TOI-3757 b: A low density gas giant orbiting a solar-metallicity M dwarf. (arXiv:2203.07178v3 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Kanodia_S/0/1/0/all/0/1">Shubham Kanodia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Libby_Roberts_J/0/1/0/all/0/1">Jessica Libby-Roberts</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Canas_C/0/1/0/all/0/1">Caleb I. Canas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ninan_J/0/1/0/all/0/1">Joe P. Ninan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mahadevan_S/0/1/0/all/0/1">Suvrath Mahadevan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stefansson_G/0/1/0/all/0/1">Gudmundur Stefansson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lin_A/0/1/0/all/0/1">Andrea S.J. Lin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jones_S/0/1/0/all/0/1">Sinclaire Jones</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Monson_A/0/1/0/all/0/1">Andrew Monson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Parker_B/0/1/0/all/0/1">Brock A. Parker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kobulnicky_H/0/1/0/all/0/1">Henry A. Kobulnicky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Swaby_T/0/1/0/all/0/1">Tera N. Swaby</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Powers_L/0/1/0/all/0/1">Luke Powers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beard_C/0/1/0/all/0/1">Corey Beard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bender_C/0/1/0/all/0/1">Chad F. Bender</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Blake_C/0/1/0/all/0/1">Cullen H. Blake</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cochran_W/0/1/0/all/0/1">William D. Cochran</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dong_J/0/1/0/all/0/1">Jiayin Dong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Diddams_S/0/1/0/all/0/1">Scott A. Diddams</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fredrick_C/0/1/0/all/0/1">Connor Fredrick</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gupta_A/0/1/0/all/0/1">Arvind F. Gupta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Halverson_S/0/1/0/all/0/1">Samuel Halverson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hearty_F/0/1/0/all/0/1">Fred Hearty</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Logsdon_S/0/1/0/all/0/1">Sarah E. Logsdon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Metcalf_A/0/1/0/all/0/1">Andrew J. Metcalf</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McElwain_M/0/1/0/all/0/1">Michael W. McElwain</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morley_C/0/1/0/all/0/1">Caroline Morley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rajagopal_J/0/1/0/all/0/1">Jayadev Rajagopal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ramsey_L/0/1/0/all/0/1">Lawrence W. Ramsey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Robertson_P/0/1/0/all/0/1">Paul Robertson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Roy_A/0/1/0/all/0/1">Arpita Roy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schwab_C/0/1/0/all/0/1">Christian Schwab</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Terrien_R/0/1/0/all/0/1">Ryan C. Terrien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wisniewski_J/0/1/0/all/0/1">John Wisniewski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wright_J/0/1/0/all/0/1">Jason T. Wright</a>

We present the discovery of a new Jovian-sized planet, TOI-3757 b, the lowest
density planet orbiting an M dwarf (M0V). It orbits a solar-metallicity M dwarf
discovered using TESS photometry and confirmed with precise radial velocities
(RV) from HPF and NEID. With a planetary radius of $12.0^{+0.4}_{-0.5}$
$R_{oplus}$ and mass of $85.3^{+8.8}_{-8.7}$ $M_{oplus}$, not only does this
object add to the small sample of gas giants ($sim 10$) around M dwarfs, but
also, its low density ($rho =$ $0.27^{+0.05}_{-0.04}$ $textrm{g~cm}^{-3}$)
provides an opportunity to test theories of planet formation. We present two
hypotheses to explain its low density; first, we posit that the low metallicity
of its stellar host ($sim$ 0.3 dex lower than the median metallicity of M
dwarfs hosting gas giants) could have played a role in the delayed formation of
a solid core massive enough to initiate runaway accretion. Second, using the
eccentricity estimate of $0.14 pm 0.06$ we determine it is also plausible for
tidal heating to at least partially be responsible for inflating the radius of
TOI-3757b b. The low density and large scale height of TOI-3757 b makes it an
excellent target for transmission spectroscopy studies of atmospheric escape
and composition (TSM $sim$ 190). We use HPF to perform transmission
spectroscopy of TOI-3757 b using the helium 10830 AA~ line. Doing this, we
place an upper limit of 6.9 % (with 90% confidence) on the maximum depth of
the absorption from the metastable transition of He at $sim$ 10830 AA, which
can help constraint the atmospheric mass loss rate in this energy limited
regime.

We present the discovery of a new Jovian-sized planet, TOI-3757 b, the lowest
density planet orbiting an M dwarf (M0V). It orbits a solar-metallicity M dwarf
discovered using TESS photometry and confirmed with precise radial velocities
(RV) from HPF and NEID. With a planetary radius of $12.0^{+0.4}_{-0.5}$
$R_{oplus}$ and mass of $85.3^{+8.8}_{-8.7}$ $M_{oplus}$, not only does this
object add to the small sample of gas giants ($sim 10$) around M dwarfs, but
also, its low density ($rho =$ $0.27^{+0.05}_{-0.04}$ $textrm{g~cm}^{-3}$)
provides an opportunity to test theories of planet formation. We present two
hypotheses to explain its low density; first, we posit that the low metallicity
of its stellar host ($sim$ 0.3 dex lower than the median metallicity of M
dwarfs hosting gas giants) could have played a role in the delayed formation of
a solid core massive enough to initiate runaway accretion. Second, using the
eccentricity estimate of $0.14 pm 0.06$ we determine it is also plausible for
tidal heating to at least partially be responsible for inflating the radius of
TOI-3757b b. The low density and large scale height of TOI-3757 b makes it an
excellent target for transmission spectroscopy studies of atmospheric escape
and composition (TSM $sim$ 190). We use HPF to perform transmission
spectroscopy of TOI-3757 b using the helium 10830 AA~ line. Doing this, we
place an upper limit of 6.9 % (with 90% confidence) on the maximum depth of
the absorption from the metastable transition of He at $sim$ 10830 AA, which
can help constraint the atmospheric mass loss rate in this energy limited
regime.

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