Accretion onto WD 2226-210, the central star of the Helix Nebula
The central star of the Helix Nebula, WD 2226$-$210 presents enigmatic hard X-ray emission and mid-IR excess. The latter has been attributed to a dusty disc or a cloud-like structure around WD 2226$-$210 formed from material of Kuiper Belt-like or comet-like objects in highly eccentric orbits. We pr...
| Authors: | , , , , , , |
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| Format: | article |
| Status: | Published version |
| Publication Date: | 2025 |
| Country: | España |
| Institution: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repository: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/380251 |
| Online Access: | http://hdl.handle.net/10261/380251 |
| Access Level: | Open access |
| Keyword: | Stars: evolution Stars: winds, outflows Planetary nebulae: general X-rays: individual: WD 2226−210 |
| Summary: | The central star of the Helix Nebula, WD 2226$-$210 presents enigmatic hard X-ray emission and mid-IR excess. The latter has been attributed to a dusty disc or a cloud-like structure around WD 2226$-$210 formed from material of Kuiper Belt-like or comet-like objects in highly eccentric orbits. We present here a detailed analysis of multi-epoch Chandra and XMM-Newton X-ray observations of WD 2226$-$210, comparing these to previous Einstein and ROSAT data. The luminosity of the hard X-ray component of WD 2226$-$210 has remained basically constant in the decade from 1992 to 2002, with very subtle evidence for variability in time-scales of hours. Under the assumption that the X-ray emission from WD 2226$-$210 is due to accretion of material, an accretion rate of $\dot{M}\approx 10^{-10}$ M$_\odot$ yr$^{-1}$ is estimated. The origin of the material accreted by WD 2226$-$210 is uncertain, and can be attributed to the disc-like structure around it or to a substellar donor companion. The accretion rate proposed for the continuous replenishment by bombardment of the mid-IR-emitting structure around WD 2226$-$210 cannot match that required by the X-ray emission. © 2024 The Author(s). |
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