J/A+A/637/A43 Membership in the Cepheus association (Klutsch+, 2020)
Discovery of new members of the nearby young stellar association in Cepheus.
Klutsch A., Frasca A., Guillout P., Montes D., Pineau F.-X., Grosso N.,
Stelzer B.
<Astron. Astrophys. 637, A43 (2020)>
=2020A&A...637A..43K 2020A&A...637A..43K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, nearby ; Stars, pre-main sequence ; X-ray sources ;
Spectroscopy ; Effective temperatures ; Radial velocities ;
Rotational velocities ; Space velocities
Keywords: stars: pre-main sequence - stars: fundamental parameters -
stars: kinematics and dynamics - X-rays: stars
Abstract:
Young field stars are hardly distinguishable from older ones because
their space motion rapidly mixes them with the stellar population of
the Galactic plane.Nevertheless, a careful target selection allows for
young stars to be spotted throughout the sky.
We aim to identify additional sources associated with the four young
comoving stars that we discovered towards the CO Cepheus void and to
provide a comprehensive view of the Cepheus association.
Based on multivariate analysis methods, we have built an extended
sample of 193 young star candidates, which are the optical and
infrared counterparts of ROSAT All-Sky Survey and XMM-Newton X-ray
sources. From optical spectroscopic observations, we measured their
radial velocity with the cross-correlation technique. We derived their
atmospheric parameters and projected rotational velocity with the code
ROTFIT. We applied the subtraction of inactive templates to measure
the lithium equivalent width, from which we infer their lithium
abundance and age. Finally, we studied their kinematics using the
second Gaia data release.
Our sample is mainly composed of young or active stars and multiple
systems. We identify two distinct populations of young stars that are
spatially and kinematically separated. Those with an age between 100
and 300Myr are mostly projected towards the Galactic plane. In
contrast, 23 of the 37 sources younger than 30Myr are located in the
CO Cepheus void, and 21 of them belong to the stellar kinematic group
that we previously reported in this sky area. We report a total of 32
bona fide members and nine candidates for this nearby
(distance=157±10pc) young (age=10-20Myr) stellar association.
According to the spatial distribution of its members, the original
cluster is already dispersed and partially mixed with the local
population of the Galactic plane.
Description:
We present the results of a spectroscopic survey of optical
counterparts of X-ray sources in the Cepheus region (near the North
Celestial pole) aimed at discovering further young objects around the
four comoving stars reported by us in Paper II (Guillout et al.,
2010A&A...520A..94G 2010A&A...520A..94G).
table 1 summarizes the optical and infrared names of each X-ray
source, along with those appearing in Simbad and some main parameters
coming from the literature.
table 3 reports the radial velocity of all the stars, including the
measurements for each component of a spectroscopic system, along with
the rotational velocity,atmospheric parameters, and lithium equivalent
widths derived for the targets identified as single stars or SB1
systems.
table 4 provides the astrometry in Gaia DR2, the Galactic positions,
and the extinction estimate of our targets, as well as the space
velocities of those identified as single stars.
table 5 lists all the sources that are comoving with one of our
targets.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 160 201 Main parameters of the young stars candidates
available in 2009, when the sample was created
table3.dat 180 326 Radial and rotational velocities, atmospheric
parameters, and lithium equivalent widths
derived for our targets during the survey
table4.dat 219 221 Galactic positions and space velocities of the
targets, along with the astrometry in Gaia DR2,
and the average RV values and lithium
equivalent widths obtained during our survey
table5.dat 147 99 *Comoving companions of our targets
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Note on table5.dat: We reported the astrometry, G magnitude and radial velocity
RV_Gaia released in the Gaia DR2 catalog. We derived their angular separation
(rho), position angle (theta), and projected physical separation (s) with
regard to the brightest star, along with the associated errors.
