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We show here that the absorptive H-alpha polarized line profile previouslyseen in many Herbig Ae/Be (HAeBe) stars is a nearly ubiquitous feature of othertypes of embedded or obscured stars. This characteristic 1% linear polarizationvariation across the absorptive part of the H-alpha line is seen in Post-AGBstars as well as RV-Tau, Delta-Scuti, and other types. Each of these starsshows evidence of obscuration by intervening circumstellar hydrogen gas and thepolarization effect is in the absorptive component, consistent with an opticalpumping model. We present ESPaDOnS spectropolarimetric observations of 9post-AGB and RV-Tau types in addition to many multi-epoch HiVIS observations ofthese targets. We find significant polarization changes across the H-alpha linein 8/9 stars with polarization amplitudes of 0.5% to over 3% (5/6 Post-AGB and3/3 RV-Tau). In all but one of these, the polarization change is dominated bythe absorptive component of the line profile. There is no evidence thatsubclasses of obscured stars showing stellar pulsations (RV-Tau for Post-AGBstars and Delta-Scuti for Herbig Ae/Be stars) show significantspectropolarimetric differences from the main class. Significant temporalvariability is evident from both HiVIS and ESPaDOnS data for several starspresented here: 89 Her, AC Her, SS Lep, MWC 120, AB Aurigae and HD144668. Themorphologies and temporal variability are comparable to existing large samplesof Herbig Ae/Be and Be type stars. Since Post-AGB stars have circumstellar gasthat is very different from Be stars, we discuss these observations in thecontext of their differing environments.

astrophysical journal/the astrophysical journal

Ubiquitous H-alpha polarized line profiles: absorptive  spectropolarimetric effects and temporal variability in Post-AGB, Herbig  Ae/Be and other stellar types