Thai national telescope studies of ultraluminous X-ray sources

• Main Authors: K. Thongpoyai, W. Luangtip, U. Sawangwit, T. P. Roberts, S. Komonjinda, V. S. Dhillon, T. R. Marsh
• Format: Conference Proceeding
• Published: 2020
• Subjects: Physics and Astronomy
• Online Access: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85077821709&origin=inward; http://cmuir.cmu.ac.th/jspui/handle/6653943832/68079
• Institution: Chiang Mai University

© Published under licence by IOP Publishing Ltd. Ultraluminous X-ray sources (ULXs) are extra-galactic, non-nuclear sources with X-ray luminosity in excess of 1039 erg s-1. It has been thought that the majority of ULX populations are stellar-mass objects accreting matter at a super-Eddington rate. Although ULX studies are often focused in the X-ray regime, this work studied the ULXs in the optical regime, identified as the ULX counterparts (CTPs). The optical variability of nine CTPs were observed using the 2.4-m Thai National Telescope. Out of the nine ULXs, we detected three ULXs exhibiting strong variability up to ∼1 magnitude, suggesting that the CTP light does not come from the donor star's emission. The paper discusses the physical origins of the variability which potentially explain the observed light curves.