Astrokit -- an Efficient Program for High-Precision Differential CCD Photometry and Search for Variable Stars

Having a need to perform differential photometry for tens of thousands stars in a several square degrees field, we developed Astrokit program. The software corrects the star brightness variations caused by variations of atmospheric transparency: to this end, the program selects for each star an individual ensemble of reference stars having similar magnitudes and positions in the frame. With ten or more reference stars in the ensemble, the differences between their spectral types and the spectral type of the object studied become unimportant. Astrokit searches for variable stars using Robust Median Statistics criterion, which allows candidate variables to be selected more efficiently than by analyzing the standard deviation of star magnitudes. The software allows very precise automatic analysis of long inhomogeneous sets of photometric observations of a large number of objects to be performed, making it possible to find "hot Jupiter" type exoplanet transits and low-amplitude variables. We describe the algorithm of the program and the results of its application to reduce the data of the photometric sky survey in Cygnus as well as observations of the open cluster NGC188 and the transit of the exoplanet WASP-11 b / HAT-P-10 b, performed with the MASTER-II-URAL telescope of the Kourovka Astronomical Observatory of the Ural Federal University.Comment: to be published in Astrophysical Bulletin, Vol. 69, No.

First results of the Kourovka Planet Search: discovery of transiting exoplanet candidates in the first three target fields

We present the first results of our search for transiting exoplanet candidates as part of the Kourovka Planet Search (KPS) project. The primary objective of the project is to search for new hot Jupiters which transit their host stars, mainly in the Galactic plane, in the $R_c$ magnitude range of 11 to 14 mag. Our observations were performed with the telescope of the MASTER robotic network, installed at the Kourovka astronomical observatory of the Ural Federal University (Russia), and the Rowe-Ackermann Schmidt Astrograph, installed at the private Acton Sky Portal Observatory (USA). As test observations, we observed three celestial fields of size $2\times2$ deg$^2$ during the period from 2012 to 2015. As a result, we discovered four transiting exoplanet candidates among the 39000 stars of the input catalogue. In this paper, we provide the description of the project and analyse additional photometric, spectral, and speckle interferometric observations of the discovered transiting exoplanet candidates. Three of the four transiting exoplanet candidates are most likely astrophysical false positives, while the nature of the fourth (most promising) candidate remains to be ascertained. Also, we propose an alternative observing strategy that could increase the project's exoplanet haul.Comment: 11 pages, 16 figures; Accepted for publication in Monthly Notices of the Royal Astronomical Society 201

Benchmarking the power of amateur observatories for TTV exoplanets detection

We perform an analysis of ~80 000 photometric measurements for the following 10 stars hosting transiting planets:WASP-2, -4, -5, -52, Kelt-1, CoRoT-2, XO-2, TrES-1, HD 189733, GJ 436. Our analysis includes mainly transit light curves from the Exoplanet Transit Database, public photometry from the literature, and some proprietary photometry privately supplied by other authors. Half of these light curves were obtained by amateurs. From this photometry we derive 306 transit timing measurements, as well as improved planetary transit parameters. Additionally, for 6 of these 10 stars we present a set of radial velocity measurements obtained from the spectra stored in the HARPS, HARPS-N and SOPHIE archives using the HARPS- TERRA pipeline. Our analysis of these transit timing and radial velocity data did not reveal significant hints of additional orbiting bodies in almost all of the cases. In the WASP-4 case, we found hints of marginally significant TTV signals having amplitude 10-20 s, although their parameters are model dependent and uncertain, while radial velocities did not reveal statistically significant Doppler signals.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

SPECULOOS: a network of robotic telescopes to hunt for terrestrial planets around the nearest ultracool dwarfs

We present here SPECULOOS, a new exoplanet transit search based on a network of 1m-class robotic telescopes targeting the $\sim$1200 ultracool (spectral type M7 and later) dwarfs bright enough in the infrared ($K$-mag $\leq 12.5$) to possibly enable the atmospheric characterization of temperate terrestrial planets with next-generation facilities like the $\textit{James Webb Space Telescope}$. The ultimate goals of the project are to reveal the frequency of temperate terrestrial planets around the lowest-mass stars and brown dwarfs, to probe the diversity of their bulk compositions, atmospheres and surface conditions, and to assess their potential habitability.Comment: 21 pages, 13 figures, 1 table. Proceedings of SPI

Fancine 2003, n. 08

Abstract not availabl

Transit timing analysis of the exoplanet TrES-5 b. Possible existence of the exoplanet TrES-5 c

peer reviewedIn this work, we present transit timing variations detected for the exoplanet TrES-5b. To obtain the necessary amount of photometric data for this exoplanet, we have organized an international campaign to search for exoplanets based on the transit-timing variation (TTV) method and as a result of this we collected 30 new light curves, 15 light curves from the Exoplanet Transit Database (ETD) and 8 light curves from the literature for the timing analysis of the exoplanet TrES-5b. We have detected timing variations with a semi-amplitude of A≈ 0.0016 d and a period of P≈ 99 d. We carried out the N-body modelling based on the three-body problem. The detected perturbation of TrES-5b may be caused by a second exoplanet in the TrES-5 system. We have calculated the possible mass and resonance of the object: M ≈ 0.24MJup at a 1:2 Resonance. © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.RSF: 14-50-0004

Benchmarking the power of amateur observatories for TTV exoplanets detection

We perform an analysis of ~80 000 photometric measurements for the following 10 stars hosting transiting planets:WASP-2, -4, -5, -52, Kelt-1, CoRoT-2, XO-2, TrES-1, HD 189733, GJ 436. Our analysis includes mainly transit light curves from the Exoplanet Transit Database, public photometry from the literature, and some proprietary photometry privately supplied by other authors. Half of these light curves were obtained by amateurs. From this photometry we derive 306 transit timing measurements, as well as improved planetary transit parameters. Additionally, for 6 of these 10 stars we present a set of radial velocity measurements obtained from the spectra stored in the HARPS, HARPS-N and SOPHIE archives using the HARPS- TERRA pipeline. Our analysis of these transit timing and radial velocity data did not reveal significant hints of additional orbiting bodies in almost all of the cases. In the WASP-4 case, we found hints of marginally significant TTV signals having amplitude 10-20 s, although their parameters are model dependent and uncertain, while radial velocities did not reveal statistically significant Doppler signals.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Early genome size increase in urodeles

AbstractUrodeles have the largest genomes among extant tetrapods, varying greatly between metamorphic and neotenic species, which have the smallest and the largest genomes of the group, respectively. The evolutionary tempo and mode of genome size expansion in urodeles are poorly documented, especially because genome size does not directly fossilize. Consequently, the ancestral state for genome size, and therefore, the polarity of its evolution in urodeles are uncertain. However, recent studies have demonstrated that osteocyte (lacuna) size is correlated with genome size. Below, we present histological data, on osteocyte lacuna size from one of the oldest known stem-urodeles, Marmorerpeton, from the Middle Jurassic (Bathonian, 166–168Ma), as well as on five extant urodele species. Our analysis of these taxa, coupled with previously published data, suggests that stem-urodeles had already evolved large genomes, typical of extant urodeles by the Bathonian

The First Post-Kepler Brightness Dips of KIC 8462852

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process