ISSN:
1572-946X
Keywords:
T Tauri stars
;
X-ray emission
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The study of star forming regions (SFR) allows us to observe many young stellar objects with both the same metallicities and distances but with different masses. Because of its close distance (∼ 140pc) Taurus-Auriga is one of the best studied SFR with more than 100 well-studied, low-mass, pre-main sequence stars, T Tauri stars (TTS). A motivation for studying X-ray emission of T associations is to understand the origin of X-rays and coronal activity. The large sample observed with the ROSAT All-Sky Survey (RASS) also enables us to compare different types of young stars. Other primary goals include star formation efficiency and the interaction of young stars with their intermediate environment (probed by absorption of X-rays). RASS detection rates are comparable withEinstein Observatory results: 43 out of 65 (66%) weak-lined TTS (WTTS) and 9 out of 79 (11%) classical TTS (CTTS) exhibit X-ray emission above RASS detection limit. A strong correlation between X-ray surface flux and stellar rotation indicates that WTTS are intrinsically more X-ray active than CTTS, because WTTS rotate faster. However, rotation is not the only parameter that determines X-ray activity. Also, we compare Taurus-Auriga TTS with TTS of southern SFR like ScoCen, Lupus, Chamaeleon, and CrA. A new result is that CTTS and WTTS can be discriminated reliably by their X-ray spectral hardness ratios. X-ray emission of CTTS appears to be harder, partly because of circumstellar absorption. Spectral fits give results consistent with Raymond-Smith spectra and emission temperatures of ∼ 1.0 keV for both WTTS and CTTS. However, we find that CTTS and WTTS have significantly different X-ray luminosity functions. Medians of absorption corrected X-ray luminosities (logL X in cgs units) are 29.701 ± 0.045 for WTTS and 29.091 ± 0.032 for CTTS. WTTS are intrinsically more luminous than CTTS, most likely because WTTS rotate on average faster than CTTS and are less absorbed. This paper concentrates on differences between CTTS and WTTS and indirect clues to be drawn from X-ray absorption and hardness ratios about circumstellar material around TTS.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00667829
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