J/A+AS/123/329 J/A+AS/123/329 New weak-line T Tauri stars in Lupus J Krautter R Wichmann J H M M Schmitt J M Alcala R Neuhaeuser L Terranegra Astron. Astrophys. Suppl. Ser. 123 329 1997 1997A&AS..123..329K IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1996) IX/11 : ROSAT Source Catalog (Voges+ 1994) J/A+A/320/185 : T Tauri UBVRIcJHKL photometry (Wichmann+ 1997) Wichmann R., Krautter J., Covino E., Alcala J.M., Neuhaeuser R., Schmitt J.H.M.M., 1997A&A...320..185W Stars, pre-main sequence X-ray sources ISM: individual (Lupus clouds) stars: formation stars: pre-main sequence surveys X-rays: stars We present first results obtained by a survey of the Lupus star forming region in search of new T Tauri stars. This study has been performed on the basis of deep pointed ROSAT observations in the Lupus dark clouds as well as data from the ROSAT All-Sky-Survey in the surrounding, less obscured regions. Our survey covers an area of about 230 square degrees, located between 15^h^6^m^ and 16^h^24^m^ in right ascension and between -47^o^ and -32^o^ in declination. Identification of ROSAT All-Sky-Survey sources in this area by means of optical spectroscopy revealed 89 T Tauri stars, 86 of them "weak-line" T Tauri stars (WTTS not known from previous studies of this region. Our pointed ROSAT observations led to the identification of 47 more T Tauri stars, giving a total of 136 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 on alarge scale. We find the new WTTS to be distributed over the whole area of our survey, indicating that their spatial distribution might extend well beyond our study area. Contrary to the Lupus T Tauri stars known prior to this study, the WTTS discovered by the ROSAT All-Sky-Survey are not clustered in the regions of highest extinction, i.e. the dark clouds.

ROSAT

No Sequential number --- Star Identifier of star --- NA Note on X-ray discovery number=1 Stars marked with '1', '2', or '3' have been discovered by pointed observations in the Lupus 1, Lupus 2 or Lupus 3 clouds, respectively. Left blank for stars discovered by the ROSAT All-Sky Survey. --- RAh Right Ascension for equinox 2000.0 number=2 If declination is given with one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. h RAm Right Ascension for equinox 2000.0 number=2 If declination is given with one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. min RAs Right Ascension for equinox 2000.0 number=2 If declination is given with one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. s DE- Declination sign --- DEd Declination for equinox 2000.0 number=2 If declination is given with one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. deg DEm Declination for equinox 2000.0 number=2 If declination is given with one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. arcmin DEs Declination for equinox 2000.0 number=2 If declination is given with one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. arcsec EWHa Equivalent width for H_alpha 0.1nm SpT Spectral type --- Vmag V magnitude number=3 Magnitudes given with two decimals are from our own measurements (Wichmann et al. 1997A&A...320..185W), those given with one decimal only are taken from the GSC. A value of zero means that no magnitude is available. mag No Sequential number --- Star Identifier of star --- NA Note on X-ray discovery number=1 Stars marked with '1', '2', or '3' have been discovered by pointed observations in the Lupus 1, Lupus 2 or Lupus 3 clouds, respectively. Left blank for stars discovered by the ROSAT All-Sky Survey. --- RAh Right Ascension for equinox 2000.0 number=2 If declination is given wit one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. h RAm Right Ascension for equinox 2000.0 number=2 If declination is given wit one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. min RAs Right Ascension for equinox 2000.0 number=2 If declination is given wit one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. s DE- Declination sign --- DEd Declination for equinox 2000.0 number=2 If declination is given wit one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. deg DEm Declination for equinox 2000.0 number=2 If declination is given wit one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. arcmin DEs Declination for equinox 2000.0 number=2 If declination is