A More Precise Mass for GJ 1214 b and the Frequency of Multi-Planet Systems Around Mid-M Dwarfs. (arXiv:2107.14732v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Cloutier_R/0/1/0/all/0/1">Ryan Cloutier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charbonneau_D/0/1/0/all/0/1">David Charbonneau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deming_D/0/1/0/all/0/1">Drake Deming</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonfils_X/0/1/0/all/0/1">Xavier Bonfils</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Astudillo_Defru_N/0/1/0/all/0/1">Nicola Astudillo-Defru</a>
We present an intensive effort to refine the mass and orbit of the enveloped
terrestrial planet GJ 1214 b using 165 radial velocity (RV) measurements taken
with the HARPS spectrograph over a period of ten years. We conduct a joint
analysis of the RVs with archival Spitzer/IRAC transits and measure a planetary
mass and radius of $8.17pm 0.43 M_{oplus}$ and $2.742^{+0.050}_{-0.053}
R_{oplus}$. Assuming GJ 1214 b is an Earth-like core surrounded by a H/He
envelope, we measure an envelope mass fraction of $X_{rm env}=
5.24^{+0.30}_{-0.29}$%. GJ 1214 b remains a prime target for secondary eclipse
observations of an enveloped terrestrial, the scheduling of which benefits from
our tight constraint on the orbital eccentricity of $<0.063$ at 95% confidence,
which narrows the secondary eclipse window to 2.8 hours. By combining GJ 1214
with other mid-M dwarf transiting systems with intensive RV follow-up, we
calculate the frequency of mid-M dwarf planetary systems with multiple small
planets and find that $90^{+5}_{-21}$% of mid-M dwarfs with a known planet with
mass $in [1,10] M_{oplus}$ and orbital period $in [0.5,50]$ days, will host
at least one additional planet. We rule out additional planets around GJ 1214
down to $3 M_{oplus}$ within 10 days such that GJ 1214 is a single-planet
system within these limits, a result that has a $44^{+9}_{-5}$% probability
given the prevalence of multi-planet systems around mid-M dwarfs. We also
investigate mid-M dwarf RV systems and show that the probability that all
reported RV planet candidates are real planets is $<12$% at 99% confidence,
although this statistical argument is unable to identify the probable false
positives.
We present an intensive effort to refine the mass and orbit of the enveloped
terrestrial planet GJ 1214 b using 165 radial velocity (RV) measurements taken
with the HARPS spectrograph over a period of ten years. We conduct a joint
analysis of the RVs with archival Spitzer/IRAC transits and measure a planetary
mass and radius of $8.17pm 0.43 M_{oplus}$ and $2.742^{+0.050}_{-0.053}
R_{oplus}$. Assuming GJ 1214 b is an Earth-like core surrounded by a H/He
envelope, we measure an envelope mass fraction of $X_{rm env}=
5.24^{+0.30}_{-0.29}$%. GJ 1214 b remains a prime target for secondary eclipse
observations of an enveloped terrestrial, the scheduling of which benefits from
our tight constraint on the orbital eccentricity of $<0.063$ at 95% confidence,
which narrows the secondary eclipse window to 2.8 hours. By combining GJ 1214
with other mid-M dwarf transiting systems with intensive RV follow-up, we
calculate the frequency of mid-M dwarf planetary systems with multiple small
planets and find that $90^{+5}_{-21}$% of mid-M dwarfs with a known planet with
mass $in [1,10] M_{oplus}$ and orbital period $in [0.5,50]$ days, will host
at least one additional planet. We rule out additional planets around GJ 1214
down to $3 M_{oplus}$ within 10 days such that GJ 1214 is a single-planet
system within these limits, a result that has a $44^{+9}_{-5}$% probability
given the prevalence of multi-planet systems around mid-M dwarfs. We also
investigate mid-M dwarf RV systems and show that the probability that all
reported RV planet candidates are real planets is $<12$% at 99% confidence,
although this statistical argument is unable to identify the probable false
positives.
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