J/A+A/431/1189 BV photometry of NGC 6822 variables (Baldacci+, 2005)
Variable stars in the dwarf irregular galaxy NGC 6822:
The photometric catalogue.
Baldacci L., Rizzi L., Clementini G., Held E.V.
<Astron. Astrophys., 431, 1189-1201 (2005)>
=2005A&A...431.1189B 2005A&A...431.1189B
ADC_Keywords: Stars, variable ; Photometry, CCD ; Photometry, UBV
Keywords: galaxies: individual: NGC 6822 - galaxies: dwarf -
galaxies: irregular - stars: variable: general -
galaxies: Local Group - stars: variables: RR Lyr
Abstract:
Deep B, V time-series photometry obtained with the ESO Very Large
Telescope has been used to identify variable stars in the dwarf
irregular galaxy NGC 6822. We surveyed a 6.8x6.8 arcmin area of the
galaxy and detected a total number of 390 candidate variables with the
optimal image subtraction technique (Alard C., 2000A&AS..144..363A 2000A&AS..144..363A).
Light curves on a magnitude scale were obtained for 262 of these
variables. Differential flux light curve are available for the
remaining sample. We were able to determine periods and pulsation
characteristics for 69 out of the 262 variables with light curves in
magnitude scale, they include: 18 RR Lyrae stars (16 ab-type and 2
c-type), 45 Cepheids and 6 binary systems. We also tentatively
calibrated 8 of the 128 objects with light curves on a differential
flux scale on the assumption that they are ab-type RR Lyrae stars.
Description:
The catalogue contains coordinates, average magnitudes and colours for
all 390 candidate variables in NGC 6822 (Table 2) and time series data
for 69+8 variables (Table 3).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 79 390 List of candidate variable stars (Table 2)
lc/* . 154 Individual B and V light curves (Table 3)
table4.dat 108 26 Mean quantities for RR Lyrae stars
table5.dat 107 45 Basic properties of Cepheids
table6.dat 107 6 Basic information on eclipsing binaries
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See also:
J/A+A/430/603 : BVI photometry of LMC bar variables (Di Fabrizio+, 2005)
J/A+A/429/837 : IJKs photometry of late-type stars in NGC 6822 (Cioni+, 2005)
J/AJ/109/173 : BVR photometry of NGC 6822 (Marconi+ 1995)
J/AJ/110/2715 : UBV photometry in NGC 6822, M31 and M33 (Massey+ 1995)
J/AJ/121/2020 : CTIO and WFPC2 photometry in NGC 6822 (Bianchi+, 2001)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Seq Star running identifier,
ordered by increasing declination
6- 11 A6 --- ID Star ID (G1)
13- 14 I2 h RAh Right Ascension J2000 (hours)
16- 17 I2 min RAm Right Ascension J2000 (minutes)
19- 23 F5.2 s RAs Right Ascension J2000 (seconds)
26 A1 --- DE- Declination J2000 (sign)
27- 28 I2 deg DEd Declination J2000 (degrees)
30- 31 I2 arcmin DEm Declination J2000 (minutes)
33- 37 F5.2 arcsec DEs Declination J2000 (seconds)
41- 46 F6.3 mag Vmag ? V magnitude (1)
49- 54 F6.3 mag B-V ? B-V colour index (1)
57- 60 A4 --- Type Star type (2)
63- 74 A12 --- Cross-id Other identifications (3)
77- 79 A3 --- Notes Notes (4)
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Note (1): Available only for stars with light curves on a magnitude scale.
Note (2): We define
-- Main Sequence variables (MSV) all objects with (B-V)<0.4,
-- Classical Instability Strip Variables (CISV) objects with 0.4<(B-V)<1.2,
-- Red Giant Branch Variables (RGBV) objects with (B-V)>1.2.
Note (3): Cross-identification of variables in common with Antonello et al.
(2002A&A...386..860A 2002A&A...386..860A) (V*, [AFM2002b] VNNNN in Simbad) and Pietrzynski
et al. (2004, Cat. J/ApJ/128/2815) (cep*, [PGU2004] cepNNN in
Simbad)
Note (4): Flag indicating the type of available light curves or light curve
calibration process as follows:
1 = Differential flux light curve, only V band available.
2 = Differential flux light curves, both B and V bands available.
3 = Not found on ISIS2.1 B "var.fits" frame, DAOPHOT/ALLFRAME
B light curve.
4 = ISIS2.1 light curves are very poor, we used the DAOPHOT/ALLFRAME
B, V light curves.
5 = Not found on ISIS2.1 B "var.fits" frame, DAOPHOT/ALLFRAME
B light curve.
Not measured on the V reference image, calibration performed
using the DAOPHOT/ALLFRAME V average magnitude.
6 = Not measured on the B, V reference images, calibration performed
using the DAOPHOT/ALLFRAME B, V average magnitudes.
7 = Differential flux light curves tentatively calibrated on the
assumption that they are ab-type RR Lyrae stars (see section 6.4
in the paper).
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Byte-by-byte Description of file: lc/*
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Bytes Format Units Label Explanations
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1- 7 F7.4 d HJD-2452100 Heliocentric Julian Day of observation
(-2452100)
11- 17 F7.4 mag mag V or B magnitude
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Byte-by-byte Description of file: table[456].dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Seq Star running identifier,
ordered by increasing declination
6- 11 A6 --- ID Star ID (G1)
13- 16 A4 -- Type RR Lyrae type
18- 22 F5.3 d P Period
24- 31 F8.4 d Ep-2452000 HJD-2452000 of maximum (pulsating variables)
or deeper minimum (binaries) light
33- 34 I2 --- o_Bmag Number of data-points available on the B curve
36- 37 I2 --- o_Vmag Number of data-points available on the V curve
39- 44 F6.3 mag <Bmag> Intensity-averaged mean B magnitude
45 A1 --- u_<Bmag> Uncertainty flag on <Bmag>
47- 52 F6.3 mag <Vmag> Intensity-averaged mean V magnitude
53 A1 --- u_<Vmag> Uncertainty flag on <Vmag>
55 A1 --- l_AB Limit flag on AB
56- 60 F5.3 mag AB Amplitude of the B light variation
62 A1 --- l_AV Limit flag on AV
63- 67 F5.3 mag AV Amplitude of the V light variation
69- 73 F5.3 mag resB ? Residual in B band (2)
75- 79 F5.3 mag resV Residual in V band (2)
81- 83 A3 --- Notes Notes (1)
86- 96 A11 --- Vlc V light curve filename in "lc" subdirectory
98-108 A11 --- Blc B light curve filename in "lc" subdirectory
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Note (1): Notes are coded as follows:
r = outside the red edge of the RR Lyrae instability strip;
rr = too red colors (stars in crowded regions close to the center of
or near to regions of active star formation).
b = outside the blue edge of the RR Lyrae instability strip;
o = overluminous;
u = uncertain. These 8 ab-type RR Lyrae stars have been approximately
scaled following the procedure described in Sect. 5.
Note (2): Residuals with respect to light curves obtained from GRATIS
best fitting models.
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Global notes:
Note (G1): ISIS2.1 "lc" number or DAOPHOT/ALLFRAME identifier depending
on the available data
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Acknowledgements: Lara Baldacci, lara.baldacci(at)bo.astro.it
(End) Patricia Vannier [CDS] 25-Feb-2005