Abstract: The COVID-19 pandemic was severely aggravated in Brazil due to its politicization by the country's federal government. However, the impact of diffuse political forces on the fatality of an epidemic is notoriously difficult to quantify. Here we introduce a method to measure this effect in the Brazilian case, based on the inhomogeneous distribution throughout the national territory of political support for the federal government. This political support is quantified by the voting rates in the last general election in Brazil. This data is correlated with the fatality rates by COVID-19 in each Brazilian state as the number of deaths grows over time. We show that the correlation between fatality rate and political support grows as the government's misinformation campaign is developed. This led to the dominance of such political factor for the pandemic impact in Brazil in 2021. Once this dominance is established, this correlation allows for an estimation of the total number of deaths due to political influence as 35070 thousand up to the end of 2021, corresponding to (5711)% of the total number of deaths.

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ADS: https://ui.adsabs.harvard.edu/abs/2022PLoSO..1764293D

Bibcode: 2022PLoSO..1764293D

Abstract: Measuring the stellar rotation of one of the components in eclipsing binaries (EBs) or planetary systems is a challenge task. The difficulty is mainly due to the complexity of analyzing, in the same light curve, the signal from the stellar rotation mixed with the transit signal of a stellar or substellar companion, like a brown dwarf or planet. There are many methods to correct the long-term trend of the light curve. However, the correction often erases the signal of the stellar rotation from spots crossing the visible stellar disk and other weaker signals like planets. In this work, we present the DiffeRencial flUx Method of cuTting Off biNariES (DRUM TONES) to identify the signal of the binary transits and disentangle it from stellar rotation planet signals. We present our technique with applications to EBs from CoRoT, Kepler, Kepler K2 and TESS missions. We also applied our method to simulated synthetic EB from the PLATO mission. Our method shows good agreement in the determination of stellar rotation periods for few observed targets from last space missions, as well it is naturally useful for future European mission, such as PLAnetary Transits and Oscillations of stars (PLATO).

Keywords: Eclipsing binaries, Data analysis, Stellar rotation, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2020ExA....50...73D

Bibcode: 2020ExA....50...73D

Abstract: We propose a new parameterization of the impact parameter u $_0$ and impact angle for microlensing systems composed by an Earth-like exoplanet around a solar-mass star at 1 au. We present the caustic topology of such system, as well as the related light curves generated by using such a new parameterization. Based on the same density of points and accuracy of regular methods, we obtain results five times faster for discovering Earth-like exoplanets. In this big data revolution of photometric astronomy, our method will impact future missions like WFIRST (NASA) and Euclid (ESA) and their data pipelines, providing a rapid and deep detection of exoplanets for this specific class of microlensing event that might otherwise be lost.

Keywords: gravitational lensing: micro, planetary systems, planets and satellites: detection, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2018AJ....156..172D

Bibcode: 2018AJ....156..172D

Abstract: The ExoClock project is an open platform aiming to monitor exoplanets by integrating observations from space- and ground-based telescopes. This study presents an updated catalog of 620 exoplanet ephemerides, integrating 30,000 measurements from ground-based telescopes (the ExoClock network), literature, and space telescopes (Kepler, K2 and TESS). The updated catalog includes 277 planets from TESS which require special observing strategies due to their shallow transits or bright host stars. This study demonstrates that data from larger telescopes, and the employment of new methodologies such as synchronous observations with small telescopes, are capable of monitoring special cases of planets. The new ephemerides show that 45% of the planets required an update while the results show an improvement of 1 order of magnitude in prediction uncertainty. The collective analysis also enabled the identification of new planets showing transit-timing variations, highlighting the importance of extensive observing coverage. Developed in the context of the ESA's Ariel space mission, with the goal of delivering a catalog with reliable ephemerides to increase the mission efficiency, ExoClock's scope and service have grown well beyond the remit of Ariel. The ExoClock project has been operating in the framework of open science, and all tools and products are accessible to everyone within academia and beyond, to support efficient scheduling of future exoplanet observations, especially from larger telescopes where the pressure for time allocation efficiency is higher (Ariel, JWST, VLT, ELT, Subaru etc.). The inclusion of diverse audiences in the process and the collaborative mode not only foster democratization of science but also enhance the quality of the results.

Keywords: Exoplanet catalogs, Amateur astronomers, Open source software, Transit photometry, 488, 34, 1866, 1709, Earth and Planetary Astrophysics, Instrumentation and Methods for Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2026ApJS..283....5K

Bibcode: 2026ApJS..283....5K

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Abstract: High-cadence multi-band imaging and polarimetry have important scientific applications in astronomy. Observations of transits of exoplanets consist of a particular application that requires robust data reduction and analysis. We present the SPARC4 Pipeline, a suite of routines developed to process photometric and polarimetric data obtained with the instrument SPARC4 installed on the 1.6 m telescope at Pico dos Dias Observatory, Brazil. The scientific data products, up to the generation of high-cadence time series, are demonstrated using observations of several transiting exoplanetary systems in both photometric and polarimetric modes. These observations are used to produce stacked calibrated images, yielding sub-arcsecond astrometric accuracy even in sparse fields. The time series of these fields enabled a photometric characterization of the instrument. Observations of polarimetric standard stars yield an instrumental polarization below 0.06% and a linear polarization accuracy of 0.2%. Furthermore, transit observations of seven exoplanets with host-star magnitudes in the range 10.2 < V < 13.9 demonstrate that SPARC4 achieves an average photometric precision of 0.02% for a 15 minute cadence and a polarimetric precision of 0.02% over hours-long time series. Finally, we jointly model the SPARC4 light curves together with TESS data (or K2 data in the case of HATS-9) using a Bayesian MCMC framework to refine the constraints on the physical parameters of the exoplanets, enabling a more accurate determination of the orbital periods and planetary radii, thereby providing improved constraints on the orbital and physical parameters of these hot Jupiters.

