J/AJ/149/78 Candidate IR variables from SAGE-SMC survey (Polsdofer+, 2015)
Examining the infrared variable star population discovered in the Small
Magellanic Cloud using the SAGE-SMC survey.
Polsdofer E., Seale J., Sewilo M., Vijh U.P., Meixner M., Marengo M.,
Terrazas M.
<Astron. J., 149, 78 (2015)>
=2015AJ....149...78P 2015AJ....149...78P
ADC_Keywords: Magellanic Clouds ; Photometry, infrared ; Photometry, UBVRI ;
Stars, variable ; Spectral types
Keywords: infrared: general - Magellanic Clouds - stars: AGB and post-AGB -
stars: early-type - stars: formation - stars: variables: general
Abstract:
We present our study on the infrared variability of point sources in
the Small Magellanic Cloud (SMC). We use the data from the Spitzer
Space Telescope Legacy Program "Surveying the Agents of Galaxy
Evolution in the Tidally Stripped, Low Metallicity Small Magellanic
Cloud" (SAGE-SMC) and the "Spitzer Survey of the Small Magellanic
Cloud" (S3MC) survey, over three different epochs, separated by
several months to 3 years. Variability in the thermal infrared is
identified using a combination of Spitzer's InfraRed Array Camera 3.6,
4.5, 5.8, and 8.0µm bands, and the Multiband Imaging Photometer for
Spitzer 24µm band. An error-weighted flux difference between each
pair of three epochs ("variability index") is used to assess the
variability of each source. A visual source inspection is used to
validate the photometry and image quality. Out of ∼2 million sources
in the SAGE-SMC catalog, 814 meet our variability criteria. We matched
the list of variable star candidates to the catalogs of SMC sources
classified with other methods, available in the literature.
Carbon-rich Asymptotic Giant Branch (AGB) stars make up the majority
(61%) of our variable sources, with about a third of all of our
sources being classified as extreme AGB stars. We find a small, but
significant population of oxygen-rich (O-rich) AGB (8.6%), Red
Supergiant (2.8%), and Red Giant Branch (<1%) stars. Other matches to
the literature include Cepheid variable stars (8.6%), early type stars
(2.8%), Young-stellar objects (5.8%), and background galaxies (1.2%).
We found a candidate OH maser star, SSTISAGE1C J005212.88-730852.8,
which is a variable O-rich AGB star, and would be the first OH/IR star
in the SMC, if confirmed. We measured the infrared variability of a
rare RV Tau variable (a post-AGB star) that has recently left the AGB
phase. 59 variable stars from our list remain unclassified.
Description:
We utilized the data taken in three separate epochs with Spitzer
during the cryogenic mission using the IRAC 3.6, 4.5, 5.8, and
8.0µm bands, and the MIPS 24µm band. The data were collected as
part of the Spitzer Space Telescope Legacy Program "Surveying the
Agents of Galaxy Evolution in the Tidally Stripped, Low Metallicity
Small Magellanic Cloud" (SAGE-SMC; cat. II/305; Gordon et al.,
2011AJ....142..102G 2011AJ....142..102G) and the "Spitzer Survey of the Small Magellanic
Cloud" (S3MC; Bolatto et al. 2007, cat. J/ApJ/655/212) surveys.
The SAGE-SMC survey mapped the Small Magellanic Cloud (SMC) in all
IRAC (3.6, 4.5, 5.8, and 8.0µm) and MIPS (24, 70, and 160µm)
bands in two separate epochs, which we identify as Epochs 1 and 2.
These two epochs are separated by ∼3months (IRAC, data obtained in
2008 June 12-19 and September 15-23) and ∼9months (MIPS, acquired in
2007 September 17-25 and 2008 June 25-28), respectively. The
observations covered the full SMC, including the Bar, Wing, and part
of the Magellanic Bridge (the Tail; see Figure 1), for a total
coverage of ∼30deg2.
The S3MC survey only mapped the Bar and Wing of the SMC (∼8 times
smaller coverage than SAGE-SMC, for a total of ∼4deg2; see white
contour in Figure 1) in one single epoch, which we refer as Epoch 0
(2004 November 6-8 for MIPS and 2005 May 7-9 for IRAC), preceding the
SAGE-SMC survey by about 3years.
