5 research outputs found
A Sub-millimeterwave ``Flare'' from GG Tau?
We have monitored the millimeter and submillimeter emission from the young
stellar object GG Tau, a T Tauri binary system surrounded by a massive
circumbinary disk. We find that between 1992 and 1994, the flux has increased
significantly at 800, 1100, and 1300 microns, resulting in a steepening of the
observed spectral energy distribution at those wavelengths. Such an increase
appears consistent with a modest increase in disk luminosity (a factor of two).
The increase in the effective disk temperature might arise from a slight change
in the disk heating processes. Alternatively, the flux increase may reflect a
sudden change in the underlying dust optical properties.Comment: 15 pages, AASTex v.4.0 format, four postscript figures, four tables,
to appear in The Astrophysical Journa
Ubiquitous H-alpha polarized line profiles: absorptive spectropolarimetric effects and temporal variability in Post-AGB, Herbig Ae/Be and other stellar types
We show here that the absorptive H-alpha polarized line profile previously
seen in many Herbig Ae/Be (HAeBe) stars is a nearly ubiquitous feature of other
types of embedded or obscured stars. This characteristic 1% linear polarization
variation across the absorptive part of the H-alpha line is seen in Post-AGB
stars as well as RV-Tau, Delta-Scuti, and other types. Each of these stars
shows evidence of obscuration by intervening circumstellar hydrogen gas and the
polarization effect is in the absorptive component, consistent with an optical
pumping model. We present ESPaDOnS spectropolarimetric observations of 9
post-AGB and RV-Tau types in addition to many multi-epoch HiVIS observations of
these targets. We find significant polarization changes across the H-alpha line
in 8/9 stars with polarization amplitudes of 0.5% to over 3% (5/6 Post-AGB and
3/3 RV-Tau). In all but one of these, the polarization change is dominated by
the absorptive component of the line profile. There is no evidence that
subclasses of obscured stars showing stellar pulsations (RV-Tau for Post-AGB
stars and Delta-Scuti for Herbig Ae/Be stars) show significant
spectropolarimetric differences from the main class. Significant temporal
variability is evident from both HiVIS and ESPaDOnS data for several stars
presented here: 89 Her, AC Her, SS Lep, MWC 120, AB Aurigae and HD144668. The
morphologies and temporal variability are comparable to existing large samples
of Herbig Ae/Be and Be type stars. Since Post-AGB stars have circumstellar gas
that is very different from Be stars, we discuss these observations in the
context of their differing environments.Comment: Accepted in ApJ, EmulateApJ - 11 pages, 11 figure