The Surprising Discovery of a New Class of Pulsating X-Ray Stars
Villanova University Astronomers Part of Team That Reveals Secret (X-Ray) Lives of Cepheids
A surprising new class of X-ray pulsating variable stars has been discovered by a team of American and Canadian astronomers led by Villanova University’s Scott Engle and Edward Guinan. Part of the Villanova Secret Lives of Cepheids program, the new X-ray observations, obtained by NASA's Chandra X-ray Observatory and published Thursday, March 23rd in The Astrophysical Journal, reveal that the bright prototype of Classical Cepheids, d Cephei, is a periodic pulsed X-ray source.
Research team members sharing in the discovery included Graham Harper, University of Colorado; Nancy Remage Evans, Harvard Center for Astrophysics; Manfred Cuntz, University of Texas, Arlington; and Hilding Neilson, University of Toronto.
The prototype star after which all Cepheids are named, d Cephei (d Cep) is, at a distance of 890 light years away, also one of the closest of its type. Cepheids are a famous class of pulsating variable stars and among the most astronomically important objects in the Universe. By measuring the pulsation periods and brightness of Cepheids astrophysicists can measure distances to other galaxies and calibrate the extragalactic distance scale. Cepheids also play an increasingly vital role in the effort to precisely measure the expansion rate of the Universe and to resolve the developing Hubble discrepancy.
Data recently returned for d Cep from the Chandra X-ray Observatory, combined with previous X-ray measures secured with the XMM-Newton X-ray satellite, have shown that d Cep has X-ray variations occurring in accord with the supergiant star's 5.4 day pulsation period. X-rays are observed at all phases of the star’s pulsations, but sharply rise by ~400% near the times when the star swells to its maximum diameter of about 45 times that of the Sun.
Read more ~ AAVSO.org
Cepheus