The near-IR JHKs data from the combined 2MASS (cat. II/246) and the
2MASS 6X Deep (6X2MASS; cat. II/281) Point Source Catalogs are the
integral part of the SAGE-SMC IRAC catalogs (cat. II/305). The
SAGE-SMC catalog is cross-matched in the SAGE-SMC database with the
optical data from the Magellanic Clouds Photometric Survey (MCPS, UBVI
bands; Zaritsky et al. 2002, cat. J/AJ/123/855) and OGLE (OGLE-III, VI
bands; Udalski et al., 2008AcA....58...69U 2008AcA....58...69U).
We adopt the V- and I-band photometry from OGLE-III when available,
and from MCPS otherwise.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 2205 814 Properties of the SAGE-SMC infrared variables
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See also:
II/305 : SAGE LMC and SMC IRAC Source Catalog (IPAC 2009)
II/281 : 2MASS 6X Point Source Working Database / Catalog (Cutri+ 2006)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/A+A/558/A3 : XMM-Newton point-source catalogue of the SMC (Sturm+, 2013)
J/ApJ/771/111 : SMC dusty OB stars. I. Optical spectroscopy (Sheets+, 2013)
J/ApJS/194/22 : Magellanic Quasars Survey: QSOs behind SMC (Kozlowski+, 2011)
J/AJ/142/103 : Cool evolved stars in SAGE-SMC (Boyer+, 2011)
J/AcA/60/91 : VI light curves of SMC type II Cepheids (Soszynski+, 2010)
J/AcA/60/17 : VI light curves of SMC classical Cepheids (Soszynski+, 2010)
J/AJ/140/416 : IR photometry of massive stars in the SMC (Bonanos+, 2010)
J/AJ/137/3139 : LMC SAGE. New variable evolved stars and YSOs (Vijh+, 2009)
J/ApJ/669/327 : S3MC: YSOs in N66, in SMC (Simon+, 2007)
J/ApJ/655/212 : S3MC IRAC and MIPS photometry (Bolatto+, 2007)
J/AJ/123/855 : Magellanic Clouds Photometric Survey: the SMC (Zaritsky+, 2002)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Star [1/825] Variable star candidate number
5- 13 F9.6 deg RAdeg Right Ascension in decimal degrees (J2000)
15- 24 F10.6 deg DEdeg Declination in decimal degrees (J2000)
26- 35 A10 --- --- [SSTISAGE0C]
37- 55 A19 --- SSTISAGE0C SAGE-SMC IRAC designation for Epoch 0
(JHHMMSS.ss+DDMMSS.s) (1)
57- 66 A10 --- --- [SSTISAGE1C]
68- 86 A19 --- SSTISAGE1C SAGE-SMC IRAC designation for Epoch 1
(JHHMMSS.ss+DDMMSS.s) (1)
88- 97 A10 --- --- [SSTISAGE2C]
99-117 A19 --- SSTISAGE2C SAGE-SMC IRAC designation for Epoch 2
(JHHMMSS.ss+DDMMSS.s) (1)
119-128 A10 --- --- [SSTM1SAGE0]
130-148 A19 --- SSTM1SAGE0 SAGE-SMC MIPS designation for Epoch 0
(JHHMMSS.ss+DDMMSS.s) (1)
150-159 A10 --- --- [SSTM1SAGE1]
161-179 A19 --- SSTM1SAGE1 SAGE-SMC MIPS designation for Epoch 1
(JHHMMSS.ss+DDMMSS.s) (1)
181-190 A10 --- --- [SSTM1SAGE2]
