SIMBAD references

2000MNRAS.319..826B - Mon. Not. R. Astron. Soc., 319, 826-836 (2000/December-2)

X-ray source populations in the region of the open clusters NGC 6633 and IC 4756.


Abstract (from CDS):

Using deep exposures (∼105s) with the ROSAT High Resolution Imager, we have performed flux-limited surveys for X-ray sources in the vicinity of the Hyades-age open stellar clusters NGC 6633 and IC 4756, detecting 31 and 13 sources, respectively. Our primary aim is to search for so-far unrecognized cluster members. We propose identifications or classifications (cluster member, field star, extragalactic field object) for the X-ray sources, based on published membership lists, and on X-ray:optical flux ratios and optical colour-magnitude diagrams.
Result. of simulating the expected X-ray-emitting source populations are compared with the ROSAT measurements and with the expected capabilities of the XMM mission. The simulations provide a novel method of comparing the activity levels of NGC 6633 and IC 4756 with that of the Hyades. The measurements and simulations confirm that cluster members are the major class of X-ray emitter in these fields at flux levels {formmu1} (0.1-2.4keV), contributing ∼40per cent of the total X-ray sources. We find six possible new members in NGC 6633 and four candidates in IC 4756; all require further observation to establish membership probability.

Abstract Copyright: 2000, Royal Astronomical Society

Journal keyword(s): surveys - stars: late-type - open clusters and associations: individual: NGC 6633 - open clusters and associations: individual: IC 4756 - X-rays: stars

Nomenclature: Table 4: [BPJ2000] NGC 6633 NN (Nos 1-32). Table 5: [BPJ2000] IC 4756 NN (Nos 1-13).

CDS comments: in ref list Heiles at al 1981ApJ.247L.73 instead of 73, Kopff 1943AN.274.69 instead of 93

Simbad objects: 50

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