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Program Information for 2019B-0219


PI: Xin Liu, U. of Illinois Urbana-Champaign, xinliuxl@illinois.edu
Address: Astronomy Department, 1002 W. Green ST, Urbana, IL 61801 United States

CoI: Tony Yu-Ching Chen, U. of Illinois Urbana-Champaign
CoI: Wei-Ting Liao, U. of Illinois Urbana-Champaign
CoI: A Miguel Holgado, U. of Illinois Urbana-Champaign
CoI: Robert Gruendl, U. of Illinois Urbana-Champaign
CoI: Eric Morganson, National Center for Supercomputing Applications
CoI: Felipe Menanteau, National Center for Supercomputing Applications
CoI: Yue Shen, U. of Illinois Urbana-Champaign
CoI: Tamara Davis, University of Queensland
CoI: Janie Hoormann, University of Queensland
CoI: Chris Lidman, Australian National U.
CoI: Paul Martini, Ohio State U.
CoI: Brad E Tucker, Australian National U.

Title: Identifying Binary Supermassive Black Holes from Continued DECam Monitoring of DES-SN Quasars

Abstract: We propose CT-4m DECam follow-up imaging to $sim$weekly monitor two Dark Energy Survey Supernova (DES-SN) fields. Our primary goal is to systematically identify candidate binary supermassive black holes from periodically variable quasars. Previous surveys lack the time baseline and/or sensitivity to find robust periodic signals from stochastic quasar variability. Our target fields (S1 and S2; 2.7 deg$^2$ each) are unique in that they are the overlapping region between the DES-SN (2012-- 2018) and SDSS Stripe 82 (1998--2007) surveys. This combined $sim- yr long baseline, as well as its high sensitivity and cadence (for the DES part at least), is crucial to both rejecting false positives and recovering false negatives due to quasar's stochastic, red noise variability. The proposed imaging will bridge the gap between DES-SN and LSST. With the extended baseline at a high sensitivity (similar to the DES part), we will: (i). better determine the robustness of any candidate periodicity by extending the existing light curves (e.g., to $> cycles, a suggested criterion to rule out stochastic variability), (ii). distinguish between different physical periodicity models (e.g., Doppler beaming or intrinsic variation such as from circumbinary accretion variability), and (iii) better constrain parameters such as the binary black hole mass ratio. Multi-band imaging is required to quantify the frequency-dependent variability amplitudes to test theoretical predictions from the Doppler beaming hypothesis. The program will enable the most robust measurement of optical quasar periodicity. The observations will also be valuable for characterizing long-term quasar variability to understand accretion disk physics more generally.

Program Type: Long Term/Extragalactic

Scheduled Nights:
Run 1 (2021B):  CT-4m/DECam -- 2n on Sep 25 2021, Sep 28 2021, Oct 01 2021, Oct 04 2021


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