GRB 180718B

M. Crnogorcevic (NASA/GSFC/UMD), G. Vianello (Stanford), J. L. Racusin (NASA/GSFC), 
M. Axelsson (KTH and Stockholm University), and E. Bissaldi (Politecnico and INFN Bari), report 
on behalf of the Fermi-LAT team:

At 18:18:24.46 UT on July, 18, 2018 Fermi-LAT detected high-energy emission from GRB 180718B, 
which was also detected by Fermi-GBM (trigger 553630709 / 180718763). 

The best LAT on-ground location is found to be
RA, Dec = 44.68, -31.5 (J2000)

with an error radius of 0.65 deg (90% containment, statistical error only). 

This was 50 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially and 
temporally correlated with the trigger with high significance. 

The highest-energy photon is a 300 MeV event which is observed 17 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi (elisabetta.bissaldi@ba.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.

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Fermi/LAT GRB 180718B. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020803

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/LAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

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

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

"At 18:18:24.46 UT on 18 July 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180718B (trigger 553630709 / 180718763).
which was also detected by the Fermi LAT (Racusin et al. 2018, GCN 22961
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 ).
The GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 48
degrees.

The GBM light curve shows a structured FRED-like peak
with a duration (T90) of about 98 s (50-300 keV).
The time-averaged spectrum from T0+0 s to T0+66 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.73 +/- 0.05 and
the cutoff energy, parameterized as Epeak, is 761 +/- 78 keV.
A Band function also fits the spectrum with Epeak = 731 +/- 83 keV,
alpha = -0.71 +/- 0.05,and beta = -2.79 +/- 0.73.

The event fluence (10-1000 keV) in this time interval is
(2.6 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.6 s in the 10-1000 keV band
is 3.6 +/- 0.2 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

E. Gorbovskoy, V. Lipunov, V.Kornilov,  N.Tiurina, 
A.Kuznetsov, V.Chazov, I. Gorbunov, D. Vlasenko, D.Zimnukhov, D.Kuvshinov, 
P.Balanutsa, V.Vladimirov
Lomonosov Moscow State University,SAI

D. Buckley,
South African Astronomical Observatory (SAAO)

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

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

R. Podesta, F. Podesta, C. Lopez, C.Francile
Observatorio Astronomico Felix Aguilar (OAFA)

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

O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University (ISU)

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


MASTER-OAFA robotic telescope (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  GRB180718.76 36087 sec after notice time and 36087 sec after 
trigger time at 2018-07-19 04:19:52 UT. On our combined images (1800 s), 
started 41401 sec after tigger time at 2018-07-19 05:48:25 UT, we 
not found  optical transient within LAT error-box (ra=44.6792 dec=-31.5 
r=1)  brighter then 20.4.


The observations made on zenit distance = 74 degrees, galaxy latitude b = 
-62 degree. The moon (44 % bright part) below the horizon (The altitude of 
the Moon is  -20 degree ).
The sun  altitude  is -71.7 degree.
The object can be observed till sunrise at 2018-07-19 11:33:26 .

The message may be cited.

B. Sbarufatti (INAF-OAB/PSU), A. A. Breeveld (UCL-MSSL), Z. Liu (NAOC /
U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N.
Burrows (PSU), A. Tohuvavohu (PSU) and P.A. Evans (U. Leicester) report
on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 180718B (Crnogorcevic et al. GCN Circ.
22961
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 ), collecting 5.0 ks of Photon Counting (PC) mode data between
T0+38.9 ks and T0+50.6 ks. 

Four uncatalogued X-ray sources have been detected, however none of
them is above the RASS limit or shows definitive signs of fading.
Therefore, at the present time we cannot identify which, if any, is the
afterglow. The UVOT finds no new optical sources at the position of any
of the four X-ray sources. Details of these sources are given below:

Source 1:
  RA (J2000.0):  44.7960  =  02:59:11.03
  Dec (J2000.0): -31.6692  =  -31:40:09.2
  Error: 3.0 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (9.0 +/- 2.4)e-3 ct s^-1	 
  Distance: 705 arcsec from Fermi/LAT position.
  Flux: (2.79 +/- 0.74)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:
  RA (J2000.0):  44.6153  =  02:58:27.68
  Dec (J2000.0): -31.6555  =  -31:39:19.9
  Error: 6.1 arcsec (radius, 90% conf.)
  Count-rate: (1.91 [+0.92, -0.71])e-3 ct s^-1	 
  Distance: 593 arcsec from Fermi/LAT position.
  Flux: (5.1 [+2.4, -1.9])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:
  RA (J2000.0):  44.7970  =  02:59:11.27
  Dec (J2000.0): -31.4797  =  -31:28:47.0
  Error: 4.0 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (2.80 [+1.14, -0.91])e-3 ct s^-1	 
  Distance: 366 arcsec from Fermi/LAT position.
  Flux: (1.19 [+0.49, -0.39])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)


Source 4:
  RA (J2000.0):  44.7053  =  02:58:49.28
  Dec (J2000.0): -31.4407  =  -31:26:26.5
  Error: 5.0 arcsec (radius, 90% conf.)
  Count-rate: (2.51 [+1.10, -0.87])e-3 ct s^-1	 
  Distance: 227 arcsec from Fermi/LAT position.
  Flux: (5.1 [+2.2, -1.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020803.

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