J/ApJ/878/7 2yr obs. of JHK variability of stars in Tr37 (Meng+, 2019)
Near-infrared variability of low-mass stars in IC 1396A and Tr 37.
Meng H.Y.A., Rieke G.H., Kim J.S., Sicilia-Aguilar A., Cross N.J.G.,
Esplin T., Rebull L.M., Hodapp K.W.
<Astrophys. J., 878, 7 (2019)>
=2019ApJ...878....7M 2019ApJ...878....7M
ADC_Keywords: Clusters, open; Photometry, infrared; Stars, variable;
Spectral types
Keywords: infrared: planetary systems ; infrared: stars ;
open clusters and associations: individual (Tr 37) ;
protoplanetary disks ; stars: pre-main sequence
Abstract:
We have monitored nearly a square degree in IC 1396A/Tr 37 over
21 epochs extending over 2014-2016 for sources variable in the JHK
bands. In our data, 65%±8% of previously identified cluster members
show variations, compared with ≤0.3% of field stars. We identify
119 members of Tr 37 on the basis of variability, forming an unbiased
sample down to the brown dwarf regime. The K-band luminosity function
in Tr 37 is similar to that of IC 348 but shifted to somewhat brighter
values, implying that the K- and M-type members of Tr 37 are younger
than those in IC 348. We introduce methods to classify the causes of
variability, based on behavior in the color-color and color-magnitude
diagrams. Accretion hot spots cause larger variations at J than at K
with substantial scatter in the diagrams; there are at least a dozen,
with the most active resembling EXors. Eleven sources are probably
dominated by intervention of dust clumps in their circumstellar disks,
with color behavior indicating the presence of grains larger than for
interstellar dust, presumably due to grain growth in their disks.
Thirteen sources have larger variations at K than at J or H. For 11 of
them, the temperature fitted to the variable component is very close
to 2000K, suggesting that the changes in output are caused by
turbulence at the inner rim of the circumstellar disk exposing
previously protected populations of grains.
Description:
Observations were conducted in J, H, and K bands with the Wide Field
Camera (WFCAM) on the United Kingdom Infrared Telescope (UKIRT) on
Maunakea, Hawaii.
The total sky coverage was a 53'x53' square, ranging from 323.082°
to 324.752° in RA and from 57.196° to 58.080° in DEC The
integration time of each exposure was 10, 5, and 5s in J, H, and K,
respectively. Each run consisted of 20 consecutive exposures in each
waveband, i.e., total integrations of 200, 100, and 100s respectively.
From 2014 July 18 to 2016 July 12, we have 21 epochs in total over a
time baseline of 725d, or almost 2yr.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 111 119 Member candidates of Tr 37 from the CMD and
variability
table4.dat 72 240 Additional variable sources in the UKIRT field
table5.dat 107 106 Summary of variability observed in bright members
of Tr 37
table6.dat 92 33 Summary of variability observed in members
of Tr 37 from Sicilia-Aguilar+ (2013, J/A+A/559/A3)
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/AJ/116/1816 : JHKLMNOPQ photometry in Orion cluster (Hillenbrand+, 1998)
J/AJ/121/3160 : JHK photometry near the Trapezium region (Carpenter+, 2001)
J/ApJ/593/1093 : IC 348 membership (Luhman+, 2003)
J/AJ/128/805 : Low-mass stars in Cepheus OB2 region (Sicilia-Aguilar+ 2004)
J/AJ/130/188 : Young stars in Trumpler37 & NGC7160 (Sicilia-Aguilar+, 2005)
J/ApJ/638/897 : IR phot. in Trumpler 37 & NGC 7160 (Sicilia-Aguilar+, 2006)
J/AJ/132/2135 : High-res. spectroscopy in Tr 37 (Sicilia-Aguilar+, 2006)
J/A+A/485/155 : HK phot. of rho Oph PMS stars (Alves de Oliveira+, 2008)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJ/702/1507 : Mid-IR photometry in IC 1396A (Morales-Calderon+, 2009)
J/A+A/503/651 : Variables in VLT/VIMOS field in Carina (Pietrukowicz+ 2009)
J/ApJS/186/111 : Spitzer observations of Taurus members (Luhman+, 2010)
J/ApJ/710/597 : Accretion in disks in Cep OB2 (Sicilia-Aguilar+, 2010)
J/MNRAS/415/103 : IPHAS T Tauri candidates in IC 1396 (Barentsen+, 2011)
J/ApJ/733/50 : MIR phot. monitoring of the ONC (Morales-Calderon+, 2011)
J/MNRAS/426/2917 : X-rays sources in Trumpler 37 (Getman+, 2012)
