Hard x-ray spectrum of Hercules X-1

Journal Article · Mon Jul 23 04:00:00 EDT 1973 · Nature (London) Phys. Sci., v. 244, no. 134, pp. 59-60

DOI:https://doi.org/10.1038/physci244059a0· OSTI ID:4433543

Manchanda, R K; Iyengar, V S; Durgaprasad, N; Gokhale, G S; Kunte, P K; Sreekantan, B V

It is stated that spectral results on ihe periodic pulsating binary x- ray source Hercules X-1 are very meagre. The only available results are from satellite experiments and for energies <40 keV. Uhuru results indicated that the intensity and spectral characteristics vary from day to day. In order to understand the peculiar features observed in this source it is necessary to extend the spectral results and study the temporal variations over different portions of the cycle, observe the finer features of the pulsating component, and determine correlations with the optical intensity variations of the optical counterpart Hz Hercules. With this in view attempts were made to determine thc spectral and pulsating characteristics of the source in the 20 to 100 keV band uslng a balloon-borne x-ray telescope at a time when Her X-1 was near the middle of its on'- state. The x-ray telescope used a Nal (Tl) crystal, and inflight calibration was provided by a /sup 241/Am source. Details are given of the experimental technique and data analysis, and spectral results are shown tabulated. Good agreement was found with the results from OSO 7 in the overlapping energy range of 20 to 40 keV. The photon flux spectrum steepened at higher energies, but all the data above 10 keV could be represented by a single steep spcctrum with a power law exponent of about 2. Her X-1 is stated to be bright enough in hard x-rays for more refined experiments to be carried out at balloon altitudes. Detailed analysis for pulsar aspects is in progress. (UK)

• Research Organization: Tata Inst. of Fundamental Research, Bombay
• NSA Number: NSA-29-001171
• OSTI ID: 4433543
• Journal Information: Nature (London) Phys. Sci., v. 244, no. 134, pp. 59-60, Journal Name: Nature (London) Phys. Sci., v. 244, no. 134, pp. 59-60; ISSN NPSCA
• Country of Publication: United Kingdom
• Language: English

Related Subjects

*COSMIC X-RAY SOURCES-- X-RAY SPECTRA
BINARY STARS
HARD X RADIATION
KEV RANGE 10-100
N56300* --Physics (Astrophysics &amp; Cosmology)--Quasi-stellar
Radio &amp; X-Ray Sources
PULSARS