Two Talks! Speakers: Tingting Liu, University Of Maryland; James Kirk, University Of Warwick

Monday January 22, 2018 12:05 pm
Marlar Lounge 37-252

Supermassive Black Hole Binary Candidates from the Pan-STARRS1 Medium Deep Survey

Speaker: Tingting Liu, University of Maryland

We present a systematic search for periodically varying quasar and supermassive black hole binary (SMBHB) candidates in the Pan-STARRS1 Medium Deep Survey. From ~9,000 color-selected quasars in a ~50 deg^2 sky area, we identify 26 candidates with more than 1.5 cycles of variation. We extend the baseline of observations via our imaging campaign with the Discovery Channel Telescope and the Las Cumbres Observatory network and reevaluate the candidates using a more rigorous, maximum likelihood method; 3 candidates remained significant, if we assume the variability of all normal quasars are characterized by the Damped Random Walk process. The down-selected “gold” sample translates to an SMBHB rate of 0.3 per 10^3 quasars out to z~2, in tension with previous work by Graham et al. (2015) and Charisi et al. (2016). We also find that the binary residence times of the “gold” sample are best matched to the expected distribution if the mass ratio q = 0.3. Using our study with MDS as a benchmark, we estimate that ~10,000 periodic quasars with more than 3 cycles could be discovered by the Large Synoptic Survey Telescope, paving the way for the direct detection of individual gravitational wave sources by future pulsar timing array experiments.

Characterising exoplanet atmospheres as part of the LRG-BEASTS survey

Speaker: James Kirk, University of Warwick

Studies of exoplanet atmospheres have revealed a startling diversity between systems, with many showing clouds and hazes which mask pressure-broadened absorption features. In the small sample of planets studied to date, no strong correlation has emerged between key planetary parameters and the presence, or absence, of clouds and hazes, although there is evidence that temperature might play a role. In order to characterise this diversity and unravel the underlying physical processes, it is essential that we expand the current sample of studied planets. This is the focus of the Low Resolution Ground-Based Exoplanet Atmosphere Survey using Transmission Spectroscopy (LRG-BEASTS, “large beasts”). I will present the latest results from LRG-BEASTS which is pioneering the use of 4-metre class telescopes for transmission spectroscopy.