Universität zu Köln

Comeron, F., Schneider, N., Djupvik, A. A. and Schnugg, C. (2018). The ionizing source of the bipolar HII region S106: A close massive binary. Astron. Astrophys., 615. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context. S106, one of the best known bipolar HII regions, has been thoroughly studied and modeled at infrared, submillimeter, and millimeter wavelengths. This region is one of the nearest examples of the late stages of massive star formation, in which the newly formed star that ionizes it is still surrounded by vast amounts of gas and dust. However, little is known about the heavily obscured central source of this region, S106IR. Aims. We investigate the possible binarity of the central source is investigated; this binarity is considered to be likely given the high binarity fraction among massive stars. Methods. We have carried out visible and near-infrared photometric monitoring looking for short-term variability, and we took special interest in that related to the presence of a close binary companion to S106IR, which may produce periodic eclipses or tidal distortion of the shape of the members of the system. Results. A periodic variability of S106IR in the J band is found with a period of 5.0 days and an amplitude of similar or equal to 0.1 mag. The light curve displays a slow rise from minimum to maximum followed by a steep decrease, and can be well reproduced by a close binary system composed of two stars with different luminosities orbiting each other in an elliptical orbit of moderate eccentricity. S106IR also shows hints of short-term variability that is possibly related to accretion. We also report variability of four other stars previously classified as members of the S106 cluster, all of which are strong X-ray emitters. Conclusions. The newly discovered close binarity of S106IR adds a new element to the modeling of the nebula and the understanding of the dynamics of the gas around the ionizing source, which suggests that the components of the binary are accreting via a circumbinary disk. Binarity also helps to explain the apparent mismatch between the spectral type of the ionizing source inferred from the nebular spectrum and its high brightness at near-infrared wavelengths.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Comeron, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schneider, N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Djupvik, A. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schnugg, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-180018
DOI:	10.1051/0004-6361/201731979
Journal or Publication Title:	Astron. Astrophys.
Volume:	615
Date:	2018
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language YOUNG STELLAR OBJECTS; STAR-FORMING REGION; PULSED ACCRETION; RADIO; MULTIWAVELENGTH; SPECTROSCOPY; CONTINUUM; EMISSION; CURVES; LIGHT Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/18001