J/A+A/460/695 Search for Associations Containing Young stars (Torres+, 2006)
Search for Associations Containing Young stars (SACY).
I. Sample & Searching Method.
Torres C.A.O., Quast G.R., da Silva L., de la Reza R., Melo C.H.F.,
Sterzik M.
<Astron. Astrophys. 460, 695 (2006)>
=2006A&A...460..695T 2006A&A...460..695T
ADC_Keywords: Stars, nearby ; Stars, late-type ; Photometry, UBVRI ;
Radial velocities ; Rotational velocities ; Equivalent widths
Spectral types ; X-ray sources
Keywords: stars: pre-main sequence - stars: formation - stars: kinematics -
stars: rotation - stars: abundances -
open clusters and associations: individual: β Pic Association
Abstract:
We report results from a high-resolution optical spectroscopic survey
aimed to search for nearby young associations and young stars among
optical counterparts of ROSAT All-Sky Survey (IX/10 and IX/29,
X-ray sources in the Southern Hemisphere. We selected 1953 late-type
(B-V≥0.6), potentially young, optical counterparts out of a total of
9574 1RXS sources for follow-up observations. At least one
high-resolution spectrum was obtained for each of 1511 targets. This
paper is the first in a series presenting the results of the SACY
survey. Here we describe our sample and our observations. We describe
a convergence method in the (UVW) velocity space to find associations.
As an example, we discuss the validity of this method in the framework
of the Beta Pic Association.
Description:
The SACY sample is defined by Hipparcos (I/239) and Tycho-2
(I/259) stars within an error radius of 2.6 times the positional
error of the ROSAT All-Sky Bright Source Catalogue (1RXS, IX/10).
The used cut-off (B-V=0.6), corresponding approximately to a G0
dwarf, is near the hottest stars where the strength of the LiI line
can be used as an youth indicator. We excluded all Hipparcos stars
having Mv<2.0. In Table 1 of the paper we give the northern boundary
limits of the survey. In addition to the 1511 stars observed at least
once we add 115 with data taken from the literature to complement the
sample.
Most of the spectroscopic observations (∼70%) were performed with the
FEROS spectrograph at the 1.5m/ESO telescope at La Silla between
January 1999 and September 2002 (ON-ESO agreement and ESO program
identification 67.C-0123). Two more runs (ESO program identifications
072.C-0393 and 077.C-0138) were carried out at the 2.2m/ESO telescope.
Another set of data (∼30%) was collected at the coude spectrograph
attached to 1.60m telescope at the Observatorio rio do Pico dos Dias
(OPD), LNA, Brazil. Some spectra are a re-analysis of the ones taken
for the PDS program. A few observations were collected using the
CORALIE attached to the Swiss Euler Telescope at La Silla.
UBV(RI)c photometry for part of the sample was obtained using FOTRAP
at the 0.60m Zeiss telescope of the OPD. When a star was not observed
photometrically by us we tried to obtain some useful photometric data
in the Hipparcos and Tycho Catalogues or in the available literature
in the SIMBAD. For multiple stars, magnitudes and colors were
corrected in order to take into account the presence of the companion.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 228 1626 Astrometric, spectroscopic and photometric data
of the SACY sample
table4.dat 228 165 Astrometric, spectroscopic and photometric data
of other observed stars
refs.dat 96 107 References (table5 of the paper)
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See also:
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
IX/29 : ROSAT All-Sky Survey Faint Source Catalog (Voges+ 2000)
Byte-by-byte Description of file: table[34].dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq Running number
7- 22 A16 --- 1RXS 1RXS (IX/10,IX/29) designation (1)
25- 40 A16 --- Name Hipparcos (I/239), Tycho-2 (II/259) or
UCAC2 (I/289) identification (2)
42- 54 A13 --- OName Other identification (HD, DM, other) (3)
56- 57 I2 h RAh Right ascension (J2000.0)
59- 60 I2 min RAm Right ascension (J2000.0)
62- 65 F4.1 s RAs Right ascension (J2000.0)
68 A1 --- DE- Declination sign (J2000.0)
69- 70 I2 deg DEd Declination (J2000.0)
72- 73 I2 arcmin DEm Declination (J2000.0)
75- 76 I2 arcsec DEs Declination (J2000.0)
79- 85 F7.1 mas/yr pmRA Proper motion in RA (pmRA*cosDE)
87- 93 F7.1 mas/yr pmDE Proper motion in DE (pmDE)
96- 98 A3 ---- r_pmRA Source of proper motions (4)
100-105 F6.1 km/s HRV Heliocentric radial velocity (5)
106 A1 --- f_HRV [:] Quality flag for RV
108-111 F4.1 km/s e_HRV ? rms of the observed RV
113-115 I3 --- Nobs ? Number of observations (6)
116 A1 --- f_Nobs [*] *: RV value comes from the literature (7)
118-120 A3 --- r_HRV ? Source of radial velocity (8)
123-127 A5 ---- n_HRV [D,SB1234 ?] Multiplicity flag (9)
129-132 F4.1 arcsec Sep ? Angular separation of visual binaries (10)
