SACY - SACY (Search for Associations Containing Young Stars) Catalog

Overview

The SACY (Search for Associations Containing Young Stars) Catalog contains the 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 X-ray sources in the Southern Hemisphere. 1953 late-type (B-V>=0.6), potentially young, optical counterparts were selected 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 in which the sample of X-ray selected stars and the supporting optical observations are described.

The SACY sample is defined by Hipparcos (CDS Cat. <I/239>) and Tycho-2 (CDS Cat. <I/259>) stars within an error radius of 2.6 times the positional error of the ROSAT All-Sky Bright Source Catalogue (1RXS, CDS Cat. <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. All Hipparcos stars having M_v < 2.0 have been excluded. The northern boundary limits of the survey are given in Table 1 of the reference paper. In addition to the 1511 stars observed at least once, 115 stars with data taken from the literature have been added in order to complement the sample. In addition to these 1626 stars in the SACY sample (sources with source number prefixes of 'S'), entries for 165 other observed stars (sources with source number prefixes of 'O') are also included in this table.

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 the authors, they tried to obtain some useful photometric data from 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(s).

Catalog Bibcode

2006A&A...460..695T

References

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

Provenance

This table was created by the HEASARC in March 2007 based on the CDS table J/A+A/460/695, files table3.dat and table4.dat

Parameters

Source_Number
A running number for the X-ray source in order of increasing J2000.0 Right Ascension. To differentiate sources from the main SACY sample (listed in Table 3 of the reference paper) from the other observed stars (listed in Table 4 of the reference paper), the HEASARC has added prefixes of 'S' (for SACY) and 'O' (for other) in front of the numerical source numbers given in these two tables so as to make them unique.

Xray_Name
The ROSAT All-Sky Survey (RASS) Bright Source Catalog designation of the X-ray source, normally from the RASS Bright Source Catalog (CDS Cat. <IX/10>), but sometimes from the RASS Faint Source Catalog (CDS Cat. <IX/29>). If there is more than one observed possible optical counterpart, then there will be multiple entries in this table having the same X-ray name, one for each counterpart. The same X-ray source may have entries in both the SACY and other observed stars samples (Tables 3 and 4 of the reference paper, respectively), and the 'best' optical candidate may be in either sample.

Name
The Hipparcos (CDS Cat. <I/239>), Tycho-2 (CDS Cat. <II/259>) or UCAC2 (CDS Cat. <I/289>) names of the optical counterpart to the ROSAT source. The order of preference of which identification is given is Hipparcos, TYCHO-2 or UCAC2, independently of which astrometric data were used.

Alt_Name
An alternative source identification for the optical counterpart to the ROSAT source. The order of preference for these identification is HD, DM, and other. GSC names are only used if there is no TYCHO-2 identification for the star.

RA
The Right Ascension of the optical counterpart to the ROSAT source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 seconds of time in the original tables.

Dec
The Declination of the optical counterpart to the ROSAT source in the selected equinox. This was given in J2000.0 coordinates to a precision of 1 arcsecond in the original tables.

LII
The Galactic Longitude of the optical counterpart to the ROSAT source.

BII
The Galactic Latitude of the optical counterpart to the ROSAT source.

PM_RA
The proper motion of the optical counterpart to the ROSAT source in the direction of Right Ascension, in mas/yr.

PM_Dec
The proper motion of the optical counterpart to the ROSAT source in the direction of Declination, in mas/yr.

Ref_PM
The reference code for the source of the quoted proper motions. The order of preference of the sources of the proper motions is the same as of the names, adding other sources, but in some cases the authors used the best value from their judgment. The key to the codes is given in the file https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/460/695/refs.dat.

Radial_Velocity
The heliocentric radial velocity of the optical counterpart to the ROSAT source, in km/s. Radial velocities from SB2 objects which were observed once or from SB1 objects are mean values, and may not represent the systemic velocities. When there is a systemic velocity from the literature, this value has been used.

Radial_Velocity_Qual
This flag parameter is set to ':' to indicate that the quality of the heliocentric radial velocity is low.

