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Der W-UMa-Stern USNO-A2.0 0825-02657246
Entdeckung und Charakterisierung

Unser Beitrag beim Wettbewerb "Junge Forscher gesucht 2018"

von Christof Wiedemair

Lisa Niederbrunner, Vera Oberhauser und Dominik Moser haben sich im Schuljahr 2017/18 intensiv mit dem, von der Astrogruppe entdeckten, variablen Stern USNO-A2.0 0825-02657246 auseinandergesetzt. Mit ihren Ergebnissen haben die Drei beim Wettbewerb "Junge Forscher gesucht" teilgenommen und am 20. April 2018 den wohlverdienten Sieg eingeheimst. Hier der Abstract in englischer Sprache:


We report about the discovery of the variability of the star USNO-A2.0 0825-02657246 in the constellation Monoceros on February 16th, 2017 in the observatory of the "Sprachen- und Realgymnasium Nikolaus Cusanus", Bruneck, South Tyrol, Italy. The USNO-A2.0 catalogue defines the coordinates 06 33 07.418 -00 02 05.25 (J2000) and a brightness of R = 14.3 mag and B = 15.1 for this entry.

In December 2017 and January 2018 we observed the star from different observatories at different sites and with different setups and got 26 partial lightcurves. These have been analyzed using the phase dispersion minimization method. Based on the resulting phase plot we classify the star to be an extrinsic variable of type W UMa with a period of 9.266 h and equal brightness dips of approximately 0.7 mag, both for unfiltered and for SDSS-r'-filtered observations. A linear ephemeris of

T_min = 2458091.5142 + 0.3859 E

has been derived from the data.

We have performed all-sky photometry using the iTelesope.net remote telescope network. We found colour indices of B-V = 0.84 mag and V-R = 0.59 mag which indicate an orange color. In collaboration with the Italian amateur astronomer Franco Lorenzo we used this information along with interstellar dust reddening information for the determination of basic physical parameters and the construction of a model of the binary star.

On the evening of January 29th 2018, the discovery of the star has been published by a team of three astronomers from Ohio State University (US) at the Association of American Variable Star Observers (AAVSO), just one day prior to our own submission. Their results fully confirm our findings regarding period, amplitude and variability type. Our phase plot has been submitted to the AAVSO1 in order to expand the data basis and has been accepted by the moderator on January 30th 2018.

Die folgenden drei Bilder zeigen die bei der Präsentation verwendeten Poster und zeigen die Grundzüge des Projektes in Englischer Sprache auf. Klicken zum Laden in einem neuen Fenster.

varmon_poster1 varmon_poster2 varmon_poster3

Wer sich für noch mehr Details interessiert, kann unseren Blog astrocusanus.blogspot.com lesen oder hier den 30-seitigen Projektbericht downloaden (2 MByte)!