J/A+A/312/439 J/A+A/312/439 New T Tauri stars in Taurus-Auriga R Wichmann J Krautter J H M M Schmitt R Neuhauser J M Alcala H Zinnecker R M Wagner R Mundt M F Sterzik Astron. Astrophys. 312 439 1996 1996A&A...312..439W J/A+A/297/391 : T Tauri stars ROSAT survey (Neuhaeuser+, 1995) Neuhauser R., Sterzik M.F., Schmitt J.H.M.M., Wichmann R., Krautter J. 1995b, =1995A&A...297..391N Stars, pre-main sequence X-ray sources stars: formation stars: late-type stars: pre-main sequence surveys X-rays: stars On the basis of the ROSAT All-Sky-Survey, a study of the Taurus-Auriga star forming region has been performed in order to search for hitherto undiscovered T Tauri stars. Our study covers an area of about 280 square degrees, located between 4^h^ and 5^h^ in right ascension and between 15deg and 34deg in declination. Identification of ROSAT All-Sky Survey sources in this area by means of optical spectroscopy revealed 2 new classical T Tauri stars (CTTS) and 66 new weak-line-T Tauri stars (WTTS) with W_{lambda}_(H{alpha})<=10A. Additional pointed ROSAT observations led to the identification of 6 more WTTS and 2 CTTS, giving a total of 76 new T Tauri stars. The large area of our study, as compared with previous works, allows us to study the spatial distribution of WTTS in this star forming region. We find the WTTS of our survey to be distributed over the whole region investigated. There is a noticeable decline of the surface density from south to north within our study area, but the spatial distribution extends most probably beyond our study region. No clustering towards the population of T Tauri stars known prior to ROSAT in Taurus-Auriga could be observed. We suggest that the WTTS found in our study might in part be somewhat older than the previously known T Tauri stars in Taurus-Auriga, and that their broad spatial distribution is due to the typical velocity dispersion of a few km/s measured for Taurus T Tauri stars, in which case for some of our WTTS an age on the order of 10^7^years would be required for reaching the observed distances from the Taurus dark clouds. We estimate a WTTS/CTTS ratio of about 6 within our study area, but conclude that because of the different spatial distribution of WTTS and CTTS this ratio will be most probably significantly larger for a more extended area.

ROSAT

No Number --- Name Identifier of star number=1 HD 285751: this star has independently been detected as T Tauri star by F.M. Walter (1994, private communication); X-ray data are also given in Neuhauser et al. (1995A&A...297..391N) RXJ0458.7+2046 discovered on the basis of preliminary RASS data, but not detected in EXSAS reduction, therefore in table5 for this star no X-ray data are given --- n_Pos Note on position number=2 X : Position is X-ray position, star is not included in Hubble GSC blank : Position is taken from Hubble GSC --- n_Xray Note on X-ray detection number=3 P : Star was discovered by pointed observations blank : Star was discovered by the ROSAT All-Sky Survey --- RAh Right Ascension for equinox 2000.0 h RAm Right Ascension for equinox 2000.0 min RAs Right Ascension for equinox 2000.0 s DEd Declination for equinox 2000.0 deg DEm Declination for equinox 2000.0 arcmin DEs Declination for equinox 2000.0 arcsec EW(Ha) Equivalent width for H_alpha 0.1nm Sp Spectral type --- Pmag Magnitude as listed in the Hubble GSC number=4 For stars not listed in the Hubble GSC a magnitude of 0.0 is given mag Name Identifier of star --- n_Pos Note on position number=1 X : Position is X-ray position, star is not included in Hubble GSC blank : Position is taken from Hubble GSC --- n_Xray Note on X-ray detection number=2 P : Star was discovered by pointed observations blank : Star was discovered by the ROSAT All-Sky Survey --- RAh Right Ascension for equinox 2000.0 h RAm Right Ascension for equinox 2000.0 min RAs Right Ascension for equinox 2000.0 s DE- Declination sign --- DEd Declination for equinox 2000.0 deg DEm Declination for equinox 2000.0 arcmin DEs Declination for equinox 2000.0 arcsec CR Background subtracted X-ray count rate (0.1-2.4keV energy range) s-1 e_CR Error in CR s-1 Sp Spectral type --- EW(Ha) Equivalent width for H_alpha 0.1nm Name Identifier of star --- n_Pos Note on X-ray data number=1 P : X-ray data are from pointed observations blank : X-ray data are from the ROSAT All-Sky Survey --- ML Maximum likelihood of existence --- Cts Background subtracted X-ray counts (0.1 to 2.4 keV energy range) --- e_Cts Errors for X-ray counts --- Exp Exposure time s HR1 Hardness ratio 1 --- e_HR1 Error in hardness ratio 1 --- HR2 Hardness ratio 2 --- e_HR2 Error in hardness ratio 2 --- log(NH) Logarithm of HI column density number=2 NH and TX are free parameters for the fits of the X-ray spectra cm-2 E_log(NH) Positive error for log(NH) cm-2 e_log(NH) Negative error for log(NH) cm-2 TX Temperature number=2 NH and TX are free parameters for the fits of the X-ray spectra keV E_TX Positive error for TX keV e_TX Negative error for TX keV LX X-ray luminosity (10^30^erg/s) number=3 For the calculation of LX a distance of 140pc has been assumed 10+23W E_LX Positive error for LX 10+23W e_LX Negative error for LX 10+23W Name Identifier of star --- RAh Right Ascension for equinox 2000.0 h RAm Right Ascension for equinox 2000.0 min RAs Right Ascension for equinox 2000.0 s DE- Declination sign --- DEd Declination for equinox 2000.0 deg DEm Declination for equinox 2000.0 arcmin DEs Declination for equinox 2000.0 arcsec Cts Background subtracted X-ray count rate (0.1-2.4 keV energy range) s-1 e_Cts Error in X-ray count rate s-1 HR1 Hardness Ratio 1 --- e_HR1 Error in Hardness Ratio 1 --- HR2 Hardness Ratio 2 --- e_HR2 Error in Hardness Ratio 2 --- table4.texLaTeX version of table4 table5.texLaTeX version of table5 table6.texLaTeX version of table6 table7.texLaTeX version of table7 figure5a.psLow-dispersion spectral atlas of new WTTS in Taurus-Auriga. Shown is the H_alpha and Li I region. figure5b.psFigure5 cont. figure5c.psFigure5 cont. figure5d.psFigure5 cont. figure5e.psFigure5 cont. figure5f.psFigure5 cont. figure5g.psFigure5 cont. figure5h.psFigure5 cont. Patricia Bauer CDS 1996Apr10Rainer Wichmann <R.Wichmann@lsw.uni-heidelberg.de> J_A+A_312_439.xml