2MASS J04435686+3723033 B: A Young Companion at the Substellar Boundary with Potential Membership in the $beta$ Pictoris Moving Group. (arXiv:2004.07250v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Phillips_C/0/1/0/all/0/1">Caprice Phillips</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bowler_B/0/1/0/all/0/1">Brendan Bowler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mace_G/0/1/0/all/0/1">Gregory Mace</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_M/0/1/0/all/0/1">Michael Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sokal_K/0/1/0/all/0/1">Kimberly Sokal</a>

We present a detailed characterization of 2MASS J04435750+3723031, a low-mass
companion orbiting the young M2 star, 2MASS J04435686+3723033, at 7.6
arcseconds (550 AU) with potential membership in the 23 Myr $beta$ Pictoris
moving group ($beta$PMG). Using near-infrared spectroscopy of the companion
from IRTF/SpeX we have found a spectral type of M6 $pm$ 1 and indications of
youth through age-sensitive absorption lines and a low surface gravity index
(VL-G). A young age is supported by H$alpha$ emission and lithium absorption
in the host. We re-evaluate the membership of this system and find that it is a
marginally consistent kinematic match to the $beta$PMG using $Gaia$ parallaxes
and new radial velocities for the host and companion. If this system does
belong to the $beta$PMG, it would be a kinematic outlier and the companion
would be over-luminous compared to other similar ultracool objects like PZ Tel
B; this would suggest 2M0443+3723 B could be a close brown dwarf binary
($approx$52+52 M$_mathrm{Jup}$ if equal-flux, compared with 99 $pm$ 5
M$_mathrm{Jup}$ if single), and would make it the sixth substellar companion
in this group. To test this hypothesis, we acquired NIR AO images with Keck
II/NIRC2, but they do not resolve the companion to be a binary down to the
diffraction limit of $sim$3 AU. If 2M0443+3723 AB does not belong to any
moving group then its age is more uncertain. In this case it is still young
($lesssim$30 Myr), and the implied mass of the companion would be between
$sim$30–110 M$_mathrm{Jup}$.

We present a detailed characterization of 2MASS J04435750+3723031, a low-mass
companion orbiting the young M2 star, 2MASS J04435686+3723033, at 7.6
arcseconds (550 AU) with potential membership in the 23 Myr $beta$ Pictoris
moving group ($beta$PMG). Using near-infrared spectroscopy of the companion
from IRTF/SpeX we have found a spectral type of M6 $pm$ 1 and indications of
youth through age-sensitive absorption lines and a low surface gravity index
(VL-G). A young age is supported by H$alpha$ emission and lithium absorption
in the host. We re-evaluate the membership of this system and find that it is a
marginally consistent kinematic match to the $beta$PMG using $Gaia$ parallaxes
and new radial velocities for the host and companion. If this system does
belong to the $beta$PMG, it would be a kinematic outlier and the companion
would be over-luminous compared to other similar ultracool objects like PZ Tel
B; this would suggest 2M0443+3723 B could be a close brown dwarf binary
($approx$52+52 M$_mathrm{Jup}$ if equal-flux, compared with 99 $pm$ 5
M$_mathrm{Jup}$ if single), and would make it the sixth substellar companion
in this group. To test this hypothesis, we acquired NIR AO images with Keck
II/NIRC2, but they do not resolve the companion to be a binary down to the
diffraction limit of $sim$3 AU. If 2M0443+3723 AB does not belong to any
moving group then its age is more uncertain. In this case it is still young
($lesssim$30 Myr), and the implied mass of the companion would be between
$sim$30–110 M$_mathrm{Jup}$.

http://arxiv.org/icons/sfx.gif