Interpretation of the 115 Day Periodic Modulation in the X-ray Flux of NGC 5408 X-1
Abstract
We comment on the recent observation of a 115 day modulation in the X-ray flux of the ultraluminous X-ray source (ULX) NGC 5408 X-1, and in particular, the interpretation of this modulation as the orbital period. We suggest that this modulation may instead be due to a precessing jet, and is thus superorbital in nature. Comparing the properties of this ULX with those of the prototypical micro-quasar SS 433, we argue that NGC 5408 X-1 is very similar to SS 433: a hyper-accreting stellar-mass black hole in a shorter-period binary. If the analogy holds, the 115 day modulation is best explained by the still poorly understood physics of inner-disk/jet precession and a longer observing baseline would be able to reveal an intrinsic phase jitter that is associated with such a precession.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2010
- DOI:
- 10.1088/0004-637X/725/2/2480
- arXiv:
- arXiv:1010.5247
- Bibcode:
- 2010ApJ...725.2480F
- Keywords:
-
- accretion;
- accretion disks;
- black hole physics;
- galaxies: individual: NGC 5408;
- X-rays: binaries;
- X-rays: individual: ULXs;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- 5 pages, 1 figure, Accepted for publication in ApJ