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+, 2003)
I/305 : The Guide Star Catalog, Version 2.3.2 (GSC2.3) (Lasker+, 2006)
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+, 1999)
IX/29 : ROSAT All-Sky Survey Faint Source Catalog (Voges+, 2000)
IX/41 : XMM-Newton Serendipitous Source Catalogue 2XMMi-DR3 (XMM-Newton, 2010)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/504/829 : Spectroscopic survey of youngest field stars (Guillout+, 2009)
J/A+A/612/A96 : Spectroscopic survey of youngest field stars II (Frasca+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Target Target name, assigned by the authors
5- 20 A16 --- 1RXS Name of the X-ray source, JHHMMSS.s+DDMMSS
22- 38 A17 --- 2MASS Name from 2MASS (Cat. II/246) catalog,
JHHMMSSss+DDMMSSs
40- 50 A11 --- GSCII Name from GSCII (Cat. I/305) catalog
52- 66 A15 --- OName Other source designation
68- 69 I2 h RAh Right ascension (J2000)
71- 72 I2 min RAm Right ascension (J2000)
74- 79 F6.3 s RAs Right ascension (J2000)
81 A1 --- DE- Declination sign (J2000)
82- 83 I2 deg DEd Declination (J2000)
85- 86 I2 arcmin DEm Declination (J2000)
88- 92 F5.2 arcsec DEs Declination (J2000)
94- 98 F5.2 mag Bmag B-band magnitude
100-101 A2 --- r_Bmag Original catalog that released B-band
magnitude (1)
103-107 F5.2 mag Vmag V-band magnitude
109-110 A2 --- r_Vmag Original catalog that released V-band
magnitude (1)
112-117 F6.3 mag Jmag J-band magnitude from 2MASS catalog
119-124 F6.3 mag Hmag H-band magnitude from 2MASS catalog
126-131 F6.3 mag Kmag Ks-band magnitude from 2MASS catalog
133-136 F4.2 mag B-V B-V color index
138-142 F5.2 mag V-J V-J color index
144 A1 --- sample [A-D] Notes on the selection method (2)
146-152 A7 --- n_Target Notes on the target (3)
154 A1 --- n_B-V [ABC] Notes on the B-V color index (4)
156 A1 --- n_V-J [AB] Notes on the V-J color index (5)
158-160 A3 --- 2MASSFlag Notes on the 2MASS magnitudes (6)
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Note (1): Original catalog as follows:
T = Hog et al. (2000, Cat. I/259)
U = Monet et al. (2003, Cat. I/284)
Y = Zacharias et al. (2004, Cat. I/289)
G = Lasker et al. (2008, Cat. I/305) where the suffix corresponds to
their B, j, or V magnitude
Note (2): Selection method as follows:
A = Stars cross-identified with a source of the RASS (Cat. IX/10 and IX/29)
catalogs
B = Stars only cross-identified with a source of the XMM-Newton (Cat. IX/41)
catalog
C = Stars in Tachihara et al. (2005A&A...437..919T 2005A&A...437..919T) not selected using our
multivariate analysis
D = Other young field stars projected towards the CO Cepheus void and its
surrounding,which also appear either in Guillout et al.
(2010, Cat. J/A+A/504/829, sources labeled as G1 to G4), or in
Frasca et al. (2018, sources labeled as F1 to F4)
Note (3): Notes on the target as follows:
A = Selected by both this study and the work of Tachihara et al.
(2005A&A...437..919T 2005A&A...437..919T)
B = Towards the CO Cepheus void
C = Multiple system (visual binary and/or spectroscopic binary)
D = This source is the companion to TYC 4500-1549-1, which turns out to be the
brighter component of a visual binary reported by Tachihara et al.
