Abstract
We present the first retrieval analysis of a substellar subdwarf, SDSS J125637.13-022452.4 (SDSS J1256-0224), using the Brewster retrieval code base. We find SDSS J1256-0224 is best fit by a cloud-free model with an ion (neutral H, H-, and electron) abundance corresponding to ion [Fe/H]=-1.5. However, this model is indistinguishable from a cloud-free model with ion [Fe/H]=-2.0 and a cloud-free model with ion Fe/H]=-1.5 assuming a subsolar carbon-to-oxygen ratio. We are able to constrain abundances for water, FeH, and CrH, with an inability to constrain any carbon-bearing species likely due to the low-metallicity of SDSS J1256-0224. We also present an updated spectral energy distribution (SED) and semi-empirical fundamental parameters. Our retrieval- and SED-based fundamental parameters agree with the Baraffe low-metallicity evolutionary models. From examining our "rejected" models (those with $\Delta$BIC>45), we find that we are able to retrieve gas abundances consistent with those of our best-fitting model. We find the cloud in these poorer fitting "cloudy" models is either pushed to the bottom of the atmosphere or made optically thin.
Original language | English |
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Number of pages | 14 |
Journal | The Astrophysical Journal |
Volume | 923 |
Issue number | 1 |
DOIs | |
Publication status | Published - 8 Dec 2021 |
Keywords
- astro-ph.SR
- astro-ph.EP