J/AJ/147/82 Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014)
CSI 2264: simultaneous optical and infrared light curves of young disk-bearing
stars in NGC 2264 with CoRoT and Spitzer -- Evidence for multiple origins of
variability.
Cody A.M., Stauffer J., Baglin A., Micela G., Rebull L.M., Flaccomio E.,
Morales-Calderon M., Aigrain S., Bouvier J., Hillenbrand L.A.,
Gutermuth R., Song I., Turner N., Alencar S.H.P., Zwintz K., Plavchan P.,
Carpenter J., Findeisen K., Carey S., Terebey S., Hartmann L., Calvet N.,
Teixeira P., Vrba F.J., Wolk S., Covey K., Poppenhaeger K., Gunther H.M.,
Forbrich J., Whitney B., Affer L., Herbst W., Hora J., Barrado D.,
Holtzman J., Marchis F., Wood K., Guimaraes M.M., Lillo Box J., Gillen E.,
McQuillan A., Espaillat C., Allen L., D'Alessio P., Favata F.
<Astron. J., 147, 82 (2014)>
=2014AJ....147...82C 2014AJ....147...82C
ADC_Keywords: Clusters, open ; Photometry, infrared
Keywords: accretion, accretion disks - circumstellar matter -
protoplanetary disks - stars: pre-main sequence -
stars: variables: T Tauri, Herbig Ae/Be - techniques: photometric
Abstract:
We present the Coordinated Synoptic Investigation of NGC 2264, a
continuous 30 day multi-wavelength photometric monitoring campaign on
more than 1000 young cluster members using 16 telescopes. The
unprecedented combination of multi-wavelength, high-precision,
high-cadence, and long-duration data opens a new window into the time
domain behavior of young stellar objects. Here we provide an overview
of the observations, focusing on results from Spitzer and CoRoT. The
highlight of this work is detailed analysis of 162 classical T Tauri
stars for which we can probe optical and mid-infrared flux variations
to 1% amplitudes and sub-hour timescales. We present a morphological
variability census and then use metrics of periodicity, stochasticity,
and symmetry to statistically separate the light curves into seven
distinct classes, which we suggest represent different physical
processes and geometric effects. We provide distributions of the
characteristic timescales and amplitudes and assess the fractional
representation within each class. The largest category (>20%) are
optical "dippers" with discrete fading events lasting ∼1-5 days. The
degree of correlation between the optical and infrared light curves is
positive but weak; notably, the independently assigned optical and
infrared morphology classes tend to be different for the same object.
Assessment of flux variation behavior with respect to (circum)stellar
properties reveals correlations of variability parameters with
Hα emission and with effective temperature. Overall, our results
point to multiple origins of young star variability, including
circumstellar obscuration events, hot spots on the star and/or disk,
accretion bursts, and rapid structural changes in the inner disk.
Description:
We selected 489 high-probability cluster members for observation by
CoRoT in 2011, along with a Spitzer FOV encompassing 1266 members. We
retain only 163 disk-bearing members in both CoRoT and Spitzer (see
Tables 3 and 4).
Warm Spitzer/IRAC observations of a ∼0.8°*0.8° region of
NGC2264 were carried out from 2011 December 3 to 2012 January 1 under
program 80040 (PI: J. Stauffer).
The CoRoT satellite was launched in 2006 and observed until 2012
November. Consisting of a 27inch diameter telescope, it performs
broadband photometric monitoring (∼3700 to 10000Å) of stars in two
10° diameter regions near the galactic center and anti-center,
known as the CoRoT "eyes." For the CSI 2264 campaign, we monitored a
∼1.3°*1.3° field in NGC2264 centered at RA=06h40m18.0s,
DE=+09°41'46.24'' from 2011 December 1 to 2012 January 9. These
observations composed the fifth CoRoT short run ("SRa05").
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 151 162 NGC 2264 members monitored with CoRoT and Spitzer
table4.dat 95 162 Variability properties of the NGC 2264 members
monitored with CoRoT and Spitzer
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See also:
B/corot : CoRoT observation log Release 13 (CoRoT, 2009-2014)
J/AJ/138/1116 : A Spitzer view of NGC 2264 (Sung+, 2009)
J/ApJ/648/1090 : Radial velocities of NGC 2264 stars (Furesz+, 2006)
J/AJ/129/829 : Hα emission stars in NGC 2264 (Dahm+, 2005)
J/AJ/127/2228 : VRI photometry of PMS stars in NGC 2264 OB (Makidon+, 2004)
J/A+A/417/557 : Rotation & variability of PMS Stars in NGC 2264 (Lamm, 2004)
J/AJ/123/1528 : UBV(RI)C and JHK photometry in NGC 2264 (Rebull+, 2002)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- --- [CSI Mon-]
9- 14 I06 --- CSI [7/6491] CSI Mon identifier (1)
15 A1 --- n_CSI [I] Indicates an object with IRAC staring data
17- 33 A17 --- 2MASS 2MASS identifier (JHHMMSSss+DDMMSSs)
35- 43 I9 --- CoRoT CoRoT identifier (from the SRa05 run) (2)
45- 49 F5.2 mag Jmag ? 2MASS J band magnitude
51- 54 F4.2 mag e_Jmag ? Error in Jmag
56- 60 F5.2 mag Hmag ? 2MASS H band magnitude
62- 65 F4.2 mag e_Hmag ? Error in Hmag
67- 71 F5.2 mag Kmag ? 2MASS Ks band magnitude
73- 76 F4.2 mag e_Kmag ? Error in Kmag
78- 82 F5.2 mag [3.6] Spitzer/IRAC 3.6µm band magnitude (3)
84- 87 F4.2 mag e_[3.6] ? Error in [3.6]
89- 93 F5.2 mag [4.5] Spitzer/IRAC 4.5µm band magnitude (3)
95- 98 F4.2 mag e_[4.5] ? Error in [4.5]
100-104 F5.2 mag [5.8] Spitzer/IRAC 5.8µm band magnitude (3)
106-109 F4.2 mag e_[5.8] Error in [5.8]
111-115 F5.2 mag [8.0] ? Spitzer/IRAC 8.0µm band magnitude (3)
117-120 F4.2 mag e_[8.0] ? Error in [8.0]
122-125 F4.2 mag [24] ? Spitzer/MIPS 24µm band magnitude (3)
127-130 F4.2 mag e_[24] ? Error in [24]
132-137 A6 --- Class Disk class (I, II, II/III, or flat) (4)
139-142 A4 --- SpT Spectral type (5)
144-149 F6.2 0.1nm EWHa ? Equivalent width of the Hα line (6)
151 A1 --- C [YN] Denotes whether the object appears to have
a Companion within 1'' (Y=Yes, N=No) (7)
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Note (1): We have assembled a list of NGC 2264 region members, candidates,
and field stars, called the Coordinated Synoptic Investigation (CSI)
Mon catalog. Here we show only the Mon identification numbers of
objects discussed in this paper.
