# Cy 7- Studying Black Holes in the Local Universe: Swift Follow-Up of Tidal Flares

Project: Research project

## Project Details

### Description

Stars passing within a distance of $\sim 5 M_7^{-2/3}$ Schwarschild radii of a massive black hole of mass $M_{\rm BH} = 10^7 \, M_7 \,M_\odot$ are ripped apart by the strong tidal gravitational field of the black hole. Tidal disruption of stars by massive black holes is predicted to be an inevitable consequence of the presence of massive black holes (MBHs) in galactic nuclei \citep{rees}. Even absent any other source of fuel, this should give rise to a detectable flare of radiation from black holes with masses $M_{\rm BH} \lessim 10^8 M_\odot$ (for more massive black holes the star is disrupted inside the horizon). Detection and characterization of tidal flares would open up a new window onto accretion physics close to MBHs. The proposed observations will allow us to estimate the black hole mass (and maybe spin) based on the specifics of the time decay. Perhaps more importantly, theoretical rates suggest that tidal disruption of stars may be the dominant source of growth for black holes with masses $\lessim 10^6-10^7 M_\odot$ \citep{mt99,wnm04}. Here we propose Swift ToO observations of two promising tidal flare events discovered by the Palomar Transients Factory (PTF), with additional triggers possible from the Allen Telescope Array (ATA), the Galaxy Evolution Explorer (GALEX), the Robotic Optical Transient Search Experiment (ROTSE), or the Catalina Sky Survey (CSS). The XRT and UVOT (and correlated ground-based) observations offer the unique potential to determine for the first time the broadband spectral and temporal properties.
Status Finished 3/28/12 → 3/27/13

### Funding

• NASA: Goddard Space Flight Center: \$15,000.00

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