Abstract
The UX Ori type variables (named after the prototype of their class) are intermediate-mass pre-main sequence objects. One of the most likely causes of their variability is the obscuration of the central star by orbiting dust clouds. We investigate the structure of the circumstellar environment of the UX~Ori star V1026 Sco (HD 142666) and test whether the disk inclination is large enough to explain the UX Ori variability. We observed the object in the low-resolution mode of the near-infrared interferometric VLTI/AMBER instrument and derived H- and K-band visibilities and closure phases. We modeled our AMBER observations, published Keck Interferometer observations, archival MIDI/VLTI visibilities, and the spectral energy distribution using geometric and temperature-gradient models. Employing a geometric inclined-ring disk model, we find a ring radius of 0.15 +- 0.06 AU in the H band and 0.18 +- 0.06 AU in the K band. The best-fit temperature-gradient model consists of a star and two concentric, ring-shaped disks. The inner disk has a temperature of 1257^{+133}_{-53} K at the inner rim and extends from 0.19 +- 0.01 AU to 0.23 +- 0.02 AU. The outer disk begins at 1.35^{+0.19}_{-0.20} AU and has an inner temperature of 334^{+35}_{-17} K. The derived inclination of 48.6^{+2.9}_{-3.6}deg approximately agrees with the inclination derived with the geometric model (49 +- 5deg in the K band and 50 +- 11deg in the H band). The position angle of the fitted geometric and temperature-gradient models are 163 +- 9deg (K band; 179 +- 17deg in the H band) and 169.3^{+4.2}_{-6.7}deg, respectively. The narrow width of the inner ring-shaped model disk and the disk gap might be an indication for a puffed-up inner rim shadowing outer parts of the disk. The intermediate inclination of ~50deg is consistent with models of UX Ori objects where dust clouds in the inclined disk obscure the central star.
Highlights
The UX Ori (UXOr) phenomenon of Herbig Ae/Be stars (HAeBes) is attributed to obscuration by circumstellar dust in an inclined disk (Grinin et al 1994; Natta et al 1997; Grinin et al 2001; Dullemond et al 2003) or unsteady accretion (Herbst & Shevchenko 1999)
The intermediate inclination of ∼50◦ is consistent with models of UX Ori objects where dust clouds in the inclined disk obscure the central star
With a geometric ring-shaped model consisting of the star and an inclined ring, we found a radius of rring,in = 0.18 ± 0.06 AU in the K band
Summary
The UX Ori (UXOr) phenomenon of Herbig Ae/Be stars (HAeBes) is attributed to obscuration by circumstellar dust in an inclined disk (Grinin et al 1994; Natta et al 1997; Grinin et al 2001; Dullemond et al 2003) or unsteady accretion (Herbst & Shevchenko 1999). The Herbig Ae star V1026 Sco (HD 142666) has a spectral type of A8Ve (Dominik et al 2003) and is classified as a UX Ori object (Meeus et al 1998). Dominik et al (2003) and van Boekel et al (2005) report distances of 116 pc and 145 ± 43 pc, respectively. The object V1026 Sco shows large, nonperiodic (Lecavelier des Etangs et al 2005) brightness variations
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