Probing local density inhomogeneities in the circumstellar disk of a be star using the new spectro-astrometry mode at the Keck Interferometer

J. U. Pott, J. Woillez, S. Ragland, P. L. Wizinowich, Joshua 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. Morrison & 6 others T. Panteleeva, B. Smith, K. Summers, K. Tsubota, C. Tyau, E. Wetherell

Research output: Contribution to journalArticle

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Abstract

We report on the successful science verification phase of a new observing mode at the Keck Interferometer, which provides a line-spread function width and sampling of 150 km s-1 at the K-band, at a current limiting magnitude of K- ∼ 7 mag with a spatial resolution of λ/2B ≈ 2.7mas and a measured differential phase stability of unprecedented precision (3 mrad at K = 5mag, which represents 3μ as on the sky or a centroiding precision of 10-3). The scientific potential of this mode is demonstrated by the presented observations of the circumstellar disk of the evolved Be-star 48 Lib. In addition to indirect methods such as multi-wavelength spectroscopy and polarimetry, the spectro-interferometric astrometry described here provides a new tool to directly constrain the radial density structure in the disk. For the first time, we resolve several Pfund emission lines, in addition to Br γ, in a single interferometric spectrum, with adequate spatial and spectral resolution and precision to analyze the radial disk structure in 48 Lib. The data suggest that the continuum and Pf -emission originates in significantly more compact regions, inside the Br γ -emission zone. Thus, spectro-interferometric astrometry opens the opportunity to directly connect the different observed line profiles of Br γ and Pfund in the total and correlated flux to different disk radii. The gravitational potential of a rotationally flattened Be star is expected to induce a one-armed density perturbation in the circumstellar disk. Such a slowly rotating disk oscillation has been used to explain the well-known periodic V/R spectral profile variability in these stars, as well as the observed V/R cycle phase shifts between different disk emission lines. The differential line properties and linear constraints set by our data are consistent with theoretical models and lend direct support to the existence of a radius-dependent disk density perturbation. The data also show decreasing gas rotation velocities at increasing stellocentric radii as expected for Keplerian disk rotation, assumed by those models.

Original languageEnglish (US)
Pages (from-to)802-808
Number of pages7
JournalAstrophysical Journal
Volume721
Issue number1
DOIs
StatePublished - Sep 20 2010

Fingerprint

astrometry
interferometer
inhomogeneity
interferometers
stars
spatial resolution
perturbation
spectral resolution
radii
oscillation
spectroscopy
wavelength
polarimetry
rotating disks
sampling
profiles
extremely high frequencies
gas
gravitational fields
sky

Keywords

  • Circumstellar matter
  • Infrared: stars
  • Stars: emission-line, Be
  • Stars: individual (48 Lib)
  • Techniques: interferometric
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Probing local density inhomogeneities in the circumstellar disk of a be star using the new spectro-astrometry mode at the Keck Interferometer. / Pott, J. U.; Woillez, J.; Ragland, S.; Wizinowich, P. L.; Eisner, Joshua A; Monnier, J. D.; Akeson, R. L.; Ghez, A. M.; Graham, J. R.; Hillenbrand, L. A.; Millan-Gabet, R.; Appleby, E.; Berkey, B.; Colavita, M. M.; Cooper, A.; Felizardo, C.; Herstein, J.; Hrynevych, M.; Medeiros, D.; Morrison, D.; Panteleeva, T.; Smith, B.; Summers, K.; Tsubota, K.; Tyau, C.; Wetherell, E.

In: Astrophysical Journal, Vol. 721, No. 1, 20.09.2010, p. 802-808.

Research output: Contribution to journalArticle

Pott, JU, Woillez, J, Ragland, S, Wizinowich, PL, Eisner, JA, Monnier, JD, Akeson, RL, Ghez, AM, Graham, JR, Hillenbrand, LA, Millan-Gabet, R, Appleby, E, Berkey, B, Colavita, MM, Cooper, A, Felizardo, C, Herstein, J, Hrynevych, M, Medeiros, D, Morrison, D, Panteleeva, T, Smith, B, Summers, K, Tsubota, K, Tyau, C & Wetherell, E 2010, 'Probing local density inhomogeneities in the circumstellar disk of a be star using the new spectro-astrometry mode at the Keck Interferometer', Astrophysical Journal, vol. 721, no. 1, pp. 802-808. https://doi.org/10.1088/0004-637X/721/1/802
Pott, J. U. ; Woillez, J. ; Ragland, S. ; Wizinowich, P. L. ; Eisner, Joshua A ; Monnier, J. D. ; Akeson, R. L. ; Ghez, A. M. ; Graham, J. R. ; Hillenbrand, L. A. ; Millan-Gabet, R. ; Appleby, E. ; Berkey, B. ; Colavita, M. M. ; Cooper, A. ; Felizardo, C. ; Herstein, J. ; Hrynevych, M. ; Medeiros, D. ; Morrison, D. ; Panteleeva, T. ; Smith, B. ; Summers, K. ; Tsubota, K. ; Tyau, C. ; Wetherell, E. / Probing local density inhomogeneities in the circumstellar disk of a be star using the new spectro-astrometry mode at the Keck Interferometer. In: Astrophysical Journal. 2010 ; Vol. 721, No. 1. pp. 802-808.
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T1 - Probing local density inhomogeneities in the circumstellar disk of a be star using the new spectro-astrometry mode at the Keck Interferometer

AU - Pott, J. U.

