ULTRASPEC observations of SWIFT J1858.6-0814
ATel #12499; K. M. Rajwade (Univ. of Manchester), V. S. Dhillon (Univ. of Sheffield), P. Gandhi (Univ. of Southampton), J. A. Paice (Univ. of Southampton), M. Kennedy (Univ. of Manchester), C. J. Clark (Univ. of Manchester), J. Wild (Univ. of Sheffield), S. Littlefair (Univ. of Sheffield), T. Marsh (Univ. of Warwick)
on 12 Feb 2019; 16:41 UT
Credential Certification: Kaustubh Rajwade (rkaustubh10@gmail.com)
Subjects: Optical, Binary, Black Hole, Neutron Star, Transient
Referred to by ATel #: 12512
Swift J1858.6-0814 is a Galactic X-ray transient discovered on 2018 October 25 (MJD 58416) (ATel #12151) and has been the subject of much multi-wavelength follow-up. It has displayed large amplitude flaring in X-rays and optical, as well as prominent reflection and absorption X-ray signatures, and it has been detected in the radio. These characteristics have led to comparisons being drawn with other Galactic microquasars such as V404 Cyg (ATel#12158, #12160, #12163, #12164, #12167, #12180, #12184, #12186, #12197, #12220). Since the last high time-resolution optical follow-up of Swift J1858.6-0814 (ATel#12186, ATel#12197), further multi-wavelength follow-up was hampered due to the proximity of the source to the Sun. On 2019 February 10 at 22:53UT, we observed the source for 2 minutes in the SDSS r' filter using the ULTRASPEC photometer (Dhillon et al. 2014, MNRAS, 444, 4009) mounted on the 2.4 m Thai National Telescope. The target was at an elevation of 20 degrees and was observed during morning twilight. We detected the source, with an r'-band magnitude of 17.28 +/- 0.11 computed from the average of 5 nearby bright stars from the Pan-STARRs (Flewelling et al. 2019) catalogue. This indicates that the source is still in an active phase with the optical magnitude comparable to that observed in November last year. We attach a figure of the Pan-STARRS r'-band image of the field (left) along with image from our ULTRASPEC observing run with the source marked in both the images. Continued multi-wavelength monitoring of the source is planned and encouraged.
ULTRASPEC image of our 2-min exposure
