Variability and rapid evolution of the protoplanetary object IRAS 18062+2410=V886 her
Abstract
We present our long-term photometric and spectroscopic observations of a high-latitude B supergiant with an infrared excess—the protoplanetary nebula IRAS 18062+2410. OurUBV observations in 2000-2006 have confirmed the rapid irregular photometric variability of the star with a maximum amplitude as high as 0.m4 in V that we found previously. The B—V and U—B color indices vary with amplitudes as high as 0.m10 and 0.m25, respectively, and show no clear correlation with the brightness. Our V-band CCD observations on 11 nights in 2006 have revealed brightness trends during the night. The variability of IRAS18062+2410 is similar in pattern to the light variations in other hot post-AGB objects and some of the nuclei of young planetary nebulae. We assume that pulsations and a variable stellar wind can be responsible for the variability of these stars. In addition to the rapid variability, our 12-year-long observations have revealed a systematic decline in the mean brightness of IRAS 18062+2410. This may be related to a rise in the temperature of the star at constant luminosity as a result of its evolution. Low-resolution spectroscopic observations have shown a systematic increase in the equivalent widths of the Hα, Hβ, [NII]λ6584 Å, OI λ8446 Å, and [OII] λ7320-7330 Å emission lines. The changes in the star's emission line spectrum are probably caused by an increase in the degree of ionization of the gas shell due to a rise in the temperature of the ionizing star. Our photometric and spectroscopic observations of IRAS 18062+2410 confirm the previously made assumptions that the star evolves very rapidly to the region of planetary nebulae.
- Publication:
-
Astronomy Letters
- Pub Date:
- September 2007
- DOI:
- 10.1134/S1063773707090046
- Bibcode:
- 2007AstL...33..604A
- Keywords:
-
- stars—structure and evolution;
- post-AGB supergiants;
- spectroscopic and photometric observations;
- planetary nebulae;
- evolution