J/ApJS/211/3 NIR photometry variability in ρ Oph (Parks+, 2014)
Periodic and aperiodic variability in the molecular cloud ρ Ophiuchus.
Parks J.R., Plavchan P., White R.J., Gee A.H.
<Astrophys. J. Suppl. Ser., 211, 3 (2014)>
=2014ApJS..211....3P 2014ApJS..211....3P
ADC_Keywords: Photometry, infrared ; Molecular clouds ; Stars, variable ; YSOs
Keywords: methods: statistical; stars: individual: rho Ophiuchus
Abstract:
Presented are the results of a near-IR photometric survey of 1678
stars in the direction of the ρ Ophiuchus (ρ Oph) star forming
region using data from the 2MASS Calibration Database. For each target
in this sample, up to 1584 individual J-, H-, and Ks-band photometric
measurements with a cadence of ∼1 day are obtained over three
observing seasons spanning ∼2.5 yr; it is the most intensive survey of
stars in this region to date. This survey identifies 101 variable
stars with ΔKs-band amplitudes from 0.044 to 2.31 mag and
Δ(J-Ks) color amplitudes ranging from 0.053 to 1.47 mag. Of the
72 young ρ Oph star cluster members included in this survey, 79%
are variable; in addition, 22 variable stars are identified as
candidate members. Based on the temporal behavior of the Ks
time-series, the variability is distinguished as either periodic, long
time-scale or irregular. This temporal behavior coupled with the
behavior of stellar colors is used to assign a dominant variability
mechanism. A new period-searching algorithm finds periodic signals in
32 variable stars with periods between 0.49 to 92 days. The chief
mechanism driving the periodic variability for 18 stars is rotational
modulation of cool starspots while 3 periodically vary due to
accretion-induced hot spots. The time-series for six variable stars
contains discrete periodic "eclipse-like" features with periods
ranging from 3 to 8 days. These features may be asymmetries in the
circumstellar disk, potentially sustained or driven by a proto-planet
at or near the co-rotation radius. Aperiodic, long time-scale
variations in stellar flux are identified in the time-series for 31
variable stars with time-scales ranging from 64 to 790 days. The chief
mechanism driving long time-scale variability is variable extinction
or mass accretion rates. The majority of the variable stars (40)
exhibit sporadic, aperiodic variability over no discernable
time-scale. No chief variability mechanism could be identified for
these variable stars.
Description:
The Two Micron All-Sky Survey (2MASS, Skrutskie et al. 2006,
Cat. II/246) imaged nearly the entire sky via simultaneous drift
scanning in three near-infrared bands (JHKs) between 1997 and 2001.
Observations were taken at the northern Mt. Hopkins Observatory and
the southern CTIO facility.
The source selection in the ρ Oph field is similar to that
described in Plavchan et al., 2008, Cat. J/ApJS/175/191. Of the 7815
stars identified in the parent sample, 1678 stars have a sufficient
number of detections for variability and periodic analysis (listed in
table 1). The magnitudes and errors listed are extracted from a
co-added image of all calibration scans in that particular band.
From the target sample of 1678 stars, 101 stars (6%) are identified as
variable (listed in table 3).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 1678 Catalog of 2MASS Stars in ρ Oph
table3.dat 68 101 Catalog of Variable Stars in ρ Oph
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See also:
II/289 : JKH photometry in LDN 1688 (Wilking+, 2008)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJ/751/22 : Candidates of the ρ Oph cluster (Barsony+, 2012)
J/A+A/519/A34 : YSOs in DROXO (Deep rho Oph XMM obs.) (Pillitteri+, 2010)
J/A+A/515/A75 : Low-mass pop. in ρ Oph cloud (Alves de Oliveira+, 2010)
J/ApJ/719/550 : Deep NIR imaging of ρ Oph cloud core (Marsh+, 2010)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJS/175/191 : Variables from 2MASS calibration fields (Plavchan+, 2008)
J/A+A/485/155 : HK photometry of rho Oph PMS stars (Alves de Oliveira+, 2008)
J/A+A/461/183 : Variability of classical T Tauri (Grankin+, 2007)
J/A+A/452/245 : Near-IR photometry of PMS stars in rho Oph (Natta+, 2006)
J/ApJ/630/381 : Mid-IR imaging in ρ Oph (Barsony+, 2005)
J/A+A/372/173 : ISOCAM obs. of the rho Ophiuchi cloud (Bontemps+, 2001)
J/A+A/359/113 : X-ray and IR study of Rho Oph dark cloud (Grosso+, 2000)
J/A+A/337/403 : Low-mass stars evolutionary models (Baraffe+ 1998)
J/ApJS/112/109 : Rho Oph Near-IR Positions and Photometry (Barsony+, 1997)
J/ApJ/438/813 : Stellar population in ρ Oph cloud core (Strom+, 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.6 deg RAdeg [246.73/246.89] Right Ascension (J2000)
12- 21 F10.6 deg DEdeg [-25.19/-24.19] Declination (J2000)
23- 25 I3 --- o_Jmag [0/263] Number of J band observations
27- 29 I3 --- o_Hmag Number of H band observations
31- 33 I3 --- o_Ksmag Number of Ks band observations
35- 40 F6.3 mag Jmag [8/17.9] 2MASS J band magnitude (1)
42- 47 F6.3 mag e_Jmag [0/0.3]?=99 Uncertainty in Jmag
49- 54 F6.3 mag Hmag [7.4/16.9] 2MASS H band magnitude (1)
56- 60 F5.3 mag e_Hmag [0/0.3]?=99 Uncertainty in Hmag
62- 67 F6.3 mag Ksmag [6.7/16.1] 2MASS Ks band magnitude (1)
69- 74 F6.3 mag e_Ksmag [0/0.2]?=99 Uncertainty in Ksmag
76- 91 A16 --- 2MASS 2MASS identification (HHMMSSss+DDMMSSs; J2000)
for the new candidate members (2)
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Note (1): Unweighted mean apparent magnitude of Cal-PSWDB photometry.
Note (2): Column added by CDS from table 4 for the 22 new candidate ρ Oph
members. See section 3.4 for further explanations.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.6 deg RAdeg [246.73/246.89] Right Ascension (J2000)
12- 21 F10.6 deg DEdeg [-25.15/-24.20] Declination (J2000)
23- 29 I07 --- Var Variability flags (1)
31- 35 F5.3 mag DKsmag [0.04/2.4] Ks-band amplitude of variability
37- 41 F5.3 mag D(J-H) [0.04/1.3]? J-H amplitude of variability
43- 47 F5.3 mag D(H-Ks) [0.009/1.4]? H-Ks amplitude of variability
49- 60 A12 --- Type Variability type: "LTV" (long time-scale
variables), "irregular", "periodic",
or "periodic/LTV")
62- 64 A3 --- Class YSO class (0, I, II or III) (2)
66- 68 A3 --- onCloud? [yes/no ] "On Cloud"? (otherwise within
the "field")
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Note (1): The first three flags correspond to flickering variability. The second
three flags correspond to excursive variability. The seventh flag
corresponds to the Stetson index.
The flag is set to 1 when true; 0 otherwise.
Note (2): Bontemps et al. 2001, Cat. J/A+A/372/173; Gutermuth et al. 2009,
Cat. J/ApJS/184/18
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Nomenclature note:
These stars are <2MASCW JHHMMSSss+DDMMSSs> in Simbad.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Apr-2014