J/AJ/144/186 Variables in LMC globular clusters. II. NGC 1786 (Kuehn+, 2012)
Variable stars in Large Magellanic Cloud globular clusters. II. NGC 1786.
Kuehn C.A., Smith H.A., Catelan M., Pritzl B.J., De Lee N., Borissova J.
<Astron. J., 144, 186 (2012)>
=2012AJ....144..186K 2012AJ....144..186K
ADC_Keywords: Magellanic Clouds ; Clusters, globular ; Stars, variable ;
Photometry, UBV
Keywords: Magellanic Clouds - stars: horizontal-branch -
stars: variables: general - stars: variables: RR Lyrae
Abstract:
This is the second in a series of papers studying the variable stars
in Large Magellanic Cloud globular clusters. The primary goal of this
series is to study how RR Lyrae stars in Oosterhoff-intermediate
systems compare to their counterparts in Oosterhoff I/II systems. In
this paper, we present the results of our new time-series B-V
photometric study of the globular cluster NGC 1786. A total of 65
variable stars were identified in our field of view. These variables
include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical
Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing
binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of
undetermined type. Photometric parameters for these variables are
presented. We present physical properties for some of the RR Lyrae
stars, derived from Fourier analysis of their light curves. We discuss
several different indicators of Oosterhoff type which indicate that
the Oosterhoff classification of NGC 1786 is not as clear cut as what
is seen in most globular clusters.
Description:
A total of 57 V and 56 B images were obtained using the SOAR (Southern
Astrophysical Research) Optical Imager (SOI) (5.2*5.2arcmin field of
view) on the SOAR 4m telescope in 2007 November and 2008 February
while 43 V and 42 B images were obtained using ANDICAM (A Novel Dual
Imaging CAMera; 6*6arcmin field of view) on the SMARTS (Small and
Moderate Aperture Research Telescope System) 1.3m telescope operated
by the SMARTS consortium (www.astro.yale.edu/smarts) from 2006
September to 2007 January. Table 1 lists the UT dates and times of
each observation, which telescope it was on, the filter, and the
seeing.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 44 198 Observing log
table2.dat 109 57 Photometric parameters for variables in NGC 1786,
excluding RRd stars
table3.dat 103 8 Photometric parameters for the RRd variables in
NGC 1786
table4.dat 68 8843 Photometry of the variable stars
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See also:
VII/239 : History and Accurate Positions for the NGC/IC Objects (Corwin, 2004)
J/AJ/142/107 : Variable stars in NGC 1466 (Kuehn+, 2011)
J/MNRAS/405/839 : Spectroscopy of globular clusters (Sharina+, 2010)
J/AcA/60/1 : VI light curves of LMC delta Scuti stars (Poleski+, 2010)
J/AcA/59/1 : VI light curves of LMC RR Lyrae stars (Soszynski+, 2009)
J/AcA/58/293 : Type-II and anomalous Cepheids in LMC (Soszynski+, 2008)
J/AcA/58/163 : VI light curves of LMC classical Cepheids (Soszynski+, 2008)
J/ApJS/161/304 : Star clusters in Milky Way & satellites (McLaughlin+, 2005)
J/AcA/53/93 : OGLE RR Lyrae in LMC (Soszynski+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "Y:M:D" Obs.date UT date of observation
12- 21 A10 "h:m:s" Obs.time UT time of observation
23 A1 --- Flt [BV] Filter (B or V)
25- 29 F5.1 s Exp Exposure time
31- 37 F7.5 arcsec Seeing Seeing
39- 44 A6 --- Tel Telescope (SOAR or SMARTS) (G1)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [V]
2- 3 I02 --- Vno Variable number
5- 9 A5 --- n_Vno [Field BL] Peculiarity (1)
11- 12 I2 h RAh Hour of Right Ascension (J2000)
14- 15 I2 min RAm Minute of Right Ascension (J2000)
17- 20 F4.1 s RAs Second of Right Ascension (J2000)
22 A1 --- DE- Sign of the Declination (J2000)
23- 24 I2 deg DEd Degree of Declination (J2000)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000)
29- 32 F4.1 arcsec DEs Arcsecond of Declination (J2000)
34 A1 --- u_Type [?] Variable of undetermined type
36- 46 A11 --- Type Variable type (RRab, RRc, Delta Scuti,
AC, Ceph, T2Ceph, Eclipse) (2)
48- 56 F9.6 d Per Period
58- 60 F3.1 d Per2 ? Second value of period (3)
62- 65 F4.2 mag Vamp ? Amplitude in V band
67- 71 F5.3 mag Bamp ? Amplitude in B band
73- 78 F6.3 mag <Vmag> ? Intensity-weighted V mean magnitude
80- 85 F6.3 mag <Bmag> ? Intensity-weighted B mean magnitude
87- 91 F5.3 mag <B-V> ? Magnitude-weighted mean B-V color index
93- 97 A5 --- Type2 OGLE-III variable type (G2)
99-103 I5 --- OGLE ? Optical Gravitational Lensing Experiment-III
(OGLE-III) database number
105-109 I5 --- OGLE2 ? Other OGLE-III database number (5)
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Note (1): Flag on Name as follows:
Field = Large Magellanic Cloud (LMC) field star. The location of NGC 1786 near
the center of the LMC means that some of the RR Lyrae stars likely
belong to the field population of the LMC and not to the cluster.
