A high-resolution spectropolarimetric survey of Herbig Ae/Be stars – I. Observations and measurements★

Abstract

This is the first in a series of papers in which we describe and report the analysis of a large survey of Herbig Ae/Be stars in circular spectropolarimetry. Using the ESPaDOnS and Narval high-resolution spectropolarimeters at the Canada-France-Hawaii and Bernard Lyot Telescopes, respectively, we have acquired 132 circularly-polarised spectra of 70 Herbig Ae/Be stars and Herbig candidates. The large majority of these spectra are characterised by a resolving power of about 65,000, and a spectral coverage from about 3700 Å to 1 µm. The peak signal-to-noise ratio per CCD pixel ranges from below 100 (for the faintest targets) to over 1000 (for the brightest). The observations were acquired with the primary aim of searching for magnetic fields in these objects. However, our spectra are suitable for a variety of other important measurements, including rotational properties, variability, binarity, chemical abundances, circumstellar environment conditions and structure, etc. In this first paper, we describe the sample selection, the observations and their reduction, and the measurements that will comprise the basis of much of our following analysis. We describe the determination of fundamental parameters for each target. We detail the Least-Squares Deconvolution that we have applied to each of our spectra, including the selection, editing and tuning of the LSD line masks. We describe the fitting of the LSD Stokes I profiles using a multi-component model that yields the rotationally-broadened photospheric profile (providing the projected rotational velocity and radial velocity for each observation) as well as circumstellar emission and absorption components. Finally, we diagnose the longitudinal Zeeman effect via the measured circular polarisation, and report the longitudinal magnetic field and Stokes V Zeeman signature detection probability. As an appendix, we provide a detailed review of each star observed.

The inner circumstellar disk of the UX Orionis star V1026 Scorpii

“…The stellar rotation of V1026 Sco is v sin i = 65.3 ± 3.1 km s −1 (Alecian et al 2013a), leading to a maximum rotational velocity of ∼86 km s −1 if the inclination of the star is comparable to the disk inclination. This is similar (Boehm & Catala 1995) or slightly lower (Alecian et al 2013b) than the average velocity of low-mass Herbig Ae/Be stars but higher than measurements of T Tauri stars (Weise et al 2010).…”

“…Other authors find slightly different parameters for the alternative distance of 145 ± 20 pc. For example Alecian et al (2013a) Meeus et al (1998); (b) Folsom et al (2012); (c) Mendigutía et al (2011). VLTI/AMBER and archival mid-infrared (MIR) VLTI/MIDI measurements into account. We describe our observations and the data reduction in Sect.…”

“…These authors suggest that dense dust clouds in an inclined disk cause the stellar reddening. Alecian et al (2013a) report on the magnetic properties of V1026 Sco (and several other Herbig Ae/Be stars). The object V1026 Sco belongs to the Meeus group IIa (Juhász et al 2010) and might, therefore, have a self-shadowed disk.…”

Discovery of new magnetic early-B stars within the MiMeS HARPSpol survey

“…Such stable and large scale fields are called fossil fields (i.e. they are not continuously maintained from dissipation, Cowling 1945Cowling , 1953Borra et al 1982) and are observed in intermediate-mass stars from the premain-sequence phase (in Herbig Ae/Be stars), throughout the main-sequence phase, and very likely even until the red giant phase of stellar evolution (Aurière et al 2008(Aurière et al , 2011Alecian et al 2013). …”

B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid nebula, one of the youngest star forming regions

“…Ferrario et al 2009). The intermediate-mass stars show a magnetic fraction during their pre-main sequence evolution similar to Herbig stars (e.g., Hubrig et al 2009Hubrig et al , 2013, and references therein; Alecian et al 2013) as their main-sequence descendants, which may speak for fossil fields. On the other hand, there are almost no close binaries amongst the magnetic intermediate-mass main-sequence Ap-type stars (e.g.…”