Table · dataset · 2026
MEGARA obs. of Ha & FeI during HD 189733b transit
Listed in IVOA Registry (Virtual Observatory)
Transmission spectroscopy allows us to detect molecules in planetary atmospheres, but is subject to contamination from inhomogeneities on the stellar surface.
Description
Quantifying the extent of this contamination is essential for accurate measurements of atmospheric composition, as stellar activity can manifest as false atmospheric signals in planetary transmission spectra. We present a study of hot Jupiter HD 189733b, which has over 50hr of JWST observations scheduled or taken, to measure the activity level of the host star at the current epoch.
We utilize high-resolution spectra of the H{alpha} line from the MEGARA spectrograph on the 10m GTC to examine the activity level of HD 189733 during a transit. We measure H{alpha} becoming shallower midtransit by an H{alpha} index of {delta}=0.00156+/-0.00026, which suggests that HD 189733b crosses an active region as it transits. We posit this deviation is likely caused by a spot along the transit chord with an approximate radius of R_spot_=3.47+/-0.30R_{Earth}_ becoming occulted during transit.
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Including an approximation for unocculted spots, we estimate that this spot could result in transit depth variations of ~17ppm at the 4.3um CO2 feature. Since this is comparable to JWST NIRCam Grism mode's noise floor of ~20ppm, it could bias atmospheric studies by altering the inferred depths of the planet's features. Thus, we suggest ground-based high-resolution monitoring of activity indicator species concurrently taken with JWST data when feasible to disentangle stellar activity signals from planetary atmospheric signals during transit.
Links
Where it is published
- Reference page cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/170/346 ↗
landing page · from IVOA Registry
Documentation and papers
- ADS 2025AJ....170..346E ui.adsabs.harvard.edu/abs/2025AJ....170..346E ↗
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/aj/170/346 ↗
catalogue entry · from IVOA Registry
Topics
- Stated by source
- Optical
- From keywords
- Astronomy & Astrophysics
- Inferred from text
- Astronomical sciences 68%
Provenance · 1 source records, 9 field assertions
| Source | Key | Last seen | Raw |
|---|---|---|---|
| IVOA Registry (Virtual Observatory) | ivo://cds.vizier/j/aj/170/346 | 6 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 (68%) |
| concepts[field].local:field:astronomy | mapping · IVOA Registry | connector:ivoa_registry@1.0.0 | |
| concepts[modality].ivoa_waveband:optical | 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 |