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GCN Circular 20842

Subject
LIGO/Virgo G275404: Swift-XRT observations of sources in the AGILE error region
Date
2017-03-09T14:45:19Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), J.A. Kennea (PSU), S.D. Barthelmy
(NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld (UCL-MSSL),
D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G.
Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB),
V.D'Elia(ASDC), P. Giommi (ASI), C. Gronwall (PSU), H.A. Krimm
(CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), F.E.
Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester),
J.A. Nousek (PSU), S.R. Oates (U. Warwick), P.T. O'Brien (U.
Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L.
Page (U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin
(NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G.
Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) on behalf of the Swift 
team

and

Francesco Verrecchia (ASDC) and Marco Tavani (INAF / University of Rome
Tor Vergata) on behalf of the AGILE team report:


Swift-XRT has performed pointed observations of two sources within the
error region of the AGILE-GRID transient AGL J1914+1043 (Tavani et al.
LVC Circ. 20754): the IR transient reported by Yoshida et al (LVC Circ.
20784) and the Galactic microquasar GRS 1915+105, observing each field
for 1ks.

No X-ray source is detected at the location of the IR transient, with a
3-sigma upper limit of 9.7e-3 ct/sec. Assuming a power-law spectrum with 
Gamma=1.7 and NH=1.43e22 cm^-2 (the Galactic column along this line of 
sight; Willingale et al. 2013) this corresponds to an observed X-ray 
flux of 7.1e-13 erg cm^-2 s^-1.

GRS 1915+105 is a known X-ray emitter and is clearly detected in the XRT 
observations, with a mean count-rate of 87.8 (+1.63, -2.05) ct/sec,
which is ~20% lower than seen in Swift observations from 2016 November.

This circular is an official produce of the Swift and AGILE teams.
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