Nagymennyiségű változócsillagászati észlelések feldolgozása és analízise = Reduction and analysis of large-scale variable star data sets

A következő három fő témakört vizsgáltuk: (a) periodikus tranzit detektálás és extraszolaris bolygók vizsgálata a HATNet es a WHAT automata távcsövek észlelései alapján; (b) a MACHO adatbázis RR Lyrae csillagainak periódus analízise; (c) pulzáló változócsillagok elméleti és empirikus vizsgálata. A következő eredményeket kaptuk. Téma (a): kis apertúrájú, teljesen automatizált távcsövek alkalmasak néhány millimagnitúdó pontosságú észlelésekre és forró Jupiterek (HJ-k) detektálására; a BLS algoritmusunk hatásos eszköz periodikus tranzitok keresésében; az adatfeldolgozás miatt fellépő szisztematikák kiszűrésének hatékony eszköze a TFA algoritmusunk; a HD 189733 HJ rendszer valójában egy hármas rendszer, K fő- es M másod-komponensekkel, valamint a főkomponens körül keringő bolygóval. Téma (b): az LMC-ben található alapmódusú RR Lyrae csillagok 12%-a mutat Blashko jelenséget. Ez az érték szignifikánsan magasabb, mint az újabb analizisünk alapján az első felhangú csillagokra kapott gyakoriság, amely a rendelkezésre álló adatok felhasználásával 7.5%-nak adódott. Téma (c): nincs ellentmondás az RR Lyrae és a Cepheida változók alapján a Baade-Wesselink módszer segítségével számított távolságok között. Az LMC távolságára konzisztens értékeket kaptunk; több irreguláris változó fénygörbéjének analizálása alapján további megerősítést kaptunk ezen csillagok kaotikus pulzációjára. | We have investigated the following three major topics: (a) periodic transit detection and extrasolar planetary studies based on large-scale photometric databases of the HATNet and WHAT automated telescopes; (b) frequency analysis of RR Lyrae stars in the MACHO database; (c) theoretical and empirical stellar pulsation studies. We obtained the following results. Topic (a): small aperture fully automated telescopes are able to gather few millimag precision photometric data and detect transits caused by hot Jupiters; our BLS algorithm is very efficient in searching for periodic transits; the effects of systematics due to errors in the data acquisition can be successfully filtered by our TFA algorithm; the hot Jupiter system HD 189733 is a triple system with a K primary and M secondary and the planet orbiting the primary. Topic (b): the incidence rate of the Blazhko stars pulsating in the fundamental mode is 12% in the LMC. This is significantly higher than that of the first overtone Blazhko stars (which is 7.5%, according to our new analysis of all available data. Topic (c): there is no contradiction between the distances derived by Baade-Wesselink analyses of RR Lyrae and Cepheid variables and they both yield consistent distances for the LMC; by analyzing the archival data of several irregular variables, we got further support for the presence of chaotic pulsations in these stars

VARTOOLS: A Program for Analyzing Astronomical Time-Series Data

This paper describes the VARTOOLS program, which is an open-source command-line utility, written in C, for analyzing astronomical time-series data, especially light curves. The program provides a general-purpose set of tools for processing light curves including signal identification, filtering, light curve manipulation, time conversions, and modeling and simulating light curves. Some of the routines implemented include the Generalized Lomb-Scargle periodogram, the Box-Least Squares transit search routine, the Analysis of Variance periodogram, the Discrete Fourier Transform including the CLEAN algorithm, the Weighted Wavelet Z-Transform, light curve arithmetic, linear and non-linear optimization of analytic functions including support for Markov Chain Monte Carlo analyses with non-trivial covariances, characterizing and/or simulating time-correlated noise, and the TFA and SYSREM filtering algorithms, among others. A mechanism is also provided for incorporating a user's own compiled processing routines into the program. VARTOOLS is designed especially for batch processing of light curves, including built-in support for parallel processing, making it useful for large time-domain surveys such as searches for transiting planets. Several examples are provided to illustrate the use of the program.Comment: 83 pages, 5 figures, accepted for publication in Astronomy and Computing, code available at http://www.astro.princeton.edu/~jhartman/vartools.htm

Testing the Titius-Bode law predictions for Kepler multi-planet systems

We use three and half years of Kepler Long Cadence data to search for the 97 predicted planets of Bovaird & Lineweaver (2013) in 56 of the multi-planet systems, based on a general Titius-Bode relation. Our search yields null results in the majority of systems. We detect five planetary candidates around their predicted periods. We also find an additional transit signal beyond those predicted in these systems. We discuss the possibility that the remaining predicted planets are not detected in the Kepler data due to their non-coplanarity or small sizes. We find that the detection rate is beyond the lower boundary of the expected number of detections, which indicates that the prediction power of the TB relation in general extra solar planetary systems is questionable. Our analysis of the distribution of the adjacent period ratios of the systems suggests that the general Titius-Bode relation may over-predict the presence of planet pairs near the 3:2 resonance.Comment: Accepted by MNRA

Extraszoláris bolygó és változócsillag kutatás nagylátómezejű fotometriával = Extrasolar planet and variable star research by wide-field photometry

