Abstract
X-RAY heating of matter accreting on to a compact object can create unstable flows leading to irregular X-ray emission1–4. Previous discussions of this instability have concentrated on the case of spherically symmetrical infall onto a stationary object. The rise-time of X-ray variations is then related to the free-fall time-scale from the choking or accretion radius, whichever is relevant. Phenomena due to the presence of a magnetosphere4 may, however, reduce this estimate. It is not clear that bursts with duty cycles as short as 10−3 can arise from the heatine instability. Such bursts are observed, and here I investigate the effect of the motion of a compact object through a relatively dense medium. The passage of the compact object through a denser shell, which builds up outside the X ray-heated gas, produces a short burst of X rays. This creates yet another hot region leading to the repetition of bursts on a crossing time. Such behaviour may be relevant to the weak bursts possibly associated with the Cómetary Globule NGC 5367 (ref. 5), and the much shorter timescale luminous X-ray bursts6, some of which are associated with globular clusters.
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References
Shvartsman, V. F. Soviet Astro. -AJ 14, 662–668 (1971).
Buff, J. & McCray, R. Astrophys. J. 189, 147–155 (1974).
Ostriker, J. P., McCray, R., Weaver, R. & Yahil, A. Astrophys. J. Lett. 208, L61–L65 (1976).
Lamb, F. K., Fabian, A. C., Pringle, J. E. & Lamb, D. Q. Astrophys. J. (in the press).
Cooke, B. A. Nature 261, 564–566 (1976).
Lewin, W. H. G. 8th Texas Symp., N. Y. Acad. Sci. (in the press).
Van Till, H., Loren, R. & Davis, J. Astrophys. J. 198, 235–239 (1975).
Cruddace, R., Paresce, F., Bowyer, S. & Lampton, M. Astrophys. J. 187, 497–504 (1974).
Slutz, S. Astrophys. J. 210, 750–756 (1976).
Schwarz, J. Astrophys. J. 182, 449–475 (1973).
Kaluzienski, L. J., Holt, S. S., Boldt, E. A. & Serlemitsos, P. J. Nature 265, 606–607 (1977).
Jones, C., Forman, W., Tananbaum, H. & Turner, M. J. L. Astrophys. J. Lett. 210, L9 (1976).
Fabian, A. C., Pringle, J. E. & Rees, M. J. Mon. Not. R. astr. Soc. 1975, 43–60 (1976).
Clark, G. I. et al. Mon. Not. R. astr. Soc. 179, 651–658 (1977).
Bahcall, N. A., Lasker, B. M. & Wamsteker, W. Astrophys. J. Lett. 213, L105–L107 (1977).
Leroy, J. L., Aurière, M. & Laques, P. Astr. Astrophys. 53, 227–230 (1976).
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FABIAN, A. X-ray bursts from dense clouds. Nature 268, 607–608 (1977). https://doi.org/10.1038/268607a0
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DOI: https://doi.org/10.1038/268607a0
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