Early optical outburst of the hard X-ray transient Swift J1836.6+0341/XTE J1837+037 with Pan-STARRS 1
ATel #3708; K. L. Li, A. K.H. Kong (NTHU, Taiwan), Y. Urata (NCU, Taiwan), P. A. Price (Princeton), E. Magnier, K. Chambers, N. Kaiser, J. Heasley, W. Sweeney, C. Waters, H. Flewelling, J. Tonry (IfA, Hawaii)
on 25 Oct 2011; 16:31 UT
Credential Certification: Albert Kong (akong@phys.nthu.edu.tw)
Subjects: Optical, X-ray, Transient
We report the discovery of the early optical outburst of the hard X-ray transient Swift J1836.6+0341 (a.k.a. XTE J1837+037; ATel #3684) in the Pan-STARRS 1 (PS1) 3Pi sky survey. During the survey, the field of Swift J1836.6+0341 was observed 36 times between 2010 March 29 and 2011 September 15. The source fell into CCD gaps for some observations (including data taken on 2011 May 29 and 2011 June 29) which makes it hard to determine the exact onset of the outburst. Using the standard PS1 data products, the source was first detected with r-mag = 18.88 +/- 0.02 on 2011 July 9 which is more than two months before the hard X-ray outburst (i.e. 2011 September 25, ATel #3684). It is worth noting that RXTE/ASM detected an increasing X-ray flux about 10 days before the optical outburst detection (ATel #3684).
Since the first optical detection, the source has been fading in the r- and z-bands steadily over the last 3 months as follows (in AB magnitude system):
r = 18.88 +/- 0.02 at 2011-07-09 UTC 08:41
r = 18.88 +/- 0.02 at 2011-07-09 UTC 08:55
g = 19.75 +/- 0.03 at 2011-07-09 UTC 10:49
z = 18.64 +/- 0.04 at 2011-08-06 UTC 05:56
z = 18.66 +/- 0.04 at 2011-08-06 UTC 06:05
z = 18.68 +/- 0.03 at 2011-09-15 UTC 06:05
z = 18.71 +/- 0.03 at 2011-09-15 UTC 06:22
z = 19.4 +/- 0.1 on 2011/10/15 and 17 (ATel #3687)
r = 20.5 +/- 0.1 on 2011/10/15 and 17 (ATel #3687)
The non-detection between March 2010 and September 2010 in the PS1 data indicated that the source was in the quiescent state, which is consistent with the previous DSS2 measurements (ATel #3687). By comparing with the r-band detection limit of our PS1 data, we estimated that the quiescent optical magnitude is >~23.
From the existing observations, Galactic cataclysmic variable or AGN could be the possible origin for Swift J1836.6+0341 (ATel #3687). Further multiwavelength monitoring of this source may provide hints to the physical nature of the source.
This discovery was enabled using the PS1 System operated by the PS1 Science Consortium (PS1SC) and its member institutions, http://www.ps1sc.org/PS1_System_ATel.htm . We would like to thank the PS1 telescope operators for their support of PS1 observations.
