Variable Radio Emission from Nova V5588 Sgr
ATel #3539; M. I. Krauss (NRAO), L. Chomiuk (CfA/NRAO), J. L. Sokoloski (Columbia U.), M. P. Rupen, A. J. Mioduszewski, N. Roy (NRAO), T. J. O'Brien (U. of Manchester), M. F. Bode (Liverpool John Moores U.), S. P. S. Eyres (U. of Central Lancashire)
on 9 Aug 2011; 20:47 UT
Credential Certification: Miriam I. Krauss (miriam@space.mit.edu)
The EVLA Nova Team reports additional radio flux measurements of the classical nova V5588 Sgr (IAUC # 9203 , CBET #2707) which indicate significant variability. Observations taken 66 days after the initial discovery of this nova yield non-detections at 5.9 and 33.1 GHz; the derived upper limits are significantly lower than our previously reported detections on day 48 (ATel #3397). On day 79, we obtained an observation at 33.1 GHz which again provided a detection. A final observation at 5.9 GHz on day 121 yielded a non-detection. Flux values and 3-sigma upper limits are presented in the table below (this table also includes values previously reported in ATels #3319 and #3397).
Comparing the 3-sigma upper limit from the 33.1 GHz observation on day 66 with the flux value at 33.1 GHz on day 79 implies that the flux increased approximately as t10. This is an extremely fast rise, which is not possible to explain in the framework of the simple model for novae of radio emission from an expanding isothermal sphere. The observed radio variability could be related to the multiple peaks in the optical light curve (see the AAVSO Light Curve Generator), perhaps related to discrete ejection episodes and associated shocks. The radio detections occur shortly before the third and fourth optical peaks.
The non-detections can be taken as upper limits to the thermal flux from the nova ejecta; these indicate that V5588 Sgr is quite distant (> 9 kpc) and likely associated with the Galactic center. Because of its distance, we are no longer monitoring this object with the EVLA.
| Date | Day | Freq | Flux Density |
| (UT) | | (GHz) | microJy |
| April 21.5 | 25 | 5.9 | < 24 |
| April 30.3 | 33 | 32.0 | < 150 |
| May 1.3 | 34 | 5.9 | < 22 |
| May 14.5 | 48 | 33.1 | 394 +/- 55 |
| May 15.4 | 49 | 5.0 | 49.3 +/- 9.1 |
| May 15.4 | 49 | 6.8 | 69.0 +/- 7.5 |
| June 2.2 | 66 | 5.9 | < 25.2 |
| June 2.2 | 66 | 32 | < 129 |
| June 15.4 | 80 | 5.9 | 841 +/- 24 |
| July 27.1 | 121 | 5.9 | < 25.5 |
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We are grateful to the EVLA scheduling and commissioning teams.
EVLA Nova Collaboration Website
