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ATEL # 2956; L. Chomiuk (CfA/NRAO), M. Krauss, M. Rupen (NRAO), J. Sokoloski (Columbia), and the EVLA Nova Team
on 19 Oct 2010; 21:27 UT
Password Certification: Laura Chomiuk (firstname.lastname@example.org)
Subjects: Radio, Request for Observations, Nova
We are monitoring the recent nova V1723 Aql (IAUC # 9166 , 9167) with the Expanded Very Large Array (EVLA) at ~5, 6.75, and 32 GHz. Our first observations took place on Sept 25, two weeks after the start of the outburst (which we take to be Sept 11, 2010); we measure a flux density of 0.4 +/- 0.1 mJy at 32 GHz and a non-detection at 6.75 GHz (rms ~ 11 microJy/beam). Our most recent measurements were on Oct 14/15 with measured flux densities of 3.0 +/- 0.6 mJy at 33 GHz and 0.6 +/- 0.1 mJy at 5.25 GHz.
The nova is evolving rapidly, with the spectral index &alpha (S&nu &prop &nu&alpha) changing from 1.5 to 0.9 between Oct 6 and Oct 14/15. Standard models (e.g., Hjellming et al. 1979) interpret this as thermal bremsstrahlung emission from the nova shell, which gradually becomes optically thin as the source expands.
If we assume the source is spherical, uniformly expanding at 1500 km/s (IAUC # 9167 ), has an electron temperature of 10^4 K, and is optically thick at 32 GHz on Sept 25, the flux density for that frequency and date imply a distance of ~3.4 kpc. This is a fairly robust upper limit for a thermal source; lower opacity requires a closer source, as do highly elongated geometries for the nova shell.
We encourage continued optical and X-ray coverage of V1723 Aql. For more detail and the most up-to-date information on the radio emission from this source, see our EVLA nova monitoring web page.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
The EVLA Nova Project