Spectral atlas of massive stars around $\ion{He}{i}$ 10 830 Å

Abstract

We present a digital atlas of peculiar, high-luminosity massive stars in the near-infrared region (10 470−11 000 Å) at medium resolution (R 7000). The spectra are centered around He i 10 830 Å, which is formed in the wind of those stars, and is a crucial line to obtain their physical parameters. The instrumental configuration also sampled a rich variety of emission lines of Fe ii, Mg ii, C i, N i, and Pa γ. Secure identifications for most spectral lines are given, based on synthetic atmosphere models calculated by our group. We also propose that two unidentified absorption features have interstellar and/or circumstellar origin. For the strongest one (10 780 Å) an empirical calibration between E(B − V) and equivalent width is provided. The atlas displays the spectra of massive stars organized in four categories, namely Be stars, OBA Iape (or luminous blue variables, LBV candidates and ex/dormant LBVs), OB supergiants and Wolf-Rayet stars. For comparison, the photospheric spectra of non emission-line stars are presented. Selected LBVs were observed in different epochs from 2001 to 2004, and their spectral variability reveals that some stars, such as η Car, AG Car and HR Car, suffered dramatic spectroscopic changes during this time interval.Key words. atlases -stars: emission-line, Be -stars: Wolf-Rayet -stars: winds, outflows -stars: early-type IntroductionIn the last decades tremendous progress has been achieved in understanding how a massive star evolves along the HR diagram. A new scenario of massive star evolution was developed after the models allowed for the effects of rotation in the stellar structure and evolution (Maeder & Meynet 2000b). Also, the physical parameters of massive stars can currently be constrained with the advent of a new generation of fully-blanketed, spherical-symmetric, non-LTE radiative transfer codes (Hubeny & Lanz 1995;Hillier & Miller 1998;Hamann & Koesterke 1998;Pauldrach et al. 2001;Gräfener et al. 2002;Puls et al. 2005). Even for extremely massive objects such as Eta Carinae (Hillier et al. 2001) we now have a much better comprehension of the physical parameters of the central star by analyzing the emerged spectrum.However, the short transitional stages of massive star evolution are still poorly understood. The radiation emitted by the photosphere of these stars interacts with the optically-thick, dense wind, which makes the spectral classification a very challenging task. In addition to the luminosity, effective temperature and surface gravity, several other stellar parameters might change the spectral morphology of these objects, notably the mass-loss rate and the wind terminal velocity. In the discussion Based on observations made at Observatório do Pico dos Dias/LNA (Brazil).Figures 5 to 18 are only available in electronic form at http://www.aanda.org Electronic version of the spectra (fichiers FITS) is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/465/993 on the...

Hαspectropolarimetry of the B[e] supergiant GG Carinae

“…In addition, Machado et al (2004) using high resolution spectra confirmed the binarity and intrinsic variability of GG Car. Groh et al (2007) detected Paγ and HeI 10830 Å in emission along with several features produced by FeII, MgII, and CI in its nearinfrared spectrum. In addition, GG Car appears to display 13 CO band emission in its mid-infrared spectrum, indicating that it is indeed a sgB[e] star (Kraus 2009) based on the enrichment of its circumstellar matter by 13 C.…”

Spectroscopic variabilities inλPavonis

“…Koen & Eyer (2002) also reported a signal 0.16 c/d (or 6.18 days) in their analyses of the Hipparcos data. Also, some authors (Groh et al 2007) argue that this object is in fact a binary star, as has been proposed recently for other Be stars such as Achernar (Kervella et al 2008). On the other hand, Eggleton & Tokovinin (2008) flag the star as a single object, and Lefèvre et al (2009) point to it as an irregular variable star.…”

“…Later on, the star reached an almost quiescent phase in 2000, and again entered an active phase in 2001. Recently, Groh et al (2007) pointed out an X-ray source near λ Pav and suggest there is a binary companion as a possible scenario. Again, the natural limitations in our time sample, made it impossible to ascribe a signal related to binarity, and also it is unlikely that ν 1 arise from that since it would lead to a very short period, which is typical of Algol-type stars.…”

“…Some rapid variabilities have been reported in the past years (Koen & Eyer 2002;Hubert & Floquet 1998) without further detailed studies. Even the binarity scenario has been proposed as a possible mechanism, as proposed by Groh et al (2007) based on the observations in the X-ray range done by the Einstein Observatory, which pointed to an X-ray source associated to this object. …”

Conception of a near-IR spectrometer for ground-based observations of massive stars

“…Its morphology ranges from an absorption line in stars with low density winds to a broad P-Cygni profile in Wolf-Rayet stars 1,2 . In some cases, the emission part of the P-Cygni profile is flat-topped, in other cases it is rounded or strongly peaked 3 . Whatever the morphology, it is related to the velocity law in the wind and can thus provide unique information.…”