GRB 150622A

D.N. Burrows (PSU), J.A. Kennea (PSU), V. Mangano (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A.
Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has conducted further observations of the field of the
MAXI-detected burst GRB 150622A (Kawakubo et al. GCN Circ. 17952
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 ). The
observations now extend from T0+14.7 ks to T0+843.1 ks. The source
previously reported by Burrows et al. (GCN Circ. 17954
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 ), "Source 1", is
fading with 3-sigma significance, and is therefore likely the GRB
afterglow. Using 483 s of PC mode data and 1 UVOT image, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 252.45633, -52.85017
which is equivalent to:

RA (J2000): 16h 49m 49.52s
Dec(J2000): -52d 51' 00.6"

with an uncertainty of 4.1 arcsec (radius, 90% confidence). This
position is 16.3 arcmin from the MAXI position.  The source is fading
with alpha >0.4.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020534.
The results of the full analysis of the tiled XRT observations are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00046.

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

D.N. Burrows (PSU), J.A. Kennea (PSU), V. Mangano (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A.
Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the MAXI-detected
burst GRB 150622A (Kawakubo et al. GCN Circ. 17952
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 ) in a series of
observations tiled on the sky. The total exposure time is 1.9 ks,
distributed over 4 tiles; the maximum exposure at a single sky location
was 1.3 ks. The data were collected between T0+14.2 ks and T0+16.2 ks,
and are entirely in Photon Counting (PC) mode. 

One uncatalogued X-ray source has been detected, it is below the RASS
limit and shows no definitive signs of fading. Therefore, at the
present time we cannot confirm this as the afterglow. Details of this
source are given below:

Source 1:
  RA (J2000.0):  252.4574  =  16:49:49.79
  Dec (J2000.0): -52.8499  =  -52:50:59.6
  Error: 5.4 arcsec (radius, 90% conf.)
  Count-rate: 0.032 +/- 0.010 ct s^-1
  Flux: (1.29 +/- 0.41)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00046.

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

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

Swift has initiated a series of observations, tiled on the sky, of the
MAXI GRB 150622A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00046

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the MAXI event is high: 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.

Y. Kawakubo (AGU), S. Nakahira, S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, 
Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, 
T. Takagi, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), 
A. Yoshida, T. Sakamoto, H. Ohtsuki (AGU), H. Tsunemi, R.Imatani (Osaka U.), 
H. Negoro, M. Nakajima, K. Tanaka, T. Masumitsu (Nihon U.), Y. Ueda, T. Kawamuro, 
T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.), M. Yamauchi, D. Itoh (Miyazaki U.), 
K. Yamaoka (Nagoya U.), M. Morii (ISM)

report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient 
source at 10:23:43 UT.  Assuming that the source flux was constant over the transit, 
we obtain the source position at

(R.A., Dec) = (252.028 deg, -52.768 deg) = (16 48 06, -52 46 04) (J2000) 

with a statistical 90% C.L. elliptical error region with long and short radii of 0.22 deg 
and 0.14 deg, respectively.  The roll angle of long axis from the north direction is 62.0 deg 
counterclockwise.  There is an additional systematic uncertainty of 0.1 deg (90% 
containment radius).  The X-ray flux averaged over the scan was 342 +- 40 mCrab
(4-10keV, 1 sigma error).  Without assumptions on the source constancy, we obtain 
a rectangular error box for the transient source with the following corners: 

(R.A., Dec) = (251.874 deg, -52.244 deg) = (16 47 29, -52 14 38) (J2000)
(R.A., Dec) = (251.283 deg, -52.506 deg) = (16 45 07, -52 30 20) (J2000)
(R.A., Dec) = (252.300 deg, -53.392 deg) = (16 49 11, -53 23 29) (J2000)
(R.A., Dec) = (252.900 deg, -53.128 deg) = (16 51 36, -53 07 39) (J2000)

There was no significant excess flux in the previous transit at 8:48 UT.