SIMBAD references

1998AJ....116.1301D - Astron. J., 116, 1301-1307 (1998/September-0)

A search for the optical counterpart of the luminous X-ray source in NGC 6652.


Abstract (from CDS):

We examine images of the field of X1832-330, the luminous (LX ∼ 1036 ergs.s–1) X-ray burst source near the center of the globular cluster NGC 6652, in order to identify the optical counterpart for further study. U and B ground-based images allow us to set a limit MB0 ≳ 3.5 for the counterpart at the time of those observations, provided that the color is (U - B)0 ∼ -1, similar to the sources known in other clusters. Archival Hubble Space Telescope observations survey most, but not all, of the 1 σ X-ray error circle and allow us to set limits MB0 > 5.9 and MB0 > 5.2 in the Wide Field Planetary Camera 1 (WF/PC-1) and Wide Field Planetary Camera 2 (WFPC2) regions, respectively.

In the WF/PC-1 images we do weakly detect a faint object with UV excess, but it is located 11".7 from the ROSAT X-ray position. This considerable (2.3 σ) discrepancy in position suggests that this candidate be treated with caution, but it remains the only reasonable one advanced thus far. We measure for this star m439 = 20.2±0.2 and m336 - m439 = -0.5±0.2 and estimate MB0 = 5.5 and (U - B)0 = -0.9, similar to other known optical counterparts. If this candidate is not the identification, our limits imply that the true counterpart, not yet identified, is probably the optically faintest cluster source yet known or, alternatively, that it did not show significant UV excess at the time of these observations. Finally, we assess the outlook for the identification of the remaining luminous globular cluster X-ray sources.

Abstract Copyright:

Journal keyword(s): Galaxy: Globular Clusters: Individual: NGC Number: NGC 6652 - Stars: Neutron - Ultraviolet Emission - X-Rays

Nomenclature: Fig.4: Cl* NGC 6652 DMA 49 N=1 among about 150.

CDS comments: X 1832-330 = RX J183544.0-325929

Simbad objects: 19

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