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Posts: 131433
Date:
Nova-like Variables
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Title: The Nova-like Variables
Authors: V.S. Dhillon

We review optical observations and theoretical models of the non-magnetic nova-like variables (UX UMa, VY Scl and SW Sex stars). A brief discussion of the classification scheme is followed by a statistical overview of the observed properties. The most important features of each of the sub-classes are then reviewed, concluding with a summary of the theoretical models invoked to understand these systems.

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Posts: 131433
Date:
Long period variables
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Title: STEREO observations of long period variables
Authors: K. T. Wraight, D. Bewsher, Glenn J. White, W. Nowotny, A. J. Norton, C. Paladini

Observations from the Heliospheric Imagers (HI-1) on both the STEREO spacecraft have been analysed to search for very long period large amplitude stellar variability, finding 6 new candidates. A total of 85 objects, mostly previously known Mira variables, were found to show convincing variability on time scales of over a hundred days. These objects range in peak brightness from about 4th magnitude to 10th magnitude in R and have periods between about 170 days and 490 days. There is a period gap between 200 and 300 days where no objects were found and this is discussed. 15 of the Miras in the sample are previously recorded as having variable periods and the possibility for these and 2 other stars to have undergone a period change or to be irregular is discussed. In addition to the 6 stars in the sample not previously recorded as variable, another 7 are recorded as variable but with no classification. Our period determination is the first to be made for 19 of these 85 stars. The sample represents a set of very long period variables that would be challenging to monitor from the Earth, or even from Earth orbit, owing to their position on the Ecliptic Plane and that their periods are often close to a year or an integer fraction thereof. The possibility for the new candidates to possess circumstellar shells is discussed.

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Posts: 131433
Date:
RE: Variables
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Russell M. Genet, director of the Orion Observatory near Santa Margarita Lake, announced that three Cuesta College students Noll Roberts, Neelie Jaggi, and Casey Milne recently discovered two new pulsating variable stars.
Students in Genet's physics research seminar at Cuesta had been using a research telescope at the observatory and an astronomical camera to take thousands of pictures from a list of nine candidate stars suspected of changing their brightness over time.
In a release, Genet explained that stars can vary their brightness for a number of reasons, including eclipses and pulsations. He reported that scientists who've reviewed the recently discovered variable stars believe them to be "very short period pulsating stars."

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Posts: 131433
Date:
Eclipsing Binary Variables
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The Eclipsing Binary Ephemeris for 2007 is now available online.

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Posts: 131433
Date:
RR Lyrae Variables
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The RR Lyrae Ephemeris for 2007 is now available online.

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Posts: 131433
Date:
Variables
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Title: Searching for Variables in One of the WHAT Fields
Authors: Avi Shporer (1), Tsevi Mazeh (1), Amit Moran (1), Gaspar Bakos (2), Geza Kovacs (3) ((1) Wise Observatory, TAU (2) CfA (3) Konkoly Observatory)

We present preliminary results on a single field observed by WHAT, a small-aperture short focal length automated telescope with an 8.2 deg x 8.2 deg field of view, located at the Wise Observatory. The system is similar to the members of HATNet and is aimed at searching for transiting extrasolar planets and variable objects. With 5 min integration time, the telescope achieved a precision of a few mmag for the brightest objects. We detect variables with peak-to-peak amplitudes less than 0.01 mag.

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