Swift localization of MAXI J1727-203
ATel #11718; Arash Bahramian (Curtin), A. P. Beardmore (Leicester), Craig O. Heinke (Alberta), J. A. Kennea (PSU)
on 15 Jun 2018; 00:56 UT
Credential Certification: Arash Bahramian (arash.bahramian@curtin.edu.au)
Subjects: X-ray, Black Hole, Neutron Star, Transient
MAXI J1727-203 is a new transient X-ray binary (ATels #11683) discovered by MAXI. Rau and Schweyer (ATel #11690) reported detection of a possible optical/NIR counterpart by GROND consistent with the X-ray position reported by NICER (ATel #11689).
We observed the source with Swift/XRT in PC mode on 2018-06-13 from 04:30:15 to 04:49:27 UT. The source is extremely bright causing substantial pile up with an XRT count rate ~410 ct/s (estimated for grade 0 events; after correcting for pile-up). We model the source point spread function with an appropriate pile up model for Swift/XRT and enhance the astrometry by applying UVOT-derived offsets. Thus we obtain the following localization for this source:
RA(J2000) = 17:28:29.8s (262.12429 deg)
Dec(J2000) = -20:22:56.5 (-20.38236 deg)
with a radial uncertainty of 1.8'' (at 90% confidence). This is 1.3'' away from the reported GROND counterpart.
We also looked for evidence of dust scattering halos around the source. This is particularly difficult as the source is currently extremely bright and the point spread profile is too distorted by pile-up to establish whether a dust scattering halo is present.
The source was also detected in UVOT in this observation with the following magnitudes (in AB magnitudes):
B = 17.17(+/-0.06)
U = 17.63(+/-0.06)
UVW1 = 18.41(+/-0.07)
UVW2 = 19.0(+/-0.1)
