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e-EVN observations of Aql X-1 in outburst

ATel #2000; V. Tudose (ASTRON), Z. Paragi (JIVE), P. Soleri, D. M. Russell, D. Maitra (UvA), F. Lewis (LCOGTN/Open University), R. P. Fender (SOTON), M. A. Garrett (ASTRON), R. E. Spencer, A. Rushton (JBO)
on 1 Apr 2009; 09:14 UT
Credential Certification: Valeriu Tudose (vtudose@science.uva.nl)

Subjects: Radio, Binary, Neutron Star, Transient

Referred to by ATel #: 2317

The neutron star X-ray binary Aql X-1 shows quasi-periodic outbursts about once a year. These active states are relatively well covered in optical/infrared and X-ray domains. In contrast, at radio wavelengths the observations are very scarce (IAUC # 5112 ; ATEL #286; ATEL #491).

Following the reports of a new outburst of the object (ATEL #1970; ATEL #1977), we observed Aql X-1 on March 25th, 2009 between 03:00-10:00 UT at 5 GHz with the European VLBI Network (EVN) using the e-VLBI technique. The radio telescopes participating in the experiment were: Effelsberg, Medicina, Onsala 25m, Torun, Westerbork, Jodrell Bank MkII and Knockin. Due to severe weather conditions or technical problems, some of the effective observing time was lost.

We did not detect the target. The upper limit to the flux density was 188 microJy (4 sigma).

Together with an unrelated project scheduled during the same observing session, these are the first experiments with full 1024 Mbps e-VLBI transfer, from 4 telescopes (Effelsberg, Onsala, Torun and Westerbork).

Quasi-simultaneous with the radio run, we observed Aql X-1 at optical/infrared wavelengths (Faulkes, Swift) and in the X-ray band (Swift, RXTE).

e-VLBI is a technique in which signals from widely separated radio telescopes are directly streamed to the central data processor (correlator) in real-time. The data are then immediately made available to the astronomers for further data analysis. For information about e-EVN observing opportunities, please see the EVN e-VLBI web pages. In case of further questions, please e-mail to support(at)expres-eu.org

e-VLBI developments in Europe are supported by the EC DG-INFSO funded Communication Network Developments project 'EXPReS', Contract No. 02662. The European VLBI Network is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils.