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 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 (ΔV∼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 Hα
emitting region as 10.4±0.5R☉ and the accretion rate as
1.8x10-7M☉/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 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 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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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 76 247 Photometric CCD observations of GM Cep during
the period June/2008-August/2014
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See also:
J/other/RAA/14.1264 : V350 Cep UBVRI long-term photometry (Ibryamov+, 2014)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "date" Date Date of observation ("DD.MM.YYYY" format)
12- 22 F11.3 d JD Julian Date
24- 28 F5.2 mag Imag ? Cousins I magnitude
30- 34 F5.2 mag Rmag ? Cousins R magnitude
36- 40 F5.2 mag Vmag ? Johnson V magnitude
42- 46 F5.2 mag Bmag ? Johnson B magnitude
48- 52 F5.2 mag Umag ? Johnson U magnitude
54- 60 A7 --- Tel Telescope used (1)
62- 67 A6 --- CCD CCD used (2)
69- 76 A8 --- Obs Name of observatory
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Note (1): Telescopes as follows:
2-m = 2-m Ritchey-Chretien-Coude telescope of the Rozhen National
Astronomical Observatory (Bulgaria)
1.3-m = 1.3-m Ritchey-Chretien telescope of the Skinakas Observatory of
the University of Crete (Greece)
Schmidt = 50/70-cm Schmidt telescope of the Rozhen National Astronomical
Observatory (Bulgaria)
60-cm = 60-cm cassegrain telescope of the Rozhen National Astronomical
Observatory (Bulgaria)
Note (2): CCD cameras as follows:
VA = VersArray 1300B
ANDOR = ANDOR DZ436-BV
STL-11 = SBIG STL-11000M
FLI = FLI PL16803 (50/70-cm Shmidt telescope)
FLI PL09000 (60-cm Cassegrain telescope)
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Acknowledgements:
Sunay I. Ibryamov, sibryamov(at)astro.bas.bg,
Bulgarian Academy of Sciences; University of Shumen, Bulgaria.
(End) Patricia Vannier [CDS] 01-Apr-2015