Berlin Exoplanet Search Telescope Research Articles

The Berlin Exoplanet Search Telescope. II. Catalog of Variable Stars. III. Census of Variable Stars in a Puppis Field

Abstract The Berlin Exoplanet Search Telescope II (BEST II) is a ground-based, small aperture, wide-angle telescope used to search for stellar light variations in the southern hemisphere. We report the results of a monitoring campaign observing a field in the Puppis constellation in late 2011/early 2012. Light curves were obtained for 130,472 stars, out of which we identify 2169 variables, including 1829 newly discovered, 26 previously known, and 314 suspected variable stars. We determine periods and variability class for two previously known, but only suspected to be, variable stars. For eight individual eclipsing binary stars, including the two previously known but unclassified binaries, the system parameters were derived at the epoch of the observation by modeling the light curves. Eventually, in a catalog for all variable stars, we present coordinates, magnitude, and elements of light variations, e.g., epoch, period, amplitude, type, and light curves. This catalog concludes the BEST/BEST II project.

THE BERLIN EXOPLANET SEARCH TELESCOPE II CATALOG OF VARIABLE STARS. II. CHARACTERIZATION OF THE CoRoT SRc02 FIELD

ABSTRACT Time-series photometry of the CoRoT field SRc02 was obtained by the Berlin Exoplanet Search Telescope II (BEST II) in 2009. The main aim was to conduct a ground-based follow-up of the CoRoT field in order to detect variable stars with better spatial resolution than what can be achieved with the CoRoT Space Telescope. A total of 1846 variable stars were detected, of which only 30 have been previously known. For nine eclipsing binaries the stellar parameters were determined by modeling their light curves.

VARIABILITY SURVEY IN THECoRoTSRa01 FIELD: IMPLICATIONS OF ECLIPSING BINARY DISTRIBUTION ON CLUSTER FORMATION IN NGC 2264

Time-series photometry of the CoRoT field SRa01 was carried out with the Berlin Exoplanet Search Telescope II (BEST II) in 2008/2009. A total of 1,161 variable stars were detected, of which 241 were previously known and 920 are newly found. Several new, variable young stellar objects have been discovered. The study of the spatial distribution of eclipsing binaries revealed the higher relative frequency of Algols toward the center of the young open cluster NGC 2264. In general Algol frequency obeys an isotropic distribution of their angular momentum vectors, except inside the cluster, where a specific orientation of the inclinations is the case. We suggest that we see the orbital plane of the binaries almost edge-on.

IMPROVED VARIABLE STAR SEARCH IN LARGE PHOTOMETRIC DATA SETS: NEW VARIABLES INCoRoTFIELD LRa02 DETECTED BY BEST II

The CoRoT field LRa02 has been observed with the Berlin Exoplanet Search Telescope II (BEST II) during the southern summer 2007/2008. A first analysis of stellar variability led to the publication of 345 newly discovered variable stars. Now, a deeper analysis of this data set was used to optimize the variability search procedure. Several methods and parameters have been tested in order to improve the selection process compared to the widely used J index for variability ranking. This paper describes an empirical approach to treat systematic trends in photometric data based upon the analysis of variance statistics that can significantly decrease the rate of false detections. Finally, the process of reanalysis and method improvement has virtually doubled the number of variable stars compared to the first analysis by Kabath et al. A supplementary catalog of 272 previously unknown periodic variables plus 52 stars with suspected variability is presented. Improved ephemerides are given for 19 known variables in the field. In addition, the BEST II results are compared with CoRoT data and its automatic variability classification.

A VARIABLE STAR CENSUS IN A PERSEUS FIELD

The Berlin Exoplanet Search Telescope is a small-aperture, wide-field telescope dedicated to time-series photometric observations. During an initial commissioning phase at the Thueringer Landessternwarte Tautenburg, Germany, and subsequent operations at the Observatoire de Haute-Provence, France, a 3.1 {\deg} x 3.1 {\deg} circumpolar field close to the galactic plane centered at ({\alpha}, {\delta}) = (02h 39m 23s, +52{\deg} 01' 46") (J 2000.0) was observed between 2001 August and 2006 December during 52 nights. From the 32129 stars observed, a subsample of 145 stars with clear stellar variability was detected out of which 125 are newly identified variable objects. For five bright objects, the system parameters were derived by modeling the light curve.

