First Keck interferometer measurements in self-phase referencing mode: Spatially resolving circum-stellar line emission of 48 Lib

J. U. Pott, J. Woillez, S. Ragland, P. L. Wizinowich, J. A. Eisner, J. D. Monnier, R. L. Akeson, A. M. Ghez, J. R. Graham, L. A. Hillenbrand, R. Millan-Gabet, E. Appleby, B. Berkey, M. M. Colavita, A. Cooper, C. Felizardo, J. Herstein, M. Hrynevych, D. Medeiros, D. MorrisonT. Panteleeva, B. Smith, K. Summers, K. Tsubota, C. Tyau, E. Wetherell

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


Recently, the Keck interferometer was upgraded to do self-phase-referencing (SPR) assisted K-band spectroscopy at R ∼ 2000. This means, combining a spectral resolution of 150 km/s with an angular resolution of 2.7 mas, while maintaining high sensitiviy. This SPR mode operates two fringe trackers in parallel, and explores several infrastructural requirements for off-axis phase-referencing, as currently being implemented as the KI-ASTRA project. The technology of self-phasereferencing opens the way to reach very high spectral resolution in near-infrared interferometry. We present the scientific capabilities of the KI-SPR mode in detail, at the example of observations of the Be-star 48 Lib. Several spectral lines of the cirumstellar disk are resolved. We describe the first detection of Pfund-lines in an interferometric spectrum of a Be star, in addition to Br γ . The differential phase signal can be used to (i) distinguish circum-stellar line emission from the star, (ii) to directly measure line asymmetries tracing an asymetric gas density distribution, (iii) to reach a differential, astrometric precision beyond single-telescope limits sufficient for studying the radial disk structure. Our data support the existence of a radius-dependent disk density perturbation, typically used to explain slow variations of Be-disk hydrogen line profiles.

Original languageEnglish (US)
Title of host publicationOptical and Infrared Interferometry II
StatePublished - 2010
EventOptical and Infrared Interferometry II - San Diego, CA, United States
Duration: Jun 27 2010Jul 2 2010

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherOptical and Infrared Interferometry II
Country/TerritoryUnited States
CitySan Diego, CA


  • Be circumstellar matter stars
  • Emission-line
  • Individual (48 lib) techniques
  • Interferometric techniques
  • Spectroscopic infrared
  • Stars

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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