Open Access Repository

Detection of compact radio emission from Circinus X-1 with the first Southern hemisphere e-VLBI experiment

Downloads

Downloads per month over past year

Phillips, CJ and Dickey, JM and Fender, RP and Tudose, V and Nicolson, GD and Deller, A and Amy, SW and Tingay, SJ and Tzioumis, AK and Reynolds, JE and Jauncey, DL and Stevens, JB and Ellingsen, SP (2007) Detection of compact radio emission from Circinus X-1 with the first Southern hemisphere e-VLBI experiment. Monthly Notices of the Royal Astronomical Society, 380 (1). L11-L14. ISSN 0035-8711

[img] PDF
4065.pdf | Request a copy
Full text restricted

Abstract

Circinus X-1 has recently returned to a state of strong radio flaring. Here we report on the first
VLBI observations, and detection, undertaken in the 25 years since the 1975–1985 period of
strong recurrent flaring activity.We detected Circinus X-1 with the first observations conducted
by a recently developed Southern hemisphere e-VLBI array, at both 1.6 and 8.4 GHz, over a
three-day period. At 1.6 GHz, the compact source has a total flux density of 11 mJy and a size of
60 ± 15 mas (Gaussian model full width at half maximum). At 8.4 GHz, the compact source is
less than 60 mas. The size variation with frequency is consistent with a broadened image
due to scattering in the turbulent, ionized interstellar medium of our Galaxy. However, these
size measurements appear inconsistent with the λ2.2 variation expected for strong interstellar
scattering and previous VLBI observations made at 2.3 GHz in the early 1980s. To explain this
apparent inconsistency, we suggest that Circinus X-1 supports a weak, non-varying component
of 35 mas extent (175 au at 5 kpc distance), corresponding to compact structure in the extended
radio nebula. No significant variation in the flux density at 1.6 GHz is evident between two
observations 24 h apart. No jet-like structures are evident on scales of tens of mas, simply a
scatter broadened source, presumably coincident with the suggested neutron star in the binary
system.

Item Type: Article
Keywords: instrumentation: interferometers • techniques: interferometric • radio continuum: stars • X-rays: stars • X-rays: individual: Circinus X
Journal or Publication Title: Monthly Notices of the Royal Astronomical Society
Publisher: Blackwell Publishing
Page Range: L11-L14
ISSN: 0035-8711
Identification Number - DOI: 10.1111/j.1745-3933.2007.00339.x
Additional Information:

The definitive version is available at www.blackwell-synergy.com

Date Deposited: 07 Apr 2008 14:20
Last Modified: 18 Nov 2014 03:34
Item Statistics: View statistics for this item

Actions (login required)

Item Control Page Item Control Page
TOP