A kis-teleszkópos/nagy-látószögű fotometriai feltérképező programjaink (HATNet es WHAT) segítségével 13 fedési extraszoláris bolygót (TEP-et) fedeztünk fel. Tömegük a Neptunétól egészen a barna törpe csillagok határához közeli értékekig terjednek (a Jupiter tömegének 8%-nak megfelelő tömegű HAT-P-11b-től a HAT-P-2b-ig, melynek tömege a Jupiterének 9-szerese). Több, a Jupiter tömegénél alacsonyobb tömegű bolygók között az alacsony tartományban kiemelekedik a HAT-P-12b, amelynek tömege a Szaturnuszénak 2/3-a. A keringési periódusok a 2 és 5.6 nap közötti tartományban szóródnak, melyek közül a leghosszabb az összes (szám szerint 69) TEP hosszú-periódus tartományának végén (annak 10%-ban) található. Más paraméterek, mint például a sűrűség vagy a pálya excentricitás, szintén széles tartományt fednek le. Fontos megemlíteni a HAT-P-13b,c-t, amely az első olyan többszörös bolygórendszer, amelynek az egyik (a rövidebb periódusú) tagja egyben fedési bolygó is. A pulzáló csillagok területén megmutattuk, hogy pulzációs és fejlődési modellek felhasználásával csupán a periódusok ismeretében lehetséges a kétmódusú RR Lyrae csillagok paramétereinek meghatározása. Ezek a paraméterek jó egyezést mutatnak a független módon meghatározott mennyiségekkel, mint példaul a fémességgel, hőmérséklettel és távolsággal. | Within the small telescope/wide field of view photometric survey projects HATNet and WHAT, we have discovered 13 transiting extrasolar planets (TEPs) spanning from the mass of Neptune (HAT-P-11b with mass 8% that of the Jupiter) to near the brown dwarf limit (HAT-P-2b, with 9 Jupiter masses). We also have a planet (HAT-P-12b) with a mass two-third that of the Saturn and several others in the sub-Jupiter mass range. Orbital periods range from 2 days to 5.6 days, the latter value is in the upper 10% at the long period tail of the 69 TEPs discovered so far. Other parameters, such as eccentricity and density also span wide ranges. We highlight HAT-P-13b,c, the first multiple system, in which the short-periodic component is transiting. In the field of pulsating variables we have shown that the physical parameters for double-mode RR Lyrae stars derived solely from their periods by using evolutionary and pulsation models are in good agreement with other, independently computed quantities, such as metallicity, temperature and distance

Determination of stellar, orbital and planetary parameters using complete Monte-Carlo analysis -- the case of HAT-P-7b

The recently discovered transiting very hot Jupiter, HAT-P-7b, a planet detected by the telescopes of HATNet, turned out to be among the ones subjected to the highest irradiation from the parent star. As known, the combination of photometric and spectroscopic data for such an object yields the stellar, orbital and planetary parameters. In order to best characterize this particular planet, we carried out a complex analysis based on a complete and simultaneous Monte-Carlo solution using all available data. We included the discovery light curves, partial follow-up light curves, the radial velocity data, and we used the stellar evolution models to infer the stellar properties. This self-consistent way of modeling provides the most precise estimate of the a posteriori distributions of all of the system parameters of interest, and avoids making assumptions on the values and uncertainties of any of the internally derived variables describing the system. This analysis demonstrates that even partial light curve information can be valuable. This may become very important for future discoveries of planets with longer periods -- and therefore longer transit durations -- where the chance of observing a full event is small.Comment: 4 pages, 2 figures. To appear in the Proceedings of IAU Symposium 253, "Transiting Planets", May 2008, Cambridge, MA, US

Astrometric exoplanet detection with Gaia

We provide a revised assessment of the number of exoplanets that should be discovered by Gaia astrometry, extending previous studies to a broader range of spectral types, distances, and magnitudes. Our assessment is based on a large representative sample of host stars from the TRILEGAL Galaxy population synthesis model, recent estimates of the exoplanet frequency distributions as a function of stellar type, and detailed simulation of the Gaia observations using the updated instrument performance and scanning law. We use two approaches to estimate detectable planetary systems: one based on the S/N of the astrometric signature per field crossing, easily reproducible and allowing comparisons with previous estimates, and a new and more robust metric based on orbit fitting to the simulated satellite data. With some plausible assumptions on planet occurrences, we find that some 21,000 (+/-6000) high-mass (1-15M_J) long-period planets should be discovered out to distances of ~500pc for the nominal 5-yr mission (including at least 1000-1500 around M dwarfs out to 100pc), rising to some 70,000 (+/-20,000) for a 10-yr mission. We indicate some of the expected features of this exoplanet population, amongst them ~25-50 intermediate-period (P~2-3yr) transiting systems.Comment: 41 pages, 12 figures; accepted for publication in Ap

HAT-P-68b: A TRANSITING HOT JUPITER AROUND A K5 DWARF STAR

We report the discovery by the ground-based HATNet survey of the transiting exoplanet HAT-P-68b, which has a mass of 0.724 ± 0.043 M_Jupiter , and radius of 1.072 ± 0.012 R_Jupiter. The planet is in a circular P = 2.2984 day orbit around a moderately bright V = 13.937 ± 0.030 magnitude K dwarf star of mass 0.673 M_Sun , and radius 0.6726 ± 0.0069 R_Sun . The planetary nature of this system is confirmed through follow-up transit photometry obtained with the FLWO 1.2 m telescope, high-precision RVs measured using Keck-I/HIRES, FLWO 1.5 m/TRES, and OHP 1.9 m/Sophie, and high-spatial-resolution speckle imaging from WIYN 3.5 m/DSSI. HAT-P-68 is at an ecliptic latitude of +3degrees and outside the field of view of both the NASA TESS primary mission and the K2 mission. The large transit depth of 0.036 mag (r-band) makes HAT-P-68b a promising target for atmospheric characterization via transmission spectroscopy