Hard x-ray emission from Her X-1

Journal Article · Mon Dec 17 04:00:00 EST 1973 · Nature (London) Phys. Sci., v. 246, no. 155, pp. 107-108

DOI:https://doi.org/10.1038/physci246107a0· OSTI ID:4317552

Sharma, D P; Jain, A K; Kasturirangan, K; Jayanthi, U B; Rao, U R

It was thought that extension of earlier observations to higher energies would be important for obtaining a better understanding of the mechanism for x- ray emission from this complex source, and results are here reported from two balloon flights from Hyderabad on December 28th 1972 and January 18th 1973, in- which x-ray observations on Her X-1 were made over the energy interval 20 to 150 keV. The dates were chosen so that the first flight coincided with the middle of the 11 day on'' state of the source and the peak of the binary period, and the second flight was 5 days prior to the onset of the next on'' state. Energy analysis of incoming x-rays for the first flight was carried out for the energy interval 29 to nterval 19 to 142 keV. A /sup 242/Am source was used for calibration purposes. Results are shown graphically. Whereas positive signals from the source were recorded in the first flight, no positive flux could be detected in the second flight when the source was in its dark phase. The lack of detection of high energy x-ray emission during the dark phase of Her X-1 indicates that the mechanism responsible for switching off'' the source at energies < 20 keV is also applicable at higher energies. Strong support was obtained for the view that the spectrum steepens at higher energies. With regard to variability, although the 1.24 sec pulsations and 1.7 day variations of the source were interpreted in terms of the pulsations of a neutron stur proceeding around a primary companion in a binary system, the reasons for the 35 day cyclic variations are less clear, although various medels were proposed. It is thought that by improving the sensitivity of balloon observations it should be possible to make meaningful measurements on Her X-1 at energies > 20 keV. In particular, measurement of the flux and energy spectrum at different times in the 35 day cycle should afford a valuable contribution to understanding the mechanism of the x-ray emission. (UK)

• Research Organization: Physical Research Lab., Ahmedabad, India
• NSA Number: NSA-29-021889
• OSTI ID: 4317552
• Journal Information: Nature (London) Phys. Sci., v. 246, no. 155, pp. 107-108, Journal Name: Nature (London) Phys. Sci., v. 246, no. 155, pp. 107-108; ISSN NPSCA
• Country of Publication: United Kingdom
• Language: English

Related Subjects

*BINARY STARS-- X-RAY SPECTRA
*COSMIC X-RAY SOURCES-- HARD X RADIATION
*NEUTRON STARS-- X-RAY SPECTRA
COSMOLOGICAL MODELS
DAILY VARIATIONS
EMISSION SPECTRA
ENERGY SPECTRA
KEV RANGE 10-100
KEV RANGE 100-1000
N56300* --Physics (Astrophysics &amp; Cosmology)--Quasi-stellar
Radio &amp; X-Ray Sources
VARIATIONS
X RADIATION
X-RAY DETECTION