J/AJ/144/192 : Spitzer survey of Orion A & B. I. YSOs (Megeath+, 2012)
J/AJ/143/61 : Hα spectroscopy in IC 1396 HII region (Nakano+, 2012)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/A+A/557/A77 : VR light curves of AA Tau in 2007-2013 (Bouvier+, 2013)
J/AN/334/673 : The stellar content of Trumpler 37 (Errmann+, 2013)
J/A+A/559/A3 : Low-mass stars in Trumpler 37 (Sicilia-Aguilar+, 2013)
J/AJ/145/113 : JHK photometry in Cyg OB7. II. Variable stars (Wolk+, 2013)
J/AJ/148/122 : YSOVAR: infrared photometry in Lynds 1688 (Gunther+, 2014)
J/ApJS/211/3 : NIR photometry variability in ρ Oph (Parks+, 2014)
J/AJ/150/118 : YSOVAR IR phot. in IRAS 20050+2720 (Poppenhaeger+, 2015)
J/AJ/150/175 : YSOVAR: infrared photometry in NGC 1333 (Rebull+, 2015)
J/AJ/150/132 : JHK photometry of 1203 variables in ONC (Rice+, 2015)
J/A+A/573/A19 : Cep OB2 Herschel/PACS view (Sicilia-Aguilar+, 2015)
J/ApJ/823/58 : Photo-reverberation mapping of YSOs in LDN1688 (Meng+, 2016)
J/ApJ/836/34 : 24um excesses in clusters & NGC2244 membership (Meng+, 2017)
J/AJ/155/99 : IR variability among YSOs in Serpens cluster (Wolk+, 2018)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [11/355] Running sequence number
5- 14 F10.6 deg RAdeg [323.14/324.73] Right Ascension (J2000)
16- 24 F9.6 deg DEdeg [57.22/58.05] Declination (J2000)
26- 30 F5.2 mag Imag [14.2/20.9] Apparent I band magnitude (G1)
32- 36 F5.2 mag Jmag [12.5/18.4] UKIRT/WFCAM apparent J band
magnitude
38- 38 A1 --- f_Jmag [c] c= nominal error between 0.01
and 0.02 mag
40- 44 F5.2 mag Hmag [11.8/17.3] UKIRT/WFCAM apparent H band
magnitude
46- 46 A1 --- f_Hmag [c] c= nominal error between 0.01
and 0.02 mag
48- 52 F5.2 mag Kmag [11.3/16.4] UKIRT/WFCAM apparent K band
magnitude
54- 57 F4.2 mag DelJ [0.04/1.3] Variability in the J band
59- 62 F4.2 mag DelH [0.05/1.2] Variability in the H band
64- 67 F4.2 mag DelK [0.05/1] Variability in the K band
69- 73 F5.2 --- [0.7/13.3] Mean Stetson index
75- 88 A14 --- VType Variable type (G2)
90 A1 --- f_VType [ed] Flag on VType (1)
92-105 A14 --- OName Previous identifier (2)
107-111 F5.2 10-6ph/cm2/s FX [0.6/49]? X-ray photon flux
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Note (1): Flag as follows:
e = illustrated in text.
d = also SA13 (Sicilia-Aguilar+ 2013A&A...559....3S 2013A&A...559....3S).
Note (2): Previous designations are given as Errmann+ (2013, J/AN/334/673).
The latter cases are with the designation from
Sicilia-Aguilar+ (2006, J/ApJ/638/897) or by SA13 if the
identification is in Sicilia-Aguilar+ (2013A&A...559....3S 2013A&A...559....3S).
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/359] Running sequence number
5 A1 --- f_Seq [bc] Flag on Seq (1)
7- 16 F10.6 deg RAdeg [323.08/324.74] Right Ascension (J2000)
18- 26 F9.6 deg DEdeg [57.21/58.08] Declination (J2000)
28- 32 F5.2 mag Imag [14.2/22.7]? Apparent I band magnitude (G1)
34- 38 F5.2 mag Jmag [13.2/19.55] UKIRT/WFCAM apparent J band
magnitude
40- 44 F5.2 mag Hmag [12.84/18.66] UKIRT/WFCAM apparent H band
magnitude
46- 50 F5.2 mag Kmag [12.65/18.22] UKIRT/WFCAM apparent K band
magnitude
52- 55 F4.2 mag DelJ [0.05/1.61] Variability in the J band
57- 60 F4.2 mag DelH [0.05/1.93] Variability in the H band
62- 65 F4.2 mag DelK [0.06/1.83] Variability in the K band
67- 70 F4.2 --- meanS [0.71/8.64] Mean Stetson index
(Stetson 1996PASP..108..851S 1996PASP..108..851S)
72 A1 --- VType [a-c] Variable type (G2)
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Note (1): Flag as follows:
b = These sources are sufficiently faint that the indication of variability
might be influenced by fainter nearby sources below the detection
limit, so the results for them are less reliable than for the brighter
sources. In addition, the errors on their measurements are larger than
the nominal 2% for bright sources.
c = Listed as a possible cluster member by Errmann+ (2013, J/AN/334/673).
For Sources 175 and 279, the lack of I magnitudes results in their not
being selected in our CMD approach, so we do not have an independent
measure of whether they are cluster members. Source 335 falls far from
the zone for Tr 37 members on the K, I - K CMD, potentially calling
its membership into question.
