The evolution of the X-ray emission of HH 2. Investigating heating and cooling processes
Abstract
Young stellar objects often drive powerful bipolar outflows, which evolve on timescales of a few years. An increasing number of these outflows has been detected in X-rays implying the existence of million degree plasma almost co-spatial with the lower temperature gas observed in the optical and near-infrared. The details of the heating and cooling processes of the X-ray emitting part of these so-called Herbig-Haro objects are still ambiguous, e.g., whether the cooling is dominated by expansion, radiation, or thermal conduction. We present a second epoch Chandra observation of the first X-ray detected Herbig-Haro object (HH 2) and derive the proper-motion of the X-ray emitting plasma and its cooling history. We argue that the most likely explanation for the constancy of the X-ray luminosity, the alignment with the optical emission and the proper-motion is that the cooling is dominated by radiative losses leading to cooling times exceeding a decade. We explain that a strong shock caused by fast material ramming into slower gas in front of it about ten years ago can explain the X-ray emission while being compatible with the available multi-wavelength data of HH 2.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2012
- DOI:
- 10.1051/0004-6361/201118605
- arXiv:
- arXiv:1205.3905
- Bibcode:
- 2012A&A...542A.123S
- Keywords:
-
- Herbig-Haro objects;
- ISM: jets and outflows;
- ISM: individual objects: HH 2;
- X-rays: ISM;
- stars: winds;
- outflows;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 5 pages with 4 figures