The evolution of a jet ejection of the ultraluminous X-ray source Holmberg II X-1

Cseh, D. and Miller-Jones, J. C. A. and Jonker, P. G. and Grisé, F. and Paragi, Z. and Frey, Sándor (2015) The evolution of a jet ejection of the ultraluminous X-ray source Holmberg II X-1. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 452. pp. 24-31. ISSN 0035-8711

Preview

Text 1506.02988.pdf Available under License Creative Commons Attribution. Download (347kB) | Preview

Abstract

We present quasi-simultaneous, multi-epoch radio and X-ray measurements of Holm- berg II X-1 using the European VLBI Network (EVN), the Karl G. Jansky Very Large Array (VLA), and the Chandra and Swift X-ray telescopes. The X-ray data show apparently hard spectra with steady X-ray luminosities 4 months apart from each other. In the high-resolution EVN radio observations, we have detected an ex- tended milli-arcsecond scale source with unboosted radio emission. The source emits non-thermal, likely optically thin synchrotron emission and its morphology is consis- tent with a jet ejection. The 9-GHz VLA data show an arcsecond-scale triple structure of Holmberg II X-1 similar to that seen at lower frequencies. However, we find that the central ejection has faded by at least a factor of 7.3 over 1.5 years. We estimate the dynamical age of the ejection to be higher than 2.1 years. We show that such a rapid cooling can be explained with simple adiabatic expansion losses. These properties of Holmberg II X-1 imply that ULX radio bubbles may be inflated by ejecta instead of self-absorbed compact jets.

Actions (login required)

Edit Item