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

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 polarized spectra of 70 Herbig Ae/Be stars and Herbig candidates. The large majority of these spectra are characterized by a resolving power of about 65 000, and a spectral coverage from about 3700 A 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 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 (LSD) 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 multicomponent 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 polarization, 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.