A Possible Isolated Neutron Star near the CrA Molecular Cloud

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Session 78 -- Pulsars and Neutron Stars
Display presentation, Wednesday, 11, 1995, 9:20am - 6:30pm

[78.13] A Possible Isolated Neutron Star near the CrA Molecular Cloud

F.M.Walter, S.J.Wolk (SUNY Stony Brook)

It is thought that there are some 10$^8$ isolated neutron stars in our galaxy. These should be bright soft X-ray/EUV sources, and were expected to make a significant contribution to the ROSAT PSPC and WFC source catalogs. To date they have not.

In a ROSAT PSPC survey of the Corona Australis molecular cloud, we discovered a bright (3~c~s$^{-1}$), soft (kT=60~eV) X-ray source. The source was also seen in the ROSAT all sky survey, two years prior to the pointed observation, with the same count rate and spectrum. The column of N$_H\sim$10$^{20}$cm$^{-2}$ suggests a distance comparable to the 120~pc to the CrA molecular cloud. There is no obvious optical counterpart; all the stars in the field brighter than V$\sim$19 are red. $\frac{F_x}{F_v}$ exceeds unity, and may exceed 2000. The observable parameters are comparable to those predicted by Blaes \& Madau (ApJ 403 , 690, 1993) for a neutron star accreting isotropically from the interstellar medium. The emitting area is 260~km$^2$ at a distance of 100~pc.

We will present arguments that this object is indeed an example of an isolated neutron star. If so, the expected UBV magnitudes are 25.7, 27.1, and 27.4, respectively. A recent ROSAT HRI position should significantly decrease the positional uncertainty and aid in the search for an optical counterpart.

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