J/ApJ/743/19 Photometry of variable star candidates in M31 (Clementini+, 2011)
Hide and seek between Andromeda's halo, disk, and giant stream.
Clementini G., Contreras Ramos R., Federici L., Macario G., Beccari G.,
Testa V., Cignoni M., Marconi M., Ripepi V., Tosi M., Bellazzini M.,
Fusi Pecci F., Diolaiti E., Cacciari C., Marano B., Giallongo E.,
Ragazzoni R., Di Paola A., Gallozzi S., Smareglia R.
<Astrophys. J., 743, 19 (2011)>
=2011ApJ...743...19C 2011ApJ...743...19C
ADC_Keywords: Stars, variable ; Photometry, UBV ; Galaxies, nearby
Keywords: galaxies: individual (M31) - galaxies: stellar content -
stars: variables: Cepheids - stars: variables: RR Lyrae
Abstract:
Photometry in B, V (down to V∼26mag) is presented for two 23'x23'
fields of the Andromeda galaxy (M31) that were observed with the blue
channel camera of the Large Binocular Telescope during the Science
Demonstration Time. Each field covers an area of about 5.1x5.1kpc2
at the distance of M31 (µM31∼24.4mag), sampling, respectively, a
northeast region close to the M31 giant stream (field S2) and an
eastern portion of the halo in the direction of the galaxy minor axis
(field H1). The stream field spans a region that includes Andromeda's
disk and giant stream, and this is reflected in the complexity of the
color-magnitude diagram of the field. One corner of the halo field
also includes a portion of the giant stream. Even though these
demonstration time data were obtained under non-optimal observing
conditions, the B photometry, which was acquired in time-series mode,
allowed us to identify 274 variable stars (among which 96 are bona
fide and 31 are candidate RR Lyrae stars, 71 are Cepheids, and 16 are
binary systems) by applying the image subtraction technique to the
selected portions of the observed fields. Differential flux light
curves were obtained for the vast majority of these variables. Our
sample mainly includes pulsating stars that populate the instability
strip from the Classical Cepheids down to the RR Lyrae stars, thus
tracing the different stellar generations in these regions of M31 down
to the horizontal branch of the oldest (t∼10Gyr) component.
Description:
B, V photometry of the M31 fields S2 (Stream: 00:49:08.31+42:16:09.4)
and H1 (Halo; 00:48:13.11+40:19:09.4) was obtained with Large
Binocular Telescope (LBT)/Large Binocular Camera (LBC)-blue during
10hr of Science Demonstration Time (SDT) of the Blue Channel in 2007
October 11-18. Both of our fields are contained in the area surveyed
by Ferguson et al. (2002AJ....124.1452F 2002AJ....124.1452F) with INT, reaching a limiting
magnitude V∼24.5mag, i.e., 1.5mag shallower than our photometry. Field
H1 contains the two HST/ACS fields of the M31 "Minor axis" observed by
Richardson et al. (2008AJ....135.1998R 2008AJ....135.1998R) and the field "halo21"
observed by Jeffery et al. (2011, Cat. J/AJ/141/171).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table9.dat 110 274 Identification and characteristics of candidate
variable stars identified in the M31 fields S2 and H1
table10.dat 78 6 Properties of confirmed variable stars in the M31
field S2 with light curves on a magnitude scale
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See also:
J/AJ/141/171 : RR Lyrae stars in six ultra-deep fields of M31 (Jeffery+, 2011)
J/ApJ/708/817 : RR Lyrae variables in M32 and M31 (Fiorentino+, 2010)
J/AJ/138/184 : RR Lyrae variables in 2 fields in M31 (Sarajedini+, 2009)
J/MNRAS/390/1437 : Stellar streams in Andromeda (M31) (Chapman+, 2008)
J/AJ/127/2738 : ACS VI photometry of M31 halo RR Lyrea (Brown+, 2004)
J/A+A/402/113 : (RI)c photometry of variables in M31 (Joshi+, 2003)
J/AJ/124/234 : M31 halo UBVRI photometry and metallicity (Reitzel+, 2002)
Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [CCD]
4 I1 --- CCD [1/2] CCD number
6- 12 A7 --- --- [- Field]
14- 15 A2 --- Fld Field location (H1 or S2)
17- 21 I5 --- ISIS [728/12408]? ISIS identification number (G1)
23- 27 I5 --- DoP [80/54011]? DoPHOT identification number (1)
29- 30 I2 h RAh [0] Hour of Right Ascension (J2000)
32- 33 I2 min RAm [47/49] Minute of Right Ascension (J2000)
35- 38 F4.1 s RAs Second of Right Ascension (J2000)
40 A1 --- DE- [+] Sign of the Declination (J2000)
41- 42 I2 deg DEd [40/42] Degree of Declination (J2000)
44- 45 I2 arcmin DEm Arcminute of Declination (J2000)
47- 48 I2 arcsec DEs Arcsecond of Declination (J2000)
50- 54 F5.3 d Per ? Period
55 A1 --- u_Per [?] Uncertainty flag on Per
57- 61 F5.2 mag Bmag [19.62/26.52]? The B band magnitude (2)
63- 67 F5.2 mag Brand ? B band random phase magnitude
69- 73 F5.2 mag Vmag ? The V band magnitude (2)
75- 79 F5.2 mag Vrand ? V band random phase magnitude
81-103 A23 --- Type Variable type (3)
105-106 A2 --- VID Confirmed variable (id from table 10)
108-110 A3 --- Note Additional note(s) (4)
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Note (1): The star identification number on the B,V images with
FWHM∼0.8-1.0". These were reduced with the DoPHOT package and
produced all the CMDs shown in the paper.
