J/A+A/554/A108 Periodic variables in NGC 3766 (Mowlavi+, 2013)
Stellar variability in open clusters.
I. A new class of variable stars in NGC 3766.
Mowlavi N., Barblan F., Saesen S., Eyer L.
<Astron. Astrophys. 554, A108 (2013)>
=2013A&A...554A.108M 2013A&A...554A.108M
ADC_Keywords: Clusters, open ; Stars, variable ; Photometry, CCD ;
Photometry, Geneva ; Stars, A-type
Keywords: Hertzsprung-Russell and C-M diagrams - stars: oscillations -
open clusters and associations: individual: NGC 3766 -
binaries: eclipsing - stars: variables: general
Abstract:
We analyze the population of periodic variable stars in the open
cluster NGC3766 based on a 7-year multiband monitoring campaign
conducted on the 1.2m Swiss Euler telescope at La Silla, Chili.
The data reduction, light curve cleaning, and period search
procedures, combined with the long observation time line, allowed us
to detect variability amplitudes down to the mmag level.
The variability properties were complemented with the positions in the
color-magnitude and color-color diagrams to classify periodic variable
stars into distinct variability types.
We find a large population (36 stars) of new variable stars between
the red edge of slowly pulsating B (SPB) stars and the blue edge of
delta Sct stars, a region in the Hertzsprung-Russell (HR) diagram
where no pulsation is predicted to occur based on standard stellar
models.
The bulk of their periods ranges from 0.1 to 0.7d, with amplitudes
between 1 and 4mmag for the majority of them. About 20% of stars in
that region of the HR diagram are found to be variable, but the number
of members of this new group is expected to be higher, with amplitudes
below our mmag detection limit.
The properties of this new group of variable stars are summarized and
arguments set forth in favor of a pulsation origin of the variability,
with g-modes sustained by stellar rotation. Potential members of
this new class of low-amplitude periodic (most probably pulsating) A
and late-B variables in the literature are discussed. We additionally
identify 16 eclipsing binary, 13 SPB, 14 delta Sct, and 12 gamma Dor
candidates, as well as 72 fainter periodic variables. All are new
discoveries.
We encourage searching for this new class of variables in other young
open clusters, especially in those hosting a rich population of Be
stars.
Description:
Coordinates, photometry and periods of variable stars detected in the
open cluster NGC3766.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 65 16 Eclipsing binaries in our FOV of NGC 3766
tablea2.dat 96 228 Periodic stars with secured frequencies in our
FOV of NGC3766
--------------------------------------------------------------------------------
See also:
J/ApJ/622/1052 : byHα photometry of NGC 3766 (McSwain+, 2005)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- GvaId [50/2663] Star identification number
6- 14 F9.6 h RAhour Right ascension in decimal hours (J2000.0)
16- 25 F10.6 deg DEdeg Declination in decimal degrees (J2000.0)
27- 32 F6.3 mag Vmag Not-calibrated Geneva CCD V band
34- 39 F6.3 mag B-V Not-calibrated Geneva CCD B-V color index
41- 46 F6.3 mag U-B Not-calibrated Geneva CCD U-B color index
48- 57 F10.6 d Per Period
58 A1 --- u_Per [)] Uncertainty flag on Per
60- 61 A2 --- Type [EABW] Type of binary star (EA, EB or EW)
63- 65 A3 --- Mmb [yes/no ] Potential cluster membership
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- GvaId [22/3525] Star identification number
5 A1 --- n_GvaId [*] * for eclipsing binaries
7- 15 F9.6 h RAhour Right ascension in decimal hours (J2000.0)
17- 26 F10.6 deg DEdeg Declination in decimal degrees (J2000.0)
28- 33 F6.3 mag Vmag Not-calibrated Geneva CCD V band
35- 40 F6.3 mag B-V Not-calibrated Geneva CCD B-V color index
41 A1 --- u_B-V [)] ) if the involved time series are not all good
43- 48 F6.3 mag U-B Not-calibrated Geneva CCD U-B color index
49 A1 --- u_U-B [)] ) if the involved time series are not all good
51- 53 A3 --- Grp Group of the variable (1-5) (1)
55- 65 F11.7 d Per Period
67- 75 F9.7 d e_Per Uncertainty on Per
77- 82 F6.2 mmag Amp Amplitude
84- 87 F4.2 mmag e_Amp Uncertainty on the amplitude
89- 92 F4.1 --- S/N Signal to noise ratio
94- 96 I3 --- MGid ? Star number given by McSwain et al.
(2008ApJ...672..590M 2008ApJ...672..590M),
<Cl* NGC 3766 MG NNN> in Simbad
--------------------------------------------------------------------------------
Note (1): Groups as follows:
1 = V<12.5mag and P>1.1d. They are two magnitudes or more brighter than the
most luminous delta Sct candidate. One fainter star at V=13.86mag is
also added to this group (see Sect. 5.1).
2 = 11<V<14mag and 0.1d<P<1.1d. They fill the magnitude range between the
delta Sct and group 1 stars.
3 = 14<V<14.9mag and P<0.1d. It is the group of delta Sct candidates. Two
fainter stars at V≃15.3mag are also added to this group (see Sect. 5.3).
4 = 14.9<V<15.5mag and P>0.1d. One fainter star at V≃17mag is also added to
this group (see Sect. 5.4).
5 = all other periodic variables, i.e. those fainter than V=15.5mag and the
red giants that were excluded from the other groups.
--------------------------------------------------------------------------------
Acknowledgements:
Nami Mowlavi, Nami.Mowlavi(at)unige.ch
(End) Patricia Vannier [CDS] 11-Jun-2013