I-band Observations of the 2019 Outburst of SXP 1062
ATel #13426; P. C. Schmidtke, A. P. Cowley (Arizona State University)
on 28 Jan 2020; 22:41 UT
Credential Certification: Paul Schmidtke (Paul.Schmidtke@asu.edu)
Subjects: Optical, X-ray, Binary, Neutron Star, Pulsar
Referred to by ATel #: 13624
The slowly rotating X-ray pulsar SXP 1062 was discovered by Henault-Brunet et al. (2012, MNRAS, 420, L13) and identified with the known Be star 2dFS 3831 (Evans et al. 2004, MNRAS, 353, 601). The OGLE-IV light curve shows recurrent outbursts with an orbital period near 656 d (Schmidtke et al. 2012, ATel #4596), which are nearly coincident with X-ray outbursts (Gonzalez-Galan et al. 2018, MNRAS 475, 2809). Based on an ephemeris linking portions of 4 optical outbursts, Schmidtke et al. (2019, ATel #12890) predicted another outburst should occur near 2019 October 26.
We obtained CCD observations of SXP 1062 on 34 nights between 2019 September 10 and December 28 with telescope T17 of the www.itelescope.net network. Each image was a 60-s exposure through an Ic filter. Differential photometry was calculated using stars [M2002] SMC 82540 and 82744 (Massey 2002. ApJS, 141, 81) as comparison and check stars, respectively, and transformed to the OGLE scale using updated OGLE-III photometry maps (Szymanski et al, 2011, Acta Astron., 61, 83) for stars in common at the western edge of our CCD images. Since these maps are tied to the OGLE-IV filter set, the I-band magnitudes presented here are directly comparable with OGLE-IV data. The estimated brightness of the comparison star is I=13.42.
Because peak brightness of the recent outburst occurred ~2 days earlier than predicted, we derive a new orbital ephemeris by aligning peaks from the 2010 and 2019 outbursts: P=655.9 +/- 0.2 d with maximum light at JD 2458779.1 +/- 0.5. A plot of the phased light curve for SXP 1062 is shown in http://www.public.asu.edu/~atpcs/SXP/SXP1062_2019_outburst.pdf . The observed peak brightness is slightly less in 2019 compared to 2010 (~0.4 vs. ~0.6 mag) but neither outburst is fully resolved. The recent outburst has a very fast rise and gradual decline, with a noticeable rebrightening near phase 0.03. In the 2010 data this second outburst does not appear to be present (see http://www.public.asu.edu/~atpcs/SXP/SXP1062_OGLEIV_outburst.pdf ). The amplitude of this second peak is too large to be caused by non-radial pulsations (see Schmidtke et al. 2012, ATel #4399). Hence, this rebrightening appears to be a feature unique to the 2019 outburst.
