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G. Pojmanski

Publications and source records attributed to G. Pojmanski.

49 records · Page 3Linked to original sources
arXiv2009

The All Sky Automated Survey. The Catalog of Variable Stars in the Kepler Field of View

We present the catalog of 947 variable stars located in the field of view of the Kepler satellite. The catalog is a result of the analysis of VI photometry obtained during the first 17-month observations in the ASAS3-North station. The variable stars we present are divided into eleven groups according to the presented variability; the groups are briefly discussed. The catalog is intended to be a source of information for target selection process and follow-up programs.

astro-ph.SR↗
arXiv2008

Coronal activity from the ASAS eclipsing binaries

We combine the catalogue of eclipsing binaries from the All Sky Automated Survey (ASAS) with the ROSAT All Sky Survey (RASS). The combination results in 836 eclipsing binaries that display coronal activity and is the largest sample of active binary stars assembled to date. By using the (V-I) colors of the ASAS eclipsing binary catalogue, we are able to determine the distances and thus bolometric luminosities for the majority of eclipsing binaries that display significant stellar activity. A typical value for the ratio of soft X-ray to bolometric luminosity is L_X/L_bol ~ a few x 10^-4, similar to the ratio of soft X-ray to bolometric flux F_X/F_bol in the most active regions of the Sun. Unlike rapidly rotating isolated late-type dwarfs -- stars with significant outer convection zones -- a tight correlation between Rossby number and activity of eclipsing binaries is absent. We find evidence for the saturation effect and marginal evidence for the so-called "super-saturation" phenomena. Our work shows that wide-field stellar variability searches can produce a high yield of binary stars with strong coronal activity. The combined ASAS and RASS catalogue, as well as the results of this work are available for download in a form of a file.

astro-ph↗
arXiv2008

Discovery of a Very Bright, Nearby Gravitational Microlensing Event

We report the serendipitous detection of a very bright, very nearby microlensing event. In late October 2006, an otherwise unremarkable A0 star at a distance ~1 kpc (GSC 3656-1328) brightened achromatically by a factor of nearly 40 over the span of several days and then decayed in an apparently symmetrical way. We present a light curve of the event based on optical photometry from the Center for Backyard Astrophysics and the All Sky Automated Survey, as well as near-infrared photometry from the Peters Automated Infrared Imaging Telescope. This light curve is well-fit by a generic microlensing model. We also report optical spectra, and Swift X-ray and UV observations that are consistent with the microlensing interpretation. We discuss and reject alternative explanations for this variability. The lens star is probably a low-mass star or brown dwarf, with a relatively high proper motion of >20 mas/yr, and may be visible using precise optical/infrared imaging taken several years from now. A modest, all-sky survey telescope could detect ~10 such events per year, which would enable searches for very low-mass planetary companions to relatively nearby stars.

astro-ph↗
arXiv2007

Beta Cephei stars in the ASAS-3 data. I. Long-term variations of periods and amplitudes

We analysed V-filter ASAS-3 photometry of 41 known Beta Cephei-type stars. The ASAS-3 photometry was combined with the archival data, if available, to determine long-term stability of periods and amplitudes of excited modes. We detected amplitude changes in three Beta Cephei stars, BW Cru, V836 Cen, and V348 Nor. Period changes were found in KK Vel and V836 Cen. Our analysis shows that intrinsic period changes are more common among multiperiodic stars, apparently because they are caused by some kind of mode interaction. In addition, we found new modes for seven stars, and for ten others we provide new solutions or remove ambiguities in the detected frequencies. One candidate hybrid Beta Cephei/SPB star, HD133823, is discovered.

astro-ph↗
arXiv2006

Eclipsing binaries in ASAS catalog

ASAS is a long term project to monitor bright variable stars over the whole sky. It has discovered 50,122 variables brighter than V < 14 mag south of declination +28 degrees, and among them 11,099 eclipsing binaries. We present a preliminary analysis of 5,384 contact, 2,957 semi-detached, and 2,758 detached systems. The statistics of the distribution provides a qualitative confirmation of decades old idea of Flannery and Lucy that W UMa type binaries evolve through a series of relaxation oscillations: ASAS finds comparable number of contact and semidetached systems. The most surprising result is a very small number of detached eclipsing binaries with periods P < 1 day, the systems believed to be the progenitors of W UMa stars. As many (perhaps all) contact binaries have companions, there is a possibility that some were formed in a Kozai cycle, as suggested by Eggleton and his associates.

astro-ph↗
arXiv2005

The All Sky Automated Survey. The Catalog of Variable Stars. V. Declinations 0 deg - 28 deg of the Northern Hemisphere

This paper contains the fifth part of the Catalog of Variable Stars created from the V-band photometric data collected by 9x9 deg camera of the All Sky Automated Survey. Preliminary list of variable stars found in the fields located between declination 0 and +28 deg of the northern hemisphere is presented. 11,509 stars brighter than V=15 were found to be variable (2,482 eclipsing, 1,397 regularly pulsating, 318 Mira and 7,310 other stars). Automated algorithm taking into account light curve properties (period, fourier coefficients) and other available data (2MASS colors, IRAS fluxes) was applied to roughly classify objects. Basic photometric properties are presented in the tables and thumbnail light curves are made available for reference. All the photometric data are available over the INTERNET at http://www.astrouw.edu.pl/~gp/asas/asas.html or http://archive.princeton.edu/~asas

astro-ph↗
arXiv2004

The All Sky Automated Survey. The Catalog of Variable Stars. IV.18^h - 24^h Quarter of the Southern Hemisphere

