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Title: Direct measurement of interstellar extinction toward young stars using atomic hydrogen Lyα absorption

Interstellar reddening corrections are necessary to reconstruct the intrinsic spectral energy distributions (SEDs) of accreting protostellar systems. The stellar SED determines the heating and chemical processes that can occur in circumstellar disks. Measurement of neutral hydrogen absorption against broad Lyα emission profiles in young stars can be used to obtain the total H I column density (N(H I)) along the line of sight. We measure N(H I) with new and archival ultraviolet observations from the Hubble Space Telescope (HST) of 31 classical T Tauri and Herbig Ae/Be stars. The H I column densities range from log{sub 10}(N(H I)) ≈19.6-21.1, with corresponding visual extinctions of A{sub V} =0.02-0.72 mag, assuming an R{sub V} of 3.1. We find that the majority of the H I absorption along the line of sight likely comes from interstellar rather than circumstellar material. Extinctions derived from new HST blue-optical spectral analyses, previous IR and optical measurements, and new X-ray column densities on average overestimate the interstellar extinction toward young stars compared to the N(H I) values by ∼0.6 mag. We discuss possible explanations for this discrepancy in the context of a protoplanetary disk geometry.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309 (United States)
  2. Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany)
  3. Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)
  4. California Institute of Technology, Department of Astrophysics, MC105-24, 1200 E. California Blvd., Pasadena, CA 91125 (United States)
  5. Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States)
  6. Five College Astronomy Department, Smith College, Northampton, MA 01063 (United States)
Publication Date:
OSTI Identifier:
22348247
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ATOMS; COMPARATIVE EVALUATIONS; CORRECTIONS; DENSITY; EMISSION; ENERGY SPECTRA; HEATING; HYDROGEN; PROTOPLANETS; SPACE; STARS; TELESCOPES; ULTRAVIOLET RADIATION; X RADIATION