NOAO >   Observing Info >   Approved Programs >   2018A-0176

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Program Information for 2018A-0176


PI: Stephen Cenko, NASA Goddard Space Flight Center, brad.cenko@nasa.gov
Address: USA

CoI: Nadia Blagorodnova, California Institute of Technology
CoI: Suvi Gezari, U. of Maryland
CoI: Erin Kara, U. of Maryland
CoI: Shri Kulkarni, California Institute of Technology
CoI: Nathan Roth, U. of Maryland
CoI: Sylvain Veilleux, U. of Maryland
CoI: Lin Yan, California Institute of Technology
CoI: Sjoert van Velzen, Johns Hopkins U.

Title: Multi-Wavelength Spectroscopy of Tidal Disruption Flares: A Legacy Sample for the LSST Era

Abstract: This is part of a joint HST-NOAO Cycle 25 proposal for which we were awarded 20 hours of Gemini North+GMOS observations (NOAO ID = 17B-0913); here we request 7 hours of that time in Semester 2018A. When a star passes within the sphere of disruption of a massive black hole, tidal forces will overcome self-gravity and unbind the star. While approximately half of the stellar debris is ejected at high velocities, the remaining material stays bound to the black hole and accretes, resulting in a luminous, long-lived transient known as a tidal disruption flare (TDF). In addition to serving as unique laboratories for accretion physics, TDFs offer the hope of measuring black hole masses in galaxies much too distant for resolved kinematic studies. In order to realize this potential, we must better understand the detailed processes by which the bound debris circularizes and forms an accretion disk. Spectroscopy is critical to this effort, as emission and absorption line diagnostics provide insight into the location and physical state (velocity, density, composition) of the emitting gas (in analogy with quasars). UV spectra are particularly critical, as most strong atomic features fall in this bandpass, and high-redshift TDF discoveries from LSST will sample rest-frame UV wavelengths. Here we propose to obtain a sequence of UV (HST) and optical (Gemini/GMOS) spectra for a sample of 5 TDFs discovered by the Zwicky Transient Facility, doubling the number of TDFs with UV spectra. Our observations will directly test models for the generation of the UV/optical emission (circularization vs reprocessing) by searching for outflows and measuring densities, temperatures, and composition as a function of time. This effort is critical to developing the framework by which we can infer black hole properties (e.g., mass) from LSST TDF discoveries.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2018A):  GEM-NQ/GMOSN -- 7hrs band 2 (GN-2018A-Q-233 )


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