NOAO >   Observing Info >   Approved Programs >   2018A-0046

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Program Information for 2018A-0046


PI: Yue Shen, U. of Illinois Urbana-Champaign, shenyue@illinois.edu
Address: Department of Astronomy, 103 Astronomy Building, 1002 West Green Street, Urbana, IL, 61801 USA

CoI: Xin Liu, U. of Illinois Urbana-Champaign
CoI: Nick Rumbaugh, U. of Illinois Urbana-Champaign
CoI: Wayne Barkhouse, U. of North Dakota

Title: GMOS Spectrocopy of Candidate Changing-Look Quasars

Abstract: Changing-look quasars (CLQs) are a rare phenomenon where a quasar undergoes a dramatic changes in continuum flux (i.e., by a factor of several), often accompanied by large changes in the broad line flux as well, leading to an apparent "type transition" between a broad-line (Type 1) object and a narrow-line (Type 2) object. The exact origin for the changing-look behavior is unknown, but spectroscopic observations of ~ a dozen of confirmed CLQs suggest that a dramatic change in the accretion rate is the cause in most of these events. The relatively short timescale (e.g., multi-years) over which a CLQ is observed challenges theoretical models of accretion flows in quasars. Here we propose to observe 16 candidate CLQs selected from the combined decade-long photometric light curves from SDSS and the Dark Energy Survey with GMOS spectroscopy. All these targets had dimmed by >1.5 magnitude (g band) in their DES epochs with respect to the earlier SDSS epochs. By comparing the new spectrum taken at the dim state with the SDSS spectrum at the bright state, we will confirm their CLQ nature with broad-line measurements. Furthermore, we will test alternative scenarios such as extinction and reddening to explain the CLQ phenomenon with spectral analysis. The confirmation of these CLQs will greatly increase the inventory of these rare systems, and enable a statistical study of their properties compared to normal quasars, which in turn will shed light on the nature of their extreme variability.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2018A):  GEM-SQ/GMOSS -- 16.4hrs band 1 (GS-2018A-Q-106 )


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2018A-0046

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