Astrophys. J., 613, 393-415 (2004/September-3)
Simultaneous Chandra and very large array observations of young stars and protostars in ρ Ophiuchus cloud core A.
GAGNE M., SKINNER S.L. and DANIEL K.J.
Abstract (from CDS):
A 96 ks Chandra X-ray observation of ρ Ophiuchus cloud core A detected 87 sources, of which 60 were identified with counterparts at other wavelengths. The X-ray detections include 12 of 14 known classical T Tauri stars (CTTSs) in the field, 15 of 17 known weak-lined TTSs (WTTSs), and 4 of 15 brown dwarf candidates. The X-ray detections are characterized by hard, heavily absorbed emission. Most X-ray detections have visual extinctions in the range AV~10-20 mag, but several sources with visual absorptions as high as AV~40-56 mag were detected. The mean photon energy of a typical source is <E>~3 keV, and more than half of the detections are variable. Prominent X-ray flares were detected in the unusual close binary system Oph S1, the X-ray-bright WTTS DoAr 21, and the brown dwarf candidate GY 31 (M5.5). Time-resolved spectroscopic analysis of the DoAr 21 flare clearly reveals a sequence of secondary flares during the decay phase that may have reheated the plasma. We find that the X-ray luminosity distributions and spectral hardnesses of CTTSs and WTTSs are similar. We also conclude that the X-ray emission of detected brown dwarf candidates is less luminous than TTSs, but spectroscopically similar. Simultaneous multifrequency Very Large Array (VLA) observations detected 31 radio sources at 6 cm, of which 10 were also detected by Chandra. We report new radio detections of the optically invisible IR source WLY 2-11 and the faint Hα emission line star Elias 24 (class II). We confirm circular polarization in Oph S1 and report a new detection of circular polarization in DoAr 21. We find no evidence that X-ray and radio luminosities are correlated in the small sample of TTSs detected simultaneously with Chandra and the VLA. We describe a new nonparametric method for estimating X-ray spectral properties from unbinned photon event lists that is applicable to both faint and bright X-ray sources. The method is used to generate fX, logT, and LXlight curves. In addition, we provide a publicly available electronic database containing multiwavelength data for 345 known X-ray, IR, and radio sources in the core A region.
Infrared: Stars - ISM: Individual: Name: ρ Ophiuchi Cloud - Radio Continuum: Stars - Stars: Formation - Stars: Pre-Main-Sequence - X-Rays: Stars
VizieR on-line data:
<Available at CDS (J/ApJ/613/393): table1.dat table3.dat notes.dat table4.dat>
Table 1: GDS JHHMMSS.s+DDMMSS N=87. Table 3: GDS JHHMMSS.s+DDMMSS N=31 (among which 11 are already in Table 1).
Objects SKS: this numbering related to the table number in 1995ApJ...438..813S is not used in SIMBAD. So, SKS 1-7 = [SKS95] 162314.6-241237, SKS 3-12 = [SKS95] 162320.8-241803, SKS 1-11 = [SKS95] 162317 .6-241729, etc...
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