PRE-DISCOVERY OBSERVATIONS OF CoRoT-1b AND CoRoT-2b WITH THE BEST SURVEY

The Berlin Exoplanet Search Telescope (BEST) wide-angle telescope installed at the Observatoire de Haute-Provence and operated in remote control from Berlin by the Institut für Planetenforschung, DLR, has observed the CoRoT target fields prior to the mission. The resulting archive of stellar photometric light curves is used to search for deep transit events announced during CoRoT's alarm mode to aid in fast photometric confirmation of these events. The "initial run" field of CoRoT (IRa01) was observed with BEST in 2006 November and December for 12 nights. The first "long run" field (LRc01) was observed from 2005 June to September for 35 nights. After standard CCD data reduction, aperture photometry has been performed using the ISIS image subtraction method. About 30,000 light curves were obtained in each field. Transits of the first detected planets by the CoRoT mission, CoRoT-1b and CoRoT-2b, were found in archived data of the BEST survey and their light curves are presented here. Such detections provide useful information at the early stage of the organization of follow-up observations of satellite alarm-mode planet candidates. In addition, no period change was found over ∼4 years between the first BEST observation and last available transit observations.

Periodic variable stars in CoRoT field LRa02 observed with BEST II

<i>Context. <i/>The Berlin Exoplanet Search Telescope II (BEST II) is a small wide field-of-view photometric survey telescope system located at the Observatorio Cerro Armazones, Chile. The high duty cycle combined with excellent observing conditions and millimagnitude photometric precision makes this instrument suitable for ground based support observations for the CoRoT space mission.<i>Aims. <i/>Photometric data of the CoRoT LRa02 target field collected between November 2008 and March 2009 were analysed for stellar variability. The presented results will help in the future analysis of the CoRoT data, particularly in additional science programs related to variable stars.<i>Methods. <i/>BEST II observes selected CoRoT target fields ahead of the space mission. The photometric data acquired are searched for stellar variability, periodic variable stars are identified with time series analysis of the obtained stellar light curves.<i>Results. <i/>We obtained the light curves of stars in the CoRoT LRa02 field over 41 nights. Variability was detected in light curves of 3726 stars of which 350 showed a regular period. These stars are, with the exception of 5 previously known variable stars, new discoveries.

CHARACTERIZATION OF CoRoT TARGET FIELDS WITH BERLIN EXOPLANET SEARCH TELESCOPE. II. IDENTIFICATION OF PERIODIC VARIABLE STARS IN THE LRc2 FIELD

In this paper we report on observations of the CoRoT LRa1 field with the Berlin Exoplanet Search Telescope (BEST). The current paper is part of the series of papers describing the results of our stellar variability survey. BEST is a small aperture telescope with a wide field-of-view (FOV). It is dedicated to search for stellar variability within the target fields of the CoRoT space mission to aid in minimizing false-alarm rates and identify potential targets for additional science. The LRa1 field is CoRoT's third observed field and the second long run field located in the galactic anticenter direction. We observed the LRa1 stellar field on 23 nights between November and March 2005/2006. From 6099 stars marked as variable, 39 were classified as periodic variable stars and 27 of them are within the CoRoT FOV. We also confirmed the variability for 4 stars listed in GCVS catalog.