AU - Woillez, J.

AU - Ragland, S.

AU - Wizinowich, P. L.

AU - Eisner, Joshua A

AU - Monnier, J. D.

AU - Akeson, R. L.

AU - Ghez, A. M.

AU - Graham, J. R.

AU - Hillenbrand, L. A.

AU - Millan-Gabet, R.

AU - Appleby, E.

AU - Berkey, B.

AU - Colavita, M. M.

AU - Cooper, A.

AU - Felizardo, C.

AU - Herstein, J.

AU - Hrynevych, M.

AU - Medeiros, D.

AU - Morrison, D.

AU - Panteleeva, T.

AU - Smith, B.

AU - Summers, K.

AU - Tsubota, K.

AU - Tyau, C.

AU - Wetherell, E.

PY - 2010/9/20

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N2 - We report on the successful science verification phase of a new observing mode at the Keck Interferometer, which provides a line-spread function width and sampling of 150 km s-1 at the K-band, at a current limiting magnitude of K- ∼ 7 mag with a spatial resolution of λ/2B ≈ 2.7mas and a measured differential phase stability of unprecedented precision (3 mrad at K = 5mag, which represents 3μ as on the sky or a centroiding precision of 10-3). The scientific potential of this mode is demonstrated by the presented observations of the circumstellar disk of the evolved Be-star 48 Lib. In addition to indirect methods such as multi-wavelength spectroscopy and polarimetry, the spectro-interferometric astrometry described here provides a new tool to directly constrain the radial density structure in the disk. For the first time, we resolve several Pfund emission lines, in addition to Br γ, in a single interferometric spectrum, with adequate spatial and spectral resolution and precision to analyze the radial disk structure in 48 Lib. The data suggest that the continuum and Pf -emission originates in significantly more compact regions, inside the Br γ -emission zone. Thus, spectro-interferometric astrometry opens the opportunity to directly connect the different observed line profiles of Br γ and Pfund in the total and correlated flux to different disk radii. The gravitational potential of a rotationally flattened Be star is expected to induce a one-armed density perturbation in the circumstellar disk. Such a slowly rotating disk oscillation has been used to explain the well-known periodic V/R spectral profile variability in these stars, as well as the observed V/R cycle phase shifts between different disk emission lines. The differential line properties and linear constraints set by our data are consistent with theoretical models and lend direct support to the existence of a radius-dependent disk density perturbation. The data also show decreasing gas rotation velocities at increasing stellocentric radii as expected for Keplerian disk rotation, assumed by those models.

AB - We report on the successful science verification phase of a new observing mode at the Keck Interferometer, which provides a line-spread function width and sampling of 150 km s-1 at the K-band, at a current limiting magnitude of K- ∼ 7 mag with a spatial resolution of λ/2B ≈ 2.7mas and a measured differential phase stability of unprecedented precision (3 mrad at K = 5mag, which represents 3μ as on the sky or a centroiding precision of 10-3). The scientific potential of this mode is demonstrated by the presented observations of the circumstellar disk of the evolved Be-star 48 Lib. In addition to indirect methods such as multi-wavelength spectroscopy and polarimetry, the spectro-interferometric astrometry described here provides a new tool to directly constrain the radial density structure in the disk. For the first time, we resolve several Pfund emission lines, in addition to Br γ, in a single interferometric spectrum, with adequate spatial and spectral resolution and precision to analyze the radial disk structure in 48 Lib. The data suggest that the continuum and Pf -emission originates in significantly more compact regions, inside the Br γ -emission zone. Thus, spectro-interferometric astrometry opens the opportunity to directly connect the different observed line profiles of Br γ and Pfund in the total and correlated flux to different disk radii. The gravitational potential of a rotationally flattened Be star is expected to induce a one-armed density perturbation in the circumstellar disk. Such a slowly rotating disk oscillation has been used to explain the well-known periodic V/R spectral profile variability in these stars, as well as the observed V/R cycle phase shifts between different disk emission lines. The differential line properties and linear constraints set by our data are consistent with theoretical models and lend direct support to the existence of a radius-dependent disk density perturbation. The data also show decreasing gas rotation velocities at increasing stellocentric radii as expected for Keplerian disk rotation, assumed by those models.

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KW - Infrared: stars

KW - Stars: emission-line, Be

KW - Stars: individual (48 Lib)

KW - Techniques: interferometric

KW - Techniques: spectroscopic

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