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ATEL # 1456; H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC), W. Baumgartner (CRESST/GSFC/UMBC), J. Cummings (CRESST/GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), J. Kennea (PSU), C. B. Markwardt (CRESST/GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (CRESTT/GSFC/UMBC), G. Sato (GSFC/ISAS), G. Skinner (CRESST/GSFC/UMBC), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
on 2 Apr 2008; 23:47 UT
Password Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)
Subjects: X-ray, Transients
Referred to by ATEL #: 1457, 1462
The hard X-ray transient monitor of the Swift Burst Alert Telescope (BAT) has detected a previously unknown galactic transient. This source, Swift J1816.7-1613, was first detected at a daily average rate of 0.005 ± 0.001 counts/sec/cm2 (20 mcrab) in the 15-50 keV band on March 24, 2008 (MJD 54549). It rose to a peak brightness of 0.008 ± 0.002 cts/sec/cm2 (35 mcrab) on March 29 and has remained between 10 and 20 mcrab for the past several days. The best BAT position was RA=274.176, Dec=-16.266 (J2000). Note that this source is on the galactic plane at coordinates L=14.587, B=0.094 degrees.
On April 1, 2008 beginning at 18:47 UTC, Swift J1816.7-1613 was observed as a target of opportunity with Swift. An X-ray source, Swift J181642.3-161320, was detected at a count rate of 0.32 ± 0.014 cts/s (0.3-10 keV) at a location:
RA = 18h 16m 42.3s (274.176458 deg)
dec = -16d 13m 20.5s (-16.222361 deg),
with an estimated error of 3.6'' radius (90% containment). This is 2.6 arc minutes from the BAT position.
A search of the USNO B1.0 catalog reveals a single star within the error circle. This star, designated 0737-0562754, has catalog magnitudes of B2=20.48 and I=17.18.
BAT transient monitor for Swift J1816.7-1613