Measurement of the masses of the neutron star, Her X-1, and its binary companion, HZ Her, as derived from the study of 1. 24-second optical pulsations from the Hz Her - Her X-1 binary system and the x ray-to-optical reprocessing reflection and transmission mechanisms

Technical Report · Wed Oct 01 04:00:00 EDT 1975

DOI:https://doi.org/10.2172/7144943· OSTI ID:7144943

Middleditch, J

Intermittent optical pulsations at the 0.1--0.3 percent level have been detected from this binary system in over 500 hours of optical observations. These pulsations are present only for well defined values of the 1.7-day (binary) and 35-day phases. Positions of the pulsation-emitting regions, projected onto the orbital plane, have been measured and three distinct regions have been resolved. A simple model is put forth which accounts for the observed binary behavior, which gives a direct determination of the mass ratio, M/sub HZ Her//M/sub Her X-1/ = 1.69 +- 0.05, and which establishes that the spin of the pulsar is prograde. Additionally it is shown that HZ Her fills its critical Roche lobe. Using the above, the known x ray eclipse duration, and the mass function, the orbital inclination is calculated to be i = 85/sup 0/ +- 5/sup 0/ and the masses to be M/sub Her X-1/ = 1.28 +- 0.08 M/sub solar/ and M/sub HZ Her/ = 2.16 +- 0.07 M/sub solar/. Constraints on the physical parameters of the accretion stream and disk are derived from the data. The nature of the 35-day modulation of the data is discussed in relation to various models.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7144943
• Report Number(s): LBL-3639
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BINARY STARS
ECLIPSE
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
MASS
MATHEMATICAL MODELS
NEUTRON STARS
PULSATIONS
RADIATIONS
STAR ACCRETION
STAR EVOLUTION
STAR MODELS
STARS
VISIBLE RADIATION
X RADIATION