Note (2): The fifth CoRoT short run (SRa05) is the ∼1.3°*1.3° field
in NGC 2264 centered at (RA=06h40m18.0s, DE=+09°41'46.24'') and
monitored from 2011 December 1 to 2012 January 9.
Note (3): We obtained archival IRAC and Multiband Imaging Photometry for
Spitzer (MIPS) data (program IDs 3441, 3469, 50773, and 37).
Note (4): Class disk is defined (more details in Section 5.1) as follows:
I = Objects more often bright than faint;
II = Object with typical brightness similar to the mean;
II/III = Object with a Class III SED based on the slope, but with significant
evidence of a weak disk based on the [3.6]-[8.0] color indice;
flat = Flat spectral energy distribution (SED).
Note (5): From Walker (1956ApJS....2..365W 1956ApJS....2..365W), Makidon et al. (2004,
J/AJ/127/2228), and Dahm & Simon (2005, J/AJ/129/829).
Note (6): We adopt the values of Rebull et al. (2002, J/AJ/123/1528)
and Dahm & Simon (2005, J/AJ/129/829).
Note (7): Detection is based on visual binarity or elongation of the
point-spread function reported by Sung et al. 2009 (J/AJ/138/1116),
or spectroscopic indications of binarity via variable radial velocity
measured by Furesz et al. 2006 (J/ApJ/648/1090). Objects with no
known companion ("N") may still be undetected binaries.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- --- [CSI Mon-]
9- 14 I06 --- CSI [7/6491] CSI Mon identifier
15 A1 --- F [e] Denotes Faint (R>15.5) variables that were
detected only by eye
17- 21 F5.3 mag sOpt [0.004/0.33] Root-mean-square (rms) deviation
of optical light curve
23 A1 --- --- [-]
25- 29 F5.3 mag s3.6 [0.008/0.15]? rms deviation in 3.6µm band
31 A1 --- --- [-]
34- 38 F5.3 --- s4.5 [0.008/0.18]? rms deviation in 4.5µm band
40- 41 A2 --- OPer [AQP N] Optical periodicity flag (8)
43- 44 A2 --- IPer [AQP N] Infrared periodicity flag (8)
46 A1 --- --- [-]
48- 52 F5.2 d Otau1 [0.6/77]? Optical time scale (9)
54- 57 F4.2 d Otau2 [0.8/7.5]? Second optical timescale value (9)
59 A1 --- --- [-]
61- 66 F6.3 d Itau1 [1/57]? Infrared timescale (9)
68- 71 F4.2 d Itau2 [5/6]? Second infrared timescale value (9)
73- 75 A3 --- Ovar Optical morphological variability type (10)
77- 79 A3 --- Ivar Infrared morphological variability type (10)
81- 85 F5.2 --- S [-1.1/7] Median running Stetson index (degree of
optical/infrared correlation) (11)
86 A1 --- u_S [*] few data points (12)
88- 95 A8 --- Type Variability type (pv=periodic, iv=irregular) (13)
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Note (8): The periodicity of the star is defined as follows:
AP = Aperiodic (by the Stetson index or rms measure);
QP = Quasi-periodic;
P = Periodic;
N = Not detected as variable.
Note (9): The derivation of which depends on whether the object is
(quasi-)periodic or aperiodic. If (quasi-)periodic, then we list the
timescale derived from the autocorrelation and periodogram analysis
(Section 6.2); if aperiodic, then we list the timescale derived from the
PeakFind algorithm (Section 6.5).
Note (10): The morphology is defined with the following codes:
S = stochastic;
U = unclassifiable variable type;
QPS = quasi-periodic symmetric;
QPD = quasi-periodic dipper;
QPB = quasi-periodic burster;
L = long-timescale variable;
N = non-variable;
B = burster;
D = dipper;
EB = eclipsing binary;
P = periodic;
MP = multi-periodic.
Note (11): Here we have averaged the values from 3.6µm and 4.5µm data
(both against optical light curves).
Note (12): Those objects only had High Dynamic Range (HDR) mode
observations and hence fewer data points.
Note (13): Assigned by Lamm et al. 2004 (J/A+A/417/557) and compiled in
their Table 4).
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 15-Jan-2015