K. Brownsberger

Publications (6)6.02 Total impact

• Source

  Available from: derckmassa.net

  Article: Far Ultraviolet Spectroscopic Explorer Spectroscopy of the O VI Resonance Doublet in Sand 2 (WO)

  Paul A. Crowther, A. W. Fullerton, D. J. Hillier, K. Brownsberger, L. Dessart, A. J. Willis, O. De Marco, M. J. Barlow, J. B. Hutchings, D. L. Massa, D. C. Morton, and G. Sonneborn
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  ABSTRACT: We present Far Ultraviolet Spectroscopic Explorer spectroscopy of Sand 2, an LMC WO-type Wolf-Rayet star, revealing the O VI resonance P Cygni doublet at 1032-1038 Å. These data are combined with Hubble Space Telescope Faint Object Spectrograph ultraviolet and Mount Stromlo 2.3 m optical spectroscopy and analyzed using a spherical, non-LTE, line-blanketed code. Our study reveals exceptional stellar parameters: T* ~ 150,000 K, v∞ = 4100 km s-1, log(L/L☉) = 5.3, and = 1 × 10-5 M☉ yr-1, if we adopt a volume filling factor of 10%. Elemental abundances of C/He ~ 0.7 ± 0.2 and O/He ~ 0.15 by number qualitatively support previous recombination line studies. We confirm that Sand 2 is more chemically enriched in carbon than LMC WC stars and that it is expected to undergo a supernova explosion within the next 5 × 104 yr.
  The Astrophysical Journal 12/2008; 538(1):L51. · 6.02 Impact Factor
• Source

  Available from: arxiv.org

  Article: Far-UV FUSE spectroscopy of the OVI resonance doublet in Sand2 (WO)

  Paul A. Crowther, A. W. Fullerton, D. J. Hillier, K. Brownsberger, L. Dessart, A. J. Willis, O. De Marco, M. J, Barlow, J. B. Hutchings, D. L. Massa, D. C. Morton, G. Sonneborn
  [show abstract] [hide abstract]
  ABSTRACT: We present Far-Ultraviolet Spectroscopic Explorer (FUSE) spectroscopy of Sand 2, a LMC WO-type Wolf-Rayet star, revealing the OVI resonance P Cygni doublet at 1032-38A. These data are combined with HST/FOS ultraviolet and Mt Stromlo 2.3m optical spectroscopy, and analysed using a spherical, non-LTE, line-blanketed code. Our study reveals exceptional stellar parameters: T*=150,000K, v_inf=4100 km/s, log (L/Lo)=5.3, and Mdot=10^-5 Mo/yr if we adopt a volume filling factor of 10%. Elemental abundances of C/He=0.7+-0.2 and O/He=0.15(-0.05+0.10) by number qualitatively support previous recombination line studies. We confirm that Sand 2 is more chemically enriched in carbon than LMC WC stars, and is expected to undergo a supernova explosion within the next 50,000 yr.
  06/2000;
• Source

  Available from: derckmassa.net

  Article: On-Orbit Performance of the Far Ultraviolet Spectroscopic Explorer (FUSE) Satellite

  D. J. Sahnow, H. W. Moos, T. Ake, J. Andersen, B.-G. Andersson, M. Andre, D. Artis, A. Berman, W. Blair, K. Brownsberger, [......], K. Roth, R. Sankrit, K. Sembach, R. Shelton, O. Siegmund, C. Silva, G. Sonneborn, S. Vaclavik, H. Weaver, E. Wilkinson
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  ABSTRACT: Launch of the Far Ultraviolet Spectroscopic Explorer (FUSE) has been followed by an extensive period of calibration and characterization as part of the preparation for normal satellite operations. Major tasks carried out during this period include initial coalignment, focusing and characterization of the four instrument channels, and a preliminary measurement of the resolution and throughput performance of the instrument. We describe the results from this test program, and present preliminary estimates of the on-orbit performance of the FUSE satellite based on a combination of this data and prelaunch laboratory measurements. Comment: 8 pages, including 3 figures. This paper will appear in the FUSE special issue of ApJ Letters
  05/2000;
• Article: FUSE observations of the resonance OVI doublet in Sand 2 (WO), the fastest stellar wind known.

  P. A. Crowther, K. Brownsberger, A. W. Fullerton, A. J. Willis, L. Bianchi, O. De Marco, J. B. Hutchings, T. Snow, FUSE Science Team
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  ABSTRACT: Oxygen sequence (WO-type) Wolf-Rayet stars represent the final, brief phase in the evolution of the most massive stars prior to a SN explosion. They are characterised by extremely broad, high excitation oxygen and carbon emission lines in their UV and optical spectrum. Sand 2 in the LMC is the only single WO star for which far-UV FUSE observations of the 1032, 1038 Angstroms OVI resonance doublet are possible, and has the fastest continuous wind of any known star ( 4,500 km/s!). We will carry out a spectral synthesis of FUSE observations of Sand 2 using state-of-the-art models -- supplemented by UV HST and ground-based MSSSO optical spectroscopy -- to help address the exact evolutionary status of WO stars. This work is supported by NASA contract NAS5-32985.
  11/1999; 31:1378.
• Article: Pre-Flight Resolution and Performance of the Far Ultraviolet Spectroscopic Explorer (FUSE)

  A. N. Cha, D. J. Sahnow, H. W. Moos, E. Wilkinson, J. C. Green, K. Brownsberger, S. Osterman
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  ABSTRACT: Spectroscopic data obtained from the spectrograph of the Far Ultraviolet Spectroscopic Explorer (FUSE) during the integration and test phase of development has been acquired and analyzed. We present the most current measurement of the resolution of FUSE as a function of wavelength over the entire bandpass of 905 - 1187 Angstroms. The FUSE instrument outputs spectra through four channels. Both H2 and PtNe emission line spectra were studied using an automated routine to determine the full width at half maximum (FWHM) of more than 100 spectral lines per channel. The resolution of the instrument has been characterized using a subset of the emission lines of both H2 and PtNe. The spectral lines chosen were determined to be unblended, and were identified as arising from only single molecular transitions. Using resolution as a diagnostic tool, we have performed a self consistency check to assure that different channels of the spectrograph image identical wavelength regions with comparable resolutions. In addition, we have studied the effects of focal plane motion on the resolution of FUSE. The results of these studies provide a prediction of the instrument's performance after launch.
  11/1998; 30:1270.
• Source

  Available from: articles.adsabs.harvard.edu

  Article: Far-Ultraviolet Spectroscopy of Wolf Rayet Stars

  A. J. Willis, P. A. Crowther, J. Hutchings, A. Fullerton, K. Brownsberger, N. R. Walborn
  304:54.