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Research in Astronomy & Astrophysics at Lehigh


Lehigh Astrophysics Group Members

Research Topics

  • Classical Be Stars:
    Be stars are a particular type of massive B stars that have emission disks around their equators. They also tend to be rotating very fast! The disks are probably a consequence of their fast rotation, so where did the rotation come from? The stars might have been born rotating fast, or they might have evolved into very fast rotators. The third possibility is that sometime in their past, a binary companion donated material to the B star and made it spin faster. I have found that this third case probably produces about 75% of Be stars. The disks are also highly transient, and they can appear and disappear over timescales of weeks to months to years.

    The Be star phi Persei, illustrated below by Bill Pounds, is a classical Be star with an evolved, stripped down, helium star companion.

    phi Persei

  • High mass X-ray and γ-ray binaries:
    LS 5039 and LS I +61 303 are two of only 5 known massive binaries that with emission in the TeV energy range. This rare class of objects may contain neutron stars or black holes, accreting material from the winds of the stars and producing relativistic bipolar jets. Or, they may not be accreting sources at all. The stellar wind may be colliding with a relativistic pulsar wind to produce high energy emission in a shock region between the star and compact object. We are currently trying to identify the true mechanism in these sources. Below is an artist's interpretation of the "microquasar" model of LS 5039, with weak jets eminating from a neutron star. Painting by Bill Pounds.

    LS 5039

Facilities Used by Lehigh Astronomers