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Radio non-detection of Aql X-1

ATel #2911; V. Tudose (ASTRON), Z. Paragi (JIVE), D. Altamirano (Amsterdam), J. C.A. Miller-Jones (ICRAR), M. Garrett (ASTRON), R. Fender (Southampton), A. Rushton (ESO), R. Spencer (Manchester), D. Maitra (Michigan)
on 7 Oct 2010; 18:47 UT
Credential Certification: Valeriu Tudose (vtudose@science.uva.nl)

Subjects: Radio, Binary, Neutron Star, Transient

Referred to by ATel #: 3686

The neutron star X-ray binary Aql X-1 is on the decaying phase of a major outburst that peaked at optical and X-ray bands in mid-September (ATEL #2850, #2871, #2891, #2902).

We observed the object at 5 GHz with the European VLBI Network (EVN) in the e-VLBI mode on 2010 October 4th between 18:20-22:09 UT. The participating stations were Cambridge, Effelsberg, Jodrell Bank (MkII), Hartebeesthoek, Medicina, Onsala, Torun, Westerbork and Yebes. We did not detect the target. The 3-sigma upper limit to the flux density was 105 microJy.

The RXTE/PCA X-ray observations showed that during the radio session the system was in a low-intensity soft X-ray state. Further radio observations are encouraged, as the radio emission is expected to increase during the transition to the hard X-ray state (Miller-Jones et al., 2010, ApJ 716, L109).

e-VLBI developments in Europe are supported by NEXPReS, an Integrated Infrastructure Initiative (I3), funded under the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement RI-261525. The European VLBI Network is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils.