Phase-dependent spectral variability in 4U 1907 + 09

Mallory S.E. Roberts, Peter F. Michelson, Denis A. Leahy, Tony A. Hall, John P. Finley, Lynn R. Cominsky, Radhika Srinivasan

Research output: Contribution to journalArticlepeer-review


We report on ASCA, RXTE, and archival observations of the high-mass X-ray binary pulsar 4U 1907+09. Spectral measurements of the absorption and flux were made at all phases of the X-ray pulsar orbit, including the first spectral measurements of an extended period of low flux during two of the ASCA observations. We find that a simple spherical wind model can fit the time-averaged light curve as measured by the RXTE All-Sky Monitor but does not fit the observed changes in the absorption column or account for the existence of the phase-locked secondary flare. An additional model component consisting of a trailing stream can account for the variations in column depth. However, these models favor a high inclination angle for the system, suggesting a companion mass more consistent with an identification as a Be star. In this case, an equatorially enhanced wind and inclined neutron star orbit may be a more appropriate interpretation of the data.

Original languageEnglish (US)
Pages (from-to)967-977
Number of pages11
JournalAstrophysical Journal
Issue number2 PART 1
StatePublished - Jul 10 2001


  • Stars: emission-line, Be
  • Stars: mass loss
  • X-rays: stars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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