The LHS 1678 system : two earth-sized transiting planets and an astrometric companion orbiting an M dwarf near the convective boundary at 20 pc

Funding: The MEarth Team gratefully acknowledges funding from the David and Lucile Packard Fellowship for Science and Engineering (awarded to D.C.). This material is based upon work supported by the National Science Foundation under grants AST-0807690, AST-1109468, AST-1004488 (Alan T. Waterman Award), and AST-1616624, and upon work supported by the National Aeronautics and Space Administration under Grant No. 80NSSC18K0476 issued through the XRP Program. This work is made possible by a grant from the John Templeton Foundation. N. A.-D. acknowledges the support of FONDECYT project 3180063. TD acknowledges support from MIT’s Kavli Institute as a Kavli postdoctoral fellow. KH acknowledges support from STFC grant ST/R000824/1. E.A.G. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant #1829740, the Brinson Foundation, and the Moore Foundation; The material is based upon work supported by NASA under award number 80GSFC21M0002. This work was supported by the lead author’s appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Universities Space Research Association under contract with NASAWe present the Transiting Exoplanet Survey Satellite (TESS) discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright (VJ = 12.5, Ks = 8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70 ± 0.04 R⊕ and 0.98 ± 0.06 R⊕ in 0.86 day and 3.69 day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. High Accuracy Radial Velocity Planet Searcher RV monitoring yields 97.7 percentile mass upper limits of 0.35 M⊕ and 1.4 M⊕ for planets b and c, respectively. The astrometric companion detected by the Cerro Tololo Inter-American Observatory/Small and Moderate Aperture Telescope System 0.9 m has an orbital period on the order of decades and is undetected by other means. Additional ground-based observations constrain the companion to being a high-mass brown dwarf or smaller. Each planet is of unique interest; the inner planet has an ultra-short period, and the outer planet is in the Venus zone. Both are promising targets for atmospheric characterization with the James Webb Space Telescope and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9 ± 0.1 R⊕ in a 4.97 day orbit is also identified in multicycle TESS data for validation in future work. The host star is associated with an observed gap in the lower main sequence of the Hertzsprung–Russell diagram. This gap is tied to the transition from partially to fully convective interiors in M dwarfs, and the effect of the associated stellar astrophysics on exoplanet evolution is currently unknown. The culmination of these system properties makes LHS 1678 a unique, compelling playground for comparative exoplanet science and understanding the formation and evolution of small, short-period exoplanets orbiting low-mass stars.Publisher PDFPeer reviewe

The LHS 1678 System: Two Earth-sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc

We present the Transiting Exoplanet Survey Satellite (TESS) discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright (V J = 12.5, K s = 8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70 ± 0.04 R ⊕ and 0.98 ± 0.06 R ⊕ in 0.86 day and 3.69 day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. High Accuracy Radial Velocity Planet Searcher RV monitoring yields 97.7 percentile mass upper limits of 0.35 M ⊕ and 1.4 M ⊕ for planets b and c, respectively. The astrometric companion detected by the Cerro Tololo Inter-American Observatory/Small and Moderate Aperture Telescope System 0.9 m has an orbital period on the order of decades and is undetected by other means. Additional ground-based observations constrain the companion to being a high-mass brown dwarf or smaller. Each planet is of unique interest; the inner planet has an ultra-short period, and the outer planet is in the Venus zone. Both are promising targets for atmospheric characterization with the James Webb Space Telescope and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9 ± 0.1 R ⊕ in a 4.97 day orbit is also identified in multicycle TESS data for validation in future work. The host star is associated with an observed gap in the lower main sequence of the Hertzsprung-Russell diagram. This gap is tied to the transition from partially to fully convective interiors in M dwarfs, and the effect of the associated stellar astrophysics on exoplanet evolution is currently unknown. The culmination of these system properties makes LHS 1678 a unique, compelling playground for comparative exoplanet science and understanding the formation and evolution of small, short-period exoplanets orbiting low-mass stars

Sexual Fate Reprogramming in the Steroid-Induced Bi-Directional Sex Change in the Protogynous Orange-Spotted Grouper, Epinephelus coioides.

Androgen administration has been widely used for masculinization in fish. The mechanism of the sex change in sexual fate regulation is not clear. Oral administration or pellet implantation was applied. We orally applied an aromatase inhibitor (AI, to decrease estrogen levels) and 17α-methyltestosterone (MT, to increase androgen levels) to induce masculinization to clarify the mechanism of the sex change in the protogynous orange-spotted grouper. After 3 mo of AI/MT administration, male characteristics were observed in the female-to-male sex change fish. These male characteristics included increased plasma 11-ketotestosterone (11-KT), decreased estradiol (E2) levels, increased male-related gene (dmrt1, sox9, and cyp11b2) expression, and decreased female-related gene (figla, foxl2, and cyp19a1a) expression. However, the reduced male characteristics and male-to-female sex change occurred after AI/MT-termination in the AI- and MT-induced maleness. Furthermore, the MT-induced oocyte-depleted follicle cells (from MT-implantation) had increased proliferating activity, and the sexual fate in a portion of female gonadal soma cells was altered to male function during the female-to-male sex change. In contrast, the gonadal soma cells were not proliferative during the early process of the male-to-female sex change. Additionally, the male gonadal soma cells did not alter to female function during the male-to-female sex change in the AI/MT-terminated fish. After MT termination in the male-to-female sex-changed fish, the differentiated male germ cells showed increased proliferating activities together with dormancy and did not show characteristics of both sexes in the early germ cells. In conclusion, these findings indicate for the first time in a single species that the mechanism involved in the replacement of soma cells is different between the female-to-male and male-to-female sex change processes in grouper. These results also demonstrate that sexual fate determination (secondary sex determination) is regulated by endogenous sex steroid levels

The sexual fates of gonadal soma cells during female-to-male sex change.

<p>(A) Time table of Brdu treatment (given on days 7 and 10) in the process of MT-implanted female-to-male sex change. The fish were collected on day 30. (B) MT-implantation (100 μg MT/mg pellet; 200 mg pellet/kg of body weight) was given for 30 days. (C) and (D) IHC analysis of a gonad with the Brdu antibody. SG, spermatogonia; SC, spermatocyte; SP, spermatozoa; L, central lumen; BV, blood vessel; Sc, Sertoli cell; Ic, interstitial cell. An asterisk indicates the spermatogonia.</p

Expression profiles of sex-related genes during sexual fate alternation in fish orally administered AI.

<p>The AI-treated fish were functional males after 3 mo oral administration (T). The AI-induced maleness was reversible, and the male-to-female sex change occurred 3 wks after AI-termination (T+3w). (A), (B), and (C) Expression of male-related genes <i>dmrt1</i>, <i>sox9</i>, and <i>cyp11b2</i>, respectively, during the male-to-female sex change that occurred after AI-termination. (D), (E), and (F) Expression of female-related genes <i>figla</i>, <i>foxl2</i>, and <i>cyp19a1a</i>, respectively, during the male-to-female sex change that occurred after AI-termination. Superscript letters indicate one-way ANOVA and a Student-Newman-Keuls multiple test (<i>P</i> < 0.05). Asterisk indicates Student <i>t</i>-test (<i>P</i> < 0.05).</p

High survival and proliferative activity in the surrounding gonadal soma cells during female-to-male sex change.

<p>Gonadal cell status was analyzed by proliferative activity (Brdu treatment) and TUNEL assay. (A) IHC staining of Brdu showed broad signals (with solid arrowheads) in the regressed oocyte-surrounding somatic cells. A hollow arrowhead indicates the cells with no Brdu-stainings. (B) Apoptotic analysis revealed slight signals in the regressed oocyte-surrounding cells (with solid arrowheads). The hollow arrowhead indicates the cells with no TUNEL staining signals. (C) In contrast, the DNase I treatment in the serial sections resulted in robust and broad TUNEL staining signals. RO, regressed oocyte.</p

AI/MT-induced masculinization with a reversible sex change after the termination of orally administered AI/MT in orange-spotted grouper.

<p>(A) The sampling program during sexual fate alternation from female to male or vice versa, including fish collected before oral administration, and 3 mo (T, the treatment period, 7- to 10-mo-old) after AI/MT-oral administration, and after 3 wks (T+3w), 5 wks (T+5w) and 9 wks (T+9w) of AI/MT-termination. The gonadal status is shown as follows: (B) Initial control female; (C) AI-induced male with active spermatogenesis 3 mo after AI-oral administration; (D), (E), and (F) Regenerated female 3 wks, 5 wks, and 9 wks after AI-termination, respectively; (G) MT-induced male with active spermatogenesis 3 mo after MT-oral administration; (H), (I), and (J) Regenerated female after 3 wks, 5 wks, and 9 wks of MT-termination, respectively. L, central lumen; OG, oogonia; PO, primary oocyte; SG, spermatogonia; SC, spermatocyte; SZ, spermatozoa; EG, early germ cell.</p

Plasma levels of sex steroids during sexual fate alternation in fish receiving oral administration of AI/MT.

<p>The AI/MT-treated fish were functional males after 3 mo oral administration (T). The AI/MT-induced maleness was reversible, and the male-to-female sex change occurred 3 wks after MT-termination (T+3w). (A) and (B) Plasma sex steroids (11-KT and E2) in AI-administered fish and control fish. (C) and (D) Plasma sex steroids (11-KT and E2) in MT-administered fish and control fish. Superscript letters indicate one-way ANOVA and a Student-Newman-Keuls multiple test (<i>P</i> < 0.05). Asterisk indicates a Student <i>t</i>-test (<i>P</i> < 0.05).</p

Expression profiles of sex-related genes during sexual fate alternation in fish orally administered MT.

<p>The MT-treated fish were functional males after 3 mo oral administration (T). The MT-induced maleness was reversible, and the male-to-female sex change occurred 3 wks after MT-termination (T+3w). (A), (B), and (C) Expression of male-related genes <i>dmrt1</i>, <i>sox9</i>, and <i>cyp11b2</i>, respectively, during the male-to-female sex change that occurred after MT termination. (D), (E), and (F) Expression of female-related genes <i>figla</i>, <i>foxl2</i>, and <i>cyp19a1a</i>, respectively, during the male-to-female sex change that occurred after MT termination. Superscript letters indicate one-way ANOVA and a Student-Newman-Keuls multiple test (<i>P</i> < 0.05). Asterisk indicates a Student <i>t</i>-test (<i>P</i> < 0.05).</p