High resolution spectroscopy of circumstellar material  around A stars

Hempel, M.; Schmitt, J. H. M. M.

doi:10.1051/0004-6361:20030946

Cited by 17 publications

(19 citation statements)

References 32 publications

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“…Secondly, δ Vel is known to have a moderate thermal infrared excess (e.g., Aumann 1985;Su et al 2006), and Spitzer observations revealed a spectacular bow shock caused by the motion of δ Vel in a dense interstellar cloud (Gáspár et al 2008). The presence of interstellar material was also reported by Hempel & Schmitt (2003), who observed two red-shifted absorbing components in absorption in the Ca II K line of probably interstellar origin. In Paper I of the present series, Kervella et al (2009) confirmed that the infrared excess is essentially emitted by the bow shock, and not warm circumstellar material located close to the stars.…”

Section: Introductionsupporting

confidence: 76%

The nearby eclipsing stellar systemδVelorum

Pribulla¹,

Mérand²,

Kervella

et al. 2011

A&A

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Context. The triple stellar system δ Vel (composed of two A-type and one F-type main-sequence stars) is particularly interesting because it contains one of the nearest and brightest eclipsing binaries. It therefore presents a unique opportunity to determine independently the physical properties of the three components of the system, as well as its distance. Aims. We aim at determining the fundamental parameters (masses, radii, luminosities, rotational velocities) of the three components of δ Vel, as well as the parallax of the system, independently from the existing Hipparcos measurement. Methods. We determined dynamical masses from high-precision astrometry of the orbits of Aab-B and Aa-Ab using adaptive optics (VLT/NACO) and optical interferometry (VLTI/AMBER). The main component is an eclipsing binary composed of two early A-type stars in rapid rotation. We modeled the photometric and radial velocity measurements of the eclipsing pair Aa-Ab using a self-consistent method based on physical parameters (mass, radius, luminosity, rotational velocity). Results. From our self-consistent modeling of the primary and secondary components of the δ Vel A eclipsing pair, we derive their fundamental parameters with a typical accuracy of 1%. We find that they have similar masses, 2.43 ± 0.02 M and 2.27 ± 0.02 M . The physical parameters of the tertiary component (δ Vel B) are also estimated, although to a lower accuracy. We obtain a parallax π = 39.8 ± 0.4 mas for the system, in satisfactory agreement (−1.2 σ) with the Hipparcos value (π Hip = 40.5 ± 0.4 mas). Conclusions. The physical parameters we derive represent a consistent set of constraints for the evolutionary modeling of this system. The agreement of the parallax we measure with the Hipparcos value to a 1% accuracy is also an interesting confirmation of the true accuracy of these two independent measurements.

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Section: Introductionsupporting

confidence: 76%

The nearby eclipsing stellar systemδVelorum

Pribulla¹,

Mérand²,

Kervella

et al. 2011

A&A

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“…This A1 III star, located at a distance of 35 pc, is often referred to as being "Vega-like," but Redfield et al [64] have failed to detect a significant mid-IR excess that is normally associated with emission from a surrounding dusty debris disk. Previous observations of this star by Hempel and Schmitt [65] have shown a variation in both the EW of the CaII K-line and its absorption velocity recorded over a sixyear time period. In addition, very high spectral resolution observations of the CaII K-line by Redfield et al [64] revealed Figure 3: The circumstellar CaII K-line absorption spectra of HD 58647 recorded on 4 nights in March 2013.…”

Section: Hd 9672mentioning

confidence: 65%

The Appearance and Disappearance of Exocomet Gas Absorption

Welsh¹,

Montgomery

2015

Advances in Astronomy

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CaII K-line (3933 Å) absorption profiles observed towards 15 A-type and two B-type stars with known (or suspected) debris disks, in addition to archival spectral data for three A-type stars, are presented. Inspection of the extracted CaII K-line absorption lines has determined that one late B-type (HD 58647) and four new A-type (HD 56537, HD 64145, HD 108767, and HD 109573) stellar systems exhibit short-term (night-to-night) absorption variation within these profiles. This variability is due to the liberation of gas from falling evaporating bodies (the so-called FEBs activity) on the grazing approach of exocomets towards their parent star. Also we present archival spectra of the FeIλ3860 Å and CaII K-lines towardsβPictoris (HD 39060) that, for the first time, reveal the absorption signatures of FEB activity at similar velocities inbothline profiles. FEB-hosting stars seem to be of an earlier type (on average spectral type Al.8 as compared with A3.1) than those where no FEB activity has been observed. This could be due to stellar activity levels (such as chromospheric activity or nonradial pulsations) being of a higher level within the atmospheres of these hotter A-type stars.

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“…we have detected nightly variations in the Ca  K line of β Pic (Hempel & Schmitt 2003). Brandeker et al (2004) analyzed the spatial structure of the β Pic gas disk in a distance range from the star from 13 AU out to 323 AU and found 88 spatially resolved emission lines in their UVES spectra.…”

Section: A Boundary Layer?mentioning

confidence: 98%

Detection of X-ray emission from β Pictoris with XMM-Newton: a cool corona, a boundary layer or what?

Hempel

Robrade

Ness

et al. 2005

A&A

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Abstract. β Pictoris (HR 2020) is the most prominent prototype of stars with circumstellar disks and has generated particular interest in the framework of young planetary systems. Given its spectral type A5, stellar activity is not expected. Nevertheless, resonance lines of C  and O  typical for a chromosphere and transition region have been unambiguously detected with FUSE. We present results from an XMM-Newton observation of β Pic and find evidence for X-ray emission. In particular, we detected an emission of O  at 21.6 Å with the MOS detectors. These findings present a challenge for the development of both stellar activity and disk models. We discuss and investigate various models to explain the observed emission including the presence of a cool corona and a boundary layer.

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High resolution spectroscopy of circumstellar material around A stars

Cited by 17 publications

References 32 publications

The nearby eclipsing stellar systemδVelorum

The nearby eclipsing stellar systemδVelorum

The Appearance and Disappearance of Exocomet Gas Absorption

Detection of X-ray emission from β Pictoris with XMM-Newton: a cool corona, a boundary layer or what?

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