J/MNRAS/493/267 Variable stars in the Sh 2-170 H II region (Sinha+, 2020)
Variable stars in the Sh 2-170 H II region.
Sinha T., Sharma S., Pandey A.K., Yadav R.K., Ogura K., Matsunaga N.,
Kobayashi N., Bisht P.S., Pandey R., Ghosh A.
<Mon. Not. R. Astron. Soc., 493, 267-287 (2020)>
=2020MNRAS.493..267S 2020MNRAS.493..267S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; YSOs ; Stars, pre-main sequence ;
Proper motions ; Parallaxes, trigonometric ; Stars, masses ;
Stars, ages ; Photometry ; Optical ; Infrared
Keywords: stars: formation -
Hertzsprung-Russell and colour-magnitude diagrams -
stars: pre-main-sequence - stars: variables: general
Abstract:
We present multi-epoch deep (∼20mag) Ic-band photometric monitoring of
the Sh 2-170 star-forming region to understand the variability
properties of pre-main-sequence (PMS) stars. We report identification
of 47 periodic and 24 non-periodic variable stars with periods and
amplitudes ranging from ∼4h to 18d and from ∼0.1 to 2.0mag,
respectively. We have further classified 49 variables as PMS stars (17
Class II and 32 Class III) and 17 as main-sequence (MS)/field star
variables. A larger fraction of MS/field variables (88 per cent) show
periodic variability as compared to the PMS variables (59 per cent).
The ages and masses of the PMS variable stars are found to be
comparable with those of T-Tauri stars. Their variability amplitudes
show an increasing trend with the near-IR/mid-IR excess. The period
distribution of the PMS variables shows two peaks, one near ∼1.5d and
the other near ∼4.5d. It is found that the younger stars with thicker
discs and envelopes seem to rotate slower than their older
counterparts. These properties of the PMS variables support the
disc-locking mechanism. Both the period and amplitude of PMS stars
show decrease with increasing mass probably due to the effective
dispersal of circumstellar discs in massive stars. Our results favour
the notion that cool spots on weak line T-Tauri stars are responsible
for most of their variations, while hot spots on classical T-Tauri
stars resulting from variable mass accretion from an inner disc
contribute to their larger amplitudes and irregular behaviours.
Description:
Optical photometric observations of the Sh 2-170 region were taken in
the Ic band on 17 nights and in the V band on five nights starting
from 2016 September 30 to 2017 November 24 with the 1.3m Devasthal
Fast Optical Telescope (DFOT, India), 0.7m Thai Robotic Telescope
(TRT-GAO, Gao Mei Gu Observatory, China), and 0.5m telescope of Thai
National Observatory (TNO, Thailand). All the telescopes have a
2048x2048 pixel square CCD for imaging. The 1.3m Devasthal telescope
covers a field of view (FOV) of 18.4arcminx18.4arcmin, whereas the
0.7m and 0.5m telescopes have a FOV of ∼20.9arcminx20.9arcmin and
∼23arcminx23 arcmin, respectively. In total, 776 and 13 frames were
taken in Ic and V filters, respectively, with exposure times of 180s
on the 1.3m, 240s on the 0.7m and 300s on the 0.5m telescopes. Details
of the observations are given in Table 1.
Since NIR and MIR data are very useful to study the spectral energy
distribution (SED) and disc properties of young stellar objects
(YSOs), we have used NIR JHKs photometric data from the 2MASS All-Sky
Point Source Catalog (Cutri et al. 2003tmc..book.....C 2003tmc..book.....C, Cat. II/246;
Skrutskie et al. 2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233); Spitzer-IRAC
observations at 3.6 and 4.5µm from the GLIMPSE360 Catalog and
Archive (Werner et al. 2004ApJS..154....1W 2004ApJS..154....1W) and MIR data at 3.4, 4.6,
12, and 22µm from the Wide-field Infrared Survey Explorer (WISE)
All-sky Survey Data release (Wright et al. 2010AJ....140.1868W 2010AJ....140.1868W).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 31 22 Log of observations
table2.dat 114 86 Sample of stars identified as members of the
Stock 18 cluster
table3.dat 182 71 Sample of identified variables and their
physical parameters as derived from CMD and/or
SED
table4.dat 129 66 Sample of identified YSOs and their physical
parameters as derived from their CMD and/or SED
table5.dat 98 71 Classification and properties of 71 identified
variables
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 I10 "Y:M:D" Date Observation date
12- 20 A9 --- Tel Telescope used for the observation
22- 24 I3 --- Frames Number of frames observed
26- 28 I3 s ExpTime Exposure time
30- 31 A2 --- Filter Filter used (V or Ic)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID Star internal identifier (MNN)
5- 12 F8.6 deg RAdeg Right ascension (J2000)
14- 22 F9.6 deg DEdeg Declination (J2000)
24- 29 F6.3 mag Vmag ? V-band magnitude
