Name: Nikita Rawat
Affiliation: Aryabhatta Research Institute of Observational Sciences
Conference ID : ASI2022_175
Title : TESS Observations of TX Col: Rapidly Varying Accretion Flow
Authors : Nikita Rawat (ARIES), J. C. pandey (ARIES), and Arti Joshi (Wuhan University)
Abstract Type: Poster
Abstract Category : Stars, ISM and Galaxy
Abstract : Intermediate Polars (IPs) are semi-detached interacting binaries containing a magnetic white dwarf (WD), which accretes material from a Roche­ lobe filling companion star. There are primarily three accepted scenarios for accretion in IPs and the feasibility of each one of them depends on the magnetic field strength of WD and mass accretion rate. The first is the disc-fed accretion, in which an accretion disc is present in the system, which is disrupted at the magnetosphere radius. From this radius, material flows along the magnetic field lines resulting in the formation of accretion curtains near the magnetic poles of the WD. The second is the disc-less or stream-fed accretion, in which the high magnetic field of the WD does not allow the formation of a disc and infalling material is channelised along the magnetic field lines to the pole caps. In the third possibility, known as disc-overflow accretion, disc-fed and stream-fed accretions can simultaneously occur as a part of the accretion stream skims over the disc and then interacts with the magnetosphere of the WD. The presence of spin, beat, orbital, and sideband frequencies in the power spectra and their amplitudes play a vital tool in distinguishing the mode of accretion in these systems. We will present a detailed investigation of the long-term optical photometry of an IP TX Col obtained from the TESS mission. The continuous data allowed us to look thoroughly at the day-wise evolution of the accretion geometry of TX Col confirming its variable disk-overflow accretion nature. For the majority of the time, it was found to be a disk-overflow with stream-fed dominance; however, pure disk-fed and pure stream-fed accretions cannot be ruled out during the observations.