Ilaria Carleo; Amadeo Castro-González; Enric Pallé; Felipe Murgas; Grzegorz Nowak; Gaia Lacedelli; Thomas Masseron; Emily W. Wong; Patrick Eggenberger; Vincent Bourrier; Dawid Jankowski; Krzysztof Goździewski; Douglas R. Alves; James S. Jenkins; Sergio Messina; Keivan G. Stassun; Jose I. Vines; Matteo Brogi; David R. Ciardi; Catherine A. Clark; William Cochran; Karen A. Collins; Hans J. Deeg; Elise Furlan; Davide Gandolfi; Samuel Geraldía González; Artie P. Hatzes; Coel Hellier; Steve B. Howell; Judith Korth; Jorge Lillo-Box; John H. Livingston; Jaume Orell-Miquel; Carina M. Persson; Seth Redfield; Boris Safonov; David Baker; Rafael Delfin Barrena Delgado; Allyson Bieryla; Andrew Boyle; Pau Bosch-Cabot; Núria Casasayas Barris; Stavros Chairetas; Jerome P. De Leon; Izuru Fukuda; Akihiko Fukui; Pere Guerra; Kai Ikuta; Kiyoe Kawauchi; Emil Knudstrup; Florence Libotte; Michael B. Lund; Rafael Luque; Eduardo Lorenzo Martín Guerrero De Escalante; Bob Massey; Edward J. Michaels; Giuseppe Morello; Norio Narita; Hannu Parvianien; Richard P. Schwarz; Avi Shporer; Monika Stangret; Noriharu Watanabe; Cristilyn N. Watkins (2026).��.��Astronomy & Astrophysics, 707, A4.��

As scientists discover more types of exoplanets (planets outside our solar system), they are rethinking what conditions might allow a planet to be habitable. Traditionally, the “habitable zone” is defined as the range of distances from a star where liquid water could exist on a planet’s surface. In this study, the authors propose a broader concept called the��“temperate zone,”��defined by the amount of stellar energy a planet receives (instellation), specifically between 0.1 and 5 times the amount Earth gets from the Sun. This wider range includes more planets that might potentially support life under different conditions.

The researchers also introduce the TEMPOS survey, which focuses on measuring the sizes of planets orbiting very cool, small stars known as M dwarfs. As part of this effort, they discovered and confirmed two planets: TOI-6716 b and TOI-7384 b. TOI-6716 b is about the same size as Earth, while TOI-7384 b is larger (closer to a “mini-Neptune”). Both orbit relatively cool M dwarf stars and complete an orbit in just a few days. The team used multiple methods—including ground-based observations, high-resolution imaging, and statistical validation—to confirm these planets and precisely measure their sizes.

Both planets receive relatively high levels of stellar energy, placing them near the hotter inner edge of the proposed temperate zone. This means they may be too warm for Earth-like conditions, but they are still valuable for studying planetary environments. Notably, TOI-6716 b could be a promising target for the James Webb Space Telescope, especially for��transmission spectroscopy��(a technique that analyzes starlight passing through a planet’s atmosphere to detect its composition), if it has retained an atmosphere. Overall, this work expands the range of planets considered potentially interesting for habitability studies and contributes new targets for future observation.

Figure 1.

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This study focuses on understanding how gas giant planets—large planets like Jupiter—form around low-mass, relatively cool stars (called M dwarfs), where such planets are thought to be rare. To improve our knowledge, the researchers launched the GATOS program, which aims to confirm and study candidate planets discovered by NASA’s TESS space telescope. They combined detailed observations from two instruments (HARPS and NIRPS) that measure��radial velocity—tiny shifts in a star’s motion caused by the gravitational pull of an orbiting planet—to confirm the planets and determine their properties. They also used brightness measurements (photometry) from TESS and ground-based telescopes to track when planets pass in front of their stars (transits). A new data-processing technique was introduced to reduce interference from Earth’s atmosphere in the measurements.

