MUSE spectroscopy of the ULX NGC 1313 X-1: A shock-ionised bubble, an X-ray photoionised nebula, and two supernova remnants
Abstract
Context. The presence of large ionised gaseous nebulae found around some ultraluminous X-ray sources (ULXs) provides the means to assess the mechanical and radiative feedback of the central source, and hence constrain the efficiency and impact on the surroundings of the super-Eddington regime powering most of these sources. NGC 1313 X-1 is an archetypal ULX, reported to be surrounded by abnormally high [O I]λ6300/Hα > 0.1 ratios, and for which high-resolution spectroscopy in X-rays has hinted at the presence of powerful outflows.
Aims: We report observations taken with the integral field unit Multi-Unit Spectroscopic Explorer (MUSE) mounted at the Very Large Telescope of NGC 1313 X-1 in order to confirm the presence of a nebula inflated by the winds, investigate its main sources of ionisation and estimate the mechanical output of the source.
Methods: We investigated the morphology, kinematics, and sources of ionisation of the bubble through the study of the main nebular lines. We compared the main line ratios with spatially resolved Baldwin-Phillips-Terlevich diagrams and with the prediction from radiative shock libraries, which allows us to differentiate regions excited by shocks from those excited by extreme ultraviolet and X-ray radiation.
Results: We detect a bubble of 452 × 266 pc in size, roughly centred around the ULX, which shows clear evidence of shock ionisation in the outer edges. We estimate shock velocities to be in the ≈160 − 180 km s−1 range based on the line ratios. This suggests that an average and continuous outflow power of ∼(2 − 4.5)×1040 erg s−1 over a timescale of (4.5 − 7.8)×105 yr is required to inflate the bubble. In the interior of the bubble and closer to the ULX we detect an extended (∼140 pc) X-ray ionised region. Additionally, we detect two supernova remnants coincidentally close to the ULX bubble of which we also report age and explosion energy estimates.
Conclusions: The elongated morphology and the kinematics of the bubble strongly suggest that the bubble is being inflated by winds and/or jets emanating from the central source, supporting the presence of winds found through X-ray spectroscopy. The estimated mechanical power is comparable to or higher than the X-ray luminosity of the source, which provides additional evidence in support of NGC 1313 X-1 harbouring a super-Eddington accretor.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- October 2022
- DOI:
- 10.1051/0004-6361/202142229
- arXiv:
- arXiv:2201.09333
- Bibcode:
- 2022A&A...666A.100G
- Keywords:
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- instrumentation: spectrographs;
- stars: black holes;
- ISM: jets and outflows;
- stars: neutron;
- X-rays: binaries;
- accretion;
- accretion disks;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 22 pages, 20 Figures, 5 Tables. Accepted for publication to A&