Astronomy and Astrophysics – Astrophysics
Scientific paper
Sep 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981apj...248..584t&link_type=abstract
Astrophysical Journal, Vol.248, P. 584, 1981
Astronomy and Astrophysics
Astrophysics
19
Scientific paper
Two 1.5-2.3 μm spectra of the candidate protoplanetary nebula HM Sge are presented and discussed. A number of the Brackett series of hydrogen are seen in emission, allowing an estimate of source excitation and extinction. In addition, one spectrum shows the photospheric absorption features that are characteristic of a late-type giant star. The second spectrum shows no such features. Using previous models and observations, the infrared line-emitting region is found to be extremely small-in agreement with the idea that the source has recently begun a period of rapid mass loss or exchange. It is suggested that the recently observed brightening of HM Sge was due to partial unveiling of the source due to the motion of a dusty shell. Such an effect may also explain the current small amplitude variation in visual extinction. The object is found to lie on the Harman-Seaton sequence, as appropriate for young, evolving protoplanetaries. A number of the observations are in agreement with a model of planetary nebula formation, although the total nebular mass appears to be at least three orders of magnitude below that found in planetary nebulae. A search for radio 12CO emission was unsuccessful, consistent with HM Sge being oxygen rich.
Harvey Paul Michael
Thronson Harley A. Jr.
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