CHARACTERIZATION OFCoRoTTARGET FIELDS WITH THE BERLIN EXOPLANET SEARCH TELESCOPE: IDENTIFICATION OF PERIODIC VARIABLE STARS IN THE LRa1 FIELD

In this paper, we report on observations of the CoRoT LRa1 field with the Berlin Exoplanet Search Telescope (BEST). The current paper is part of a series of papers describing the results of our stellar variability survey. The BEST is a small aperture telescope with a wide field of view (FOV). It is dedicated to searching for stellar variability within the target fields of the CoRoT space mission to aid in minimizing false-alarm rates and identify potential targets for additional science. The LRa1 field is CoRoT's second long run field located in the galactic anticenter direction. We observed the LRa1 stellar field on 23 nights between November and March 2005/2006. From 6099 stars marked as variable, 39 were classified as periodic variable stars and 27 of them are within the CoRoT FOV. We also confirmed the variability for four stars listed in the General Catalogue of Variable Stars (GCVS).

Characterization ofCOROTTarget Fields with BEST: Identification of Periodic Variable Stars in the IR01 Field

We report on observations of the COROT IR01 field with the Berlin Exoplanet Search Telescope (BEST). BEST is a small-aperture telescope with a wide field of view (FOV). It is dedicated to searching for variable stars within the target fields of the COROT space mission to aid in minimizing false-alarm rates, and identifying potential targets for additional science. COROT's observational program started in 2007 February, with the initial run field (IR01) observed for about 2 months. BEST observed this field for 12 nights spread over 3 months in winter 2006. From the total of 30,426 stars observed in the IR01 field, 3769 were marked as suspected variable stars, and 54 of these showed clear periodicity. From these, 19 periodic stars are within the part of the COROT FOV covered in our data set.

Identification of Variable Stars inCOROT's First Main Observing Field (LRc1)

The COROT space mission will monitor several target fields for up to 150 days to perform asteroseismology and to search for extrasolar planets by photometric transits. Variable stars in the target fields are important objects for additional scientific studies but can also disturb the search for planetary transits. A variability characterization of the target fields prior to COROT observations is therefore important for two reasons: to find interesting variable stars to monitor further and to make an analysis of the impact of the variable stars on detecting extrasolar planet transits with COROT. The Berlin Exoplanet Search Telescope (BEST) is a small wide-angle telescope dedicated to high-precision photometry. It has observed a 9 deg2 field of view centered at (α, δ) = (19h00m00.0s, + 00°01'55.2'') (J2000.0) over 98 nights to search for variable stars in the surroundings of the first long-run target field (LRc1) of the COROT space mission. In this data set we identified 92 periodic variable stars, 86 of which are new discoveries and 6 of which are known from the General Catalogue of Variable Stars (GCVS). For five of the GCVS stars, variability could not be confirmed. Forty-three of the 92 detected periodic variable stars are identified as eclipsing binaries. We have evaluated the completeness of our survey for eclipsing binaries by comparing it to the expected fraction of eclipsing binaries based on Hipparcos observations. From this evaluation we show that the BEST data set presented here has a completeness of 20%-30% for periods longer than 1 day and is complete relative to Hipparcos for short-period binaries.

New results from BEST: the search for planetary transits

AbstractThe Berlin Exoplanet Search Telescope (BEST) is a small‐aperture, wide‐field telescope dedicated to the search of photometric transits of close‐in Jupiter‐sized exoplanets. Regular observations of several fields have been performed from 2001 to 2003 at Thüringer Landessternwarte Tautenburg, Germany. Planetary transit candidates have been found and followed further with radial velocity measurements. In addition, a substantial number of variable stars have been detected. During the second half of 2004 the system will be relocated to southern France and perform variability characterization of the target fields of the COROT space mission. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

The Berlin Exoplanet Search Telescope System

ABSTRACTWe describe a small telescope system, the Berlin Exoplanet Search Telescope (BEST), dedicated to the search for planetary transits of Jupiter‐sized planets on close‐in orbits. This system consists of a commercial 20 cm telescope equipped with a 2048 × 2048 pixel CCD. Observations have been performed for almost 2 years, including a commissioning phase and regular observations. Planetary transit candidates have been found and followed further with radial velocity measurements. One example is discussed here: transit events detected around GSC 3566‐1556 have been identified as being caused by a binary system consisting of a G0 V primary orbited by an M star. The radii of both stars have been determined.