Abstract:We present new L-band spectra of 13 outbursting Be stars obtained with ISAAC at the ESO Paranal observatory. These stars can be classified in three groups depending on the presence/absence of emission lines and the strength of Brα and Pfγ emission lines relative to those of Humphreys lines from transitions 6-14 to the end of the series. These groups are representative of circumstellar envelopes with different optical depths. For the group showing Brα and Pfγ lines stronger than Humphreys lines, the Humphreys d… Show more
“…Mennickent et al (2009) and Granada, Arias, & Cidale (2010) analyzed independently L-band spectra of different samples of outbursting Galactic Be stars. They found changes in the optical density of the CDDs that could be consistent with the model proposed by de Wit et al (2006).…”
ABSTRACT. We present the result of a search for southern Galactic Be star candidates within the group of miscellaneous variables of the ASAS-2 catalog of variable stars, using statistical, morphological, photometric, and color criteria. This search lead us to obtain a catalog of 213 new Be star candidates. The I-band light curves of these candidates show outbursts (Type-1 stars) only in 9% of the sample, and stochastic variations (Type-4 stars) in 91% of the sample. We do not find stars showing clear high and low states (Type-2 stars) or showing outbursts and high and low states simultaneously (Type-1/Type-2 stars). Our sample of southern Galactic Be star candidates provide valuable new bright targets for high resolution spectroscopic studies with small/medium size telescopes.
“…Mennickent et al (2009) and Granada, Arias, & Cidale (2010) analyzed independently L-band spectra of different samples of outbursting Galactic Be stars. They found changes in the optical density of the CDDs that could be consistent with the model proposed by de Wit et al (2006).…”
ABSTRACT. We present the result of a search for southern Galactic Be star candidates within the group of miscellaneous variables of the ASAS-2 catalog of variable stars, using statistical, morphological, photometric, and color criteria. This search lead us to obtain a catalog of 213 new Be star candidates. The I-band light curves of these candidates show outbursts (Type-1 stars) only in 9% of the sample, and stochastic variations (Type-4 stars) in 91% of the sample. We do not find stars showing clear high and low states (Type-2 stars) or showing outbursts and high and low states simultaneously (Type-1/Type-2 stars). Our sample of southern Galactic Be star candidates provide valuable new bright targets for high resolution spectroscopic studies with small/medium size telescopes.
“…Their profiles are sensitive to the physical properties and dynamical structure of the line-forming regions and thus become useful probes of circumstellar environments. An inspection of the L-band hydrogen spectra of Be stars allows a classification in three groups following Mennickent et al (2009): Group I contains the stars with Brα and Pfγ equally intense as Hu lines, Group II consists of those with Brα and Pfγ more intense than Hu lines, and Group III is made up of those with no detected emission. This classification scheme reflects the optical depth conditions in the Be star envelope.…”
Section: Introductionmentioning
confidence: 99%
“…We describe the behaviour of IR hydrogen emission lines of a sample of Be stars and discuss the physical properties of the circumstellar envelopes of Be stars classified in Groups I and II (Mennickent et al 2009). We find that while Humphreys and Pfund lines of Group I stars form in an optically thick envelope/disk, Group II stars show Pfund lines that form in an optically thick medium and Humphreys lines originating in optically thinner regions.…”
Abstract. We describe the behaviour of IR hydrogen emission lines of a sample of Be stars and discuss the physical properties of the circumstellar envelopes of Be stars classified in Groups I and II (Mennickent et al. 2009). We find that while Humphreys and Pfund lines of Group I stars form in an optically thick envelope/disk, Group II stars show Pfund lines that form in an optically thick medium and Humphreys lines originating in optically thinner regions. The transition between Groups I and II could be understood in terms of the evolution of the circumstellar disk of the star and might bring clues on the mechanism originating the Be phenomenon.
“…The same kind of variable stars were found in the Large Magellanic Cloud (Sabogal et al 2005) and in the direction of the Galactic Bulge (Sabogal et al 2008). Samples of Type-1 stars were studied by de Wit et al (2006) and by Mennickent et al (2009). These studies showed that Type-1 stars could be stars with an optically thick circumstellar envelope that evolves in an optically thin one before to dissipate into the interstellar medium.…”
Abstract. Photometric searches for Be stars in environments with different metallicities have led to the discovery of many Be-like star variables. The knowledge of these types of variables is still fragmentary. This work presents the preliminary results of analyzing FLAMES+GIRAFFE spectra of a sample of these Be-like stars that we have found in the Small Magellanic Cloud (SMC).
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