Table · dataset · 2025
Radio flux variability in UCHII regions
Listed in IVOA Registry (Virtual Observatory)
Theoretical models of early accretion during the formation process of massive stars have predicted that HII regions exhibit radio variability on timescales of decades.
Description
However, large-scale searches for such temporal variations with sufficient sensitivity have not yet been carried out. We aim to identify HII regions with variable radio wavelength fluxes and to investigate the properties of the identified objects, especially those with the highest level of variability.
We compared the peak flux densities of 86 ultracompact HII (UCHII) regions measured by the GLOSTAR and CORNISH surveys and identified variables that show flux variations higher than 30% over ~8yr timespan between these surveys. We found a sample of 38 variable UCHII regions, which is the largest sample identified to date. The overall occurrence of variability is 44+/-5%, suggesting that variation in UCHII regions is significantly more common than prediction.
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The variable UCHII regions are found to be younger than non-variable UCHII regions, with over 50% of them meeting the size criterion of hypercompact (HC) HII regions. We studied the 7 UCHII regions (the "Top7") that show the highest variability with variations >100%. The Top7 variable UCHII regions are optically thick at 4-8GHz and compact, suggesting they are in a very early evolutionary stage of HCHII or UCHII regions.
There is a significant correlation between variability and the spectral index of the radio emission. No dependence is observed between the variations and the properties of the sources' natal clumps traced by submillimeter continuum emission from dust, although variable HII regions are found in clumps at an earlier evolutionary stage.
Links
Where it is published
- Reference page cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/694/A26 ↗
landing page · from IVOA Registry
Documentation and papers
- ADS 2025A&A...694A..26Y ui.adsabs.harvard.edu/abs/2025A%26A...694A..26Y ↗
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/694/a26 ↗
catalogue entry · from IVOA Registry
Topics
- Stated by source
- Radio
- From keywords
- Astronomy & Astrophysics
- Inferred from text
- Astronomical sciences 71%
Provenance · 1 source records, 9 field assertions
| Source | Key | Last seen | Raw |
|---|---|---|---|
| IVOA Registry (Virtual Observatory) | ivo://cds.vizier/j/a+a/694/a26 | 15 d ago | JSON v1 |
| Field | Assertion | Extractor | Evidence |
|---|---|---|---|
| access_level | source · IVOA Registry | connector:ivoa_registry@1.0.0 | |
| concepts[field].anzsrc:group:5101 | enrichment · IVOA Registry | taxonomy-embedding@1.1.0 | title+keywords+description (71%) |
| concepts[field].local:field:astronomy | mapping · IVOA Registry | connector:ivoa_registry@1.0.0 | |
| concepts[modality].ivoa_waveband:radio | 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 |