Searching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+
Atmospheric mass loss is thought to induce the bimodality in the small planet population as we observe it today. Observationally, active mass loss can be traced by excess absorption in spectral lines of lighter species, such as the hydrogen Ly α line and the metastable helium triplet. We search for...
Saved in:
| Main Authors: | , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
|
| Series: | The Astronomical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-3881/ade1da |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1849239595665850368 |
|---|---|
| author | Ava Morrissey George Zhou Chelsea X. Huang Duncan Wright Neale Gibson Keighley E. Rockcliffe Elisabeth R. Newton James Kirk Daniel Bayliss |
| author_facet | Ava Morrissey George Zhou Chelsea X. Huang Duncan Wright Neale Gibson Keighley E. Rockcliffe Elisabeth R. Newton James Kirk Daniel Bayliss |
| author_sort | Ava Morrissey |
| collection | DOAJ |
| description | Atmospheric mass loss is thought to induce the bimodality in the small planet population as we observe it today. Observationally, active mass loss can be traced by excess absorption in spectral lines of lighter species, such as the hydrogen Ly α line and the metastable helium triplet. We search for helium escape from the young (120 Myr old) sub-Neptune (3 R _⊕ ) HIP94235b. We obtained two transit observations of HIP94235b using the CRyogenic InfraRed Echelle Spectrograph on the Very Large Telescope. We find no evidence for escaping helium across both visits, allowing us to place a mass loss rate upper limit of 10 ^11 g s ^−1 , based on 1D Parker wind models. Additionally, we search for molecular spectral features in the planet’s transmission spectrum, and cross correlate our observations with high-resolution template spectra for H _2 O, the dominating molecule in the Y band. We detect no significant absorption. We demonstrate that some atmosphere models at 10× solar metallicity would have been retrievable if present. Through the null detection of neutral hydrogen and helium escape, we conclude the atmosphere of HIP94235b likely lacks a large hydrogen-helium envelope. This is consistent with the expectation of small planet photoevaporation models, which suggest most planets lose their primordial hydrogen-helium envelopes within 100 Myr of evolution. |
| format | Article |
| id | doaj-art-94bcffd9378b44939404cbb8e05258c8 |
| institution | Kabale University |
| issn | 1538-3881 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astronomical Journal |
| spelling | doaj-art-94bcffd9378b44939404cbb8e05258c82025-08-20T04:00:54ZengIOP PublishingThe Astronomical Journal1538-38812025-01-01170316210.3847/1538-3881/ade1daSearching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+Ava Morrissey0https://orcid.org/0009-0000-3527-8860George Zhou1https://orcid.org/0000-0002-4891-3517Chelsea X. Huang2https://orcid.org/0000-0003-0918-7484Duncan Wright3https://orcid.org/0000-0001-7294-5386Neale Gibson4https://orcid.org/0000-0002-9308-2353Keighley E. Rockcliffe5https://orcid.org/0000-0003-1337-723XElisabeth R. Newton6https://orcid.org/0000-0003-4150-841XJames Kirk7https://orcid.org/0000-0002-4207-6615Daniel Bayliss8https://orcid.org/0000-0001-6023-1335University of Southern Queensland, Centre for Astrophysics , West Street, Toowoomba, QLD 4350, Australia ; ava.morrissey@unisq.edu.auUniversity of Southern Queensland, Centre for Astrophysics , West Street, Toowoomba, QLD 4350, Australia ; ava.morrissey@unisq.edu.auUniversity of Southern Queensland, Centre for Astrophysics , West Street, Toowoomba, QLD 4350, Australia ; ava.morrissey@unisq.edu.auUniversity of Southern Queensland, Centre for Astrophysics , West Street, Toowoomba, QLD 4350, Australia ; ava.morrissey@unisq.edu.auSchool of Physics, Trinity College Dublin, University of Dublin , Dublin 2, IrelandExoplanets and Stellar Astrophysics Laboratory , NASA Goddard Space Flight Center, Greenbelt, MD, USADepartment of Physics and Astronomy, Dartmouth College , Hanover, NH 03755, USADepartment of Physics, Imperial College London , Prince Consort Road, SW7 2AZ, London, UKDepartment of Physics, University of Warwick , Gibbet Hill Road, Coventry CV 4 7AL, UK; Centre for Exoplanets and Habitability, University of Warwick , Gibbet Hill Road, Coventry CV 4 7AL, UKAtmospheric mass loss is thought to induce the bimodality in the small planet population as we observe it today. Observationally, active mass loss can be traced by excess absorption in spectral lines of lighter species, such as the hydrogen Ly α line and the metastable helium triplet. We search for helium escape from the young (120 Myr old) sub-Neptune (3 R _⊕ ) HIP94235b. We obtained two transit observations of HIP94235b using the CRyogenic InfraRed Echelle Spectrograph on the Very Large Telescope. We find no evidence for escaping helium across both visits, allowing us to place a mass loss rate upper limit of 10 ^11 g s ^−1 , based on 1D Parker wind models. Additionally, we search for molecular spectral features in the planet’s transmission spectrum, and cross correlate our observations with high-resolution template spectra for H _2 O, the dominating molecule in the Y band. We detect no significant absorption. We demonstrate that some atmosphere models at 10× solar metallicity would have been retrievable if present. Through the null detection of neutral hydrogen and helium escape, we conclude the atmosphere of HIP94235b likely lacks a large hydrogen-helium envelope. This is consistent with the expectation of small planet photoevaporation models, which suggest most planets lose their primordial hydrogen-helium envelopes within 100 Myr of evolution.https://doi.org/10.3847/1538-3881/ade1daObservational astronomyExoplanet astronomyExoplanet atmospheresExoplanet atmospheric evolution |
| spellingShingle | Ava Morrissey George Zhou Chelsea X. Huang Duncan Wright Neale Gibson Keighley E. Rockcliffe Elisabeth R. Newton James Kirk Daniel Bayliss Searching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+ The Astronomical Journal Observational astronomy Exoplanet astronomy Exoplanet atmospheres Exoplanet atmospheric evolution |
| title | Searching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+ |
| title_full | Searching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+ |
| title_fullStr | Searching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+ |
| title_full_unstemmed | Searching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+ |
| title_short | Searching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+ |
| title_sort | searching for helium escape and a low density atmosphere around the 120 myr old sub neptune hip94235b using crires |
| topic | Observational astronomy Exoplanet astronomy Exoplanet atmospheres Exoplanet atmospheric evolution |
| url | https://doi.org/10.3847/1538-3881/ade1da |
| work_keys_str_mv | AT avamorrissey searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires AT georgezhou searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires AT chelseaxhuang searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires AT duncanwright searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires AT nealegibson searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires AT keighleyerockcliffe searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires AT elisabethrnewton searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires AT jameskirk searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires AT danielbayliss searchingforheliumescapeandalowdensityatmospherearoundthe120myroldsubneptunehip94235busingcrires |