Tidal Disruption Events
A tidal disruption event, or TDE, occurs when a star passes too close to a supermassive black hole, where the tidal forces from the black hole overwhelm the star's self-gravity, tearing it apart. Most of the stellar material is ejected from the system, but a fraction remains bound and accretes onto the black hole, resulting in a luminous accretion flare that can last for a year or more. TDEs allow us to study quiescent black holes which otherwise would be impossible to study and give unique insights into accretion physics as we can see the accretion turn on and turn off.
TDEs have only begun to be discovered in significant numbers in the last few years, as all-sky surveys like ASAS-SN have become more common, and still have not been discovered in large enough numbers to develop general theoretical models for TDE emission. ASAS-SN in particular has been a significant source of new TDE discoveries, finding or detecting 10 since 2014. A primary focus of my research has been to obtain high-quality, multi-wavelength datasets for these TDEs in order to build a large sample of well-observed TDEs with which to test our theoretical models of TDE emission and study black holes and accretion. Because TDE emission is often dominated by UV and X-ray emission, these studies have involved data from space telescopes like Swift, Hubble, and Chandra as well as numerous ground-based telescopes.
In addition to early follow-up after discovery, I am also interested in late-time (years after discovery) emission from TDEs, as these observations can illuminate properties of the stellar debris and accretion disk that can't be studied with early emission. I have ongoing projects to continue observing nearby TDEs and their hosts with the Magellan and LBT telescopes to obtain late-time data that has not previously existed.
For more about the TDE papers I have led or been heavily involved in, please see below.
Holoien, T. W.-S. et al., Submitted to ApJ (2018)
This is a discovery paper for the TDE PS18kh combining data from Pan-STARRS, ASAS-SN, and ATLAS and using a non-axisymmetric disk model to fit the double-peaked spectroscopic emission lines.
Holoien, T. W.-S. et al., MNRAS 480, 5689 (2018)
This paper presents observations of ASASSN-15oi going out to 600 days after discovery and discusses its unusual late-time X-ray brightening.
Holoien, T. W.-S. et al., MNRAS 463, 3813 (2016)
This discovery paper for ASASSN-15oi presents our early light curves and spectra for this nearby TDE.
Holoien, T. W.-S. et al., MNRAS 455, 2918 (2016)
This is a discovery paper for ASASSN-14li, the brightest TDE ever discovered, which has been extensively studied from X-ray through radio wavelengths.
Holoien, T. W.-S. et al., MNRAS 445, 3263 (2014)
This is a discovery paper for ASASSN-14ae, the first TDE discovered by ASAS-SN. It was the subject of an OSU press release.
Brown, J. S., Kochanek, C. S., Holoien, T. W.-S. et al., MNRAS, 473, 1130 (2018)
Brown, J. S., Holoien, T. W.-S. et al., MNRAS, 466, 4904 (2017)
Brown, J. S., Shappee, B. J., Holoien, T. W.-S. et al., MNRAS, 462, 3993 (2016)
Banner image credit NASA/JPL-Caltech.