ULTRAVIOLET-EXCESS SELECTION OF THE COUNTERPART TO A GLOBULAR-CLUSTER X-RAY BURSTER - HUBBLE-SPACE-TELESCOPE IMAGES OF THE CORE OF NGC-6712

被引:24
作者
ANDERSON, SF [1 ]
MARGON, B [1 ]
DEUTSCH, EW [1 ]
DOWNES, RA [1 ]
机构
[1] SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218
关键词
D O I
10.1086/116702
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Using the Planetary Camera on the Hubble Space Telescope, we have obtained high spatial resolution, multicolor images and photometry of the core of the globular cluster NGC 6712. A comparison of our blue and ultraviolet images unambiguously reveals a faint (B almost-equal-to 21), UV-excess object, ''star S,'' within the Einstein error box for the bursting x-ray source X1850-086. The unusual color of star S is immediately apparent even in a cursory visual comparison of the images, and is more quantitatively (U-B approximately -1) confirmed via photometry. A variety of different candidate optical counterparts to the x-ray source have previously been suggested from ground-based work, but our images indicate that star S is almost certainly the only viable candidate brighter than U almost-equal-to 21. Compared with the mean values for low mass x-ray binaries in the field, star S has a typical (U-B) color, and a moderate-to-high x-ray-to-optical luminosity ratio, but its luminosity (M(B) almost-equal-to 5) is approximately 4 mag fainter than average.
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页码:1049 / 1054
页数:6
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