The discovery of a shell-like event in the O-type star HD 120678

GAMEN, R. C.; ARIAS, J.; BARBÁ, R.; MORRELL, N. I.; WALBORN, N.; SOTA, A.; MAÍZ APELLÁNIZ, J.; ALFARO, E.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2012 vol. 546 p. 92 - 99

0004-6361

Aims. To report the detection of a shell-like event in the Oe-type star HD 120678.Methods. HD 120678 has been intensively observed as part of a high-resolution spectroscopic monitoring program of SouthernGalactic O stars and Wolf-Rayet stars of the nitrogen sequence.Results. An optical spectrogram of HD 120678 obtained in June 2008 shows strong H and He i absorption lines instead of thedouble-peaked emission profiles observed both previously and subsequently, as well as a variety of previously undetected absorptionfeatures, mainly of O ii, Si iii and Fe iii. Photometric data reveal that the development of the absorption spectrum coincided with aremarkable dip in the V-band lightcurve. The ?shell phase? of HD 120678 did not persist for very long: the V magnitude recoveredits previous average value in fewer than 120 days, whereas H and He emission lines became detectable one year later. Similar spectralvariations have been observed in a few Be stars, and they are usually interpreted as changes in the circumstellar disk.