192-210 A19 --- SSTM1SAGE2 SAGE-SMC MIPS designation for Epoch 2
(JHHMMSS.ss+DDMMSS.s) (1)
212-222 E11.6 arcsec rI01 [0/0.015]? Distance between SAGE-SMC IRAC
position at Epochs 0 & 1 (2)
224-234 F11.9 arcsec rI02 [0/0.019]? Distance between SAGE-SMC IRAC
position at Epochs 0 & 2 (2)
236-246 F11.9 arcsec rI12 [0/0.016]? Distance between SAGE-SMC IRAC
position at Epochs 1 & 2 (2)
248-258 F11.9 arcsec rM0 [0/0.036]? Distance between SAGE-SMC IRAC and
MIPS position at Epochs 0 (2)
260-279 F20.18 arcsec rM1 [0/0.038]? Distance between SAGE-SMC IRAC and
MIPS position at Epochs 1 (2)
281-291 F11.9 arcsec rM2 [0/0.044]? Distance between SAGE-SMC IRAC and
MIPS position at Epochs 2 (2)
293 I1 --- V01 [0/1] Variability flag between Epochs 0 & 1 (3)
295 I1 --- V02 [0/1] Variability flag between Epochs 0 & 2 (3)
297 I1 --- V12 [0/1] Variability flag between Epochs 1 & 2 (3)
299-305 A7 --- Cl0 Classification of source at Epoch 0 (4)
307-323 A17 --- SpT0 Spectral type of Epoch 0 source
325-330 A6 --- Cl1 Classification of source at Epoch 1 (4)
332-339 A8 --- SpT1 Spectral type of Epoch 1 source
341-343 A3 --- Cl2 Classification of source at Epoch 2 (4)
345-364 F20.16 --- V3.6-01 [-16.1/23.6]? Variability index between Epochs
0 and 1 for Spitzer/IRAC 3.6µm band (5)
366-385 F20.16 --- V4.5-01 [-19.3/31.4]? Variability index between Epochs
0 and 1 for Spitzer/IRAC 4.5µm band (5)
387-406 F20.16 --- V5.8-01 [-22.7/29.63]? Variability index between Epochs
0 and 1 for Spitzer/IRAC 5.8µm band (5)
408-428 F21.17 --- V8.0-01 [-24.4/24.9]? Variability index between Epochs
0 and 1 for Spitzer/IRAC 8.0µm band (5)
430-450 F21.17 --- V24-01 [-46.3/47.1]? Variability index between Epochs
0 and 1 for Spitzer/MIPS 24µm band (5)
452-472 F21.17 --- V3.6-02 [-18.6/21.0]? Variability index between Epochs
0 and 2 for Spitzer/IRAC 3.6µm band (5)
474-494 F21.17 --- V4.5-02 [-19.1/26.5]? Variability index between Epochs
0 and 2 for Spitzer/IRAC 4.5µm band (5)
496-515 F20.16 --- V5.8-02 [-22.7/30.3]? Variability index between Epochs
0 and 2 for Spitzer/IRAC 5.8µm band (5)
517-536 F20.16 --- V8.0-02 [-20.7/28.4]? Variability index between Epochs
0 and 2 forSpitzer/IRAC 8.0µm band (5)
538-557 F20.16 --- V24-02 [-83.4/76.1]? Variability index between Epochs
0 and 2 for Spitzer/MIPS 24µm band (5)
559-579 F21.17 --- V3.6-12 [-16.9/15.2]? Variability index between Epochs
1 and 2 for Spitzer/IRAC 3.6µm band (5)
581-601 F21.17 --- V4.5-12 [-14.6/17.2]? Variability index between Epochs
1 and 2 for Spitzer/IRAC 4.5µm band (5)
603-623 F21.17 --- V5.8-12 [-21.3/21.0]? Variability index between Epochs
