Effect of accreting tidally disrupted stars on the spin evolution of $\sim 10^6{M}_{\odot }$ black holes

Abstract

Accretion of tidally disrupted stars (TDSs) is expected to contribute significantly to the growth of massive black holes (MBHs) with mass $\sim 10^6{M}_{\odot }$ in galactic centers. In this paper, we quantitatively investigate the effect of the TDS accretion on the spin evolution of these relatively small MBHs, by also considering the accretion of gas-clouds with (many) chaotic episodes. We find that the accretion of TDSs can play an important role or even a dominant role in shaping the spin distribution of $\sim 10^6{M}_{\odot }$ MBHs, depending on the contribution fraction ($f_{\mathrm{TDE}}$) of the TDS accretion to the MBH growth. If $f_{\mathrm{TDE}}$ is as large as $\gtrsim 0.9$, most $\sim 10^6{M}_{\odot }$ MBHs have low spins ($|a|\lesssim 0.3$); if $f_{\mathrm{TDE}}$ is as small as $\lesssim 0.1$, most $\sim 10^6{M}_{\odot }$ MBHs have high spins ($|a|\gtrsim 0.7$). We also find that (1) the fraction of highly spinning $\sim 10^6{M}_{\odot }$ MBHs in the TDS accretion states is smaller than that in the gas-cloud (AGN) accretion states, which is a consequence of more rapid spin decrease during the period of consecutive TDS accretion than the spin increase during the AGN periods when the spin is large; (2) the fraction of retrograde spin accretion in the TDS accretion states is almost the same as that of prograde spin accretion, while it is negligible in the gas-cloud (AGN) accretion states. Current scarce sample of AGNs ($\sim 10^6{M}_{\odot }$) with spin measurements hints an insignificant contribution from TDS accretion to MBH growth. Future measurements on spins of $\sim 10^6{M}_{\odot }$ MBHs may provide stronger constraints on the importance of both AGN and TDS accretion states in their growth history.

15pages, 8 figures, to appear in the Astrophysical Journal

References in corpus (17)

• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• Constraining Black Hole Spin Via X-ray Spectroscopy
• The Evolution of Black Hole Mass and Spin in Active Galactic Nuclei
• UV/Optical Detections of Candidate Tidal Disruption Events by GALEX and CFHTLS
• Fuelling Active Galactic Nuclei
• Evolution of tidal disruption candidates discovered by XMM-Newton
• Black-Hole Spin and Galactic Morphology
• Self-gravitating accretion disk in Sgr A* few million years ago: was Sgr A* a failed quasar?
• Measurement of the rate of stellar tidal disruption flares
• A 200-s Quasi-Periodicity Following the Tidal Disruption of a Star by a Dormant Black Hole
• Alignment and Precession of a Black Hole with a Warped Accretion Disc
• Evolution of linear warps in accretion discs and applications to protoplanetary discs in binaries
• The Most Massive Active Black-Holes at z~1.5-3.5 Have High Spins and Radiative Efficiencies
• Contribution of Stellar Tidal Disruptions to the X-Ray Luminosity Function of Active Galaxies
• On Constraining the Growth History of Massive Black Holes via Their Distribution on the Spin-Mass Plane
• Relativistic Fe K$\alpha$ Line Revealed in the Composite X-ray Spectrum of Narrow Line Seyfert 1 Galaxies --- do their black holes have averagely low or intermediate spins?
• The molecular H2 and stellar discs in the nuclear region of NGC 4258

Cited by in corpus (7)

• A Tidal Disruption Event Candidate Discovered in the Active Galactic Nucleus SDSS J022700.77-042020.6
• Effects of spin on constraining the seeds and growth of $\gtrsim 10^9{M}_{\odot }$ supermassive black holes in $z>6.5$ Quasars
• The correlations of stellar tidal disruption rates with properties of massive black holes and their host galaxies
• Growth of A Massive Black Hole Via Tidal Disruption Accretion
• Radio signals from early direct collapse black holes
• On the Power to Constrain the Accretion History of Massive Black Holes via Spin Measurements by Upcoming X-Ray Telescopes
• The Faintest, Extremely Variable X-ray Tidal Disruption Event from a Supermassive Black Hole Binary?