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Radio upper limits for the accreting millisecond X-ray pulsar IGR J17511-3057

ATel #2232; J. C. A. Miller-Jones (NRAO, Charlottesville), D. M. Russell (University of Amsterdam), S. Migliari (ESAC, Spain)
on 7 Oct 2009; 20:25 UT
Credential Certification: David M. Russell (D.M.Russell@uva.nl)

Subjects: Radio, Binary, Neutron Star, Transient, Pulsar

We report on recent radio observations of the newly-detected accreting millisecond X-ray pulsar, IGR J17511-3057 (ATels #2196, #2197, #2198, #2199, #2215, #2216, #2220, #2221). We used the Very Large Array (VLA) to observe the source under observing program AM971. The array was in its relatively compact 'C' and 'DNC' configurations, and the observations were made at 8.46 GHz. In no case was the source significantly detected. The derived upper limits were:

Date MJD 3-sigma upper limit (mJy)
2009 Sep. 16 55090.14 0.16
2009 Sep. 18 55092.13 0.18
2009 Sep. 25 55099.13 0.17

After stacking the data from all three observations, the source was still not significantly detected, to a 3-sigma upper limit of 0.10 mJy.

Accreting millisecond X-ray pulsars detected at radio frequencies have previously been observed with peak flux densities in the range 0.8 - 1.1 mJy (ATel #355, Gaensler et al. 1999, ApJ, 522, L117) for sources at distances of less than ~ 3 kpc. The distance to IGR J17511-3057 is currently unknown, but if it lies at ~ 5 kpc or closer, its radio luminosity is likely to be intrinsically fainter than other known accreting millisecond X-ray pulsars. Alternatively, if the peak radio luminosity of IGR J17511-3057 was similar to the other known accreting millisecond X-ray pulsars, our upper limit is consistent with a source at the distance of the Galactic Center.