orbital periods
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2022 ◽  
Vol 163 (2) ◽  
pp. 61
Paul A. Dalba ◽  
Stephen R. Kane ◽  
Diana Dragomir ◽  
Steven Villanueva ◽  
Karen A. Collins ◽  

Abstract We report the discovery of TOI-2180 b, a 2.8 M J giant planet orbiting a slightly evolved G5 host star. This planet transited only once in Cycle 2 of the primary Transiting Exoplanet Survey Satellite (TESS) mission. Citizen scientists identified the 24 hr single-transit event shortly after the data were released, allowing a Doppler monitoring campaign with the Automated Planet Finder telescope at Lick Observatory to begin promptly. The radial velocity observations refined the orbital period of TOI-2180 b to be 260.8 ± 0.6 days, revealed an orbital eccentricity of 0.368 ± 0.007, and discovered long-term acceleration from a more distant massive companion. We conducted ground-based photometry from 14 sites spread around the globe in an attempt to detect another transit. Although we did not make a clear transit detection, the nondetections improved the precision of the orbital period. We predict that TESS will likely detect another transit of TOI-2180 b in Sector 48 of its extended mission. We use giant planet structure models to retrieve the bulk heavy-element content of TOI-2180 b. When considered alongside other giant planets with orbital periods over 100 days, we find tentative evidence that the correlation between planet mass and metal enrichment relative to stellar is dependent on orbital properties. Single-transit discoveries like TOI-2180 b highlight the exciting potential of the TESS mission to find planets with long orbital periods and low irradiation fluxes despite the selection biases associated with the transit method.

Min Dai ◽  
Xiaodian Chen ◽  
Kun WANG ◽  
Yangping Luo ◽  
Shu Wang ◽  

Abstract The development of large-scale time-domain surveys provides an opportunity to study the physical properties as well as the evolutionary scenario of B-type subdwarfs (sdB) and M-type dwarfs (dM). Here, we obtained 33 sdB+dM eclipsing binaries based on the Zwicky Transient Facility (ZTF) light curves and {\sl Gaia} early data release 3 (EDR3) parallaxes. By using the PHOEBE code for light curve analysis, we obtain probability distributions for parameters of 29 sdB+dM. $R_1$, $R_2$, and $i$ are well determined, and the average uncertainty of mass ratio $q$ is 0.08. Our parameters are in good agreement with previous works if a typical mass of sdB is assumed. Based on parameters of 29 sdB+dM, we find that both the mass ratio $q$ and the companion's radius $R_2$ decrease with the shortening of the orbital period. For the three sdB+dMs with orbital periods less than 0.075 days, their companions are all brown dwarfs. The masses and radii of the companions satisfy the mass--radius relation for low-mass stars and brown dwarfs. Companions with radii between $0.12R_\odot$ and $0.15R_\odot$ seem to be missing in the observations. As more short-period sdB+dM eclipsing binaries are discovered and classified in the future with ZTF and {\sl Gaia}, we will have more information to constrain the evolutionary ending of sdB+dM.

Dennis Jack ◽  
Missael Alejandro Hernández Huerta ◽  
Faiber Danilo Rosas‐Portilla ◽  
Klaus‐Peter Schröder

2022 ◽  
Vol 163 (2) ◽  
pp. 41
Chantanelle Nava ◽  
Mercedes López-Morales ◽  
Annelies Mortier ◽  
Li Zeng ◽  
Helen A. C. Giles ◽  

Abstract We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting active G-type stars observed with HARPS-N and K2. Their respective 10.99 day and 15.39 day orbital periods fall near periods of signals induced by stellar magnetic activity. The two signals might therefore interfere and lead to an inaccurate estimate of exoplanet mass. We present a method to mitigate these effects when radial velocity (RV) and activity-indicator observations are available over multiple observing seasons and the orbital period of the exoplanet is known. We perform correlation and periodogram analyses on subsets composed of each target's two observing seasons, in addition to the full data sets. For both targets, these analyses reveal an optimal season with little to no interference at the orbital period of the known exoplanet. We make a confident mass detection of each exoplanet by confirming agreement between fits to the full RV set and the optimal season. For K2-79b, we measure a mass of 11.8 ± 3.6 M ⊕ and a radius of 4.09 ± 0.17 R ⊕. For K2-222b, we measure a mass of 8.0 ± 1.8 M ⊕ and a radius of 2.35 ± 0.08 R ⊕. According to model predictions, K2-79b is a highly irradiated Uranus analog and K2-222b hosts significant amounts of water ice. We also present a RV solution for a candidate second companion orbiting K2-222 at 147.5 days.

2022 ◽  
Vol 924 (2) ◽  
pp. 67
Jules P. Halpern ◽  
John R. Thorstensen

Abstract We conducted time-resolved optical spectroscopy and/or photometry of 10 cataclysmic binaries that were discovered in hard X-ray surveys, with the goal of measuring their orbital periods and searching for evidence that they are magnetic. Four of the objects in this study are new optical identifications: IGR J18017−3542, PBC J1841.1+0138, IGR J18434−0508, and Swift J1909.3+0124. A 311.8 s, coherent optical pulsation is detected from PBC J1841.1+0138, as well as eclipses with a period of 0.221909 days. A 152.49 s coherent period is detected from IGR J18434−0508. A probable period of 389 s is seen in IGR J18151−1052, in agreement with a known X-ray spin period. We also detect a period of 803.5 s in an archival X-ray observation of Swift J0717.8−2156. The last four objects are thus confirmed magnetic cataclysmic variables of the intermediate polar class. An optical period of 1554 s in AX J1832.3−0840 also confirms the known X-ray spin period, but a stronger signal at 2303 s is present whose interpretation is not obvious. We also studied the candidate intermediate polar Swift J0820.6−2805, which has low and high states differing by ≈4 mag and optical periods or quasi-periodic oscillations not in agreement with proposed X-ray periods. Of note is an unusually long 2.06-day orbital period for Swift J1909.3+0124, manifest in the radial velocity variation of photospheric absorption lines of an early K-type companion star. The star must be somewhat evolved if it is to fill its Roche lobe.

2022 ◽  
Vol 924 (1) ◽  
pp. 9
Tim Hallatt ◽  
Eve J. Lee

Abstract The sub-Saturn (∼4–8 R ⊕) occurrence rate rises with orbital period out to at least ∼300 days. In this work we adopt and test the hypothesis that the decrease in their occurrence toward the star is a result of atmospheric mass loss, which can transform sub-Saturns into sub-Neptunes (≲4 R ⊕) more efficiently at shorter periods. We show that under the mass-loss hypothesis, the sub-Saturn occurrence rate can be leveraged to infer their underlying core mass function, and, by extension, that of gas giants. We determine that lognormal core mass functions peaked near ∼10–20 M ⊕ are compatible with the sub-Saturn period distribution, the distribution of observationally inferred sub-Saturn cores, and gas-accretion theories. Our theory predicts that close-in sub-Saturns should be ∼50% less common and ∼30% more massive around rapidly rotating stars; this should be directly testable for stars younger than ≲500 Myr. We also predict that the sub-Jovian desert becomes less pronounced and opens up at smaller orbital periods around M stars compared to solar-type stars (∼0.7 days versus ∼3 days). We demonstrate that exceptionally low-density sub-Saturns, “super-puffs,” can survive intense hydrodynamic escape to the present day if they are born with even larger atmospheres than they currently harbor; in this picture, Kepler 223 d began with an envelope ∼1.5× the mass of its core and is currently losing its envelope at a rate of ∼2 × 10−3 M ⊕ Myr−1. If the predictions from our theory are confirmed by observations, the core mass function we predict can also serve to constrain core formation theories of gas-rich planets.

2021 ◽  
Vol 923 (1) ◽  
pp. L16
Matthew S. Clement ◽  
Sean N. Raymond ◽  
John E. Chambers

Abstract In spite of substantial advancements in simulating planet formation, the planet Mercury’s diminutive mass and isolated orbit and the absence of planets with shorter orbital periods in the solar system continue to befuddle numerical accretion models. Recent studies have shown that if massive embryos (or even giant planet cores) formed early in the innermost parts of the Sun’s gaseous disk, they would have migrated outward. This migration may have reshaped the surface density profile of terrestrial planet-forming material and generated conditions favorable to the formation of Mercury-like planets. Here we continue to develop this model with an updated suite of numerical simulations. We favor a scenario where Earth’s and Venus’s progenitor nuclei form closer to the Sun and subsequently sculpt the Mercury-forming region by migrating toward their modern orbits. This rapid formation of ∼0.5 M ⊕ cores at ∼0.1–0.5 au is consistent with modern high-resolution simulations of planetesimal accretion. In successful realizations, Earth and Venus accrete mostly dry, enstatite chondrite–like material as they migrate, thus providing a simple explanation for the masses of all four terrestrial planets, the inferred isotopic differences between Earth and Mars, and Mercury’s isolated orbit. Furthermore, our models predict that Venus’s composition should be similar to the Earth’s and possibly derived from a larger fraction of dry material. Conversely, Mercury analogs in our simulations attain a range of final compositions.

2021 ◽  
Vol 923 (1) ◽  
pp. 125
Tin Long Sunny Wong ◽  
Lars Bildsten

Abstract We calculate the stellar evolution of both white dwarfs (WDs) in AM CVn binaries with orbital periods of P orb ≈ 5–70 minutes. We focus on the cases where the donor starts as a M He < 0.2M ⊙ helium WD and the accretor is a M WD > 0.6 M ⊙ WD. Using Modules for Experiments in Stellar Astrophysics, we simultaneously evolve both WDs assuming conservative mass transfer and angular momentum loss from gravitational radiation. This self-consistent evolution yields important feedback of the properties of the donor on the mass-transfer rate, M ̇ , as well as the thermal evolution of the accreting WD. Consistent with earlier work, we find that the high M ̇ 's at early times forces an adiabatic evolution of the donor for P orb < 30 minutes so that its mass–radius relation depends primarily on its initial entropy. As the donor reaches M He ≈ 0.02–0.03 M ⊙ at P orb ≃ 30 minutes, it becomes fully convective and could lose entropy and expand much less than expected under further mass loss. However, we show that the lack of reliable opacities for the donor’s surface inhibit a secure prediction for this possible cooling. Our calculations capture the core heating that occurs during the first ≈107 yr of accretion and continue the evolution into the phase of WD cooling that follows. When compared to existing data for accreting WDs, as seen by Cheng and collaborators for isolated WDs, we also find that the accreting WDs are not as cool as we would expect given the amount of time they have had to cool.

2021 ◽  
Vol 21 (11) ◽  
pp. 295
Burak Ulaş

Abstract We present the first evidence for the binarity of four targets in the TESS field. The temperatures are estimated by SED analysis and the orbital periods are determined. The TESS light curves of the systems are analyzed and the orbital and the absolute parameters are derived. The targets are also compared to well-studied binary systems with the same morphological type and their evolutionary states are discussed. Our results indicate that the stars belong to the class of eclipsing detached binary systems.

2021 ◽  
Vol 923 (1) ◽  
pp. L18
Alessia Franchini ◽  
Rebecca G. Martin

Abstract Be star X-ray binaries are transient systems that show two different types of outbursts. Type I outbursts occur each orbital period while type II outbursts have a period and duration that are not related to any periodicity of the binary system. Type II outbursts may be caused by mass transfer to the neutron star from a highly eccentric Be star disk. A sufficiently misaligned Be star decretion disk undergoes secular Von Zeipel–Lidov–Kozai (ZLK) oscillations of eccentricity and inclination. Observations show that in some systems the type II outbursts come in pairs with the second being of lower luminosity. We use numerical hydrodynamical simulations to explore the dynamics of the highly misaligned disk that forms around the neutron star as a consequence of mass transfer from the Be star disk. We show that the neutron star disk may also be ZLK unstable and that the eccentricity growth leads to an enhancement in the accretion rate onto the neutron star that lasts for several orbital periods, resembling a type II outburst. We suggest that in a type II outburst pair, the first outburst is caused by mass transfer from the eccentric Be star disk while the second and smaller outburst is caused by the eccentric neutron star disk. We find that the timescale between outbursts in a pair may be compatible with the observed estimates.

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