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Identifier
(<[SHB2004] Trumpler 37 NN-NNNN> in Simbad) (1)
9 A1 --- f_Name [a] Flag on Name (2)
11- 18 A8 --- SpType Spectral type
from Sicilia-Aguilar+ 2006, J/AJ/132/2135
20- 21 I2 h RAh [21] Hour of Right Ascension (J2000)
23- 24 I2 min RAm [34/38] Minute of Right Ascension (J2000)
26- 30 F5.2 s RAs Second of Right Ascension (J2000)
32 A1 --- DE- [+] Sign of the Declination (J2000)
33- 34 I2 deg DEd [57/58] Degree of Declination (J2000)
36- 37 I2 arcmin DEm Arcminute of Declination (J2000)
39- 42 F4.1 arcsec DEs Arcsecond of Declination (J2000)
44- 54 A11 --- RIvar RI variability type
56- 69 A14 --- JHKvar JHK variability type
71- 78 A8 --- W1W2var W1-W2 variability type
80- 82 A3 --- f_W1W2var [ i-k,] Flag(s) on W1W2var (2)
84- 88 F5.2 --- W1-W2 [-0.21/0.72]? ALLWISE (W1-W2) color index
90 A1 --- f_W1-W2 [dehi] Flag on W1-W2 (2)
92-101 A10 --- Acc Accretion from
Sicilia-Aguilar+ 2010, J/ApJ/710/597
103-105 A3 --- Memb Membership from
Sicilia-Aguilar+ 2006, J/AJ/132/2135 (3)
107 A1 --- f_Memb [l] Flag on Memb (2)
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Note (1): 12-232 is very likely a misprint for 13-232; corrected at CDS.
Note (2): Flag as follows:
a = Only listed in Sicilia-Aguilar+ 2004, J/AJ/128/805
d = Indicated error 0.04 to 0.06.
e = Indicated error 0.06 to 0.08.
h = Two very bright stars (6th mag) within 2'; detection possibly
contaminated by diffraction spike.
i = From Morales-Calderon+ 2009, J/ApJ/702/1507
j = Very close fainter object that is integrated into the WISE PSF with
little effect, but undermines the PSF fitting with the UKIRT data
given its ∼six times higher resolution.
k = A nearby source interferes with the UKIRT PSF fitting but is outside
the region where the WISE deblending is not valid.
l = Gaia parallax suggests this object is foreground to the cluster.
Note (3): Y & Y indicated as "Y"; Y & P indicated as "Y";
P & P indicated as "P"; Y indicated as "P"; P indicated as "P";
Y & PN indicated as "P:"; Y & N indicated as "PN"; PN indicated as "PN".
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- ID Source identifier (S13-0NN)
(<[SKS2013] JHHMMSSss+DDMMSSs> in Simbad)
9- 18 F10.6 deg RAOdeg [324.09/324.63] Optical Right Ascension (J2000)
20- 28 F9.6 deg DEOdeg [57.28/57.8] Optical Declination degrees (J2000)
30- 39 F10.6 deg RAdeg [324.09/324.63] IR Right Ascension (J2000)
41- 49 F9.6 deg DEdeg [57.28/57.8] IR Declination (J2000)
51- 56 F6.3 mag Jmag [13.28/16.01] UKIRT/WFCAM apparent J band magnitude
58- 63 F6.3 mag Hmag [12.42/15.31] UKIRT/WFCAM apparent H band magnitude
65- 70 F6.3 mag Kmag [11.85/14.97] UKIRT/WFCAM apparent K band magnitude
72- 76 F5.3 mag JAmp [0.025/1.11] The J band amplitude
78- 82 F5.3 mag HAmp [0.028/0.71] The H band amplitude
84- 88 F5.3 mag KAmp [0.03/0.45] The K band amplitude
90 A1 --- Var [NV] Variable?
92 A1 --- f_Var [a] a: indicates probable foreground star
from Gaia parallax
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Global notes:
Note (G1): We have derived I magnitudes by reference to the ICFH12K band, with
an effective wavelength of 8090Å. We derive these magnitudes by
transformation from Pan-STARRS, defined from the photometry in IC 348
by Luhman+ (2016ApJ...827...52L 2016ApJ...827...52L).
Equation (7):
ICFH12K=1.0291zP1+0.2469(iP1-zP1)-0.5894
The difference between Vega and AB magnitude systems is not a problem
here, as the transformation equation should have accounted for the
zero-point fluxes.
See Appendix A1.
Note (G2): If the source is illustrated in the text as a variability type, the
information is also provided. The relative sizes of the variations in
J and K provide hints of the type of variations: category "a" is
likely to vary through instabilities at the inner edge of the
circumstellar disk resulting in different exposure of the disk dust;
category "c" can arise either through extinction or accretion hot
spots; in general the ratio ΔJ/ΔK is <2 for extinction
variations and >2 for hot spot ones.
a = variability is >30% larger in magnitudes at K than at J;
b = variability is within 30% of the same in magnitudes at J and K;
c = variability is >30% larger at J than at K.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 25-Nov-2020