/ftp/cats/J_other/PASA/32.11



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J/other/PASA/32.11   Long-term UBVRI photometry of GM Cephei (Semkov+, 2015)
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Beginning of ReadMe : J/other/PASA/32.11 Long-term UBVRI photometry of GM Cep (Semkov+, 2015) ================================================================================ The Unusual Photometric Variability of the PMS Star GM Cep. Semkov E., Ibryamov S., Peneva S., Milanov T., Stoyanov K., Stateva I., Kjurkchieva D., Dimitrov D., Radeva V. <Publ. Astron. Soc. Australia, 32, 11 (2015)> =2015PASA...32...11S ================================================================================ ADC_Keywords: Stars, variable ; Stars, pre-main sequence ; Photometry, UBVRI Keywords: stars: pre-main sequence - star: variable: T Tauri - stars: individual: GM Cep Abstract: Results from UBVRI photometric observations of the pre-main sequence star GM Cephei obtained in the period April 2011 - August 2014 are reported in the paper. Presented data are a continuation of our photometric monitoring of the star started in 2008. GM Cep is located in the field of the young open cluster Trumpler 37 and over the past years it has been an object of intense photometric and spectral studies. The star shows a strong photometric variability interpreted as a possible outburst from EXor type in previous studies. Our photometric data for a period of over six years show a large amplitude variability (DeltaV 2.3mag) and several deep minimums in brightness are observed. The analysis of the collected multicolor photometric data show the typical of UX Ori variables a colour reversal during the minimums in brightness. The observed decreases in brightness have a different shape, and evidences of periodicity are not detected. At the same time, high amplitude rapid variations in brightness typical for the classical T Tauri stars also present on the light curve of GM Cep. The spectrum of GM Cep shows the typical of classical T Tauri stars wide H alpha emission line and absorption lines of some metals. We calculate the outer radius of the Halpha emitting region as 10.4+/-0.5R_sun_ and the accretion rate as 1.8x10^-7^M_sun_/yr. Description: UBVRI photometric data of GM Cephei during the period from June 2008 to August 2014 are presented. The CCD observations were performed in two observatories, with four telescopes. These are the 2-m Ritchey-Chretien-Coude (RCC), the 50/70-cm Schmidt and the 60-cm Cassegrain telescopes of the Rozhen National Astronomical Observatory of the Bulgarian Academy of Sciences and the 1.3-m Ritchey-Chretien (RC) telescope of the Skinakas Observatory of the University of Crete (Greece). The observations were performed with five different types of CCD cameras - VersArray 1300B at the 2-m RCC telescope; ANDOR DZ436-BV at the 1.3-m RC telescope; SBIG STL-11000M and FLI PL16803 at the 50/70-cm Schmidt telescope; and FLI PL09000 at the 60-cm Cassegrain telescope. All frames were taken through a standard Johnson-Cousins set of filters. The photometric data were reduced by IDL package (standard subroutine DAOPHOT). As references, we used the comparison sequence of fifteen stars in the field around GM Cep, published in Semkov & Peneva (2012Ap&SS.338...95S). All data were analyzed using the same aperture, which was chosen to have a 6-arcsec radius, while the background annulus was taken from 10-arcsec to 15-arcsec. The mean value of the errors in the reported magnitudes are: 0.01-0.02mag for I- and R-band data, 0.01-0.03mag for V-band data, 0.01-0.05mag for B-band data and 0.04-0.08mag for U-band data. The BVRI photometric data, obtained in the period from June 2008 to February 2011 are presented in Semkov & Peneva (2012Ap&SS.338...95S). Objects: ------------------------------------------------------------ RA (2000) DE Designation(s) ------------------------------------------------------------ 21 38 17.32 +57 31 22.0 GM Cep = 2MASS J21381731+5731220 ------------------------------------------------------------

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