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Swift confirmation and localization of the new Transient MAXI J1621-501

ATel #10874; A. Bahramian (MSU), J. A. Kennea (PSU), P. A. Evans, A. P. Beardmore (U Leicester), H. A. Krimm (CRESST/GSFC/USRA), P. Romano (INAF-IASFPA), K. Yamaoka (Nagoya U.), M. Serino (RIKEN), H. Negoro (Nihon U.), R. Wijnands (Amsterdam), J. In 't Zand (SRON)
on 19 Oct 2017; 22:38 UT
Credential Certification: Arash Bahramian (bahramian@pa.msu.edu)

Subjects: X-ray, Binary, Neutron Star

Referred to by ATel #: 10876, 11067, 11272

Following report of a new transient by MAXI (ATel #10869), we observed the MAXI error region with a set of 7-tile Swift/XRT observations in PC mode. We detect a new bright source with enhanced coordinates RA=245.09171, Dec=-50.01989 (J2000), which translate to:

RA: 16:20:22.01
Dec: -50:01:11.6

With radial uncertainty of 3.4''. This is not consistent with any previously identified X-ray source.

We extract a spectrum (and correct for pile up) from the observation and fit it with both absorbed disk blackbody and absorbed powerlaw. The absorbed diskbb provide a slightly superior fit with a reduced chi-squared of 0.94 for 17 degrees of freedom (compared to red. chi2 of 1.12 for the absorbed powerlaw, with the same number of d.o.f). The diskbb fit indicates a hydrogen column density of NH=9(-2/+3)e22 cm^-2, inner disk temperature of Tin = 2.1(-0.5/+0.7) keV and an unabsorbed flux of 2.1(-0.3/+0.5)e-9 erg/s/cm2 in the 0.5-10 keV band.

Swift monitoring of this source is planned. Multi-wavelength observations are encouraged. We thank the Swift team for rapidly scheduling our observations.