The Disk and Environment of a Young Vega Analog: HD 169142

• Published in: The Astrophysical journal Vol. 665; no. 2; pp. 1391 - 1406
• Main Authors: Grady, C. A, Schneider, G, Hamaguchi, K, Sitko, M. L, Carpenter, W. J, Hines, D, Collins, K. A, Williger, G. M, Woodgate, B. E, Henning, Th, Ménard, F, Wilner, D, Petre, R, Palunas, P, Quirrenbach, A, Nuth III, J. A, Silverstone, M. D, Kim, J. S
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 20-08-2007; University of Chicago Press; American Astronomical Society
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Norway, Vega; stars: individual (2MASS 18242929-2946559, HD 22128, HD 36112, HD 142666, HD 169142, HD 220750); planetary systems: protoplanetary disks; Low-mass stars; Pre-main-sequence stars; Brown dwarf stars; binaries: visual; Visual binary stars; stars: pre-main-sequence; Planetary system; stars: low-mass, brown dwarfs; Proto planetary nebula
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/519757

We trace the disk of HD 169142 (A8 Ve) from 0.57" to 1.4" ( approximately 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 approximately 5 mJy arcsec super(-2) at 0.57" from the star, and drops [unk]. 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 [unk] less than or equal to 10 super(-9) M [unk] yr-1. We estimate the age of HD 169142 to be [unk] 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 less than or equal to 1". HD 169142 has previously been Interpreted as a slowly rotating, chemically peculiar star. However, by combining the disk inclination and [unk] from the literature, we find that the star has [unk] approximately 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.