Reference : Evolutionary status of the Of?p star HD 148937 and of its surrounding nebula NGC 6164/5
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/211735
Evolutionary status of the Of?p star HD 148937 and of its surrounding nebula NGC 6164/5
English
Mahy, Laurent mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Hutsemekers, Damien mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Nazé, Yaël mailto [Université de Liège > > Groupe d'astrophysique des hautes énergies (GAPHE) >]
Royer, P. [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, Bus 2401, 3001, Leuven, Belgium]
Lebouteiller, V. [Laboratoire AIM Paris-Saclay, CEA/IRFU - CNRS/INSU - Université Paris Diderot, Service d'Astrophysique, Bât. 709, CEA-Saclay, 91191, Gif-sur-Yvette Cedex, France]
Waelkens, C. [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, Bus 2401, 3001, Leuven, Belgium)]
1-Mar-2017
Astronomy and Astrophysics
EDP Sciences
599
A61
17
Yes (verified by ORBi)
International
0004-6361
1432-0746
Les Ulis
France
[en] infrared: stars ; stars: individual: HD 148937 ; ISM: individual objects: NGC 6164/5 ; stars: abundances ; circumstellar matter
[en] <BR /> Aims: The magnetic star HD 148937 is the only Galactic Of?p star surrounded by a nebula. The structure of this nebula is particularly complex and is composed, from the center out outwards, of a close bipolar ejecta nebula (NGC 6164/5), an ellipsoidal wind-blown shell, and a spherically symmetric Strömgren sphere. The exact formation process of this nebula and its precise relation to the star's evolution remain unknown. <BR /> Methods: We analyzed infrared Spitzer IRS and far-infrared Herschel/PACS observations of the NGC 6164/5 nebula. The Herschel imaging allowed us to constrain the global morphology of the nebula. We also combined the infrared spectra with optical spectra of the central star to constrain its evolutionary status. We used these data to derive the abundances in the ejected material. To relate this information to the evolutionary status of the star, we also determined the fundamental parameters of HD 148937 using the CMFGEN atmosphere code. <BR /> Results: The Hα image displays a bipolar or "8"-shaped ionized nebula, whilst the infrared images show dust to be more concentrated around the central object. We determine nebular abundance ratios of N/O = 1.06 close to the star, and N/O = 1.54 in the bright lobe constituting NGC 6164. Interestingly, the parts of the nebula located further from HD 148937 appear more enriched in stellar material than the part located closer to the star. Evolutionary tracks suggest that these ejecta have occured 1.2-1.3 and 0.6 Myr ago, respectively. In addition, we derive abundances of argon for the nebula compatible with the solar values and we find a depletion of neon and sulfur. The combined analyses of the known kinematics and of the new abundances of the nebula suggest either a helical morphology for the nebula, possibly linked to the magnetic geometry, or the occurrence of a binary merger. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Based in part on observations collected at the European Southern Observatory, in Chile.
Researchers ; Professionals
http://hdl.handle.net/2268/211735
10.1051/0004-6361/201629585
http://cdsads.u-strasbg.fr/abs/2017A%26A...599A..61M

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