given wit one decimal only, the coordinates refer to the position of the X-ray source, otherwise the coordinates are taken from the Guide Star Catalogue. arcsec CTS ROSAT X-Ray count rate number=3 Background and vignetting corrected broadband X-ray count rate. ct/s e_CTS Error of ROSAT X-Ray count rate ct/s SpT Spectral type --- EWHa Equivalent width for H_alpha 0.1nm Vmag V magnitude number=4 Magnitudes are taken from the GSC. A value of zero means that no magnitude is available. mag No Sequential number --- Star Identifier of X-ray source --- NA Note on X-ray discovery number=1 Stars marked with 'S' are also detected in the ROSAT All-Sky Survey. --- RAh Right Ascension for equinox 2000.0 number=2 Coordinates always refer to the position of the X-ray source. h RAm Right Ascension for equinox 2000.0 number=2 Coordinates always refer to the position of the X-ray source. min RAs Right Ascension for equinox 2000.0 number=2 Coordinates always refer to the position of the X-ray source. s DE- Declination sign --- DEd Declination for equinox 2000.0 number=2 Coordinates always refer to the position of the X-ray source. deg DEm Declination for equinox 2000.0 number=2 Coordinates always refer to the position of the X-ray source. arcmin DEs Declination for equinox 2000.0 number=2 Coordinates always refer to the position of the X-ray source. arcsec ML Likelihood of existence --- ExpTime Exposure time s CTS ROSAT X-Ray count rate number=3 Background and vignetting corrected broadband X-ray count rate. ct/s e_CTS Error of ROSAT X-Ray count rate ct/s HR1 ROSAT hardness ratio 1 --- e_HR1 Error of ROSAT hardness ratio 1 --- HR2 ROSAT hardness ratio 2 --- e_HR2 Error of ROSAT hardness ratio 2 --- X-ray Identifier of X-ray source number=1 RXJ1507.9-4515, RXJ1533.0-3930, RXJ1539.2-4455 were found due to the SASS reduction of the RASS, but could not be detected as X-ray sources in the EXSAS reduction of the RASS. Therefore, no X-ray data are given for these stars. --- NA Note on X-ray discovery number=2 Stars marked with '1', '2', or '3' have been discovered by pointed observations in the Lupus 1, Lupus 2 or Lupus 3 clouds, respectively, and X-ray data are from pointed observations. Otherwise, X-ray data refer to the ROSAT All-Sky Survey. --- RAh Right Ascension for equinox 2000.0 number=3 Coordinates refer to the position of the X-ray source. h RAm Right Ascension for equinox 2000.0 number=3 Coordinates refer to the position of the X-ray source. min RAs Right Ascension for equinox 2000.0 number=3 Coordinates refer to the position of the X-ray source. s DE- Declination sign --- DEd Declination for equinox 2000.0 number=3 Coordinates refer to the position of the X-ray source. deg DEm Declination for equinox 2000.0 number=3 Coordinates refer to the position of the X-ray source. arcmin DEs Declination for equinox 2000.0 number=3 Coordinates refer to the position of the X-ray source. arcsec ML Likelihood of existence --- ExpTime Exposure time s CTS ROSAT X-Ray count rate number=4 Background and vignetting corrected broadband X-ray count rate. ct/s e_CTS Error of ROSAT X-Ray count rate ct/s HR1 ROSAT hardness ratio 1 --- e_HR1 Error of ROSAT hardness ratio 1 --- HR2 ROSAT hardness ratio 2 --- e_HR2 Error of ROSAT hardness ratio 2 --- N Number --- Star Identifier of star number=1 RXJ1507.9-4515, RXJ1533.0-3930, RXJ1539.2-4455 were found due to the SASS reduction of the RASS, but could not be detected as X-ray sources in the EXSAS reduction of the RASS. Therefore, no X-ray data are given for these stars. --- NA Note on X-ray discovery number=2 Stars marked with '1', '2', or '3' have been discovered by pointed observations in the Lupus 1, Lupus 2 or Lupus 3 clouds, respectively, and X-ray data are from pointed observations. Otherwise, X-ray data refer to the ROSAT All-Sky Survey. --- AV Extinction A(V) from photometry number=3 Data from Wichmann et al., 1997A&A...320..185W mag log(HI) Absorbing HI column density number=4 Calculated from AV as given in row 4 cm-2 kTX Temperature of X-ray emitting plasma number=5 Spectral fits with hardness ratio performed with either both TX and NH as free fit parameters if no AV known, or with NH fixed and TX free if AV known. In a few cases, where AV is known, no good fit with NH fixed could be performed, hence fit was performed with both