Naslov
Binary supermassive black hole candidate in Stripe 82 region

Autori
Fatović, Marta ; Palaversa, Lovro ; Tisanić, Krešimir ; Thanjavur, Karun ; Ivezić, Željko ; Kovačević, Anđelka ; Ilić, Dragana ; Popović, Luka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, neobjavljeni rad, znanstveni

Skup
Transient sky with Gaia

Mjesto i datum
Coimbra, Portugal, 13.10.2022. - 14.10.2022

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Podatak o recenziji nije dostupan

Ključne riječi
Astronomy data analysis ; Period determination ; Time series analysis ; Quasars

Sažetak
I will report the results of a search for long-period P = [100, 600] days sources with small-amplitude (A larger than 0.03 mag) periodic variability in SDSS Stripe 82 region. The SDSS coverage of Stripe 82 enables such a search because there are on average 20 observations per band in ugriz bands for about 1 million sources, collected over about 6 years, with a faint limit of r~22 mag and precisely calibrated 1-2% photometry. Lomb-Scargle periodograms of candidate variable sources from this sample were calculated and carefully scrutinized in order to select only those sources with the highest likelihood of being true periodic variables and avoid the possibility of false periodicity caused by stochastic variability. In addition to periodogram analysis, we cross-matched the candidate periodically variable sources to other surveys across the EM spectrum (photometry and spectroscopy) in order to confirm their variability, its origin and the type of the source. Our analysis yields 11 candidate periodically variable sources and is reinforced by Pan-STARRS and ZTF time series extending the observational baseline to more than 20 years. Furthermore, most of the candidates have optical spectra that allowed determination of the type of the source. The candidate list is dominated by quasars (inferred from the spectroscopy). The highest-ranked candidate has a spectrum consistent with a quasar and a period of 278 days. It is furthermore flagged as a variable source in the Chandra X-ray catalogue. Multiple explanations for the observed periodic behaviour of quasars are found in the literature: radio jet precession, tilted or warped accretion disks, tidal disruption remnants and other accretion-related effects. While these effects can be caused by a single black hole, most models require super-massive binary black holes (SMBBH). If this object indeed proves to be a SMBBH -- one of the loudest sources of gravitational waves, it would become the SMBBH with the shortest known period and therefore likely most compact orbit and remaining time before the merger and emission of GWs. In order to ascertain the nature of this object, and hopefully prepare for longer-term monitoring of it and similar systems, we have received 2.18hrs of Director's Discretionary Time on Gemini telescope’s GMOS-N instrument. This will allow us to study the conspicuous Mg II line visible in extant spectra of lower resolution and signal-to-noise ratio for the presence of asymmetries and additional peaks that could indicate the presence of SMBBH. I would also like to put these finding into the context of future Gaia data releases and time-domain surveys such as Vera C. Rubin Legacy Survey of Space and Time. It has been shown that full 10-year Gaia data could astrometrically resolve orbital motion of final-stage (sub-pc separation) SMBBHs up to z=0.02 and in the magnitude range V = [10, 13] (D’Orazio and Loeb, 2019). On the other hand, LSST’s etendue and expected exquisite photometric precision will allow searches in a much larger volume.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

POVEZANOST RADA