1 and 2 for Spitzer/IRAC 5.8µm band (5)
625-645 F21.17 --- V8.0-12 [-16.6/14.7]? Variability index between Epochs
1 and 2 for Spitzer/IRAC 8.0µm band (5)
647-667 F21.17 --- V24-12 [-72.5/80.8]? Variability index between Epochs
1 and 2 for Spitzer/MIPS 24µm band (5)
669-688 F20.17 mJy SU.M [0/24.2]? MCPS U band flux density (6)
690-709 F20.18 mJy e_SU.M [0/3.21]? Uncertainty in SU.M
711-730 F20.17 mJy SB.M [0/47.8]? MCPS B band flux density (6)
732-751 F20.18 mJy e_SB.M [0/3.35]? Uncertainty in SB.M
753-772 F20.17 mJy SV.M [0/94.8]? MCPS V band flux density (6)
774-793 F20.18 mJy e_SV.M [0/4.7]? Uncertainty in SV.M
795-815 F21.17 mJy SI.M [0/256.2]? MCPS I band flux density (6)
817-837 F21.18 mJy e_SI.M [0.0003/26.43]? Uncertainty in SI.M
839-858 F20.17 mJy SV.O [0/19.3]? OGLE-III V band flux density (7)
860-878 F19.16 mJy SI.O [0/22.4]? OGLE-III I band flux density (7)
880-898 F19.15 mJy SJ.2 [0.1/797]? 2MASS J band flux density (8)
900-918 F19.16 mJy e_SJ.2 [0.01/15]? Uncertainty in SJ.2 (8)
920-939 F20.15 mJy SH.2 [0.1/1264]? 2MASS H band flux density (8)
941-959 F19.16 mJy e_SH.2 [0.026/49]? Uncertainty in SH.2 (8)
961-980 F20.15 mJy SK.2 [0.1/1084]? 2MASS Ks band flux density (8)
982-1000 F19.16 mJy e_SK.2 [0.034/21]? Uncertainty in SK.2 (8)
1002-1020 F19.15 mJy S3.6-0 [0.2/447]? Epoch 0 Spitzer/IRAC 3.6µm
band flux density (9)
1022-1040 F19.17 mJy e_S3.6-0 [0.006/7]? Uncertainty in 0S3.6 (9)
1042-1060 F19.15 mJy S4.5-0 [0.1/303]? Epoch 0 Spitzer/IRAC 4.5µm
band flux density (9)
1062-1080 F19.17 mJy e_S4.5-0 [0.004/5]? Uncertainty in 0S4.5 (9)
1082-1100 F19.15 mJy S5.8-0 [0.1/240]? Epoch 0 Spitzer/IRAC 5.8µm
band flux density (9)
1102-1119 F18.16 mJy e_S5.8-0 [0.01/4.4]? Uncertainty in 0S5.8 (9)
1121-1139 F19.15 mJy S8.0-0 [0.1/249]? Epoch 0 Spitzer/IRAC 8.0µm
band flux density (9)
1141-1158 F18.16 mJy e_S8.0-0 [0.01/4.7]? Uncertainty in 0S8.0 (9)
1160-1168 F9.4 mJy S24-0 [0.4/1492]? Epoch 0 Spitzer/MIPS 24µm band
flux density (9)
1170-1177 F8.5 mJy e_S24-0 [0.08/10.5]? Uncertainty in 0S24 (9)
1179-1197 F19.15 mJy S3.6-1 [0.2/728]? Epoch 1 Spitzer/IRAC 3.6µm band
flux density (9)
1199-1217 F19.16 mJy e_S3.6-1 [0.012/31]? Uncertainty in S3.6-1 (9)
1219-1237 F19.15 mJy S4.5-1 [0.19/495]? Epoch 1 Spitzer/IRAC 4.5µm band
flux density (9)
1239-1257 F19.16 mJy e_S4.5-1 [0.01/16.9]? Uncertainty in S4.5-1 (9)
1259-1277 F19.15 mJy S5.8-1 [0.19/376]? Epoch 1 Spitzer/IRAC 5.8µm band
flux density (9)
1279-1297 F19.16 mJy e_S5.8-1 [0.01/12]? Uncertainty in S5.8-1 (9)
1299-1317 F19.15 mJy S8.0-1 [0.2/288]? Epoch 1 Spitzer/IRAC 8.0µm band