(2005A&A...437..919T 2005A&A...437..919T)
E = The X-ray emission seems to be produced from the galaxy
2MASX 19221485+6739143
Note (4): B-V color index as follows:
A = In the Johnson-Cousins system
B = The GCS II photographic color index
C = Mixture of Johnson-Cousins and photographic magnitudes
Note (5): V-J color index as follows:
A = In the Johnson-Cousins system
B = V magnitude is not in the Johnson-Cousins system or J magnitude is an upper
limit or a poor quality value (see 2MASSFlag)
Note (6): Three character flag, one character per 2MASS band [JHK]:
A = Accurate magnitude
B = Upper limit on magnitude or a poor quality value
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Target Target name assigned by the authors
5- 6 A2 --- Ap Aperture number (1)
8- 13 A6 --- Inst Spectrograph
15- 27 F13.7 d HJD Reduced Heliocentric Julian day (HJD-2400000)
29- 36 F8.3 km/s RV ? Heliocentric radial velocity
38- 43 F6.3 km/s e_RV ? Error on heliocentric radial velocity
45- 50 F6.2 km/s vsini ? Projected rotational velocity
52- 56 F5.2 km/s e_vsini ? Error on projected rotational velocity
58- 65 A8 --- SpType ? Spectral type in MK or HD
67- 70 I4 K Teff ? Effective temperature
72- 74 I3 K e_Teff ? Error on effective temperature
76- 79 F4.2 cm/s2 logg ? Logarithm of surface gravity
81- 84 F4.2 cm/s2 e_logg ? Error on logarithm of surface gravity
86- 90 F5.2 [Sun] [Fe/H] ? Iron abundance relative to the Sun
92- 95 F4.2 [Sun] e_[Fe/H] ? Error on iron abundance relative to the Sun
97- 99 I3 0.1pm EW(Li) ? Lithium equivalent width
101-103 I3 0.1pm e_EW(Li) ? rms uncertainty on lithium equivalent width
105-180 A76 --- Notes Individual notes (2)
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Note (1): During one IDS observation, several apertures might be visible on the
cuts perpendicular to the spectral direction. In such a case, we ranked the
sources in reverse order to their maximum intensity
(i.e., "c1" = the brightest one).
Note (2): Notes as follows:
SB1 = Single-lined spectroscopic binary
SB1? = Possible single-lined spectroscopic binary
SB2 = Double-lined spectroscopic binary
SB2? = Possible double-lined spectroscopic binary
SB3 = Triple spectroscopic system
RV1 = Radial velocity of the primary component
RV2 = Radial velocity of the secondary component
RV3 = Radial velocity of the tertiary component
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Target Target name assigned by the authors
5- 6 A2 --- Ap Aperture number (1)
8- 14 F7.4 mas Plx ? Parallax
16- 21 F6.4 mas e_Plx ? Standard error of parallax
23- 30 F8.3 mas/yr pmRA ? Proper motion in right ascension direction,
pmRA*cosDE
32- 36 F5.3 mas/yr e_pmRA ? Standard error of pmRA
38- 45 F8.3 mas/yr pmDE ? Proper motion in declination direction
47- 51 F5.3 mas/yr e_pmDE ? Standard error of pmDE
53- 60 F8.3 km/s RV ? Mean Heliocentric radial velocity
62- 67 F6.3 km/s e_RV ? Error on heliocentric radial velocity
69- 77 F9.4 pc Xpos ? Heliocentric position towards the Galactic
anti-center
79- 87 F9.4 pc e_Xpos ? Uncertainty on Xpos
89- 97 F9.4 pc Ypos ? Heliocentric position towards the Galactic
rotation
99-107 F9.4 pc e_Ypos ? Uncertainty on Ypos
109-117 F9.4 pc Zpos ? Heliocentric position towards the North
Galactic pole
119-126 F8.4 pc e_Zpos ? Uncertainty on Zpos
128-134 F7.2 km/s Uvel ? Heliocentric space velocity component
towards the Galactic anti-center
136-140 F5.2 km/s e_Uvel ? Uncertainty on Uvel
142-147 F6.2 km/s Vvel ? Heliocentric space velocity component
towards the Galactic rotation
149-153 F5.2 km/s e_Vvel ? Uncertainty on Vvel
155-160 F6.2 km/s Wvel ? Heliocentric space velocity component
towards the North Galactic pole
162-166 F5.2 km/s e_Wvel ? Uncertainty on Wvel
168-172 F5.1 0.1pm EW(Li) ? Mean lithium equivalent width
174-178 F5.1 0.1pm e_EW(Li) ? rms uncertainty on lithium equivalent width
180-183 F4.2 mag Av ? Visible extinction estimated from the SED
analysis
185-217 A33 --- Notes Individual notes (2)
219 A1 --- n_Target Notes on the target (3)
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Note (1): During one IDS observation, several apertures might be visible on the
cuts perpendicular to the spectral direction. In such a case, we ranked the
sources in reverse order to their maximum intensity
(i.e., "c1" = the brightest one).