BL = Possible Blazhko star (see Section 3.2. for more details).
Note (2): Variable type as follows:
AC = Anomalous Cepheid;
Ceph = classical Cepheid;
T2Ceph = Type II Cepheid;
Eclipse = Eclipsing binary.
RRab = RR Lyrae RRab;
RRc = RR Lyrae RRc.
Note (3): We dit not have enough observations to definitively determine periods
of the two eclipsing binaries V31 and V34.
Note (5): OGLE-III RR LYR-02746 was classified as an RRd star by Soszynski
et al. (2009, cat. J/AcA/59/1) but is only slightly separated on the
sky from OGLE-III RRLYR-02743 (∼0.15arcsec) and these can potentially
be a single star. Our photometry only found one variable star at this
location, V24.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [V]
2- 3 I02 --- Vno Variable number
5- 6 I2 h RAh Hour of Right Ascension (J2000)
8- 9 I2 min RAm Minute of Right Ascension (J2000)
11- 14 F4.1 s RAs Second of Right Ascension (J2000)
16 A1 --- DE- Sign of the Declination (J2000)
17- 18 I2 deg DEd Degree of Declination (J2000)
20- 21 I2 arcmin DEm Arcminute of Declination (J2000)
23- 26 F4.1 arcsec DEs Arcsecond of Declination (J2000)
28- 30 A3 --- Type [RRd] Variable type
32- 37 F6.4 d P0 Fundamental mode period
39- 44 F6.4 d P1 First overtone period
46- 51 F6.4 d P1/P0 Period ratio
53- 56 F4.2 mag Vamp0 ? Fundamental mode amplitude in V band
58- 61 F4.2 mag Vamp1 ? First overtone amplitude in V band
63- 66 F4.2 mag Bamp0 ? Fundamental mode amplitude in B band
68- 71 F4.2 mag Bamp1 ? First overtone amplitude in B band
73- 78 F6.3 mag <Vmag> ? Intensity-weighted V mean magnitude
80- 85 F6.3 mag <Bmag> ? Intensity-weighted B mean magnitude
87- 91 F5.3 mag <B-V> ? Magnitude-weighted B-V mean color index
93- 97 A5 --- Type2 OGLE-III variable type (G2)
99-103 I5 --- OGLE Optical Gravitational Lensing Experiment-III
(OGLE-III) database number
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [V]
2- 3 I02 --- Vno Variable number
5 A1 --- Flt [BV] Filter (B or V)
7- 20 F14.6 d HJD Heliocentric Julian Date
22- 28 F7.5 --- Phase Phase (1)
30- 35 F6.3 mag mag ? Magnitude in Flt (2)
37- 46 F10.3 --- dflux ? Differential flux in Flt (2)
48- 52 F5.3 mag e_mag ? Error in mag
54- 61 F8.3 --- e_dflux ? Error in dflux
63- 68 A6 --- Tel Telescope (SOAR or SMARTS) (G1)
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Note (1): Computed such that maximum light occurs at phase 0.
Note (2): For the nine RR Lyrae stars (V15 in filter B, V16, V53, V57, V59,
V63-V66) that were only found by the image subtraction package ISIS
(the location of these stars in the extremely crowded center of the
cluster did not allow Daophot light curves to be obtained), brightness
is expressed in the form of differential flux.
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Global notes:
Note (G1): Telescope as follows:
SOAR = Southern Astrophysical Research 4m telescope;
SMARTS = Small & Moderate Aperture Research Telescope System 1.3m telescope
(operated by the SMARTS consortium, http://www.astro.yale.edu/smarts).
Note (G2): Variable type from OGLE-III as follows:
ACEP = Anomalous Cepheid (Soszynski et al., 2008, cat. J/AcA/58/293);
CEP = Cepheid (Soszynski et al., 2008, cat. J/AcA/58/163);
DSCT = Delta Scuti (Poleski et al., 2010, cat. J/AcA/60/1);
RRLYR = RR Lyrae (Soszynski et al., 2009, cat. J/AcA/59/1);
T2CEP = Type II Cepheid (Soszynski et al., 2008, cat. J/AcA/58/293).
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History:
From electronic version of the journal
References:
Kuehn et al., Paper I, 2011AJ....142..107K 2011AJ....142..107K, Cat. J/AJ/142/107
Kuehn et al., Paper III, 2013AJ....145..160K 2013AJ....145..160K, Cat. J/AJ/145/160
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 10-Jan-2014