flux density (9)
1319-1336 F18.16 mJy e_S8.0-1 [0.01/9.8]? Uncertainty in S8.0-1 (9)
1338-1346 F9.4 mJy S24-1 [0.49/1436]? Epoch 1 Spitzer/MIPS 24µm band
flux density (9)
1348-1355 F8.5 mJy e_S24-1 [0.06/11.7]? Uncertainty in S24-1 (9)
1357-1375 F19.15 mJy S3.6-2 [0.25/713]? Epoch 2 Spitzer/IRAC 3.6µm band
flux density (9)
1377-1395 F19.16 mJy e_S3.6-2 [0.01/42]? Uncertainty in S3.6-2 (9)
1397-1415 F19.15 mJy S4.5-2 [0.19/482]? Epoch 2 Spitzer/IRAC 4.5µm band
flux density (9)
1417-1436 F20.17 mJy e_S4.5-2 [0.009/21]? Uncertainty in S4.5-2 (9)
1438-1456 F19.15 mJy S5.8-2 [0.17/380]? Epoch 2 Spitzer/IRAC 5.8µm band
flux density (9)
1458-1476 F19.16 mJy e_S5.8-2 [0.01/11]? Uncertainty in S5.8-2 (9)
1478-1496 F19.15 mJy S8.0-2 [0.2/280]? Epoch 2 Spitzer/IRAC 8.0µm band
flux density (9)
1498-1515 F18.16 mJy e_S8.0-2 [0.014/8.44]? Uncertainty in S8.0-2 (9)
1517-1525 F9.4 mJy S24-2 [0.5/1275]? Epoch 2 Spitzer/MIPS 24µm band
flux density (9)
1527-1534 F8.5 mJy e_S24-2 [0.091/13.75]? Uncertainty in S24-2 (9)
1536-1541 F6.3 mag Umag [12.2/22]? MCPS U band magnitude (10)
1543-1547 F5.3 mag e_Umag ? Uncertainty in Umag (10)
1549-1554 F6.3 mag Bmag [12.3/23]? MCPS B band magnitude (10)
1556-1560 F5.3 mag e_Bmag ? Uncertainty in Bmag (10)
1562-1567 F6.3 mag Vmag [11.4/22.3]? MCPS V band magnitude (10)
1569-1573 F5.3 mag e_Vmag ? Uncertainty in Vmag (10)
1575-1580 F6.3 mag Imag [9.9/20.9]? MCPS I band magnitude (10)
1582-1586 F5.3 mag e_Imag ? Uncertainty in Imag (10)
1588-1604 F17.14 mag Jmag [8.2/17.5]? 2MASS J band magnitude (8)
1606-1623 F18.16 mag e_Jmag [0.01/0.253]? Uncertainty in Jmag (8)
1625-1641 F17.14 mag Hmag [7.2/16.9]? 2MASS H band magnitude (8)
1643-1660 F18.16 mag e_Hmag [0.020/0.278]? Uncertainty in Hmag (8)
1662-1678 F17.14 mag Kmag [6.9/16.4]? 2MASS Ks band magnitude (8)
1680-1697 F18.16 mag e_Kmag [0.017/0.205]? Uncertainty in Kmag (8)
1699-1715 F17.14 mag [3.6]0 [6.9/15]? Epoch 0 Spitzer/IRAC 3.6µm band
magnitude (9)
1717-1736 F20.17 mag e_[3.6]0 [0.009/0.143]? Uncertainty in [3.6]0 (9)
1738-1754 F17.14 mag [4.5]0 [6.9/15]? Epoch 0 Spitzer/IRAC 4.5µm band
magnitude (9)
1756-1775 F20.17 mag e_[4.5]0 [0.008/0.058]? Uncertainty in [4.5]0 (9)
1777-1793 F17.14 mag [5.8]0 [6.7/14.7]? Epoch 0 Spitzer/IRAC 5.8µm
band magnitude (9)
1795-1814 F20.17 mag e_[5.8]0 [0.008/0.112]? Uncertainty in [5.8]0 (9)
1816-1832 F17.14 mag [8.0]0 [6/14.3]? Epoch 0 Spitzer/IRAC 8.0µm band
magnitude (9)
1834-1853 F20.17 mag e_[8.0]0 [0.008/0.108]? Uncertainty in [8.0]0 (9)
1855-1860 F6.3 mag [24]0 [1.7/10.5]? Epoch 0 Spitzer/MIPS 24µm band
