ISSN 2309-5539 (online)
Published by The VS-COMPAS Project © 2011-2014
Hrodna, 230005, Belarus

Variable Stars Observer Bulletin is all about variable stars science. It's made by amateurs and for amateurs. Here simplified contemporary data about different aspects of variable stars research is published. The bulletin is scheduled for six issues per year.

January-February 2014 (#4)

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Contents

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BL Lacertae objects - Blazars by Ivan Adamin

BL Lacertae objects demonstrate the most violent behavior known among active galactic nuclei (AGN). These objects are mostly notable for being strongly and rapidly variable at all wavelengths, displaying substantial variations in brightness over a short period of time. Their properties also include high optical polarization and the lack of optical emission lines. They are named after the prototype object BL Lacertae, located in the constellation Lacerta (the Lizard), which was initially believed to be a variable star in our galaxy. Read more >>

VV Cephei: an extraordinary binary system by Ivan Adamin

VV Cephei eclipsing binary systems offer the most detailed method of studying mass loss from cool supergiant stars. The long-period of VV Cephei gives it a unique place among eclipsing binaries, but 20.4 years between eclipses make it really hard for scientists to study the system. Such a long interval gives only a couple of eclipse events in a working astronomical career for a human. Similar binaries are always good targets to follow, as the opportunity to obtain quality photometry and spectrometry of the eclipse is quite rare, but rewarding. Read more >>

Pulsating variable stars and the Hertzsprung-Russell diagram
by Siarhey Hadon, Ivan Adamin

Studying intrinsically pulsating variable stars plays a very important role in stellar evolution under-standing. The Hertzsprung-Russell diagram is a powerful tool to track which stage of stellar life is represen-ted by a particular type of variable stars. Let's see what major pulsating variable star types are and learn about their place on the H-R diagram. This approach is very useful, as it also allows to make a decision about a variability type of a star for which the properties are known partially. Read more >>

Stellar spectral classification: a brief story of early steps by Ivan Adamin

In the early XX century, astronomers began photographing the spectra of stars, but the diversity of spectral features was too confusing and complex to explain. Edward Pickering (1846-1919) re-arranged the spectral sequence, taking into consideration the changes in other lines. Building upon this idea, a team of astronomers at the Harvard Observatory, led by Annie Cannon (1863-1941), grouped similar appearing spectra together, designated by letters: A, B, C, etc. They also started a project on spectra classification. Soon, a smooth sequence of spectral types was found, and the assigned letters combined into O-B-A-F-G-K-M. Read more >>

Stellar associations: a variable stars nursery by Valery Tsehmeystrenko

The study of stellar associations and star formation regions is an important activity in the research of stars evolution and their systems. Stellar associations are concentrated along the spiral arms of our galaxy and come in several types. As a place where stars are born, these regions contain different kinds of objects, including variable stars, at the early stages of their life. Read more >>

Discovery of a Second Radial Mode in the High Amplitude Delta Scuti Star NSVS 10590484 (GSC 01489-00914) by Klaus Bernhard, Stefan Hümmerich

During an investigation of the pulsational behaviour of Delta Scuti stars, we have identified a second radial mode in the High Amplitude Delta Scuti star NSVS 10590484 (GSC 01489-00914) which was discovered by Alexandr Ditkovsky of the VS-COMPAS team. Therefore, NSVS 10590484 is an HADS(B) star with the following elements: P0= 0.0541911 d; P1= 0.0419105 d (P1/P0= 0.7734). Read more >>

Notable long-period eclipsing binaries. Part I. by Ivan Adamin

Long-period eclipsing binary stars are very important for stellar astrophysicists, because they offer the chance to study the characteristics of isolated stars with a high degree of precision and accuracy. The most interesting fact about eclipsing binaries is that all kinds of stars are found as members of binaries: from normal main sequence stars, variable stars, evolved giants and supergiants, to collap-sed objects. Here a list of several interesting long-periodic systems is presented. Read more >>

Eclipsing variable TX UMa: my observations by Andrey Semenyuta

TX UMa is an eclipsing binary system. This article presents a summary of my visual observations, made from the city of Pavlodar, Kazakhstan. The measurements were made time-to-time throughout several years, so the task was mostly an interesting challenge and eye training at the same time. The result has a good match with the known period. Read more >>

Want to contribute an article? Feel free to contact us at:
http://www.vs-compas.belastro.net/bulletin-contribute

or please simply drop an email to [ivan dot adamin at gmail dot com]