Article (Scientific journals)
First evidence of pulsations in Vega?. Results of today's most extensive spectroscopic search
Böhm, T.; Lignières, F.; Wade, G. et al.
2012In Astronomy and Astrophysics, 537, p. 90
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Keywords :
stars: oscillations; stars: rotation; stars: individual: Vega; asteroseismology
Abstract :
[en] Context. The impact of rapid rotation on stellar evolution theory remains poorly understood as of today. Vega is a special object in this context as spectroscopic and interferometric studies have shown that it is a rapid rotator seen nearly pole one, a rare orientation particularly interesting for seismic studies. In this paper, we present a first systematic search for pulsations in Vega. <BR /> Aims: The goal of the present work is to detect for the first time pulsations in a rapidly rotating star seen nearly pole-on. <BR /> Methods: Vega was monitored in quasi-continuous high-resolution echelle spectroscopy. A total of 4478 spectra were obtained. More precisely in 2008 we obtained 1213 spectra during 19.9 h on 3 nights (26th, 27th and 29th of July 2008) with NARVAL/TBL (at R = 65 000 and R = 75 000), in 2009 we obtained 1293 spectra during 13.7 h on 3 nights (9th-11th of September 2009) with ESPaDOnS/CFHT (at R = 68 000) and in 2010 we gathered again 1972 with NARVAL/TBL during 28.8 h on five nights (July 15th-19th). This data set should represent the most extensive high S/N, high resolution quasi-continuous survey obtained on Vega as of today. Least square deconvolved (LSD) profiles were obtained for each spectrum representing the photospheric absorption profile potentially deformed by the presence of pulsations. In addition, we calculated for each spectrum a telluric line LSD profile subsequently used as radial velocity reference. LSD profile centroids were adjusted and velocity differences (stellar-telluric) determined. These residual velocities were analysed and periodic low amplitude variations, potentially indicative of stellar pulsations, detected. In a subsequent step, the temporal line profile variations during the longest (2010) data set was calculated for each individual velocity bin of 1.8 km s[SUP]-1[/SUP] by computing a 2D (velocity-frequency) Lomb-Scargle periodogram. <BR /> Results: Based on high resolution echelle spectroscopy, we have obtained indications of periodic variations of very small amplitudes within the residual radial velocity curves of Vega. All three data sets revealed the presence of residual periodic variations: 5.32 and 9.19 d[SUP]-1[/SUP] (A ≈ 6 m s[SUP]-1[/SUP]) in 2008, 12.71 and 13.25 d[SUP]-1[/SUP] (A ≈ 8 m s[SUP]-1[/SUP]) in 2009 and 5.42 and 10.82 d[SUP]-1[/SUP] (A ≈ 3-4 m s[SUP]-1[/SUP]) in 2010. However, it is too early to conclude that the variations are due to stellar pulsations, and a confirmation of the detection with a highly stable spectrograph is a necessary next step. <BR /> Conclusions: If pulsations are confirmed, their very small amplitudes show that the star would belong to a category of very "quiet" pulsators. Based on observations obtained at the Bernard Lyot Telescope (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory, which is operated by the Institut National des Sciences de l'Univers (INSU) of the Centre National de la Recherche Scientifique of France (CNRS), and at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, INSU/CNRS and the University of Hawaii.
Disciplines :
Physics
Author, co-author :
Böhm, T.;  Université de Toulouse ; UPS-OMP ; IRAP ; , Toulouse, France ; CNRS ; IRAP, 14 avenue Edouard Belin, 31400, Toulouse, France
Lignières, F.;  Université de Toulouse ; UPS-OMP ; IRAP ; , Toulouse, France ; CNRS ; IRAP, 14 avenue Edouard Belin, 31400, Toulouse, France
Wade, G.;  Dept. of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, K7KK 7B4, Canada
Petit, Pascal
Aurière, M.;  Université de Toulouse ; UPS-OMP ; IRAP ; , Toulouse, France ; CNRS ; IRAP, 14 avenue Edouard Belin, 31400, Toulouse, France
Zima, W.;  Instituut voor Sterrenkunde, Celestijnenlaan 200D BUS 2401, Belgium
Fumel, Aurélie ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique et traitement de l'image
Alecian, E.;  Observatoire de Paris-Meudon, LESIA, 92190, Meudon, France
Language :
English
Title :
First evidence of pulsations in Vega?. Results of today's most extensive spectroscopic search
Publication date :
12 January 2012
Journal title :
Astronomy and Astrophysics
ISSN :
0004-6361
eISSN :
1432-0746
Publisher :
EDP Sciences, Les Ulis, France
Volume :
537
Pages :
90
Peer reviewed :
Peer Reviewed verified by ORBi
Commentary :
7 pages, 12 figures
Available on ORBi :
since 21 March 2012

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