Hercules X-1

Hercules X-1

An X-ray binary star, the second to be established as such (after Centaurus X-3), based on Uhuru satellite observations. It exhibits a complex behavior, with regular 1.24 second X-ray pulsations, eclipses (by the binary companion star) every 1.75 days, and longer-term modulation of the X-ray intensity over a 35-day cycle. Her X-1 was the first X-ray binary to be optically identified; the low-mass optical counterpart, HZ Her, varies through the binary period from spectral type A/F to B due to X-ray heating. Its mass (about 1.5 times that of the Sun) and the 1.24-second pulsations strongly suggest the X-ray component to be a rotating neutron star. It is thus often referred to as an X-ray pulsar, with the X-ray pulsations arising most probably from channeling of the accreting gas onto the magnetic poles of the neutron star. The discovery in 1976 of a hard X-ray ‘emission line’ at 55 keV, attributed to cyclotron radiation from near the star's surface, provides support for this view and gave a direct measure of the intense polar magnetic field (about 108 tesla). More recent X-ray spectra have led to the re-interpretation of this feature as an absorption line, at 38 keV, arising from cyclotron absorption of electrons in a magnetic field of 3 × 108 tesla.

Hercules X-1

[′hər·kyə‚lēz ¦eks ′wən]
(astrophysics)
A source of x-rays that pulses with a period of 1.237 seconds, and is eclipsed for 6 of every 42 hours, associated with a variable star, designated HZ Herculis, that also has a period of 42 hours and faint 1.237-second pulsations; believed to be a binary star whose invisible member is a rotating neutron star. Abbreviated Her X-1.
References in periodicals archive ?
The most controversial -- and potentially exciting -- observations involve Hercules X-1, another binary system possessing a neutron star.
National Laboratory show that the neutron star Hercules X-1, about 15,000 light-years away, is the source of surprisingly powerful pulses of what appear to be neutral particles.
Hercules X-1, composed mainly of neutrons, is one member of a double-star, or binary, system.
24 PHYSICAL REVIEW LETTERS, the Los Alamos detectors record particle showers initiated in the upper atmosphere when particles or gamma rays from Hercules X-1 strike atoms in the air.
For Hercules X-1 and Cygnus X-3, we see only occasional emission episodes," Nagle says.
A particularly likely class of candidates is the binary star X-ray sources in our galaxy, such as Cygnus X-3, Hercules X-1 and Vela X-1.
Presumably these muons are produced in the detector by some highly energetic, extremely penetrating radiation that comes from certain sources in the sky-- Cygnus X-3 and Hercules X-1 are among those implicated--and can penetrate the earth's atmosphere and several thousand feet of rock to reach the detector.
In this case the source seems also to be Hercules X-1.
Yodh told the Heavenly Accelerators workshop, which met recently at Johns Hopkins University in Baltimore, that just a few months ago a series of air showers initiated by gamma rays that seem to come from Hercules X-1 had "too many muons' associated with them--that is, more than known and accepted physics would expect--and therefore something strange is going on.
Astronomers have now found several objects that do, including the Crab nebula, the Crab pulsar, the Vela pulsar, Hercules X-1, Cygnus X-3, 4U0115 63, Centaurus X-3, PSR1953 29 and LMC X-4.
Gorham of the University of Hawaii at Manoa described some of the observations of Hercules X-1 done at the Whipple Observatory and some theoretical conclusions he drew from them and expressed in his recent doctoral dissertation.
Now they claim similar radiation from four more binary X-ray sources: Hercules X-1, Scorpio X-1, 4U0115 63 and 1E2259 586.