In this paper we present the fourth part of the photometric data from the 9x9 deg ASAS camera monitoring the whole southern hemisphere in V-band. Preliminary list (based on observations obtained since January 2001) of variable stars located between RA 18^h - 24^h is released. 10311 stars brighter than V=14 were found to be variable (1641 eclipsing, 1116 regularly pulsating, 938 Mira and 6616 other stars). Light curves have been classified using the automated algorithm taking into account periods, amplitudes, fourier coefficients of the light curves, 2MASS colors and IRAS infrared fluxes. Basic photometric properties are presented in the tables and some examples of thumbnail light curves are printed for reference. All photometric data are available over the INTERNET at http://www.astrouw.edu.pl/~gp/asas/asas.html or http://archive.princeton.edu/~asas

astro-ph↗
arXiv2004

The All Sky Automated Survey. The Catalog of Variable Stars. III. 12h - 18h Quarter of the Southern Hemisphere

This paper describes the third part of the photometric data from the 9 x 9 deg ASAS camera monitoring the whole southern hemisphere in V-band. Preliminary list of variable stars based on observations obtained since January 2001 is presented. Over 3,200,000 stars brighter than V=15 on 18,000 frames were analyzed and 10453 were found to be variable (1718 eclipsing, 731 regularly pulsating, 849 Mira and 7155 other stars). Light curves have been classified using the improved automated algorithm, which now takes into account 2MASS colors and IRAS infrared fluxes. Basic photometric properties are presented in the tables and some examples of thumbnail light curves are printed for reference. All photometric data are available over the INTERNET at http://www.astrouw.edu.pl/~gp/asas/asas.html or http://archive.princeton.edu/~asas

astro-ph↗
arXiv2004

The All Sky Automated Survey. The Catalog of Variable Stars. II.6h-12h Quarter of the Southern Hemisphere

This paper describes the second part of the photometric data from the 9x9 deg ASAS camera monitoring the whole southern hemisphere in the V-band. Preliminary list of variable stars based on observations obtained since January 2001 is presented. Over 2,800,000 stars brighter than V=15 mag on 18,000 frames were analyzed and 11357 were found to be variable (2685 eclipsing, 907 regularly pulsating, 521 Mira and 7244 other, mostly SR, IRR and LPV stars). Periodic light curves have been classified using the automated algorithm, which now takes into account IRAS infrared fluxes. Basic photometric properties are presented in the tables and some examples of thumbnail light curves are printed for reference. All photometric data are available over the INTERNET at http://www.astrouw.edu.pl/~gp/asas/asas.html or http://archive.princeton.edu/~asas

astro-ph↗
arXiv2002

The All Sky Automated Survey. Variable Stars in the 0h - 6h Quarter of the Southern Hemisphere

This paper describes the first part of the photometric data from the 9x9 deg ASAS cameras monitoring the whole southern hemisphere in V-band. Data acquisition and reduction pipeline is described and preliminary list of variable stars is presented. Over 1,300,000 stars brighter than V=15 on 40,000 frames were analyzed and 3126 were found to be variable (1046 eclipsing, 778 regular pulsating, 132 Mira and 1170 other, mostly SR, IR and LPV stars). Periodic light curves have been classified using the fully automated algorithm, which is described in detail. Basic photometric properties are presented in the tables and thumbnail light curves are printed for reference. All photometric data is available over the INTERNET at http://www.astrouw.edu.pl/~gp/asas/asas.html or http://archive.princeton.edu/~asas .

astro-ph↗
arXiv1998

The All Sky Automated Survey. The Catalog of the Short Period Variable Stars in the Selected Fields

Results of the first two month of observations using the All Sky Automated Survey prototype camera are presented. More than 45 000 stars in 24 Selected Fields covering 140 sq. degrees were monitored a few times a night resulting in the I-band catalog containing 10^7 individual measurements. Period search revealed 126 periodic variables brighter than 13 mag. Only 30 of them are known variables included in GCVS. The other 90 objects are newly detected variables - mainly eclipsing binaries (75%) and pulsating stars (17%). We estimate that completeness of the current catalogs of variable stars is smaller than 50% already for the stars brighter than 9 mag. The Catalog is accessible over the WWW: http://www.astrouw.edu.pl/$\sim$gp/asas/asas.html

astro-ph↗
arXiv1997

The All Sky Automated Survey

Technical description of the new project called All Sky Automated Survey and results of the tests of our prototype instrument are presented. The ultimate goal of this project is photometric monitoring of the large area of the sky with fully automated, low cost instruments. Possible applications of the project are indicated and future prospects discussed. At present over hundred square degrees is observed 5-10 times each night in I-band, alowing us to monitor over 30 000 stars brighter than 12-13 magnitude. Full description, pictures and current status of the project can be found at http://sirius.astrouw.edu.pl/~gp/asas/asas.html .

astro-ph↗