Note (2): Bmag, Vmag values are from the DoPHOT photometry of the B, V images
obtained with FWHM∼0.8-1.0". They correspond to values taken at a
random phase on the light curves. We list the average values for six
variables that have full coverage of the light curve (see Table 10)
over the full light cycle.
Note (3): Variability classes are written:
AC = Anomalous Cepheid
spCC = short-period Classical Cepheids (CC)
Bin. = Binary system
Be = Be star
RRab = RR Lyrae (ab type)
RRc = RR Lyrae (c type)
Note (4): Note as follows:
c = This candidate variable falls in the portion of the V frame that was
trimmed during the read-out of the CCDs.
d = The star is on or close to a dead column of the CCD in the B frame.
e = The star was not measured on the 0.8" FWHM V frame because too bright
and close to saturation.
f = Variable star which has full coverage of the light curve,
(see Table 10).
g = The star is close to the spike of a saturated star.
h = The star is close to a dead column of the CCD in the V frame.
i = Candidate variable stars identified during a preliminary search with
ISIS on the whole CCD1 of field S2. Stars with DoPHOT IDs 14532 and
5707 are located in the Southern part of CCD1 of Field S2.
l = The star is on a defect of the CCD in the B frames.
m = The star is contaminated by a bright companion.
n = The star is saturated in both the V and B 0.8 arcsec FWHM frames.
o = The classification as an AC is mainly based on the star luminosity, but
is inconsistent with the typical metal abundance of the underlying
stellar population (see discussion in Section 4.4).
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Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- VID Variable name
4- 7 I4 --- ISIS [4562/9171]? ISIS identification number (G1)
9- 10 I2 h RAh [0] Hour of right ascension (J2000)
12- 13 I2 min RAm [48] Minute of right ascension (J2000)
15- 18 F4.1 s RAs Second of right ascension (J2000)
20 A1 --- DE- [+] Sign of declination (J2000)
21- 22 I2 deg DEd [42] Degree of declination (J2000)
24- 25 I2 arcmin DEm Arcminute of declination (J2000)
27- 28 I2 arcsec DEs Arcsecond of declination (J2000)
30- 36 A7 --- Type Variable type (RRab, Cepheid or Binary)
38- 42 F5.3 d Per [0.574/9.4] Period
43 A1 --- u_Per Uncertainty flag on Per
45- 52 F8.3 d Epoch Epoch (JD-2450000) (1)
53 A1 --- u_Epoch Uncertainty flag on Epoch
55 I1 --- NV Number of V measurements
57- 58 I2 --- NB Number of B measurements
60- 64 F5.2 mag <Bmag> Intensity-averaged mean B magnitude
65 A1 --- u_<Bmag> Uncertainty flag on <Bmag>
67- 70 F4.2 mag AB B-band extinction
71 A1 --- u_AB Uncertainty flag on AB
73- 77 F5.2 mag <Vmag> Intensity-averaged mean V magnitude (2)
78 A1 --- u_<Vmag> Uncertainty flag on <Vmag>
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Note (1): Epochs correspond to the time of maximum light for the pulsating
variables and to the time of the main minimum light for the binary
system.
Note (2): The <Vmag> values were derived by scaling from the B light curves
according to the procedure described at the end of Section 4.2.
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Global notes:
Note (G1): ISIS is the image substraction technique from Alard, C.
2000A&AS..144..363A 2000A&AS..144..363A; available at
http://www.iap.fr/users/alard/package.html
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 26-Apr-2013