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MAXI J1828-249: Swift detection and localization

ATel #5478; J. A. Kennea (PSU), M. Linares (IAC, Spain), H. A. Krimm (CRESST/GSFC/USRA), P. A. Evans (U Leicester),, P. Romano (INAF-IASF PA), V. Mangano (PSU), P. Curran (Curtin), K. Yamaoka (Nagoya U) and H. Negoro (Nihon U.)
on 16 Oct 2013; 21:41 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)

Subjects: X-ray, Transient

Referred to by ATel #: 5479, 5482, 5483, 5484, 5559

At 15:04UT on October 16th, 2013, Swift began a target-of-opportunity observation of the MAXI error region of MAXI J1828-249 (Nakahira et al, ATEL #5474), utilizing a 4-point tiling to cover the entire region. Swift/XRT detects a bright, uncatalogued point source at the following location: RA/Dec(J2000) = 277.2427, -25.0304, which is equivalent to:

RA(J2000) = 18h 28m 58.24s
Dec(J2000) = -25d 01m 49.3s

with an estimated uncertainty of 3.6 arc-seconds (radius; 90% confidence). This position lies 41 arc-seconds from center of the reported INTEGRAL error circle (Filippova et al., ATEL #5476), and consistent with that position.

Swift/XRT Photon Counting mode data are highly piled up due to source brightness (estimated at ~220 XRT count/s, although with the high level of pile-up this figure is uncertain), making accurate spectral analysis difficult. We have requested follow-up observations in Windowed Timing mode to obtain an accurate spectrum of this source.

This source is also seen in the BAT hard X-ray transient monitor starting on 15 October 2013 (MJD 56580) at a rate of 0.0064 +/- 0.0008 ct/sec/cm2 (~30 mCrab). The source appears to be brightening: up to ~45 mCrab on 16 October based on limited data.

Daily monitoring observations of MAXI J1828-249 by Swift have been approved and will begin shortly. These observations were taken as part of an approved Swift Cycle 9 Guest Investigator program.