Radial_Velocity_Error
The RMS of the observed heliocentric radial velocity of the optical counterpart to the ROSAT source, in km/s.

Radial_Velocity_Num_Obs
The number of radial velocity observations. A null value means that no published number of observations was given in the literature reference cited in the ref_radial_velocity parameter. Values from SACY include the references with reference codes of 25 and 26.

Radial_Velocity_Flag
This flag parameter is set to 'L' to indicate that the quoted value of radial_velocity_num_obs is the number of spectral observations for this star obtained in the SACY project, but that the systemic heliocentric radial velocity value was taken from the literature. For V1005 Ori, the non-variable radial velocity is from the literature, as the authors' spectrum was not properly calibrated.

Ref_Radial_Velocity
The reference code for the source of the quoted heliocentric radial velocity. The key to the codes is given in the file https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/460/695/refs.dat. If there is no code given then the radial velocity comes from the present study.

Multiplicity_Flag
A flag indicating the multiplicity of the optical counterpart to the ROSAT source. 'D' means visual binary; sometimes the components were observed separately and there is another entry, designated by A, B, C... in this table for this same object. If the bright component is also an SB, the D is given in the entry of the fainter component. 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 alarge rms in the radial velocity, 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.

Vb_Angular_Separation
The angular separation of the counterpart, if a visual binary, in arcseconds. This separation between the visual components is given, even if in the multiplicity flag there is a 'SBn' value. This means there is a value of 'D' for a faint companion in the multiplicity_flag of another counterpart entry.

Vb_Delta_Mag
The magnitude difference between the bfaint companions and the bright component of the visual binary. A negative value means that the faint companions together are brighter than the primary, or that 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 sample.

Vb_Delta_Mag_Flag
This flag parameter is set to '?' to indicate that the magnitude difference between the components is uncertain.

Vrot_Sini
The rotational velocity v sin i of the counterpart, in km/s.

Vrot_Sini_Error
The RMS uncertainty in the rotational velocity, in km/s.

Ref_Vrot_Sini
The reference code for the source of the quoted rotational velocity. The key to the codes is given in the file https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/460/695/refs.dat. If there is no code given then the rotational velocity comes from the present study.

Parallax
The trigonometric parallax of the counterpart, in milliarcseconds (mas).

Parallax_Error
The standard error in the trigonometric parallax, in mas.

Ref_Parallax
The reference code for the source of the quoted trigonometric parallax. The key to the codes is given in the file https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/460/695/refs.dat.

Vmag
The Johnson V magnitude of the optical counterpart.

Variability_Flag
This flag parameter is set to 'V' to indicate the presence of photometric variability.

BV_Color
The Johnson B-V color index of the optical counterpart.

VI_Color
The Cousins V-I color index of the optical counterpart.

Ref_Photometry
The reference code for the source of the quoted optical photometry. A blank value means that the magnitude has been estimated. The key to the codes is given in the file https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/460/695/refs.dat.

Photometry_Flag
This flag parameter is set to 'C' to indicate that the photometry has been corrected for companions. For the purposes of the SACY, the photometric measures for close visual doubles and SBs were corrected to take into account the secondaries. As these values are model-dependent, they must be used with caution.

Spect_Type
The MK spectral type of the optical counterpart.

Li_I_Equiv_Width
The Li-I 6708 Angstroms equivalent width measured in the optical counterpart's spectrum, in milli-Angstroms. For objects which are SB2 or SB3, the values are tentatively corrected for the continuum flux ratios.

Li_I_Equiv_Width_Flag
This flag parameter is set to ':' or '?' to indicate caveats about the quality of the Li-I equivalent width.

Halpha_Equiv_Width
The H-alpha emission equivalent width measured in the optical counterpart's spectrum, in Angstroms.

Ref_Spectroscopy
The reference code for the source of the quoted optical spectroscopy. The key to the codes is given in the file https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/460/695/refs.dat.

Class
The HEASARC Browse object classification, based on the value of the spect_type parameter (the optical counterpart spectral type).

Contact Person

Questions regarding the SACY database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:34:19 EDT