Multiwavelength observations of Hercules X-1/HZ Herculis

Abstract

view Abstract Citations (46) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multiwavelength Observations of Hercules X-1/HZ Herculis Vrtilek, S. D. ; Mihara, T. ; Primini, F. A. ; Kahabka, P. ; Marshall, H. ; Agerer, F. ; Charles, P. A. ; Cheng, F. H. ; Dennerl, K. ; La Dous, C. ; Hu, E. M. ; Rutten, R. ; Serlemitsos, P. ; Soong, Y. ; Stull, J. ; Truemper, J. ; Voges, W. ; Wagner, R. M. ; Wilson, R. Abstract We present first results from a multiwavelength campaign to observe the binary pulsar system Her X-1/ HZ Her. The campaign spanned 4 days during 1993 August: observations were taken with five satellites (IUE, EUVE, ROSAT, ASCA, and CGRO/BATSE) and several ground-based facilities. A substantial, unexpected drop in flux at X-ray energies, with no change in absorbing column density, was observed. The pulse period has increased from the previous measurement, contrary to the usual spin-up, and no pulsed emission is detected above 0.9 keV in the low state. The optical and UV fluxes continued to show 1.7 day modulation attributed to X-ray heating of the companion star. However, the significant reduction in UV flux observed around eclipse implies an absence of the normally observed excess attributed to X-ray heating of the disk. We conclude that we have observed an anomalous low state, seen only once before (Parmar et al. 1985), in which the X-ray flux is not redistributed but obscured. We suggest explanations for the behavior of the flux at different wavelengths. Publication: The Astrophysical Journal Pub Date: November 1994 DOI: 10.1086/187621 Bibcode: 1994ApJ...436L...9V Keywords: Accretion Disks; Eclipsing Binary Stars; Pulsars; Spaceborne Astronomy; X Ray Astronomy; X Ray Binaries; Companion Stars; Light Curve; Stellar Luminosity; X Ray Spectra; Astrophysics; STARS: PULSARS: INDIVIDUAL NAME: HERCULES X-1 full text sources ADS | data products SIMBAD (3) MAST (2) HEASARC (1)