1,096 research outputs found
XMM-Newton Detection of Hot Gas in the Eskimo Nebula: Shocked Stellar Wind or Collimated Outflows?
The Eskimo Nebula (NGC 2392) is a double-shell planetary nebula (PN) known
for the exceptionally large expansion velocity of its inner shell, ~90 km/s,
and the existence of a fast bipolar outflow with a line-of-sight expansion
velocity approaching 200 km/s. We have obtained XMM-Newton observations of the
Eskimo and detected diffuse X-ray emission within its inner shell. The X-ray
spectra suggest thin plasma emission with a temperature of ~2x10^6 K and an
X-ray luminosity of L_X = (2.6+/-1.0)x10^31 (d/1150 pc)^2 ergs/s, where d is
the distance in parsecs. The diffuse X-ray emission shows noticeably different
spatial distributions between the 0.2-0.65 keV and 0.65-2.0 keV bands.
High-resolution X-ray images of the Eskimo are needed to determine whether its
diffuse X-ray emission originates from shocked fast wind or bipolar outflows.Comment: 4 pages, 2 figures, accepted in Astronomy and Astrophysics Letter
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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