31- 36 F6.4 mag e_Vmag ? Error on Vmag
38- 43 F6.3 mag Icmag ? Ic-band magnitude
45- 50 F6.4 mag e_Icmag ? Error on Icmag
52 A1 --- ref [ab] References for Vmag and Icmag (1)
54- 60 F7.4 mas/yr pmRA Proper motion in right ascension
62- 67 F6.4 mas/yr e_pmRA Error on pmRA
69- 75 F7.4 mas/yr pmDE Proper motion in declination
77- 82 F6.4 mas/yr e_pmDE Error on pmDE
84- 90 F7.4 mas plx Parallax
92- 97 F6.4 mas e_plx Error on plx
99-101 I3 % Prob Membership probability
103-108 F6.3 mag Gmag Gaia DR2 G-band magnitude
110-114 F5.3 mag BP-RP ? Gaia DR2 BP-RP colour
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Note (1): References as follows:
a = V and Ic data taken from Bhatt et al. (2012NewA...17..160B 2012NewA...17..160B,
Cat. J/other/NewA/17.160)
b = V and Ic data taken from the present observations
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Name Variable name (VNN)
5- 12 F8.6 deg RAdeg Right ascension (J2000)
14- 22 F9.6 deg DEdeg Declination (J2000)
24- 29 F6.3 mag Vmag ? V-band magnitude
31- 35 F5.3 mag e_Vmag ? Error on Vmag
37- 42 F6.3 mag Icmag ? Ic-band magnitude
44- 48 F5.3 mag e_Icmag ? Error on Icmag
50 A1 --- ref [abc] References for Vmag and Icmag (G1)
52- 57 F6.3 d Period ? Variability period
59- 63 F5.3 d e_Period ? Error on Period
65- 68 F4.2 mag Amp Amplitude of variation
70- 73 F4.2 mag e_Amp ? Error on Amp
75- 79 F5.3 mag RMS RMS dispersion of the magnitudes
81- 86 F6.3 mag D(Ic-Ks) ? NIR colour index Δ(Ic-Ks) (1)
88- 92 F5.3 mag e_D(Ic-Ks) ? Error on D(Ic-Ks)
94- 99 F6.3 mag 3.6-4.5 ? 3.6-4.5 MIR colour index
101-105 F5.3 mag e_3.6-4.5 ? Error on 3.6-4.5
107-109 F3.1 Myr AgeCMD ? Age derived from colour-magnitude diagram
111-113 F3.1 Myr e_AgeCMD ? Error on AgeCMD
115-117 F3.1 Msun MassCMD ? Mass derived from colour-magnitude diagram
119-121 F3.1 Msun e_MassCMD ? Error on MassCMD
123-124 I2 --- Ndp ? Number of data points
126-130 F5.1 --- chi2SED ? Chi-squared for the SED fitting
132-134 F3.1 Myr AgeSED ? Age derived from SED fitting
136-138 F3.1 Myr e_AgeSED ? Error on AgeSED
140-142 F3.1 Msun MassSED ? Mass derived from SED fitting
144-146 F3.1 Msun e_MassSED ? Error on MassSED
148-155 E8.3 Msun Mdisc ? Disc mass from SED fitting
157-164 E8.3 Msun e_Mdisc ? Error on Mdisc
166-173 E8.3 Msun/yr Accrate ? Disc accretion rate from SED fitting
175-182 E8.3 Msun/yr e_Accrate ? Error on Accrate
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Note (1): Δ(Ic-Ks)=(Ic-Ks)obs-(AIc-AKs)-(Ic-Ks)0, where
(Ic-Ks)obs is the observed colour of the star, (Ic-Ks)0 is the
intrinsic colour and AIc and AKs are the interstellar extinction
in the Ic and Ks bands, respectively.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Name YSO identifier (YNN)
5- 12 F8.6 deg RAdeg Right ascension (J2000)
14- 22 F9.6 deg DEdeg Declination (J2000)
24- 29 F6.3 mag Vmag ? V-band magnitude
31- 35 F5.3 mag e_Vmag ? Error on Vmag
37- 42 F6.3 mag Icmag ? Ic-band magnitude
44- 48 F5.3 mag e_Icmag ? Error on Icmag
50- 53 F4.1 Myr AgeCMD ? Age derived from colour-magnitude diagram
55- 57 F3.1 Myr e_AgeCMD ? Error on AgeCMD
59- 61 F3.1 Msun MassCMD ? Mass derived from colour-magnitude diagram
63- 65 F3.1 Msun e_MassCMD ? Error on MassCMD
67 A1 --- ref [abc] References for Vmag and Icmag (G1)
69- 70 I2 --- Ndp ? Number of data points
72- 76 F5.1 --- chi2SED ? Chi-squared for the SED fitting
78- 80 F3.1 Myr AgeSED ? Age derived from SED fitting
82- 84 F3.1 Myr e_AgeSED ? Error on AgeSED
86- 89 F4.1 Msun MassSED ? Mass derived from SED fitting
91- 93 F3.1 Msun e_MassSED ? Error on MassSED
95-102 E8.3 Msun Mdisc ? Disc mass from SED fitting
104-111 E8.3 Msun e_Mdisc ? Error on Mdisc
113-120 E8.3 Msun/yr Accrate ? Disc accretion rate from SED fitting
122-129 E8.3 Msun/yr e_Accrate ? Error on Accrate
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Global Notes:
Note (G1): References as follows:
a = V and Ic data taken from Bhatt et al. (2012NewA...17..160B 2012NewA...17..160B,
Cat. J/other/NewA/17.160)
b = V and Ic data taken from the present observations
c = Converted to V and Ic from SDSS data
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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- 3 A3 --- Name Variable name (VNN)
5- 20 A16 --- Type Star classification (1)
22- 30 A9 --- nClass Comment on classification
32- 98 A67 --- nVar Comment on variability
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Note (1): Classification as follows:
PMS = Pre-main-sequence star (49/71)
MS = Main-sequence field star (17/71)
WTT = Weak-line T-Tauri star (19/71)
CTT = Classical T-Tauri star (7/71)
ClassII = Class II YSO (16/71)
ClassIII = Class III YSO (32/71)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 29-Mar-2023