Modeling of PMS Ae/Fe stars using UV spectra

Abstract

Context. Spectral classification of PMS Ae/Fe stars, based on visual observations, may lead to ambiguous conclusions. Aims. We aim to reduce these ambiguities by using UV spectra for the classification of these stars, because the rise of the continuum in the UV is highly sensitive to the stellar spectral type of A/F-type stars. Methods. We analyse the low-resolution UV spectra in terms of a 3-component model, that consists of spectra of a central star, of an optically-thick accretion disc, and of a boundary-layer between the disc and star. The disc-component was calculated as a juxtaposition of Planck spectra, while the 2 other components were simulated by the low-resolution UV spectra of well-classified standard stars (taken from the IUE spectral atlases). The hot boundary-layer shows strong similarities to the spectra of late-B type supergiants (see Appendix A). Results. We modeled the low-resolution UV spectra of 37 PMS Ae/Fe stars. Each spectral match provides 8 model parameters: spectral type and luminosity-class of photosphere and boundary-layer, temperature and width of the boundary-layer, disc-inclination and circumstellar extinction. From the results of these analyses, combined with available theoretical PMS evolutionary tracks, we could estimate their masses and ages and derive their mass-accretion rates. For a number of analysed PMS stars we calculated the corresponding SEDs and compared these with the observed SEDs. Conclusions. All stars (except β Pic) show indications of accretion, that affect the resulting spectral type of the stellar photosphere. Formerly this led to ambiguities in classificaton of PMS stars as the boundary-layer was not taken into consideration. We give evidence for an increase of the mass-accretion rate with stellar mass and for a decreases of this rate with stellar age.

Multiwavelength interferometric observations and modeling of circumstellar disks

“…It has a spectral type of A 7 III (e.g., Blondel et al 2006). The source belongs to the star formation region R 1 in Scorpius (Vieira et al 2003).…”

Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks

“…Certainly, the advantage of using high resolution spectropolarimeters such as ESPaDOnS at the Canada-France-Hawaii Bernacca & Perinotto (1970), c Grady et al (1996), d van den Ancker et al (1998), e Acke & Waelkens (2004), f Hamidouche et al (2008), g this work, h Dunkin et al (1997), i Hubrig et al (2007b), j Alencar et al (2003), k Royer et al (2007), l Mora et al (2001), m Slettebak (1982), n de la Reza & Pinzón (2004), o Beskrovnaya et al (2004), p Alecian et al (2008), q Landstreet et al (2008) Pontoppidan et al (2007b), aa Siebenmorgen et al (2000), bb Kessler-Silacci et al (2005), cc Okamoto et al (2004), dd Schütz et al (2005b), ee Dommanget & Nys (1994), f f Baines et al (2006), gg Corporon & Lagrange (1999), hh Stelzer et al (2006), ii Chen et al (2006a), j j Augereau et al (2001), kk Carmona et al (2007), ll Stecklum et al (1995), mm Reipurth & Zinnecker (1993), nn Roberge et al (2002), oo Grady et al (2007), pp Stauffer et al (1995), qq SIMBAD, rr Eisner et al (2004), ss Grady et al (2004), tt Pirzkal et al (1997), uu Schnerr et al (2007), vv Blondel et al (2006), ww van den Ancker et al (1997), xx Wade et al (2007), yy …”

“…Radii marked as this study were calculated using T eff and bolometric luminosity, both taken from the literature. References: a Doering et al (2007), b Doucet et al (2007), c Ardila et al (2007), d Augereau et al (2001) Vieira et al (2003), z Mora et al (2001), aa Bernacca & Perinotto (1970), bb Pogodin et al (2005), cc de la Reza & Pinzón (2004), dd Blondel & Tjin (2006), ee Hillenbrand et al (1992), f f Wade et al (2007), gg this study (see table caption), hh Tatulli et al (2008), ii Hughes et al (2008), and j j di Folco et al (2004). Comments on the inclination angles deduced in this study, mainly from IUE (LWR and LWP cameras) through analysis of line profile types.…”

Multi-site photometry of the pulsating Herbig Ae star V346 Ori

“…Considering spectroscopic measurements, V346 Ori has been classified as A2IV (Mora et al 2001), A5IIIe (Herbig 1960), A7III (Gray & Corbally 1998), A7III (Blondel et al 2006), A8 (Valenti et al 2000), A8V (Vieira et al 2003), and A9 (Hernández et al 2006) 6 . Thus, our estimate is consistent with the last three values, and marginally with the A7III evaluation by Gray & Corbally (1998) and Blondel et al (2006). It is inconsistent with Herbig (1960) and Mora et al (2001).…”