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Post Info TOPIC: Longmore 4
Blobrana


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RE: Longmore 4
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Lo4

Longmore 4.kmz
Google Sky file

A PG 1159 star is a star with a hydrogen-deficient atmosphere which is in transition between being the central star of a planetary nebula and being a hot white dwarf. These stars are hot, with surface temperatures between 75,000 K and 200,000 K, and are characterized by atmospheres with little hydrogen and absorption lines for helium, carbon and oxygen. Their surface gravity is typically between 10^4 and 10^6 meters per second squared. Some PG 1159 stars are still fusing helium. The PG 1159 stars are named after their prototype, PG 1159-035. This star, found in the Palomar-Green survey of ultraviolet-excess stellar objects, was the first PG 1159 star discovered.

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Blobrana


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Title: Transient Mass-Loss Events in the PG 1159 Central Star of Longmore 4
Authors: Howard E. Bond (Space Telescope Science Institute)

A spectacular, transient mass-loss event in the hydrogen-deficient central star of the planetary nebula Longmore 4 was discovered in 1992 by Werner et al. During that event, the star temporarily changed from its normal PG 1159 spectrum to that of an emission-line [WCE] star. I have been monitoring the spectrum of Lo 4 since 2003. Out of 31 spectra, two of them reveal mass-loss outbursts similar to the one seen in 1992, showing that the phenomenon recurs. I speculate on possible mechanisms for these unique outbursts, but emphasise that we still have no fully convincing explanation.

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Position: RA 19:09:47 Dec -55° 35.1'

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