- ... cloud
- Partly based on
observations collected at the 1.52 m and 3.5 m telescopes of the European
Southern Observatory, Chile, in programs 55.E-0549, 57.E-0646, and 63.L-0023,
and on observations collected at the 0.9 m, 1.5 m, and 4.0 m CTIO telescope.
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- ... TTS
-
Because most wTTS lack the IR excess typical for cTTS and, hence, are
probably not surrounded by circumstellar disks, Walter (1986) called
them naked TTS. However, because wTTS and nTTS populate both the
convective and radiative PMS tracks, the wTTS and nTTS population
is different from the so-called post-TTS population. Post-TTS are
older than cTTS and do not show signatures of circumstellar disks
and accretion (H
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UV, IR); post-TTS are expected to exist in large
numbers, if star formation has been going on for longer than the typical
life-time of circumstellar disks (Herbig 1978).
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- ... sources
- Four new PMS stars were already identified among ROSAT sources:
GSC 07916-00050 as the optical counterpart to RXJ1855.1-3754 (Neuhäuser et al. 1997),
an X-ray source found with the ROSAT High Resolution Imager (HRI) in a deep pointed
observation centered on RXJ1856.5-3754, an isolated radio-quiet neutron
star (Walter et al. 1996; Walter & Matthews 1997). Neuhäuser et al. (1997)
identified GSC 07916-00050 in order to confirm that it is the true
(i.e. possibly X-ray emitting) counterpart to RXJ1855.1-3754, to be able to
perform a correct boresight correction of the position of the central HRI source.
In addition, Patten (1998) identified three new PMS stars among X-ray sources
found in a pointed observation with the ROSAT Positional Sensitive Proportional
Counter (PSPC), also listed in Table 1.
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- ... data
- Prior to the optical follow-up observations, we reduced the earlier version of
the ROSAT data (RASS I) with an earlier version of EXSAS; although the source
lists and X-ray properties are sightly different, all newly identified young stars are
detected in both RASS I and RASS II.
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- ... ESO-3.5 m-NTT
- Taken during ESO program 63.L-0023 at the end of the
night 18/19 April 1999, when the main targets of that run were not visible anymore.
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- ... K)
- X-ray emitting M-type stars with lithium
are always pre-MS stars, as they burn all Lithium before reaching the MS
(see e.g. Covino et al. 1997).
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- ...
CIRIM
- See Elston 1999 athttp://www.ctio.noao.edu/instruments/ir-instruments/cirim/ cirim.html
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- ...
package
- http://sbast3.ess.sunysb.edu/fwalter/CIRIM/cirim.html
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- ...pc)
- This can also be
seen in Fig. 1, where the Z-direction is more or less perpendicular to the
b=-15
line, whereas the Y-direction is parallel to this line (the new
TTS lying north of the central cloud is RXJ1901.4-3422, a young foreground
star, see Sect. 7.3).
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