Table · dataset · 2026
Ultraviolet spectroscopy of MWC 656
Listed in IVOA Registry (Virtual Observatory)
The Galactic Be star binary MWC 656 was long considered the only known Be star +black hole (BH) system, making it a critical benchmark for models of massive binary evolution and for the expected X-ray emission of Be+BH binaries.
Description
However, recent dynamical measurements cast doubt on the presence of a BH companion. We present new multi-epoch ultraviolet spectroscopy from the Hubble Space Telescope, combined with high-resolution optical spectra, to reassess the nature of the companion.
The far-ultraviolet spectra reveal high-ionisation features -- including prominent NV and HeII lines -- which are absent in the spectra of normal Be stars and are indicative of a hot, luminous companion. Spectral modelling shows that these features cannot originate from the Be star or from an accretion disc around a compact object. Instead, we find that the data are best explained by a hot (T_eff_~85kK), compact, hydrogen-deficient star with strong wind signatures, consistent with an intermediate-mass stripped star.
Read the rest (2 more)
Our revised orbital solution and composite spectroscopic modelling yield a companion mass of M_2_=1.48^+0.55^_-0.46_M_{sun}_, definitively ruling out a BH and disfavouring a white dwarf. MWC 656 thus joins the growing class of Be+stripped star binaries. The system's unusual properties -- including a high companion temperature and wind strength -- extend the known parameter space of such binaries.
The continued absence of confirmed OBe+BH binaries in the Galaxy highlights a growing tension with population synthesis models.
Links
Where it is published
- Reference page cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/708/A187 ↗
landing page · from IVOA Registry
Documentation and papers
- ADS 2026A&A...708A.187M ui.adsabs.harvard.edu/abs/2026A%26A...708A.187M ↗
publication · from IVOA Registry
Catalogue records · 2
- VOResource record dc.g-vo.org/oai.xml?verb=GetRecord&metadataPrefix=ivo_vor&identifier=ivo%3… ↗
metadata API · from IVOA Registry
- Registry record (GAVO) dc.g-vo.org/I/cds.vizier/j/a%2Ba/708/a187 ↗
catalogue entry · from IVOA Registry
Topics
- Stated by source
- Uv
- From keywords
- Astronomy & Astrophysics
Provenance · 1 source records, 8 field assertions
| Source | Key | Last seen | Raw |
|---|---|---|---|
| IVOA Registry (Virtual Observatory) | ivo://cds.vizier/j/a+a/708/a187 | 14 d ago | JSON v1 |
| Field | Assertion | Extractor | Evidence |
|---|---|---|---|
| access_level | source · IVOA Registry | connector:ivoa_registry@1.0.0 | |
| concepts[field].local:field:astronomy | mapping · IVOA Registry | connector:ivoa_registry@1.0.0 | |
| concepts[modality].ivoa_waveband:uv | source · IVOA Registry | connector:ivoa_registry@1.0.0 | |
| description | source · IVOA Registry | connector:ivoa_registry@1.0.0 | rr.resource.res_description |
| license_text | source · IVOA Registry | connector:ivoa_registry@1.0.0 | |
| publication_date | source · IVOA Registry | connector:ivoa_registry@1.0.0 | |
| title | source · IVOA Registry | connector:ivoa_registry@1.0.0 | rr.resource.res_title |
| updated_date | source · IVOA Registry | connector:ivoa_registry@1.0.0 |