The third transit of snow-line exoplanet Kepler-421b

The Kepler Mission has uncovered a handful of long-period transiting exoplanets that orbit from the cold outer reaches of their systems, despite their low transit probabilities. The atmospheres of these cold gas giant exoplanets are amenable to transit transmission spectroscopy enabling tests of planetary formation and evolution theories. Of particular scientific interest is Kepler-421b, a Neptune-sized exoplanet with a 704-day orbital period residing near the snow-line. Since the Kepler Spacecraft only observed two transits of Kepler-421b, the transit ephemeris is relatively uncertain. We observed Kepler-421 during the anticipated third transit of Kepler-421b in order to constrain the existence and extent of transit timing variations (TTVs). Barring significant TTVs, our visible light, time-series observations from the 4.3-meter Discovery Channel Telescope (DCT) were designed to capture pre-transit baseline and the partial transit of Kepler-421b. We find strong evidence in favor of transit models with no TTVs, suggesting that Kepler-421b is either alone in its system or is only experiencing minor dynamic interactions with an unseen companion. With the combined Kepler and DCT observations, we calculate the timing of future transits and discuss the unique opportunity to characterize the atmosphere of this cold, long-period exoplanet via transmission spectroscopy.http://adsabs.harvard.edu/abs/2016DPS....4812208DPublished versio

Observational Effects of Strong Gravity in Vicinity of Supermassive Black Holes

Here we discuss the effects of strong gravity that can be observed in electromagnetic spectra of active galactic nuclei (AGN). According to the unification model of an AGN, there is a supermassive black hole ($10^7 - 10^9 M_\odot$) in its center, surrounded by an accretion disk that radiates in the X-ray band. Accretion disks could have different forms, dimensions, and emission, depending on the type of central black hole (BH), whether it is rotating (Kerr metric) or nonrotating (Schwarzschild metric). We modeled the emission of an accretion disk around supermassive BH using numerical simulations based on a ray-tracing method in the Kerr metric. A broad emission line Fe K$\alpha$ at 6.4 keV with asymmetric profile (narrow bright blue peak and a wide faint red wing) has been observed in a number of type 1 AGN. The effects of strong gravitational field are investigated by comparison between the modeled and observed iron K$\alpha$ line profiles. The results of our modeling show that the parameters of the Fe K$\alpha$ line emitting region have significant influence on the line profile and thus, allow us to determine the space-time geometry (metric) in vicinity of the central BH of AGN, and also can give us information about the plasma conditions in these regions.Comment: 5 pages, 3 figures. Accepted for publication in Fortschr. Phys. (proceedings of the BW2007 WORKSHOP "III Southeastern European Workshop Challenges Beyond the Standard Model"