Using this approach, the team confirmed two gas giant planets orbiting small stars. One is a “hot Jupiter” (a gas giant very close to its star) orbiting TOI-3288 A every 1.43 days, and the other is a slightly cooler “warm Jupiter” orbiting TOI-4666 every 2.91 days. They measured each planet’s mass and size, finding them comparable to Jupiter but with different temperatures due to their distances from their stars. Looking more broadly at similar systems, the researchers observed that smaller, cooler stars tend to host less massive gas giants, unless the stars are rich in heavier elements (referred to as “metallicity”), which seems to support the formation of larger planets. They also found that gas giants around low-mass stars are more common in binary star systems (where two stars orbit each other), suggesting that gravitational interactions between stars may help trigger planet formation or alter planetary orbits. Overall, these findings help explain how giant planets can form in environments where they were previously thought to be unlikely.

HR diagram of all��Gaia��DR3 nearby stars with a parallax of��π��≥ 5 mas, using the broad-band��G��magnitude versus the colour��G_BP��(blue) minus��G_RP��(red). The colours indicate log(g). Stars without a log(g) measurement are shown in grey. The six targets presented in this paper as part of the NIRPS-GTO giants sub-programme are overplotted (outlined black circles), along with five stars identified as giant stars using this method. TOI-3288 and TOI-4666 (outlined black squares), hosting gas giants, are visible on the main sequence. This figure can be generated using��Gaia-HR, available at��.

Astronomers have observed that planets similar in size to Neptune are rarely found orbiting Sun-like stars with very short orbital periods of about four days or less. This region is known as the Neptune desert. Because such planets are uncommon, each new discovery provides important clues about how these planets form and evolve.

We report the discovery of TOI-333b, a planet located in the Neptune desert. It has a mass of about 20 times that of Earth (20.1 ± 2.4 Earth masses), a radius about 4.3 times Earth’s, and a bulk density of 1.42 g/cm³. The planet orbits an F7V-type star every 3.78 days. Its host star is slightly more massive and hotter than the Sun, with a mass of 1.2 solar masses and an effective temperature of about 6240 K. The system is likely younger than 1 billion years, based on the strength of the lithium absorption line near 6708 angstroms, which is commonly used as an age indicator in stars.

Models suggest that TOI-333b likely has a relatively small hydrogen and helium (H/He) gas envelope, making up only about 8 to 19 percent of its total mass. Other models, such as those for irradiated ocean worlds, suggest it could instead contain a significant amount of water, with about 20 percent of its mass in H2O and a rocky core making up roughly one third of the planet. Overall, the planet is likely dominated either by a mostly rocky interior with very little gas or by a rocky world with a large water component.

Compared with other known planets in the Neptune desert, TOI-333b is more massive than about 77 percent of them and larger than about 82 percent. Its host star is also among the hottest known for planets in this region. Because of these properties, the TOI-333 system provides a valuable opportunity to study how Neptune-sized planets evolve in close orbits around hot stars.

Fig 1: Left��: TESS-detrended light curve phase-folded to the best-fitting period listed in����and zoomed to show the transit event. The blue and white circles correspond to modelled photometric data and binned data with the associated photon noise error. The blue line and shaded region show the median transit model and its 1σ confidence interval.��Centre��: same as the left panel for the LCOGT-SAAO telescope.��Right��: same as the left panel for the NGTS mission.��Bottom��: Residuals of the best-fit model.

Extreme ultraviolet (EUV; 100–912 angstroms) radiation from stars plays a major role in shaping planets. EUV photons can ionize hydrogen and other atoms, which affects how planetary atmospheres form, change, and sometimes erode over time. However, for most stars that host exoplanets, their EUV radiation is difficult to measure directly and is therefore not well known.

In this study, we used a modeling method called the differential emission measure (DEM) technique to estimate the EUV spectra of eight nearby stars. These stars were previously observed with high-quality data by the Extreme Ultraviolet Explorer (EUVE) satellite between 1992 and 2002. The sample includes stars of different spectral types, from cooler M-type stars to hotter F-type stars, such as AD Leo, ε Eridani, κ¹ Ceti, Procyon, α Centauri A and B, and ξ Boötis A and B.

Our DEM-based model spectra closely match the original EUVE measurements. For most individual data points, the modeled values are within a factor of three of the observed flux densities, and for the total energy emitted between 100 and 300 angstroms, the agreement is within 30 percent. We provide the atomic data, X-ray, EUV, and far-ultraviolet observations used as inputs, along with the DEM models and the predicted EUV spectra. These predicted spectra extend beyond the original EUVE wavelength range of 90–510 angstroms.

