J/AJ/124/2039 LMC Blue variable stars from MACHO (Keller+, 2002)
Blue variable stars from the MACHO database.
I. Photometry and spectroscopy of the Large Magellanic Cloud sample.
Keller S.C., Bessell M.S., Cook K.H., Geha M., Syphers D.
<Astron. J. 124, 2039 (2002)>
=2002AJ....124.2039K 2002AJ....124.2039K
ADC_Keywords: Magellanic Clouds ; Stars, variable ; Stars, blue ;
Photometry, VRI
Keywords: galaxies: individual (Large Magellanic Cloud) -
stars: emission-line, Be - stars: variables: other
Abstract:
We present the photometric properties of 1280 blue variable stars
within the Large Megallanic Cloud. Photometry is derived from the
MACHO database. The light curves of the sample exhibit a variety of
quasi-periodic and aperiodic outburst behavior. A characteristic
feature of the photometric variation is that the objects are reddest
when at maximum outburst. A subset of 102 objects were examined
spectroscopically. Within this subset, 91% exhibited Balmer emission
in at least one epoch, in some cases with spectacular spectral
variability. The variability observed in the sample is consistent with
the establishment and maintenance of the Be phenomenon.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 55 1280 Positions and mean photometry for the sample of
1280 blue variables
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See also:
II/247 : MACHO Variable Stars in the Magellanic Clouds (MACHO, 2001)
J/A+A/313/841 : MACHO LMC No.1 microlensing event (Dominik+, 1996)
J/AJ/114/326 : MACHO Variables V. (Alcock+ 1997)
J/ApJ/542/257 : MACHO LMC first-overtone RR Lyrae (Alcock+, 2000)
J/ApJ/562/337 : High proper-motion stars from MACHO astrometry (Alcock+, 2001)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- MACHO The MACHO identification number (1)
14- 15 I2 h RAh Hour of Right Ascension (J2000)
17- 18 I2 min RAm Minute of Right Ascension (J2000)
20- 25 F6.3 s RAs Second of Right Ascension (J2000)
27 A1 --- DE- Sign of the Declination (J2000)
28- 29 I2 deg DEd Degree of Declination (J2000)
31- 32 I2 arcmin DEm Arcminute of Declination (J2000)
34- 38 F5.2 arcsec DEs Arcsecond of Declination (J2000)
40- 45 F6.3 mag Vmag ?=99.999 The V band magnitude (2)
47- 52 F6.3 mag V-R ?=99.999 The (V-R) color (2)
54- 55 I2 --- Mode The dominant mode of variability (3)
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Note (1): Where the identification sequences is field.tile.sequence (fts).
Note (2): 99.999 = Photometry not available
Note (3): Modes are from 1 to 5. Combinations of modes are denoted
in the table as follows mode 1 + mode 3 = "13"
1: Bumper events. These events are typically δV=0.2-0.4mag in
amplitude and duration of 100-800 days
2: Flicker events. Rapid, generally low-amplitude
(δV=0.05-0.15mag) variation. Duration of outburst ranges
from 10 to 50 days. Rise time is very short (several days)
followed by exponential decay. Larger outbursts result in longer
durations. Flickering behavior is often associated with maximum
light of bumper modes (Fig. 2).
3: Step events. Within the course of 10-50 days the brightness
increases; δV=0.2-0.3mag.
4: Baseline variation. Long-term trend of thousands of days with
amplitudes up to δV∼0.4mag.
5: Fading events. Drop in V luminosity of up to δV∼0.4mag with
timescales 200-600 days.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 12-Nov-2002