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Search for associations containing young stars (SACY). I. Sample and searching method
We report results from a high-resolution optical spectroscopic surveyaimed to search for nearby young associations and young stars amongoptical counterparts of ROSAT All-Sky Survey X-ray sources in theSouthern Hemisphere. We selected 1953 late-type (B-V~≥~0.6),potentially young, optical counterparts out of a total of 9574 1RXSsources for follow-up observations. At least one high-resolutionspectrum was obtained for each of 1511 targets. This paper is the firstin a series presenting the results of the SACY survey. Here we describeour sample and our observations. We describe a convergence method in the(UVW) velocity space to find associations. As an example, we discuss thevalidity of this method in the framework of the β Pic Association.
| The ROSAT Bright Survey: II. Catalogue of all high-galactic latitude RASS sources with PSPC countrate CR > 0.2 s-1
We present a summary of an identification program of the more than 2000X-ray sources detected during the ROSAT All-Sky Survey (Voges et al.1999) at high galactic latitude, |b| > 30degr , with countrate above0.2 s-1. This program, termed the ROSAT Bright Survey RBS, isto more than 99.5% complete. A sub-sample of 931 sources with countrateabove 0.2 s-1 in the hard spectral band between 0.5 and 2.0keV is to 100% identified. The total survey area comprises 20391deg2 at a flux limit of 2.4 x 10-12 ergcm-2 s-1 in the 0.5 - 2.0 keV band. About 1500sources of the complete sample could be identified by correlating theRBS with SIMBAD and the NED. The remaining ~ 500 sources were identifiedby low-resolution optical spectroscopy and CCD imaging utilizingtelescopes at La Silla, Calar Alto, Zelenchukskaya and Mauna Kea. Apartfrom completely untouched sources, catalogued clusters and galaxieswithout published redshift as well as catalogued galaxies with unusualhigh X-ray luminosity were included in the spectroscopic identificationprogram. Details of the observations with an on-line presentation of thefinding charts and the optical spectra will be published separately.Here we summarize our identifications in a table which contains opticaland X-ray information for each source. As a result we present the mostmassive complete sample of X-ray selected AGNs with a total of 669members and a well populated X-ray selected sample of 302 clusters ofgalaxies with redshifts up to 0.70. Three fields studied by us remainwithout optical counterpart (RBS0378, RBS1223, RBS1556). While the firstis a possible X-ray transient, the two latter are isolated neutron starcandidates (Motch et al. 1999, Schwope et al. 1999).
| Extreme Ultraviolet Explorer Right Angle Program observations of cool stars
The Extreme Ultraviolet Explorer (EUVE) Right Angle Program (RAP)obtains photometric data in four bands centered at 100 (Lexan/B), 200(Al/Ti/C), 400 (Ti/Sb/Al), and 550 (Sn/SiO) during pointed spectroscopicobservations. RAP observations are up to 20 times more sensitive thanthose in the EUVE all-sky survey. We present RAP observations of twodozen late-type stars. We derive surface fluxes from the Lexan/B andAl/Ti/C count rates and cataloged ROSAT Position Sensitive ProportionalCounter (PSPC) data. The EUVE surface fluxes are reasonably correlatedwith surface fluxes calculated from PSPC measurements. The timevariability of the sources has been examined. Most of the sources showno significant variability at the 99 percent confidence level. Flareswere detected from the K7 V star Melotte 25 VA 334, the K3 V star V834Tau (HD 29697), and the K3 + K8 Hyades binary BD +22669. The BD +22669count rate at the peak of the flare is a factor of 6 higher than thequiescent count rate, with a peak Lexan/B luminosity of 7.9 1029 ergs/s.The V834 Tau flare was detected in both Lexan/B and Al/Ti/C bands. Thepeak luminosity of the flare is 1.6 1029 and 8 1028 ergs/s for Lexan/Band Al/Ti/C, respectively.
| The Second Extreme-Ultraviolet Explorer Source Catalog
We present the second catalog of extreme-ultraviolet objects detected bythe Extreme-Ultraviolet Explorer. The data include (1) all-sky surveydetections from the initial 6 month scanner-survey phase, (2) additionalscanner detections made subsequently during specially programmedobservations designed to fill in low-exposure sky areas of the initialsurvey, (3) sources detected with deep-survey-telescope observationsalong the ecliptic, (4) objects detected by the scanner telescopesduring targeted spectroscopy observations, and ( 3) other observations.We adopt an innovative source detection method that separates the usuallikelihood function into two parts: an intensity diagnostic and aprofile diagnostic. These diagnostics allow each candidate detection tobe tested separately for both signal-to-noise ratio and conformance withthe known instrumental point-spread function. We discuss the dependenceof the false-alarm rate and the survey's completeness on the survey'ssensitivity threshold. We provide three lists of the EUV sourcesdetected: the all-sky survey detections, the deep-survey detections, andsources detected during other phases of the mission. Each list givespositions and intensities in each wave band. The total number of objectslisted is 734. For approximately 65% of these we also provide plausibleoptical, UV, radio, and/or X-ray identifications.
| EUVE Right Angle Program Observations of Late-Type Stars
The EUVE Right Angle Program (RAP) obtains photometric data in fourbands centered at ~ 100 Angstroms (Lexan/B), ~ 200 Angstroms (Al/Ti/C),~ 400 Angstroms (Ti/Sb/Al), and ~ 550 Angstroms (Sn/SiO). RAPobservations are up to 20 times more sensitive than the all-sky survey.We present RAP observations of the late-type stars: BD+03 301, BD+05300, HR 1262, BD+23 635, BD+22 669, Melotte 25 VA 334, Melotte 25 1366,Melotte 25 59, Melotte 25 65, theta (1) Tau, V834 Tau, GJ 2037, BD-211074, GJ 205, RE J0532-030, GJ 9287A, HT Vir, BD+46 1944, Proxima Cen,alpha Cen A/B, HR 6094, CPD-48 10901, and HR 8883. We derive fluxes andemission measures from Lexan/B and Al/Ti/C count rates. The timevariability of the sources has been examined. Most of the sources showno significant variability at the 99% confidence level. Flares weredetected from the K3V star V834 Tau (HD 29697) and the K0 star BD+22669. The BD+22 669 count rate at the peak of the flare is a factor of 10higher than the quiescent count rate with a peak Lexan/B luminosity of7.9 x 10(29) erg s(-1) . The V834 Tau flare was detected in both Lexan/Band Al/Ti/C bands. The peak luminosity of the flare is 1.6 x 10(29) ergs(-1) and 8 x 10(28) ergs s(-1) for Lexan/B and Al/Ti/C, respectively.This is a factor of 4.3 higher than the quiescent luminosity in Lexan/B,and a factor of 4.6 in Al/Ti/C\@. This work is supported by NASAcontract NAS5-29298.
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