135-138 F4.1 mag dV ? Magnitude difference of components (11)
139 A1 --- u_dV [?] Uncertainty flag on dV
142-146 F5.1 km/s vsini ? Rotational velocity
148-151 F4.1 km/s e_vsini ? rms uncertainty on vsini
154-156 A3 ---- r_vsini ? Source of vsini (8)
159-163 F5.1 mas Plx ? Trigonometric parallax
166-169 F4.1 mas e_Plx ? Standard error in Plx
172-174 A3 --- r_Plx Source of Plx (8)
177-181 F5.2 mag Vmag Johnson V magnitude
182 A1 ---- f_Vmag [V] Quality flag indicating variability (12)
183-187 F5.2 mag B-V ? Johnson B-V colour index
189-193 F5.2 mag V-I ? Cousins V-I colour index
196-198 A3 --- r_Vmag Source of photometry (13)
199 A1 --- n_Vmag [*] *: photometry corrected for companions (14)
203-210 A8 --- SpType MK spectral type
212-214 I3 0.1pm EWLi ? LiI equivalent width in milli-Angstroms (15)
215 A1 ---- f_EWLi [:?] Quality flag for EWLi
217-221 F5.1 0.1nm EWHa ? Hα line emission in Angstroms
224-228 A5 ---- r_EWLi Source of spectral information (16)
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Note (1):
ROSAT All-Sky Survey Catalogue source name, in general from the Bright
Source Catalogue (IX/10) but sometimes refers to the Faint Source
Catalogue (IX/29). A repeated entry means more than one observed
possible optical counterpart. The same source may have entries in both
Tables 3 and 4, but the best optical candidate may be in any of the
tables.
Note (2):
Order of preference of the identification is Hipparcos, TYCHO-2 or
UCAC2, independently of the astrometric data used.
Note (3):
Order of preference is HD, DM, and other. GSC is only used if there is
no TYCHO-2 identification for the star.
Note (4):
Order of preference of the sources of the proper motions is the same
as of the Name, adding other sources, but in some cases we used the
best value from our judgment.
Note (5):
Radial velocities from SB2 observed once or SB1 are mean values, and
may not represent the systemic velocity. When there is a systemic
velocity from the literature, it is the used value.
Note (6):
Null refers to no published number of observations in the literature
cited in r_HRV. Nobs from SACY includes references N=25 and 26.
Note (7):
The * means that this is the number of spectral observations in the
SACY project, but the systemic HRV value was taken from the literature.
For V1005 Ori the non variable HRV is from literature as our spectrum
was not properly calibrated.
Note (8):
If there is no number, the radial velocity is from this work.
Note (9):
D means visual binary; sometimes the components were observed
separately and there is another entry, designated by A, B, C...,
in Table 3 or Table 4. If the bright component is also a SB the D
is given in the entry of the faint one.
A ? means possible evidence for radial velocity variations, sometimes
by comparing with published data. In some cases it is difficult to
decide between high rotation (+ spots?) and SB2. For other SB2? with
low rotation and large e_HRV the star should be considered at least
a SB1. For close visual doubles observed together, one of the
spectroscopic components may be also the visual one, mainly in
SB3 cases. For SBn all other data of this line are for the bright
component. In the future we will publish the data for spectroscopic
binaries found in the SACY project.
Note (10):
Separation between the visual components, even if in n_HRV there is a
SBn. This means there is D for a faint companion in n_HRV in another
entry.
Note (11):
Magnitude difference between faint companions and the bright one. A
negative value means that the faint companions together are brighter
than the primary, or the so called primary is a fainter companion with
sharper lines.
For visual binaries the negative value means that primary is also a
SBn, and the visual difference is given in this entry or the primary
is in the other table.
Note (12):
V: photometric variability.
Note (13): Source of photometry:
H = origin of the photometry from Hipparcos (I/239)
T = from TYCHO2 (I/259) converted to Johnson
blank = estimated magnitude
Note (14):
for the proposes of the SACY the photometric measures for close visual
doubles and SBs are corrected to take into account the secondaries. As
these values are model dependent they must be used with caution.
Note (15):
For SB2 or SB3 the values are tentatively corrected for the continuum
flux ratios.
Note (16): For observations from this paper:
F = observation with ESO/FEROS
d = observation with the OPD coude spectrograph
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Ref Reference number or letter
5- 23 A19 --- BibCode BibCode
25- 48 A24 --- Aut Author's name
49- 96 A48 --- Com Comments
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Acknowledgements: Carlos Torres, beto(at)lna.br
History:
16-Mar-2007: In table3, cross-id of No 305 corrected (from author)
(End) Patricia Vannier [CDS] 30-Nov-2006