magnitude (9)
1862-1869 F8.6 mag e_[24]0 [0.004249/0.2166]? Uncertainty in [24]0 (9)
1871-1887 F17.14 mag [3.6]1 [6.4/15]? Epoch 1 Spitzer/IRAC 3.6µm band
magnitude (9)
1889-1907 F19.16 mag e_[3.6]1 [0.01/0.146]? Uncertainty in [3.6]1 (9)
1909-1925 F17.14 mag [4.5]1 [6.4/15]? Epoch 1 Spitzer/IRAC 4.5µm band
magnitude (9)
1927-1945 F19.16 mag e_[4.5]1 [0.017/0.12]? Uncertainty in [4.5]1 (9)
1947-1963 F17.14 mag [5.8]1 [6.2/14.5]? Epoch 1 Spitzer/IRAC 5.8µm band
magnitude (9)
1965-1983 F19.16 mag e_[5.8]1 [0.016/0.178]? Uncertainty in [5.8]1 (9)
1985-2001 F17.14 mag [8.0]1 [5.8/13.7]? Epoch 1 Spitzer/IRAC 8.0µm band
magnitude (9)
2003-2021 F19.16 mag e_[8.0]1 [0.014/0.109]? Uncertainty in [8.0]1 (9)
2023-2028 F6.3 mag [24]1 [1.7/10.5]? Epoch 1 Spitzer/MIPS 24µm band
magnitude (9)
2030-2037 F8.6 mag e_[24]1 [0.005278/0.1613]? Uncertainty in [24]1 (9)
2039-2055 F17.14 mag [3.6]2 [6.4/15.2]? Epoch 2 Spitzer/IRAC 3.6µm band
magnitude (9)
2057-2075 F19.16 mag e_[3.6]2 [0.017/0.127]? Uncertainty in [3.6]2 (9)
2077-2093 F17.14 mag [4.5]2 [6.4/15]? Epoch 2 Spitzer/IRAC 4.5µm band
magnitude (9)
2095-2113 F19.16 mag e_[4.5]2 [0.016/0.11]? Uncertainty in [4.5]2 (9)
2115-2131 F17.14 mag [5.8]2 [6.2/14.6]? Epoch 2 Spitzer/IRAC 5.8µm band
magnitude (9)
2133-2151 F19.16 mag e_[5.8]2 [0.014/0.173]? Uncertainty in [5.8]2 (9)
2153-2169 F17.14 mag [8.0]2 [5.9/13.8]? Epoch 2 Spitzer/IRAC 8.0µm band
magnitude (9)
2171-2189 F19.16 mag e_[8.0]2 [0.013/0.109]? Uncertainty in [8.0]2 (9)
2191-2196 F6.3 mag [24]2 [1.8/10.4]? Epoch 2 Spitzer/MIPS 24µm band
magnitude (9)
2198-2205 F8.6 mag e_[24]2 [0.00308/0.1963]? Uncertainty in [24]2 (9)
--------------------------------------------------------------------------------
Note (1): We utilized the data taken in three separate epochs with Spitzer:
MIPS epoch 0 = 2004-11-06/08 (Spitzer Survey of the Small Magellanic Cloud,
S3MC; Bolatto et al. 2007, cat. J/ApJ/655/212);
IRAC epoch 0 = 2005-05-07/09 (S3MC survey);
MIPS epoch 1 = 2007-09-17/25 (Surveying the Agents of Galaxy Evolution in
the Tidally Stripped, Low Metallicity Small Magellanic Cloud;
SAGE-SMC; cat. II/305; Gordon et al., 2011AJ....142..102G 2011AJ....142..102G);
IRAC epoch 1 = 2008-06-12/19 (SAGE-SMC, II/305);
MIPS epoch 2 = 2008-06-25/28 (SAGE-SMC, II/305);
IRAC epoch 2 = 2008-09-15/23 (SAGE-SMC, II/305).
Note (2): We generated a list of all the sources that had coordinates within 1''
of each other within at least two of the three epochs of the SAGE-SMC IRAC
data (Epoch0=2005-05-07/09, Epoch1=2008-06-12219, Epoch2=2008-09-15/23).
