Nancy A. Levenson
Science Highlights
Figure 1.
GNIRS continuumsubtracted spectra of
two newly identified
B[e] supergiants in
M31 (black), exhibiting
the hydrogen Pfund
series and both 12CO
and 13CO. The red lines
represent model fits to
the observations.
Gemini data help to understand the first B[e] supergiant stars in
M31, support modeling of a young star’s disk, and identify lowmass stars in young groups of stars.
Discovery of the First B[e] Supergiants in M31
Michaela Kraus (Akademie ved Ceske republiky, Czech Republic) and collaborators from Argentina and Brazil have used the Gemini Near-Infrared Spectrograph (GNIRS) on Gemini
North to identify the first B[e] supergiants in the nearby galaxy M31. These stars represent a
short-lived phase of evolution of massive stars, after their time on the main sequence.
These stars are broadly relevant first in the context of stellar evolution and seconc as sources
of metal enhancements in galaxies. B[e] supergiants deposit enriched material in the interstellar medium through mass loss (during
post-main-sequence phases) and ultimately as
supernovae. The mass loss can result in disks
and rings, and the progenitor of supernova
1987A in the Large Magellanic Cloud may, in
fact, be a B[e] supergiant. Besides increasing the
known population of these rare objects, M31
offers an interesting host environment, having
higher metallicity (about twice solar) compared
with previous examples.
One challenge in identifying B[e] supergiants is
to distinguish them from luminous blue variable
(LBV) stars — another short-lived phase in the
post-main sequence evolution of massive stars.
This study’s original targets were selected from
stars previously identified as “LBV candidates.”
These newly discovered examples lie in a typical
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GeminiFocus
April 2014