Note (2): Binary flag as follows:
VB = Visual binary
SB1 = Single-lined spectroscopic binary
SB1? = Possible single-lined spectroscopic binary
SB2 = Double-lined spectroscopic binary
SB2? = Possible double-lined spectroscopic binary
SB3 = Triple spectroscopic system
Multi. syst. = Multiple system
Note (3): Notes as followS:
A = Astrometry from the URAT Parallax Catalog (UPC - Zacharias et al.
2015AJ....150..101Z 2015AJ....150..101Z; Finch & Zacharias 2016, Cat. I/329).
B = Radial velocity and lithium equivalent width from Frasca et al.
(2018, Cat. J/A+A/612/A96)
C = Lithium equivalent width from Paper III (Frasca et al., 2018,
Cat. J/A+A/612/A96. Radial velocity near the conjunction reported in
Frasca et al. (2018, Cat. J/A+A/612/A96)
(i.e., at HJD = 2455077.6191)
D = We used the RV measurement quoted in Gaia DR2 (Cat. I/345) catalog to
compute the space-velocity components.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Target Target name assigned by the authors
5- 32 A28 --- Name Name from Gaia DR2 catalog
34- 40 F7.4 mas Plx Parallax from Gaia DR2 (Cat. I/345) catalog
42- 47 F6.4 mas e_Plx Standard error of parallax
49- 55 F7.3 mas/yr pmRA Proper motion in right ascension direction
from Gaia DR2 catalog, pmRA*cosDE
57- 61 F5.3 mas/yr e_pmRA Standard error of pmRA
63- 70 F8.3 mas/yr pmDE Proper motion in declination direction from
Gaia DR2 catalog
72- 76 F5.3 mas/yr e_pmDE Standard error of pmDE
78- 84 F7.4 mag Gmag G-band mean magnitude from Gaia DR2 catalog
86- 91 F6.4 mag e_Gmag Standard error of G-band mean magnitude from
Gaia DR2 catalog
93- 98 F6.2 km/s RVGaia ? Radial velocity in the solar barycentric
reference frame from Gaia DR2 catalog
100-104 F5.2 km/s e_RVGaia ? Radial velocity error from Gaia DR2 catalog
106-111 F6.2 arcsec rho ? Angular separation
113-117 F5.3 mas e_rho ? Standard error of angular separation
119-124 F6.2 deg theta ? Position angle
126-133 F8.3 arcsec e_theta ? Standard error of position angle
135-141 F7.1 AU s ? Projected physical separation
143-147 F5.1 AU e_s ? Standard error of pojected physical
separation
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Acknowledgements:
Alexis Klutsch, alexis.klutsch(at)astro.uni-tuebingen.de
References:
Guillout et al., Paper I 2009A&A...504..829G 2009A&A...504..829G, Cat. J/A+A/504/829
Guillout et al., Paper II 2010A&A...520A..94G 2010A&A...520A..94G
Frasca et al., Paper III 2018A&A...612A..96F 2018A&A...612A..96F, Cat. J/A+A/612/A96
(End) Patricia Vannier [CDS] 30-Mar-2020