We also found that different layers of a star’s outer atmosphere contribute differently to its EUV emission. The transition region and the corona both produce EUV radiation, but their relative contributions vary from star to star. The corona, in particular, is strongly affected by stellar flares, which cause temporary and unpredictable increases in EUV radiation at certain wavelengths. The amount and pattern of this variability depend on the star’s temperature structure, flare activity, and magnetic activity cycle.

These findings are important because many studies of planetary atmospheric evolution rely on estimates of stellar EUV radiation. Understanding how EUV emission varies over time helps improve models of how exoplanet atmospheres respond to their host stars.

Figure 1.��Demonstration of the DEM technique applied to SIRS (T. N. Woods et al.��). The top-left panel shows the median DEM value across 10⁵��draws from the posterior distribution (solid green line) with shading spanning the interval between the 16th–84th percentile of the DEM draw values and the horizontal bars are the flux constraints discussed in Section��. The bars labeled with ion species correspond to measured integrated line fluxes from that species while the unlabeled bars correspond to spectral bins where the contribution function is a sum from unresolved blends of lines and continuum processes. The top-right panel and its associated color bar show the��Gλ(T) contribution function matrix calculated using atomic data, with the position of dark patches along a single wavelength column corresponding to the plasma temperature that contributes more observed emission at that wavelength (assuming an equal distribution of plasma at all temperatures). The bottom panel compares the model-generated DEM spectrum (green) to the original data (black) with the shaded interval representing the model uncertainty determined by sampling from the posterior distribution of DEM shapes and systematic uncertainty inflation��s-factors.

We report the confirmation and characterization of four hot Jupiter-type exoplanets initially detected by TESS: TOI-1295 b, TOI-2580 b, TOI-6016 b, and TOI-6130 b. Using observations with the high-resolution echelle spectrograph MaHPS on the 2.1 m telescope at Wendelstein Observatory, together with NEID at Kitt Peak National Observatory and TRES at the Fred Lawrence Whipple Observatory, we confirmed the planetary nature of these four planet candidates. We also performed precise mass measurements. All four planets are found to be hot Jupiters with orbital periods between 2.4 and 4.0 days. The sizes of these planets range from 1.29 to 1.64 Jupiter radii, while their masses range from 0.6 to 1.5 Jupiter masses. Additionally, we investigated whether there are signs of other planets in the systems but have found none. Lastly, we compared the radii of our four objects to the results of an empirical study of radius inflation and see that all four demonstrate a good fit with the current models. These four planets belong to the first array of planets confirmed with MaHPS data, supporting the ability of the spectrograph to detect planets around fainter stars as faint as��V��= 12.

Fig. 1

Speckle sensitivity curve and auto correlation function (ACF) of TOI-1295 obtained with the SAI Speckle polarimeter.

The star K2-19 is known to host two Neptune-sized planets that orbit very close to each other in a precise gravitational pattern called a 3:2 resonance, meaning their orbital periods are tightly linked. Because of this interaction, the planets do not pass in front of their star at perfectly regular intervals, producing strong variations in transit timing that carry information about their masses and orbits. Earlier studies, based on about 3 years of data, estimated relatively large planetary masses and unexpectedly high orbital eccentricities, or deviations from circular orbits. These high eccentricities were difficult to explain with standard models of planet formation, which motivated a new analysis using a much longer observational record.

In this study, we analyzed 10 years of transit observations using a detailed photodynamical model that accounts for the planets’ mutual gravitational effects. The longer data set confirms the earlier mass estimates for both planets, but significantly revises their orbital shapes. Instead of highly elongated orbits, the planets are now found to have much lower eccentricities, which are more in line with what is expected from conventional planet formation theories, although the orbits are still not perfectly circular. We show that the previously reported high eccentricities were driven by a single problematic transit observation taken during twilight, where observational effects caused the start of the transit to be misidentified, leading to a timing error of about 12 minutes.

Using data that span multiple long-term interaction cycles between the planets, we also applied a simpler analytical approach based on Fourier analysis of the transit-timing variations. This method reproduced the planet mass estimates to within about 2% of the full photodynamical results and did so without being sensitive to the exact eccentricities. In addition, we report evidence for a possible third planet located farther out in the system. Finally, updated modeling of the internal structure of the inner planet, K2-19 b, suggests a metal content consistent with formation through core accretion, the standard process thought to build most planets.

