5,427 research outputs found
The Spectropolarimetric Evolution of V838 Monocerotis
I review photo-polarimetric and spectropolarimetric observations of V838 Mon,
which revealed that it had an asymmetrical inner circumstellar envelope
following its 2nd photometric outburst. Electron scattering, modified by pre-
or post-scattering H absorption, is the polarizing mechanism in V838 Mon's
envelope. The simplest geometry implied by these observations is that of a
spheroidal shell, flattened by at least 10% and having a projected position
angle on the sky of . Analysis of V838 Mon's polarized flux
reveals that this electron scattering shell lies interior to the envelope
region in which H and Ca II triplet emission originates. To date, none
of the theoretical models proposed for V838 Mon have demonstrated that they can
reproduce the evolution of V838 Mon's inner circumstellar environment, as
probed by spectropolarimetry.Comment: 8 pages, to appear in ASP Conf. Ser., The Nature of V838 Mon and Its
Light Echo, eds. R.L.M. Corradi and U. Munar
Discovery of a New Dusty B[e] Star in the Small Magellanic Cloud
We present new optical spectroscopic and archival Spitzer IRAC photometric
observations of a B-type star in the SMC cluster NGC 346, NGC 346:KWBBe 200. We
detect numerous Fe II, [O I], and [Fe II] lines, as well as strong P-Cygni
profile H I emission lines in its optical spectrum. The star's near-IR color
and optical to IR SED clearly indicate the presence of an infrared excess,
consistent with the presence of gas and warm, T ~800 K, circumstellar dust.
Based on a crude estimate of the star's luminosity and the observed
spectroscopic line profile morphologies, we find that the star is likely to be
a B-type supergiant. We suggest that NGC 346:KWBBe 200 is a newly discovered
B[e] supergiant star, and represents the fifth such object to be identified in
the SMC.Comment: 12 pages, accepted by Ap
The Spectropolarimetric Evolution of V838 Mon
I review photo-polarimetric and spectropolarimetric observations of V838 Mon, which revealed that it had an asymmetrical inner circumstellar envelope following its 2nd photometric outburst. Electron scattering, modified by preor post-scattering H absorption, is the polarizing mechanism in V838 Mon's envelope. The simplest geometry implied by these observations is that of a spheroidal shell, flattened by at least 20% and having a projected position angle on the sky of approx. 37 degrees. Analysis of V838 Mon's polarized flux reveals that this electron scattering shell lies interior to the envelope region in which Halpha and Ca II triplet emission originates. To date, none of the theoretical models proposed for V838 Mon have demonstrated that they can reproduce the evolution of V838 Mon's inner circumstellar environment, as probed by spectropolarimetry
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