A Model-Independent Mass and Moderate Eccentricity for $beta$ Pic b. (arXiv:1812.11530v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Dupuy_T/0/1/0/all/0/1">Trent J. Dupuy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brandt_T/0/1/0/all/0/1">Timothy D. Brandt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kratter_K/0/1/0/all/0/1">Kaitlin M. Kratter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bowler_B/0/1/0/all/0/1">Brendan P. Bowler</a>
We use a cross-calibration of Hipparcos and Gaia DR2 astrometry for $beta$
Pic to measure the mass of the giant planet $beta$ Pic b $(13pm3$ $M_{rm
Jup})$ in a comprehensive joint orbit analysis that includes published relative
astrometry and radial velocities. Our mass uncertainty is somewhat higher than
previous work because our astrometry from the Hipparcos-Gaia Catalog of
Accelerations accounts for the error inflation and systematic terms that are
required to bring the two data sets onto a common astrometric reference frame,
and because we fit freely for the host-star mass $(1.84pm0.05$ $M_{odot})$.
This first model-independent mass for a directly imaged planet is inconsistent
with cold-start models given the age of the $beta$ Pic moving group $(22pm6$
Myr) but consistent with hot- and warm-start models, concordant with past work.
We find a higher eccentricity $(0.24pm0.06)$ for $beta$ Pic b compared to
previous orbital fits. If confirmed by future observations, this eccentricity
may help explain inner edge, scale height, and brightness asymmetry of $beta$
Pic’s disk. It could also potentially signal that $beta$ Pic b has migrated
inward to its current location, acquiring its eccentricity from interaction
with the 3:1 outer Lindblad resonance in the disk.
We use a cross-calibration of Hipparcos and Gaia DR2 astrometry for $beta$
Pic to measure the mass of the giant planet $beta$ Pic b $(13pm3$ $M_{rm
Jup})$ in a comprehensive joint orbit analysis that includes published relative
astrometry and radial velocities. Our mass uncertainty is somewhat higher than
previous work because our astrometry from the Hipparcos-Gaia Catalog of
Accelerations accounts for the error inflation and systematic terms that are
required to bring the two data sets onto a common astrometric reference frame,
and because we fit freely for the host-star mass $(1.84pm0.05$ $M_{odot})$.
This first model-independent mass for a directly imaged planet is inconsistent
with cold-start models given the age of the $beta$ Pic moving group $(22pm6$
Myr) but consistent with hot- and warm-start models, concordant with past work.
We find a higher eccentricity $(0.24pm0.06)$ for $beta$ Pic b compared to
previous orbital fits. If confirmed by future observations, this eccentricity
may help explain inner edge, scale height, and brightness asymmetry of $beta$
Pic’s disk. It could also potentially signal that $beta$ Pic b has migrated
inward to its current location, acquiring its eccentricity from interaction
with the 3:1 outer Lindblad resonance in the disk.
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