220 research outputs found
Star Formation in the LMC: Gravitational Instability and Dynamical Triggering
Evidence for triggered star formation is difficult to establish because
energy feedback from massive stars tend to erase the interstellar conditions
that led to the star formation. Young stellar objects (YSOs) mark sites of {\it
current} star formation whose ambient conditions have not been significantly
altered. Spitzer observations of the Large Magellanic Cloud (LMC) effectively
reveal massive YSOs. The inventory of massive YSOs, in conjunction with surveys
of interstellar medium, allows us to examine the conditions for star formation:
spontaneous or triggered. We examine the relationship between star formation
and gravitational instability on a global scale, and we present evidence of
triggered star formation on local scales in the LMC.Comment: 6 pages, 6 figures, IAU Symposium 237, Triggered Star Formation in a
Turbulent Medium, eds. Elmegreen and Palou
A Search for Jovian Planets around Hot White Dwarfs
Current searches for extrasolar planets have concentrated on observing the
reflex Doppler shift of solar-type stars. Little is known, however, about
planetary systems around non-solar-type stars. We suggest a new method to
extend planetary searches to hot white dwarfs. Near a hot white dwarf, the
atmosphere of a Jovian planet will be photoionized and emit hydrogen
recombination lines, which may be detected by high- dispersion spectroscopic
observations. Multi-epoch monitoring can be used to distinguish between non-LTE
stellar emission and planetary emission, and to establish the orbital
parameters of the detected planets. In the future, high-precision astrometric
measurements of the hot white dwarf will allow the masses of the detected
planets to be determined. Searches for Jovian planets around hot white dwarfs
will provide invaluable new insight on the development of planetary systems
around stars more massive than the Sun and on how stellar evolution affects
these systems. We present high-dispersion spectroscopic observations of the
white dwarf Feige 34 to demonstrate the complexity and feasibility of the
search method.Comment: 10 pages, 2 figures, accepted for publication in the ApJ Letter
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