Fig. 1

Detection of the candidate planet e.��Left: gray data points represent the K2 data without the transits of planets b, c, and d. The orange data points show the mean GP model. The black light curve indicates the four transits we found.��Center: periodogram of the nuance algorithm.��Right: phased light curve without the noise model (gray points), binned (dark gray), and transit model (black line).

]]> /valiant/2025/12/19/toi-7166-b-a-habitable-zone-mini-neptune-planet-around-a-nearby-low-mass-star/ Fri, 19 Dec 2025 16:49:55 +0000 /valiant/?p=5567 Barkaoui, K., Pozuelos, F. J., Rackham, B. V., Burgasser, A. J., Triaud, A. H. M. J., Serra-Ricart, M., Timmermans, M., Yalçinkaya, S., Soubkiou, A., Stassun, K. G., Collins, K. A., Amado, P. J., Baştürk, Ö., Burdanov, A. Yu., Davis, Y. T., de Wit, J., Demory, B.-O., Deveny, S. J., Dransfield, G., Ducrot, E., Gillon, M., Chew, Y. G. M., Hooton, M. J., Hörne, K. D., Howell, S. B., Muñoz, C. J., Jehin, E., Jenkins, J. M., Littlefield, C., Martín, E. L., Niraula, P., Pedersen, P. P., Queloz, D., Scott, M. G., Sefako, R. R., Shporer, A., Stockdale, C. J., Softich, E. R., Sota, A., Tofflemire, B. M., Şimşir, Ö., Varas, R., Lang, F. Z., & Zúniga-Fernández, S. S. (2025).��.��Monthly Notices of the Royal Astronomical Society,��544(2), 2637–2652.��

We report the discovery and confirmation of a new exoplanet, called TOI-7166 b, that orbits a nearby, small, cool star. The planet was confirmed by combining observations from NASA’s Transiting Exoplanet Survey Satellite (TESS) with very precise brightness measurements from ground-based telescopes taken in multiple colors. These data were supported by additional information from spectroscopy, high-contrast imaging, archival images, and statistical tests to rule out false signals. The host star is an M4-type red dwarf located about 35 parsecs from the Sun and has a relatively small mass and radius compared with the Sun.

TOI-7166 b completes one orbit every 12.9 days. This places it near the inner edge of the star’s Habitable Zone, the region where temperatures could allow liquid water to exist under the right conditions. Based on how much energy it receives from its star (its insolation flux), the planet’s estimated equilibrium temperature is about K, assuming it reflects no light (a zero Bond albedo). Because the host star is relatively bright, TOI-7166 b is well suited for follow-up studies using the radial velocity method, which can measure the planet’s mass and overall density.

In addition, the combination of the star’s strong infrared brightness and the planet’s size relative to the star makes TOI-7166 b an excellent candidate for transmission spectroscopy with the James Webb Space Telescope. These observations could reveal details about the planet’s atmosphere, including its composition, making TOI-7166 b a particularly valuable target for future studies of potentially habitable worlds around low-mass stars.

Figure 1.

TESS��target pixel file image of TOI-7166 observed in Sectors 82 made by��tpfplotter��(A. Aller et��al.��2020). Red dots show the location of��Gaia��DR3 sources and the yellow shaded regions show the photometric apertures used for photometric measurements extraction.

]]> /valiant/2025/12/19/calibration-of-binary-population-synthesis-models-using-white-dwarf-binaries-from-apogee-galex-and-gaia/ Fri, 19 Dec 2025 16:46:02 +0000 /valiant/?p=5560 Rubio, A. C., Breivik, K., Badenes, C., El-Badry, K., Anguiano, B., Linck, E., Majewski, S. R., & Stassun, K. G. (2025).��.��Astronomy and Astrophysics,��704, A6.��

This study looks at how pairs of stars (binary systems) exchange mass over time and how this process shapes their final outcomes. In many binary systems, material can flow from one star to the other, but this mass transfer can be either stable or unstable, and in some cases the two stars briefly share a common envelope of gas. These processes are complex, so astronomers often use fast computer models called binary population synthesis codes, which simplify the physics by using adjustable parameters to describe how stable mass transfer is, how efficiently mass is accreted, and how effectively a common envelope is ejected. The goal of this work is to better determine realistic values for these uncertain parameters by comparing model predictions with real astronomical observations.

