J/AJ/137/3139 LMC SAGE. New variable evolved stars and YSOs (Vijh+, 2009)
Variable evolved stars and young stellar objects discovered in the Large
Magellanic Cloud using the SAGE survey.
Vijh U.P., Meixner M., Babler B., Block M., Bracker S., Engelbracht C.W.,
For B., Gordon K., Hora J., Indebetouw R., Leitherer C., Meade M.,
Misselt K., Sewilo M., Srinivasan S., Whitney B.
<Astron. J., 137, 3139-3148 (2009)>
=2009AJ....137.3139V 2009AJ....137.3139V
ADC_Keywords: Magellanic Clouds ; Infrared sources ; Photometry, infrared
Keywords: infrared: stars - galaxies: individual (LMC) -
stars: AGB and post-AGB - stars: formation - stars: mass loss -
stars: variables: other
Abstract:
We present initial results and source lists of variable sources in the
Large Magellanic Cloud (LMC) for which we detect thermal infrared
variability from the Surveying the Agents of a Galaxy's Evolution
(SAGE) survey, which had two epochs of photometry separated by 3
months. The SAGE survey mapped a 7°x7° region of the LMC using
the Infrared Array Camera (IRAC) and the MIPS instruments on board
Spitzer. Variable sources are identified using a combination of the
IRAC 3.6, 4.5, 5.8, 8.0um bands and the MIPS 24um bands. An
error-weighted flux difference between the two epochs is used to
assess the variability. Of the ∼3 million sources detected at both
epochs, we find ∼2000 variable sources for which we provide electronic
catalogs. Most of the variable sources can be classified as asymptotic
giant branch (AGB) stars. A large fraction (>66%) of the extreme AGB
stars are variable and only smaller fractions of carbon-rich (6.1%)
and oxygen-rich (2.0%) stars are detected as variable sources. We also
detect a population of variable young stellar object candidates.
Description:
SAGE is a Legacy project on the Spitzer Space Telescope (SST) ,
which mapped a 7x7deg2 region of the LMC using the IRAC camera in
the [3.6]um, [4.5]um, [5.8]um, and [8.0]um bands and the MIPS camera
in the [24]um, [70]um, and [160]um filters.
The IRAC epoch 1 data were taken on 2005 July 15-26 and epoch 2 on
2005 October 26-November 2, and the MIPS epoch 1 data were taken on
2005 July 27-August 3 and epoch 2 on 2005 November 2-9.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 219 3934 *Properties of the 1967 SAGE Variables
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Note on table2.dat: each source appears twice on two consecutive lines, one
line per epoch; variability indices and fractional fluxes are given
only on the first of the 2 lines (corresponding to first epoch)
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See also:
J/AJ/99/784 : IR photometry of LMC long-period variables (Hughes+ 1990)
J/A+A/303/137 : EROS Variables: Cepheids in the bar of LMC (Beaulieu+ 1995)
J/AJ/114/326 : MACHO Variables V. (Alcock+ 1997)
J/A+A/344/521 : LMC variable X-ray sources (Haberl+, 1999)
J/A+A/462/599 : JHKs photometry of LMC cluster Cepheids (Testa+, 2007)
J/AcA/51/317 : OGLE DIA. Catalog of LMC and SMC images (Zebrun+, 2001)
J/AJ/124/2039 : LMC blue variable stars from MACHO (Keller+, 2002)
J/MNRAS/330/137 : LMC long-period red variables VRc observations (Noda+, 2002)
J/AJ/136/1242 : LMC long-period variables from MACHO (Fraser+, 2008)
J/AJ/135/726 : Spitzer SAGE observations of LMC PNe (Hora+, 2008)
J/AJ/136/18 : LMC SAGE. New candidate YSOs (Whitney+, 2008)
J/PASP/122/683 : SAGE-Spec Spitzer legacy program (Kemper+, 2010)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- --- [SSTISAGE]
9 A1 --- I [12] IRAC survey epoch (1=2008-Jun, 2=2008-Sep)
10 A1 --- --- [C] (catalog)
12- 30 A19 --- SSTISAGE IRAC designation (SSTISAGE1C JHHMMSS.ss+DDMMSS.s
or SSTISAGE2C JHHMMSS.ss+DDMMSS.s)
32- 40 A9 --- --- [SSTM1SAGE]
41 A1 --- M [12] MIPS survey epoch (1=2007-Sep, 2=2008-Jun)
43- 61 A19 --- SSTM1SAGE MIPS designation (SSTM1SAGE1 JHHMMSS.ss+DDMMSS.s
or SSTM1SAGE2 JHHMMSS.ss+DDMMSS.s)
63 I1 --- Ep [1/2] Epoch
65- 71 F7.4 deg RAdeg Right Ascension in decimal degrees (J2000)
73- 80 F8.4 deg DEdeg Declination in decimal degrees (J2000)
82 A1 --- cl [COUXY] Source classification (1)
84- 90 F7.2 mJy F3.6 ?=-999.90 Spitzer/IRAC 3.6µm flux density
92- 98 F7.2 mJy e_F3.6 ?=-999.90 Error in F3.6
100-104 F5.1 --- V3.6 ? Variability index at 3.6 microns (2)
106-110 F5.2 --- f3.6 [-2/2]? Fractional flux at 3.6 microns (3)
112-118 F7.2 mJy F4.5 ?=-999.90 Spitzer/IRAC 4.5µm flux density
120-126 F7.2 mJy e_F4.5 ?=-999.90 Error in F4.5
128-132 F5.1 --- V4.5 ? Variability index at 4.5 microns (2)
134-138 F5.2 --- f4.5 [-2/2]? Fractional flux at 4.5 microns (3)
140-146 F7.2 mJy F5.8 ?=-999.90 Spitzer/IRAC 5.8µm flux density
148-154 F7.2 mJy e_F5.8 ?=-999.90 Error in F5.8
156-160 F5.1 --- V5.8 ? Variability index at 5.8 microns (2)
162-166 F5.2 --- f5.8 [-2/2]? Fractional flux at 5.8 microns (3)
168-174 F7.2 mJy F8.0 ?=-999.90 Spitzer/IRAC 8.0µm flux density
176-182 F7.2 mJy e_F8.0 ?=-999.90 Error in F8.0
184-188 F5.1 --- V8.0 ? Variability index at 8.0 microns (2)
190-194 F5.2 --- f8.0 [-2/2]? Fractional flux at 8.0 microns (3)
196-202 F7.2 mJy F24 ?=-999.90 Spitzer/MIPS 24µm flux density
204-207 F4.2 mJy e_F24 ?=-999.90 Error in F24
209-213 F5.1 --- V24 ? Variability index at 24 microns (2)
215-219 F5.2 --- f24 [-2/2]? Fractional flux at 24 microns (3)
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Note (1): Source classification as follows:
U = Unclassified source
C = C-rich AGB star
O = O-rich AGB star
X = Extreme AGB star
Y = YSO candidate
Note (2): the variability index is defined by
V = (f1-f2)/sqrt(var(f1)+var(f2))
if f1 and f2 are the fluxes at the 2 epochs. Sources are considered
as variable if |V|>3 (see section 2 of paper)
Note (3): the fractional flux fF is defined by
fF = 2(f1-f2)/(f1+f2)
if f1 and f2 are the fluxes at the 2 epochs.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 24-Aug-2011