J/A+AS/124/449 Young stars south of Taurus-Auriga (Magazzu+ 1997)
Search for young low-mass stars in a ROSAT selected sample south of the
Taurus-Auriga molecular clouds
Magazzu A., Martin E.L., Sterzik M.F., Neuhaeuser R., Covino E.,
Alcala J.M.
<Astron. Astrophys. Suppl. Ser. 124, 449 (1997)>
=1997A&AS..124..449M 1997A&AS..124..449M
ADC_Keywords: X-ray sources ; Stars, pre-main sequence ; Magnitudes
Keywords: Stars: formation - Stars: late-type - Stars: pre-main sequence -
X-rays: stars
Abstract:
We present results of intermediate resolution spectroscopy of 131
optical counterparts to 115 ROSAT All-Sky Survey X-ray sources south
of the Taurus-Auriga dark cloud complex. These objects have been
selected as candidate young stars from a total of 1084 ROSAT sources
in a ∼300 square degree area. We identify 30 objects as low-mass PMS
stars on the basis of the LiIλ6708Å doublet in their
spectrum, a signature of their young age. All these stars have a
spectral type later than F7 and show spectral characteristics typical
of weak-line and post-T Tauri stars. The presence of young objects
several parsecs away from the regions of ongoing star formation is
discussed in the light of the current models of T Tauri dispersal.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 115 X-ray data for our sample
table2.dat 84 115 Closest optical counterparts.
table3.dat 71 16 Other optical counterparts observed.
table4.dat 70 131 Results of spectroscopy of all counterparts
tables.tex 195 696 LaTeX version of the tables
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- ROSAT ROSAT (Cat. IX/11) name
16- 20 F5.1 --- Counts Number of counts in the broad ROSAT band
22- 25 F4.1 --- e_Counts rms uncertainty on Counts
27- 31 F5.1 s Exp Exposure time
33- 36 F4.2 --- HR1 Hardness ratio 1
38- 41 F4.2 --- e_HR1 rms uncertainty on HR1
43- 47 F5.2 --- HR2 Hardness ratio 2
49- 52 F4.2 --- e_HR2 rms uncertainty on HR2
54- 58 F5.1 --- ML Maximum likelihood of existence
60- 63 F4.2 keV kTx Emission energy (typical error ±0.55keV)
65- 69 F5.2 [cm-2] log(NH) Absorbing foreground column density
(typical error ±0.77, in log(NH) cm-2)
71- 76 F6.2 10-13mW/m2 FX X-ray flux (typical error±1.87x10-13mW/m2)
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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- 14 A14 --- ROSAT ROSAT name
15- 16 A2 --- m_ROSAT Multiplicity index on ROSAT name
18 I1 h RAh Optical right ascension (J2000.0) (1)
20- 21 I2 min RAm Optical right ascension (J2000.0) (1)
23- 27 F5.2 s RAs Optical right ascension (J2000.0) (1)
29 A1 --- DE- Declination sign
30- 31 I2 deg DEd Optical declination (J2000.0) (1)
33- 34 I2 arcmin DEm Optical declination (J2000.0) (1)
36- 39 F4.1 arcsec DEs Optical declination (J2000.0) (1)
41- 45 F5.1 arcsec oRA Offset between X-ray and optical right ascension
47- 51 F5.1 arcsec oDE Offset between X-ray and optical declination
53- 56 F4.1 mag Vmag V magnitude (from the GSC II/143 or
Simbad if n_Vmag=:)
57 A1 --- n_Vmag [:] : indicates that V magnitude is from Simbad
59- 63 F5.2 --- log(FX/FV) X-ray to optical flux ratio
65- 68 F4.2 --- Prob Discrimination probability
70- 84 A15 --- Rem Remarks (2)
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Note (1): From the GSC (or Simbad if available)
Note (2): Some GSC counterparts appear on several GSC plates which may have
different colors and different filters; we have always chosen the
closest counterpart, i.e. we neither try to average the magnitudes
nor indicate the plate color as GSC magnitudes are very uncertain
anyway (about half a magnitude)
1: Not listed in the GSC
2: HD 23793 B (F5V) and the early-type star HR 1174 (B3) are an
optical pair with 9" separation (Lindroos 1986A&A...156..223L 1986A&A...156..223L);
the later type star is more likely to be the true optical
counterpart of the X-ray source (e.g. Schmitt et al.
1993ApJ...402L..13S 1993ApJ...402L..13S)
3: Companion N is an unresolved binary itself
4: Not listed in the GSC.
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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- 14 A14 --- ROSAT ROSAT name
15- 16 A2 --- m_ROSAT Multiplicity index on ROSAT name
18 I1 h RAh Optical right ascension (J2000.0)
20- 21 I2 min RAm Optical right ascension (J2000.0)
23- 24 I2 s RAs Optical right ascension (J2000.0)
26 A1 --- DE- Declination sign
27- 28 I2 deg DEd Optical declination (J2000.0)
30- 31 I2 arcmin DEm Optical declination (J2000.0)
33- 34 I2 arcsec DEs Optical declination (J2000.0)
36- 54 A19 --- Pos Relative position to the counterpart listed
in Table 2
56- 59 F4.1 mag Vmag V magnitude (from the GCS)
61- 71 A11 --- Rem Remarks (1)
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Note (1): Remarks are either GSC, Simbad, or visual inspection of plates
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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- 14 A14 --- ROSAT ROSAT name
15- 16 A2 --- m_ROSAT Multiplicity index on ROSAT name
18- 20 A3 --- Tel Telescope used (1)
23- 27 F5.2 0.1nm EW(Halpha) ?Hα equivalent width (negative when in
emission)
28 A1 --- n_EW(Halpha) [af] Note on EW(Halpha) (2)
30- 33 F4.2 0.1nm EW(Li) ?Lithium 6708Å absorption equivalent width
34 A1 --- n_EW(Li) [:ny] Note on EW(Li) (3)
36- 41 A6 --- SpType Spectral type (always luminosity class V
unless otherwise noted)
43- 49 A7 --- Nature Nature of object (see text)
51- 70 A20 --- Rem Individual notes (4)
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Note (1): Telescope used to observe the star:
INT for the Isaac Newton Telescope
ESO for the ESO1.52m telescope
Note (2): f: indicates that Hα emission is filling in the absorption line
a: for absorption without available equivalent width
Note (3): presence of Lithium:
':': indicates large uncertainty
n: no
y: yes
Note (4): the numbers refer to the following remarks:
1: Spectrum blue-shifted by 2Å
2: Star A itself is SB, with the secondary having almost the same
spectral type as the primary
3: Also observed at INT
4: Spectrum blue-shifted by 1Å, Hα line shows a P Cyg profile
5: Hα line shows an inverse P Cyg profile
6: Spectrum red-shifted by 2Å
7: SB: the primary is F8 with Hα in absorption and
Wλ(Ca)<Wλ(Li)=0.16Å, the secondary has
Wλ(Ca)>Wλ(Li)=0.13Å, thus the system may by
a close PMS binary; Hα line shows a P Cyg profile
8: Very noisy spectrum
9: Secondary seems to have a slightly earlier spectral type.
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Acknowledgements: Antonio Magazzu
(End) Patricia Bauer [CDS] 17-Dec-1996