The disk and environment of a young Vega analog: HD 169142


We trace the disk of HD169142 (A8 Ve) from 0.57" to 1.4" (approximate to 80-200 AU projected distance) in 1.1 mu m scattered light with HST NICMOS coronagraphy. The azimuthally symmetric disk has a peak azimuthally medianed surface brightness (SB) of approximate to 5 mJy arcsec(-2) at 0.57" from the star, and drops alpha r(-3). This radial SB profile is consistent with the presence of spatially resolved PAH emission and a Meeus group I IR SED only if the inner disk is either substantially flatter than the outer disk or partially devoid of material. Analysis of new HST ACS FUV imagery in tandem with archival IUE data indicates. M-acc <= 10(-9) M circle dot yr(-1). We estimate the age of HD 169142 to be 6(-3)(+6) Myr by identifying 2MASS 18242929-2946559, located 9.3" to the southwest, as a 130 mas separation weak-line T Tauri binary that is comoving with HD 169142 at the 4 sigma confidence level. We find no evidence for any additional stellar companion in either the ACS or Chandra ACIS-S data at r <= 1". HD 169142 has previously been interpreted as a slowly rotating, chemically peculiar star. However, by combining the disk inclination and v sin i from the literature, we find that the star has upsilon(equatorial) approximate to 240 km s(-1), making it a rapid rotator, similar to Altair or Vega. The UV data for HD 169142 are consistent with gravity darkening, while the X-ray luminosity and spectrum resembles early F stars at the age of the beta Pictoris moving group, rather than mid-A stars. In this context, spectral features previously interpreted as evidence for chemical peculiarity are more likely to reflect the presence of a strong photospheric latitudinal temperature gradient. With such a gradient, HD 169142 should closely resemble Vega at the epoch of central disk clearing.

binaries : visual, planetary systems : protoplanetary disks, stars : individual (2MASS 18242929-2946559, HD 22128, HD 36112, HD 142666, HD 169142, HD 220750), stars : low-mass, brown dwarfs, stars : pre-main-sequence, HERBIG-AE/BE STARS, X-RAY-EMISSION, 2-DIMENSIONAL RADIATIVE-TRANSFER, HIGH-RESOLUTION SPECTROSCOPY, SPITZER-SPACE-TELESCOPE, RAPIDLY ROTATING STAR, MAIN-SEQUENCE STARS, T-TAURI STARS, AE STAR, PROTOSTELLAR ENVELOPES, Astronomy & Astrophysics
Grady, C.A., et al. (2007): The Disk and Environment of a Young Vega Analog: HD 169142. The Astronomical Journal, 655(2). DOI: