The SOPHIE search for northern extrasolar planets-XIX. A system including a cold sub-Neptune potentially transiting a V = 6.5 star HD88986. (arXiv:2311.13513v1 [astro-ph.EP])

The SOPHIE search for northern extrasolar planets-XIX. A system including a cold sub-Neptune potentially transiting a V = 6.5 star HD88986. (arXiv:2311.13513v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Heidari_N/0/1/0/all/0/1">N. Heidari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boisse_I/0/1/0/all/0/1">I. Boisse</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hara_N/0/1/0/all/0/1">N. C. Hara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wilson_T/0/1/0/all/0/1">T. G. Wilson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kiefer_F/0/1/0/all/0/1">F. Kiefer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hebrard_G/0/1/0/all/0/1">G. Hébrard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Philipot_F/0/1/0/all/0/1">F. Philipot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hoyer_S/0/1/0/all/0/1">S. Hoyer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stassun_K/0/1/0/all/0/1">K. G. Stassun</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henry_G/0/1/0/all/0/1">G. W. Henry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Santos_N/0/1/0/all/0/1">N. C. Santos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Acuna_L/0/1/0/all/0/1">L. Acuña</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Almasian_D/0/1/0/all/0/1">D. Almasian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arnold_L/0/1/0/all/0/1">L. Arnold</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Astudillo_Defru_N/0/1/0/all/0/1">N. Astudillo-Defru</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Attia_O/0/1/0/all/0/1">O. Attia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonfils_X/0/1/0/all/0/1">X. Bonfils</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bouchy_F/0/1/0/all/0/1">F. Bouchy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bourrier_V/0/1/0/all/0/1">V. Bourrier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Collet_B/0/1/0/all/0/1">B. Collet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cortes_Zuleta_P/0/1/0/all/0/1">P. Cortés-Zuleta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carmona_A/0/1/0/all/0/1">A. Carmona</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Delfosse_X/0/1/0/all/0/1">X. Delfosse</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dalal_S/0/1/0/all/0/1">S. Dalal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deleuil_M/0/1/0/all/0/1">M. Deleuil</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Demangeon_O/0/1/0/all/0/1">O. D. S. Demangeon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Diaz_R/0/1/0/all/0/1">R. F. Díaz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dumusque_X/0/1/0/all/0/1">X. Dumusque</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ehrenreich_D/0/1/0/all/0/1">D. Ehrenreich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Forveille_T/0/1/0/all/0/1">T. Forveille</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hobson_M/0/1/0/all/0/1">M. J. Hobson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jenkins_J/0/1/0/all/0/1">J. S. Jenkins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jenkins_J/0/1/0/all/0/1">J. M. Jenkins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lagrange_A/0/1/0/all/0/1">A. M. Lagrange</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Latham_D/0/1/0/all/0/1">D. W. Latham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Larue_P/0/1/0/all/0/1">P. Larue</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_J/0/1/0/all/0/1">J. Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moutou_C/0/1/0/all/0/1">C. Moutou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mignon_L/0/1/0/all/0/1">L. Mignon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Osborn_H/0/1/0/all/0/1">H. P. Osborn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pepe_F/0/1/0/all/0/1">F. Pepe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rapetti_D/0/1/0/all/0/1">D. Rapetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodrigues_J/0/1/0/all/0/1">J. Rodrigues</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Santerne_A/0/1/0/all/0/1">A. Santerne</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Segransan_D/0/1/0/all/0/1">D. Segransan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shporer_A/0/1/0/all/0/1">A. Shporer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sulis_S/0/1/0/all/0/1">S. Sulis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Torres_G/0/1/0/all/0/1">G. Torres</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Udry_S/0/1/0/all/0/1">S. Udry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vakili_F/0/1/0/all/0/1">F. Vakili</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vanderburg_A/0/1/0/all/0/1">A. Vanderburg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Venot_O/0/1/0/all/0/1">O. Venot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vivien_H/0/1/0/all/0/1">H. G. Vivien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vines_J/0/1/0/all/0/1">J. I. Vines</a>

Transiting planets with orbital periods longer than 40 d are extremely rare
among the 5000+ planets discovered so far. The lack of discoveries of this
population poses a challenge to research into planetary demographics,
formation, and evolution. Here, we present the detection and characterization
of HD88986b, a potentially transiting sub-Neptune, possessing the longest
orbital period among known transiting small planets (< 4 R$_{oplus}$) with a
precise mass measurement ($sigma_M/M$ > 25%). Additionally, we identified the
presence of a massive companion in a wider orbit around HD88986. Our analysis
reveals that HD88986b, based on two potential single transits on sector 21 and
sector 48 which are both consistent with the predicted transit time from the RV
model, is potentially transiting. The joint analysis of RV and photometric data
show that HD88986b has a radius of 2.49$pm$0.18 R$_{oplus}$, a mass of
17.2$^{+4.0}_{-3.8}$ M$_{oplus}$, and it orbits every 146.05$^{+0.43}_{-0.40}$
d around a subgiant HD88986 which is one of the closest and brightest exoplanet
host stars (G2V type, R=1.543 $pm$0.065 R$_{odot}$, V=$6.47pm 0.01$ mag,
distance=33.37$pm$0.04 pc). The nature of the outer, massive companion is
still to be confirmed; a joint analysis of RVs, Hipparcos, and Gaia astrometric
data shows that with a 3$sigma$ confidence interval, its semi-major axis is
between 16.7 and 38.8 au and its mass is between 68 and 284 M$_{Jup}$.
HD88986b’s wide orbit suggests the planet did not undergo significant mass loss
due to extreme-ultraviolet radiation from its host star. Therefore, it probably
maintained its primordial composition, allowing us to probe its formation
scenario. Furthermore, the cold nature of HD88986b (460$pm$8 K), thanks to its
long orbital period, will open up exciting opportunities for future studies of
cold atmosphere composition characterization.

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