Binary systems made up of a white dwarf and a main-sequence star are especially useful for this purpose because they can form through different evolutionary paths: stable mass transfer, unstable mass transfer with a common-envelope phase, or even with little interaction at all. These different histories leave clear signatures in today’s systems, such as their orbital periods and stellar masses. The authors use the APOGEE–GALEX–Gaia Catalog (AGGC), which contains over 500 such binaries with well-measured radial velocities, as a benchmark. They compare the observed distribution of the maximum change in radial velocity (ΔRVₘₐₓ) with simulated populations generated using COSMIC, a publicly available binary population synthesis code. In the simulations, they vary how stable mass transfer is at different giant-star stages, how efficiently stars eject their envelopes during common-envelope phases, and how much mass is retained during stable transfer.

The comparison shows that the observed data favor models in which a larger fraction of systems undergo stable mass transfer when the donor star is on the first ascent of the giant branch, as well as models where common-envelope ejection is very efficient. For the smaller number of systems where white dwarf masses can be estimated, the results slightly favor nonconservative stable mass transfer, meaning some mass is lost from the system rather than fully accreted. Because COSMIC and similar models link envelope ejection efficiency and envelope binding energy together, the finding of high ejection efficiency may imply either that extra energy sources, such as recombination energy in the envelope, help expel it, or that the envelope is less tightly bound than previously assumed. The authors note that future datasets, including upcoming Gaia releases and observations from the LISA mission, will allow even stronger tests of these models across a wider range of binary systems.

Fig 1.

Overview of the WD binaries in the APOGEE-Gaia-Galex catalog (AGGC). The left panel shows the full APOGEE dataset in blue and the companions of WDs in orange. The right panel shows the ΔRV_max��distribution for different cuts in the data: MS+MS binaries from the full APOGEE dataset in blue, all WD binaries in the AGGC in green, and WD+MS binaries in black. The full APOGEE dataset contains 455796 targets; the MS binaries in that sample number 151266. The full AGGC has 1157 candidate WD binaries, while the WD+MS systems number 588.

]]> /valiant/2025/11/23/procedures-for-constraining-robotic-fiber-positioning-for-highly-multiplexed-spectroscopic-surveys-the-case-of-fps-for-sdss-v/ Sun, 23 Nov 2025 16:59:38 +0000 /valiant/?p=5441 Medan, Ilija., Dwelly, Tom., Covey, Kevin R., Zari, Eleonora., Blanton, Michael R., Carlberg, Joleen K., Chojnowski, Drew D., Ji, Alexander P., Shen, Yue., Donor, John., Sánchez-Gallego, José Ramón., Morrison, Sean S., Ibarra-Medel, Héctor J., Sayres, Conor., & Stassun, Keivan Guadalupe. [2025]. .��Astronomical Journal,��170(5), 267.��

Planning a large astronomical survey requires figuring out how to observe the sky in a way that produces the best possible data. This becomes especially challenging when a survey has many different scientific goals and needs to observe a wide variety of objects. The Sloan Digital Sky Survey V [SDSS-V] fits this description, especially now that it uses the Focal Plane System [FPS]—a robotic system that precisely places optical fibers to collect light for its spectrographs. The FPS increases efficiency and expands the number and types of targets the survey can observe, but it also introduces new constraints: each fiber must be positioned carefully so that multiple science programs can observe their targets at the same time without interfering with one another.

These fiber-placement constraints depend on properties of the targets themselves, such as their type, brightness, and how close they are to other objects in the same field of view. They also depend on the scientific purpose of each observation and the expected sky conditions. In this work, we describe the��SDSS-V data collection scenarios, which are sets of parameters that define how fibers can be arranged for different observational needs. These parameters were determined through previous experience and new tests conducted specifically for SDSS-V, all of which we outline here. Together, they create a framework that allows SDSS-V to plan observations algorithmically—maximizing scientific output while ensuring high data quality throughout the survey.

Figure 1. Comparison of the reduced spectrum of an object [Spec] when using the number of standards [N_sph] and skies [N_sky] in the legend relative to the spectrum of the object when using all of the calibrators [Spec_0]. The sample shown is for plate-MJD 7339–57428. The left panel is for the 67 brightest galaxies [mr < 20] on the plate and the right panel is the faintest galaxies [mr > 20].