J/AJ/167/221 Emerging stars optical variability classification (Jiang+, 2024)
The Emerging Stellar Complex in Mon R2: Membership and Optical Variability
Classification.
Jiang S.D., Hillenbrand L.A.
<Astron. J., 167, 221 (2024)>
=2024AJ....167..221J 2024AJ....167..221J
ADC_Keywords: YSOs; Stars, pre-main sequence; Star Forming Region; Optical
Keywords: Pre-main sequence stars ; Stellar associations ; Star forming
regions ; T Tauri stars ; Variable stars ; Young stellar
objects
Abstract:
Monoceros R2 (Mon R2) is one of the closest large active star-forming
regions. This extremely young and partially embedded region provides
an excellent laboratory for studying star formation and the early
evolution of young stellar objects (YSOs). In this paper, we conduct
an optical study of the greater Mon R2 region. Beginning with 1690
previously identified candidate YSOs, we used 496 sources with good
proper motions and parallaxes from Gaia Data Release (DR) 3 to
determine the astrometric properties for likely members of Mon R2. We
then used both astrometric and photometric (isochronal and
variability) criteria to determine that 308 of these stars are highly
probable members. Using the same criteria, we considered a broad area
search around Mon R2 in Gaia DR3 and separated candidate members from
field stars. In total, we selected 651 likely new cluster members that
had been missed in the previous X-ray and infrared excess selection
techniques used in the past to establish cluster membership. Revised
astrometric properties of the cluster were found using the combined
sample of ∼959 highly probable member stars. For the literature plus
the new candidate member list, optical light curves were compiled from
the Zwicky Transient Facility. For 470 identified variable sources, we
attempted classification based on the flux asymmetry (M) and
quasiperiodicity (Q) metrics. We find that Mon R2 is dominated by
quasiperiodic symmetric variables, with aperiodic sources also a
significant population. A few tens of large-amplitude variables are
identified that may be of interest for further study.
Objects:
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RA (2000) DE Designation(s)
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06 07 47.57 -06 22 42.5 Mon R2 = NAME Mon R2
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Description:
ZTF is a survey using the Samuel Oschin 48inch telescope (P48) at
Palomar Observatory. ZTF catalogs over a billion stars in the northern
sky and measures photometric time series, primarily in the r band
(lambdateff=6340Å) and g band (lambdaeff=4722Å). Due to the
red nature of our sources, we consider only r-band light curves due to
their higher signal-to-noise ratio. We utilize photometry from ZTF
DR12, spanning a 4yr period from 2018 March to 2022 May.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 84 959 Final members from Literature (YSOC)
and new query (Gaia)
table5.dat 162 470 All variable stars and their variability metrics
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
J/ApJS/94/615 : Molecular outflow sources (Hodapp, 1994)
J/AJ/114/198 : The Monoceros R2 Cluster (Carpenter+ 1997)
J/ApJ/567/423 : CHANDRA obs. of YSOs in Monoceros R2 (Kohno+, 2002)
J/PASJ/55/635 : Chandra observations of Monoceros R2 (Nakajima+, 2003)
J/AJ/132/2296 : NICMOS observations of Mon R2 cluster (Andersen+, 2006)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/AJ/144/31 : Spitzer+2MASS photom protostar candidates (Kryukova+, 2012)
J/AJ/147/82 : Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014)
J/ApJ/815/4 : V899 Mon long-term monitoring (Ninan+, 2015)
J/ApJS/229/28 : SFiNCs X-ray, IR and membership catalogs (Getman+, 2017)
J/A+A/607/A22 : Monoceros R2 filament hub FIR observations (Rayner+, 2017)
J/ApJ/884/4 : KEYSTONE ammonia structures in Galactic GMCs (Keown+, 2019)
J/ApJ/870/32 : Kinematics young star clusters & associations (Kuhn+, 2019)
J/MNRAS/483/407 : LMT/AzTEC 1.1mm Survey of Mon R2 dense cores (Sokol+, 2019)
J/ApJ/923/171 : V899 Mon opt-NIR spectra and light curves (Park+, 2021)
J/AJ/163/263 : 323 YSOs properties with ZTF (Hillenbrand+, 2022)
J/MNRAS/524/1826 : Mon R2 photometry (Orcajo+, 2023)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 28 A28 --- ID Object identifier (1)
30- 37 F8.5 deg RAdeg [88/98] Right Ascension in decimal degrees (J2000)
39- 47 F9.5 deg DEdeg [-11/-4] Declination in decimal degrees (J2000)
49- 53 F5.2 mas/yr pmRA [-5.5/-0.6]? Proper motion along RA
55- 59 F5.2 mas/yr pmDE [-1.05/3.01]? Proper motion along DE
61- 64 F4.2 mas plx [0.54/1.86]? Parallax
66- 69 F4.2 --- PISO [0.0/1.0]? Probability membership based on
location on Gaia photometry isochrones
71- 74 F4.2 --- PASTRO [0.25/1.0]? Probability membership based on
astrometry value in comparison to cluster's
median values
76- 79 F4.2 --- PVAR [0.0/1.0]? Probability membership based on based
on object's variability
81- 84 F4.2 --- PTot [0.5/1.0] Total membership probability calculated
with weighted average
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Note (1): From either previous literature obtained from YSOC or Gaia DR3 number.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 28 A28 --- ID Object identifier (1)
30- 37 F8.5 deg RAdeg [88/94] Right Ascension (J2000)
39- 47 F9.5 deg DEdeg [-11/-4] Declination (J2000)
49- 53 F5.2 mag magMed [12.95/20.55] Median ZTF light curve magnitude
55- 59 F5.2 mag magAvg [12.96/20.55] Average ZTF light curve magnitude
61- 64 F4.2 mag magErr [0.01/0.15] Median of the magnitude error
66- 69 F4.2 mag magStd [0.02/0.79] Standard deviation of the magnitude
71- 75 F5.2 --- magSkew [-3.68/4.19] Skew or measure of symmetry of
magnitude
77- 83 F7.2 --- chi2 [1.46/3234] Chi-Square of the magnitude
85- 88 F4.2 --- eta [0.0/2.46] Inverse von-neumann statistic
90- 93 A4 --- mKurt Kurtosis or "tailedness" of light curve (2)
95-101 F7.3 d Per [0.181/284] Highest peak on Lomb-Scargle
Periodogram, verified by visual inspection
103-111 E9.2 --- FAP [8.33e-154/0.988]? False Alarm Probability
calculated by Lomb-Scargle Peridogram
113-117 F5.2 --- M [-1.22/1.3] M-metric (3)
119-122 F4.2 --- Q [0.11/1.01] Q-metric (4)
124-147 A24 --- Primary Primary QM classification (5)
149-162 A14 --- Secondary Secondary classification (6)
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Note (1): From either previous literature obtained from YSOC or Gaia DR3 number.
Note (2): High kurtosis sources have light curve data points cut to only
within 3 standard deviations of median (eliminate errors).
Note (3): A measure of Flux Asymmetry, calculated using variability
metrics, Equation 5.
Note (4): A measure of Quad-Periodicity, calculated using variability
and Period metrics, Equation 6.
Note (5): Based on Q and M value, See Table 2 for all names.
Note (6): Assigned through visual inspection (Longtime/LT or Multiperiodic/MP).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 11-Jun-2024