Randich, S. ; Singh, K. P. ; Simon, T. ; Drake, S. A. ; Schmitt, J. H. M. M. (1998) ROSAT HRI observations of the intermediate-age open cluster IC 4756 Astronomy & Astrophysics, 337 (2). pp. 372-378. ISSN 0004-6361
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Official URL: http://aa.springer.de/bibs/8337002/2300372/small.h...
Related URL: http://dx.doi.org/10.1088/0031-8949/5/4-5/012
Abstract
We have obtained an 88 kilosecond ROSAT HRI exposure of the intermediate-age open cluster IC 4756 with the purpose of detecting stars in the high luminosity tail (log LX ≥1029 erg s−1) of its X-ray luminosity distribution. However, only 1 cluster member (HSS 201) out of the 60 members inside the central high-sensitivity region of the HRI field of view (FOV) was detected. This star has spectral type A8, suggesting a close binary system with a low mass X-ray emitting companion. We compare the distribution of upper limits for F and G-type dwarfs in IC 4756 with the X-ray distribution functions of the similarly aged Hyades and Praesepe clusters. The results of this statistical analysis are inconclusive for G-type stars, but suggest that at least F-type stars in IC 4756 are not as X-ray luminous as their Hyades counterparts, thus indicating intrinsic differences between the two clusters. Finally, our data indicate a deficit of very active binaries with respect to both Hyades and Praesepe, and older open clusters.
Item Type: | Article |
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Source: | Copyright of this article belongs to EDP Sciences. |
Keywords: | Stars: Activity; X-rays: Stars; Open Clusters and Associations: Individual; IC 4756 |
ID Code: | 59000 |
Deposited On: | 03 Sep 2011 12:12 |
Last Modified: | 18 May 2016 09:42 |
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