TX and NH free (in such cases both NH and NH_FIT are given). (If for TX, NH_FIT, and LX, no errors are given, no good fit could be performed, possibly because a single-temperature Raymond-Smith model is not adequate to model the star's X-ray spectrum.) keV E_kTX 1 sigma upper error bar of kTX keV e_kTX 1 sigma lower error bar of kTX keV log(NH)fit Fitted absorbing HI column density number=5 Spectral fits with hardness ratio performed with either both TX and NH as free fit parameters if no AV known, or with NH fixed and TX free if AV known. In a few cases, where AV is known, no good fit with NH fixed could be performed, hence fit was performed with both TX and NH free (in such cases both NH and NH_FIT are given). (If for TX, NH_FIT, and LX, no errors are given, no good fit could be performed, possibly because a single-temperature Raymond-Smith model is not adequate to model the star's X-ray spectrum.) cm-2 E_log(NH)fit 1 sigma upper error bar of log(NH)fit cm-2 e_log(NH)fit 1 sigma lower error bar of log(NH)fit cm-2 LX X-ray luminosity (LX/10^30^) 10-7W E_LX 1 sigma upper error bar of LX 10-7W e_LX 1 sigma lower error bar of LX 10-7W Star Identifier of star from Schwartz (1977ApJS...35..161S) --- CTS ROSAT X-Ray count rate number=1 Background and vignetting corrected broadband X-ray count rate. Absence of error indicates that count rate is upper limit. ct/s e_CTS Error of ROSAT X-Ray count rate number=1 Background and vignetting corrected broadband X-ray count rate. Absence of error indicates that count rate is upper limit. ct/s HR1 ROSAT hardness ratio 1 --- e_HR1 Error of ROSAT hardness ratio 1 --- HR2 ROSAT hardness ratio 2 --- e_HR2 Error of ROSAT hardness ratio 2 --- AV Extinction A(V) number=2 Data from Hughes et al., 1994AJ....108.1071H mag log(NH) Absorbing HI column density number=3 Spectral fits with hardness ratio were performed with TX as free fit parameter and NH calculated from AV (Hughes et al., 1994AJ....108.1071H) In a few cases, where AV is known, no good fit with NH fixed could be performed, hence fit was performed with both TX and NH free (in such cases NH (fitted) is given). Sz 124: no good fit could be performed, possibly because a single-temperature Raymond-Smith model is not adequate to model the star's X-ray spectrum. Thus the quoted values are quite uncertain. For stars where only upper limits are known, luminosities were calculated for a Raymond-Smith spectrum with the mean temperature of kTX = 1.014 keV and NH calculated from AV. cm-2 E_log(NH) 1 sigma upper error bar of log(NH) cm-2 e_log(NH) 1 sigma lower error bar of log(NH) cm-2 kTX Temperature of X-ray emitting plasma number=3 Spectral fits with hardness ratio were performed with TX as free fit parameter and NH calculated from AV (Hughes et al., 1994AJ....108.1071H) In a few cases, where AV is known, no good fit with NH fixed could be performed, hence fit was performed with both TX and NH free (in such cases NH (fitted) is given). Sz 124: no good fit could be performed, possibly because a single-temperature Raymond-Smith model is not adequate to model the star's X-ray spectrum. Thus the quoted values are quite uncertain. For stars where only upper limits are known, luminosities were calculated for a Raymond-Smith spectrum with the mean temperature of kTX = 1.014 keV and NH calculated from AV. keV E_kTX 1 sigma upper error bar of kTX keV e_kTX 1 sigma lower error bar of kTX keV LX X-ray luminosity (LX/10^30) number=3 Spectral fits with hardness ratio were performed with TX as free fit parameter and NH calculated from AV (Hughes et al., 1994AJ....108.1071H) In a few cases, where AV is known, no good fit with NH fixed could be performed, hence fit was performed with both TX and NH free (in such cases NH (fitted) is given). Sz 124: no good fit could be performed, possibly because a single-temperature Raymond-Smith model is not adequate to model the star's X-ray spectrum. Thus the quoted values are quite uncertain. For stars where only upper limits are known, luminosities were calculated for a Raymond-Smith spectrum with the mean temperature of kTX = 1.014 keV and NH calculated from AV. 10-7W E_LX 1 sigma upper error bar of LX 10-7W e_LX 1 sigma lower error bar of LX 10-7W Patricia Bauer CDS 1996Oct09Rainer Wichmann <R.Wichmann@lsw.uni-heidelberg.de> J_A+AS_123_329.xml