606 research outputs found

    Monitoring All Sky for Variability

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    A few percent of all stars are variable, yet over 90% of variables brighter than 12 magnitude have not been discovered yet. There is a need for an all sky search and for the early detection of any unexpected events: optical flashes from gamma-ray bursts, novae, dwarf novae, supernovae, `killer asteroids'. The ongoing projects like ROTSE, ASAS, TASS, and others, using instruments with just 4 inch aperture, have already discovered thousands of new variable stars, a flash from an explosion at a cosmological distance, and the first partial eclipse of a nearby star by its Jupiter like planet. About one million variables may be discovered with such small instruments, and many more with larger telescopes. The critical elements are software and full automation of the hardware. A complete census of the brightest eclipsing binaries is needed to select objects for a robust empirical calibration of the the accurate distance determination to the Magellanic Clouds, the first step towards the Hubble constant. An archive to be generated by a large number of small instruments will be very valuable for data mining projects. The real time alerts will provide great targets of opportunity for the follow-up observations with the largest telescopes.Comment: 6 pages, latex, minor changes, published in the Publications of the Astronomical Society of the Pacific as one of Millennium Essays: 2000, PASP, 112, 1281-128

    Astronomy with Small Telescopes

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    The All Sky Automated Survey (ASAS) is monitoring all sky to about 14 mag with a cadence of about 1 day; it has discovered about 10^5 variable stars, most of them new. The instrument used for the survey had aperture of 7 cm. A search for planetary transits has lead to the discovery of about a dozen confirmed planets, so called 'hot Jupiters', providing the information of planetary masses and radii. Most discoveries were done with telescopes with aperture of 10 cm. We propose a search for optical transients covering all sky with a cadence of 10 - 30 minutes and the limit of 12 - 14 mag, with an instant verification of all candidate events. The search will be made with a large number of 10 cm instruments, and the verification will be done with 30 cm instruments. We also propose a system to be located at the L_1 point of the Earth - Sun system to detect 'killer asteroids'. With a limiting magnitude of about 18 mag it could detect 10 m boulders several hours prior to their impact, provide warning against Tunguska-like events, as well as to provide news about spectacular but harmless more modest impacts.Comment: 11 pages, accepted to PASP minor changes to the tex

    A Catalogue of RR Lyrae Stars from the Northern Sky Variability Survey

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    A search for RR Lyrae stars has been conducted in the publicly available data of the Northern Sky Variability Survey (NSVS). Candidates have been selected by the statistical properties of their variation; the standard deviation, skewness and kurtosis with appropriate limits determined from a sample 314 known RRab and RRc stars listed in the GCVS. From the period analysis and light curve shape of over 3000 candidates 785 RR Lyrae have been identified of which 188 are previously unknown. The light curves were examined for the Blazhko effect and several new stars showing this were found. Six double-mode RR Lyrae stars were also found of which two are new discoveries. Some previously known variables have been reclassified as RR Lyrae stars and similarly some RR Lyrae stars have been found to be other types of variable, or not variable at all.Comment: Accepted for publication in MNRAS. Tables 1 and 2 are available here in full, but not in the printed editio

    Contact Binary Variables as X-ray Sources

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    We present cross-identification of archived X-ray point sources with W UMa variable stars found in the All-Sky Automated Survey (ASAS). In a surveyed sky area of 300 square degrees of ASAS, 36 W UMa stars have been found associated with X-ray emission. We compute the distances of these W UMa systems and hence their X-ray luminosities. Our data support the "supersaturation" phenomenon seen in these fast rotators, namely that the faster a W UMa star rotates, the weaker its X-ray luminosity.Comment: 10 pages, 2 figures, 1 table; submitted to A
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