Using Campaign 15 data from the K2 mission, we have discovered a triply-eclipsing triple star system: EPIC 249432662. The inner eclipsing binary system has a period of 8.23 days, with shallow ∼3% eclipses. During the entire 80-day campaign, there is also a single eclipse event of a third-body in the system that reaches a depth of nearly 50% and has a total duration of 1.7 days, longer than for any previously known thirdbody eclipse involving unevolved stars. The binary eclipses exhibit clear eclipse timing variations. A combination of photodynamical modeling of the lightcurve, as well as seven follow-up radial velocity measurements, has led to a prediction of the subsequent eclipses of the third star with a period of 188 days. A campaign of follow-up groundbased photometry was able to capture the subsequent pair of third-body events as well as two further 8-day eclipses. A combined photo-spectro-dynamical analysis then leads to the determination of many of the system parameters. The 8-day binary consists of a pair of M stars, while most of the system light is from a K star around which the pair of M stars orbits.1 In this paper, we use the following notations. The orbital elements of the inner and outer orbits are subscripted by numbers '1' and '2', respectively. Regarding the three stars, we label them as A, Ba, and Bb, where A denotes the brightest and most massive component, i.e., the distant, third star, while Ba and Bb refer to the primary and the secondary components of the close, inner 8-day binary. When we refer to physical quantities of individual stars, we use these subscripts. In such a way, for example, m A or m Ba stands for the masses of components A or Ba, respectively, but m B denotes the total mass of the inner binary, (m Ba + m Bb ), while m AB refers to the total mass of the entire triple system.

We monitored the Seyfert-1 galaxy 3C 120 between September 2014 and March 2015 at the Universitätssternwarte Bochum near Cerro Armazones in BVRI JK and a narrowband filter covering the redshifted Hα line. In addition we obtained a single contemporary spectrum with the spectrograph FAST at Mt. Hopkins. Compared to earlier epochs 3C 120 is about a factor of three brighter, allowing us to study the shape of the broad line region (BLR) and the dust torus in a high luminosity phase. The analysis of the light curves yields that the dust echo is rather sharp and symmetric in contrast to the more complex broad Hα BLR echo. We investigated how far this supports an optically thick bowl-shaped BLR and dust torus geometry.The comparison with several parameterizations of these models supports the following geometry: The BLR clouds lie inside the bowl closely above the bowl rim up to a halfcovering angle 0 • < θ < 40 • (measured against the equatorial plane). Then the BLR is spread over many isodelay surfaces, yielding a smeared and structured echo as observed. Furthermore, if the BLR clouds shield the bottom of the bowl rim against radiation from the nucleus, the hot dust emission comes essentially from the top edge of the bowl (40 • < θ < 45 • ). Then, for small inclinations as for 3C120, the top dust edge forms a ring that largely coincides with a narrow range of isodelay surfaces, yielding the observed sharp dust echo. The scale height of the BLR increases with radial distance from the black hole (BH). This leads to luminosity dependent foreshortening effects of the lag. We discuss the implications and possible corrections of the foreshortening for the BH mass determination and consequences for the lag (size) -luminosity relationships and the difference from interferometric torus sizes.

We monitored the z = 0.158 quasar 3C 273 between 2015 and 2019 in the optical (BVrz) and near-infrared (JHK) with the aim to perform dust reverberation mapping. Accounting for host galaxy and accretion disk contributions, we obtained pure dust light curves in JHK. Cross correlations between the V band and the dust light curves yield an average rest-frame delay for the hot dust of τ cent ∼ 410 days. This is a factor of two shorter than that expected from the the dust ring radius R x  ∼ 900 lt-day reported from interferometric studies. The dust covering factor (CF) is about 8%, much smaller than that predicted from the half covering angle of 45° found for active galactic nuclei (AGNs). We analyze the asymmetric shape of the correlation functions and explore whether an inclined biconical bowl-shaped dust torus geometry could bring these findings (τ cent, R x and CF) into a consistent picture. The hot varying dust emission originates from the edge of the bowl rim with a small covering angle 40° < θ < 45°, and we see only the near side of the biconus. Such a dust gloriole with R x  = 900 ± 200 lt-day and an inclination 12° matches the data remarkably well. Comparing the results of 3C 273 with literature for less luminous AGN, we find a lag–luminosity relation τ ∝ L α with α = 0.33–0.40, flatter than the widely adopted relation with α ∼ 0.5. We address several explanations for the new lag–luminosity relation.

We present the results of a two year optical continuum photometric reverberation mapping campaign carried out on the nucleus of the Seyfert-1 galaxy Mrk509. Specially designed narrow-band filters were used in order to mitigate the line and pseudo-continuum contamination of the signal from the broad line region, while allowing for high-accuracy flux-calibration over a large field of view. We obtained light curves with a sub-day time sampling and typical flux uncertainties of 1%. The high photometric precision allowed us to measure inter-band continuum time delays of up to ∼2 days across the optical range. The time delays are consistent with the relation τ∝λ4/3 predicted for an optically thick and geometrically thin accretion disk model. The size of the disk is, however, a factor of 1.8 larger than predictions based on the standard thin-disk theory. We argue that, for the particular case of Mrk509, a larger black hole mass due to the unknown geometry scaling factor can reconcile the difference between the observations and theory.