Outburst and Possible Orbital Period of Swift J1816.7-1613
ATel #6253; Robin H. D. Corbet (UMBC/NASA GSFC), Hans A. Krimm (USRA/NASA GSFC)
on 20 Jun 2014; 20:46 UT
Credential Certification: Robin Corbet (corbet@umbc.edu)
Subjects: X-ray, Neutron Star, Transient, Variables
The transient X-ray source Swift J1816.7-1613 was discovered with the Swift
BAT by Krimm et al. (2008; ATel #1456). A pulse period of 143 s was
found by Halpern & Gotthelf (2008; ATel #1457) from Chandra
observations and this was confirmed by Krimm et al. (2013, ApJ Supp,
209, 14) from RXTE PCA data.
Recent Swift BAT observations of Swift J1816.7-1613 indicate a low
amplitude outburst occurred from approximately May 28 to June 13,
2014, peaking around June 8 (MJD 56816) at a daily average rate of
0.006 +/- 0.001 ct/s/cm^2 (~30 mCrab; 15-50 keV). Krimm et al. (2013)
also noted a number of other outbursts in 2008, 2009 and 2011. In
addition, we note a weak outburst around Oct 6, 2013 (MJD 56571) with a
peak of 0.003 +/- 0.001 ct/s/cm^2 (~15 mCrab). A power spectrum of the
entire Swift BAT transient monitor light curve suggests a possible
underlying periodicity of 151.4 +/- 1 days. However, a visual
inspection of the light curve suggests that the source does not always
exhibit outbursts based on this ephemeris.
The combination of a 143 s pulse period and a 151 day orbital period
would be suggestive of a Be/neutron star binary (Corbet 1986, MNRAS, 220,
1047). This classification would also be consistent with the
apparently sporadic nature of the outbursts. If this period is
correct, then the next outburst is expected around MJD 56967
(Nov. 6, 2014).
Swift BAT light curve of Swift J1816.7-1613
