A catalogue of calibrator stars for long baseline stellar interferometry

Abstract

Abstract. Long baseline stellar interferometry shares with other techniques the need for calibrator stars in order to correct for instrumental and atmospheric effects. We present a catalogue of 374 stars carefully selected to be used for that purpose in the near infrared. Owing to several convergent criteria with the work of Cohen et al. (1999), this catalogue is in essence a subset of their self-consistent all-sky network of spectro-photometric calibrator stars. For every star, we provide the angular limb-darkened diameter, uniform disc angular diameters in the J, H and K bands, the Johnson photometry and other useful parameters. Most stars are type III giants with spectral types K or M0, magnitudes V = 3-7 and K = 0-3. Their angular limb-darkened diameters range from 1 to 3 mas with a median uncertainty as low as 1.2%. The median distance from a given point on the sky to the closest reference is 5.2• , whereas this distance never exceeds 16.4• for any celestial location.Key words. catalogs -stars: fundamental parameters -instrumentation: interferometers -techniques: interferometric Interferometry and calibrationA stellar interferometer collects and recombines light from separate apertures. The interferometric observable, called the visibility, is a measure of the spatio-temporal coherence of the target. It is a complex quantity whose modulus and phase are respectively derived from the contrast and the position of the fringe packet resulting from the recombination process. In order to take into account instrumental and atmospheric effects, observations of the target should be bracketed by observations of calibrator stars. Thus, the object visibility V can be deduced from the measured object and reference fringe contrasts µ and µ ref by A single star appears as a straightforward reference source whose simplest model is a uniform disc (UD) fully described by its angular diameter (single-parameter model). In the following, we will call calibrator star such a reference source. In this case, the visibility V ref is given bywhere B is the interferometric baseline projected on the sky, θ UD the stellar angular diameter and λ the wavelength. A more elaborate model would be a limb-darkened disc (LDD) with two parameters, the stellar angular diameter and either the coefficient of a linear law or the exponent of a power law for limbdarkening (e.g. Hestroffer 1997). However, for the purpose of calibration, the UD model is in general fully satisfactory provided the visibility is large enough. For instance, if V ≥ 50%, UD and LD models do not differ by more than 1% in the K band (Perrin et al. 1998).To improve calibration, µ and µ ref should be measured with the same instrumental and preferably atmospheric conditions, hence the need for a catalogue of calibrator stars with a sky coverage as complete as possible. Therefore, in the framework of the simplest single-parameter UD model, a dense grid of reference stars along with their angular diameters has to be worked out. Since only few stellar angular diameters have been direc...

The inner circumstellar disk of the UX Orionis star V1026 Scorpii

“…(a) Lafrasse et al (2010); (b) Richichi et al (2005); (c) Bordé et al (2002). Table 2) and temperature-gradient model B 3 : the panels show the wavelength-dependent H and K band visibilities of our AMBER observations.…”

Multiwavelength interferometric observations and modeling of circumstellar disks

“…For data calibration, we observed the main-sequence stars HD 134758, HD 143033, and HD 139663 with the uniform disk (UD) diameters (1.42 ± 0.02) mas, (1.36 ± 0.02) mas, and (1.99 ± 0.02) mas, respectively, in H band (Merand et al 2005;Bordé et al 2002). The projected baseline lengths as well as the position angles during our interferometric observations with IOTA are listed in Table 2.…”

Ellipsoidal primary of the RS CVn binaryζ Andromedae

“…Observations of ζ And and μ Peg were interleaved with observations of the interferometric calibration stars θ Psc (K1 III, K = 1.86, Θ LD = 2.00 ± 0.02 mas), 41 Psc (K3 III, K = 2.43, Θ LD = 1.81 ± 0.02 mas), HD 7087 (G9 III, K = 2.48, Θ LD = 1.59 ± 0.02 mas), and HD 15694 (K3 III, K = 2.48, Θ LD = 1.77 ± 0.02 mas). The angular diameters for θ Psc and 41 Psc are from Bordé et al (2002) and those for HD 7087 and HD 15694 are from Mérand et al (2006).…”