We then matched the resulting IRAC lists with their corresponding
MIPS 24µm data for each epoch (Epoch0=2004-11-06/08,
Epoch1=2007-09-17/25, Epoch2=2008-06-25/28), again requiring a match
within 1''. See Section 3.1 for additional details.
Note (3): Variability based on the data from two epochs is defined as:
1 = A source is a variable, i.e., its absolute variability index is larger
than 3 in at least two consecutive bands;
0 = A source does not vary or there is not enough photometric data
available.
Note (4): The classes from literature matching for SAGE-SMC variable sources
are defined as follows:
AGN = Active Galactic Nuclei;
PNe = Planetary Nebulae
Radio = Radio source;
Cepheid = Classic Cepheid or Type II Cepheid;
sgBe = supergiant Be star;
LBV = Luminous Blue Variable;
O = O-type star;
QSO = Quasar;
RGB = Red Giant Branch;
RSG = Red SuperGiant;
YSO = Young Stellar Object;
oAGB = oxygen-rich Asymptotic Giant Branch (AGB) star;
aoAGB = "anomalous" oxygen-rich AGB star;
cAGB = carbon-rich AGB star;
acAGB = "anomalous" carbon-rich AGB star;
xAGB = extreme AGB star;
bexrb = X-ray binary star;
dustyOB = dusty OB star (reported as early type star);
earlyB = early B star;
lateB = late B star;
unid = unidentified;
xray = X-RAY source.
Note (5): Defined by Vijh et al. 2009 (J/AJ/137/3139) as the error-weighted
flux difference between each pair of epochs:
V = (fi-fj)/((σ2fi+σ2fj)0.5), Equation (1),
where fi and fj are fluxes in a certain band for a single source in
epochs i and j (for SAGE-SMC IRAC data: Epoch0=2005-05-07/09,
Epoch1=2008-06-12/19, Epoch2=2008-09-15/23; and for MIPS 24µm data:
Epoch0=2004-11-06/08, Epoch1=2007-09-17/25, Epoch2=2008-06-25/28),
respectively, and σfi and σfj are respective flux
uncertainties. A source was considered to be variable if |V|>3 (flux
changes >3σ; see Section 3.2 for further details.
Note (6): The Magellanic Clouds Photometric Survey (MCPS) catalog (Zaritsky
et al. 2002, cat. J/AJ/123/855) provides magnitudes only. The U-, B-, V-,
and I-band fluxes and flux uncertainties were derived using the zero
magnitude flux of 1790, 4063, 3636, and 2416Jy, respectively.
Note (7): The OGLE-III catalog provides magnitudes only. The V- and I-band
fluxes were derived using the zero magnitude flux of 3636Jy and 2416Jy,
respectively. No photometric uncertainties are available for the OGLE-III
data.
Note (8): The near-IR JHKs data from the combined 2MASS (cat. II/246) and the
2MASS 6X Deep (6X2MASS; cat. II/281) Point Source Catalogs are the integral
part of the SAGE-SMC IRAC catalogs (cat. II/305).
Note (9): We utilized the data taken in three separate epochs (for IRAC data:
Epoch0=2005-05-07/09, Epoch1=2008-06-12/19, Epoch2=2008-09-15/23; and for
MIPS 24µm data: Epoch0=2004-11-06/08, Epoch1=2007-09-17/25,
Epoch2=2008-06-25/28) with Spitzer during the cryogenic mission using the
IRAC 3.6, 4.5, 5.8, and 8.0µm bands, and the MIPS 24µm band. The data
were collected as part of the Spitzer Space Telescope Legacy Program
"Surveying the Agents of Galaxy Evolution in the Tidally Stripped, Low
Metallicity Small Magellanic Cloud" (SAGE-SMC; cat. II/305; Gordon et al.,
2011AJ....142..102G 2011AJ....142..102G; ) and the "Spitzer Survey of the Small Magellanic
Cloud" (S3MC; Bolatto et al. 2007, cat. J/ApJ/655/212) surveys.
Note (10): From the Magellanic Clouds Photometric Survey (MCPS) catalog
(Zaritsky et al. 2002, cat. J/AJ/123/855).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 02-Mar-2015