ~T+45 s. The brightest peak occurs at
~T+2 s. T90 (15-350 keV) is 40.14 +- 1.40 sec (estimated error including
systematics).

The time-averaged spectrum from T-21.30 to T+44.47 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.41 +- 0.03.  The fluence in the 15-150 keV band is 1.8 +- 0.03 x 10^-5
erg/cm2.
The 1-sec peak photon flux measured from T+1.13 sec in the 15-150 keV band
is 20.9 +- 0.7 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/916733/BA/

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

The long-duration GRB 190727B
(Swift-BAT detection: Lien et al., GCN Circ. 25176
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 ;
Fermi-GBM observations: Veres and Meegan, GCN Circ. 25180
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 ;
Fermi-LAT detection: Kovacevic et al., GCN Circ. 25186
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 )
triggered Konus-Wind at T0=73072.783 s UT (20:17:52.783).

The burst light curve shows a multi-peaked structure
which starts at ~T0-3.8 s and has a total duration of ~62 s.
The emission is seen up to ~6 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190727_T73072/

As observed by Konus-Wind, the burst
had a fluence of 9.92(-1.04,+1.04)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+21.040 s,
of 1.82(-0.34,+0.33)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+44.800 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 = -1.11(-0.07,+0.07),
the high energy photon index beta = -2.27(-0.29,+0.16),
the peak energy Ep = 402(-49,+64) keV
(chi2 = 106/97 dof).

The spectrum near the maximum count rate
(measured from T0+16.640 to T0+21.504 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 = -1.07(-0.08,+0.09),
the high energy photon index beta = -2.38(-0.85,+0.24),
the peak energy Ep = 566(-98,+136) keV
(chi2 = 94/97 dof).

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