Beta Pictoris

MIRI MRS Observations Of Beta Pictoris I. The Inner Dust, The Planet, And The Gas

By Keith Cowing
Status Report
January 31, 2024
Filed under , , , , , , ,
MIRI MRS Observations Of Beta Pictoris I. The Inner Dust, The Planet, And The Gas
Binned 5.2 µm slice of the PSF subtracted spectral cube showing the extended emission from hot dust. We apply an image normalization where vmin = −200 MJy/sr and vmax = 800 MJy/sr to emphasize emission from a spatially extended disk. The purple line shows a 5σ contour of the dust emission, the red circle shows the angular resolution of Spitzer at 5 µm (assuming it is diffraction limited) and the black circle shows the extraction aperture used for the MRS. The red cross shows the location of the central star. — astro-ph.EP

We present JWST MIRI Medium Resolution Spectrograph (MRS) observations of the β Pictoris system. We detect an infrared excess from the central unresolved point source from 5 to 7.5 μm which is indicative of dust within the inner ∼7 au of the system.

We perform PSF subtraction on the MRS data cubes and detect a spatially resolved dust population emitting at 5 μm. This spatially resolved hot dust population is best explained if the dust grains are in the small grain limit (2πa≪λ). The combination of unresolved and resolved dust at 5 μm could suggest that dust grains are being produced in the inner few au of the system and are then radiatively driven outwards, where the particles could accrete onto the known planets in the system β Pic b and c.

We also report the detection of an emission line at 6.986 μm that we attribute to be [Ar II]. We find that the [Ar II] emission is spatially resolved with JWST and appears to be aligned with the dust disk. Through PSF subtraction techniques, we detect β Pic b at the 5σ level in our MRS data cubes and present the first mid-IR spectrum of the planet from 5 to 7 μm.

The planet’s spectrum is consistent with having absorption from water vapor between 5 and 6.5 μm. We perform atmosphere model grid fitting on spectra and photometry of β Pic b and find that the planet’s atmosphere likely has a sub-stellar C/O ratio.

Kadin Worthen, Christine H. Chen, David R. Law, Cicero X. Lu, Kielan Hoch, Yiwei Chai, G.C. Sloan, B. A. Sargent, Jens Kammerer, Dean C. Hines, Isabel Rebollido, William O. Balmer, Marshall D. Perrin, Dan M. Watson, Laurent Pueyo, Julien H. Girard, Carey M. Lisse, Christopher C. Stark

Comments: Accepted for Publication in ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2401.16361 [astro-ph.EP] (or arXiv:2401.16361v1 [astro-ph.EP] for this version)
Submission history
From: Kadin Worthen
[v1] Mon, 29 Jan 2024 18:01:49 UTC (6,275 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