Keywords: Astronomy data reduction, Photometry, Polarimetry, Exoplanets, 1861, 1234, 1278, 498, Earth and Planetary Astrophysics, Instrumentation and Methods for Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2026PASP..138e4502M

Bibcode: 2026PASP..138e4502M

Abstract: We present observations and analysis of two low planet/host mass-ratio ($q$) microlensing planets discovered in high-magnification events. KMT-2025-BLG-0811Lb has $q 4.5 10^-5$, and a Bayesian analysis favors a super-Earth/mini-Neptune orbiting an M- or K-dwarf host at a projected separation of $ 3$ au. KMT-2025-BLG-0912Lb has $q = 2.6 10^-4$ and likely hosts a super-Earth/mini-Neptune around either a low-mass M dwarf or a brown dwarf at $ 1$ au. Even with an observing cadence of $Γ> 30 hr^-1$ during the planetary signal, KMT-2025-BLG-0811 still exhibits the ``central-resonant'' degeneracy. Reviewing nine such events, we find that the ``central-resonant'' degeneracy can be divided into two distinct types that occupy separate regions in the plane of $q$ and normalized source radius ($ρ$). Type~I events have similar $q$ but substantially different $ρ$ and are more difficult to resolve from the light curves. For Type~II events, the ``resonant'' solutions have relatively lower $q$ and larger $ρ$. Our review provides guidance for searching for the alternative solution once one solution has been identified.

Keywords: Earth and Planetary Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2026arXiv260309045T

Bibcode: 2026arXiv260309045T

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Abstract: PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2REarth) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5%, 10%, 10% for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO's target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile towards the end of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.

Keywords: PLATO mission, Exoplanets, Asteroseismology, Physical Sciences, Astronomical and Space Sciences, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2025ExA....59...26R

Bibcode: 2025ExA....59...26R

Abstract: We present HIP 8522, a young solar twin with the lowest detected lithium abundance, potentially a field blue straggler or the result of episodic early accretion. Its stellar parameters (T$_eff$ = 5729 7 K, = 4.532 0.016 dex, [Fe/H] = 0.005 0.010 dex, and v$_t$ = 1.08 0.02 km s$^-1$) and chemical composition were determined via spectroscopic equilibrium using high-resolution spectra (R = 60,000─165,000). The age of HIP 8522 was estimated to have an upper limit of <1 Gyr through isochrone fitting and was further confirmed using chemical clocks. Spectral synthesis of the lithium line at 6707.8 Å yielded an upper lithium abundance limit of A(Li) < 0.8 dex. This value is unusually low for solar twins of similar age, which typically have A(Li) values ranging from 2.0 to 3.3 dex, suggesting that 2 dex of lithium is missing. We investigate various scenarios, such as planet engulfment, substellar mergers, and extra mixing. However, two distinct hypotheses provide plausible explanations for the significant depletion of lithium: one suggests that HIP 8522 is a field blue straggler formed by the merger of a close binary, while the other proposes that HIP 8522 experienced early episodic accretion. The young solar twin HIP 8522 presents an exceptional opportunity to rigorously test stellar evolution models and gain crucial insights into the internal mixing mechanisms responsible for the significant destruction of lithium. *This research is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan (NAOJ). We are honored and grateful for the opportunity of observing the Universe from the Maunakea, which has cultural, historical, and natural significance in Hawaii. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory (LCO), Chile.

Keywords: Spectroscopy, Stellar abundances, Stellar atmospheres, Fundamental parameters of stars, Solar analogs, Blue straggler stars, Accretion, 1558, 1577, 1584, 555, 1941, 168, 14, Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2025ApJ...983...70Y

Bibcode: 2025ApJ...983...70Y

Abstract: Measuring starspot temperatures is crucial for understanding stellar magnetic activity as it affects stellar brightness variations, influences exoplanet transit measurements, and provides constraints on the physical conditions and energy transport in active regions, offering insights into stellar dynamos. Our goal is to determine the temperature of starspots on the active star CoRoT-2 to enhance our understanding of magnetic activity in young, solar-like stars. Multiwavelength observations were conducted using the Simultaneous Polarimeter and Rapid Camera in Four bands instrument on the 1.6 m telescope at Pico dos Dias Observatory (Brazil), capturing simultaneous transit data in four photometric bands (g, r, i, and z). The ECLIPSE model, combined with Markov Chain Monte Carlo fitting, was used to model spot characteristics during the planetary transit of CoRoT-2 b. The spot intensities were analyzed considering three different methods: the assumption of blackbody emission, the PHOENIX atmospheric model, and multiwavelength fitting assuming the same spot parameters for all wavelengths. Two starspots were detected in the residuals of the light curve, yielding temperature estimates of 5040─5280 K based on the three different methods. These values align more closely with the temperatures of solar penumbrae than with typical umbral temperatures, suggesting relatively moderate magnetic activity. The radius of the spots ranged from 0.34 to 0.61 the planetary radius, or equivalently (38─69) × 10$^6$ m, much larger than sunspots. This study provides a method to estimate spot temperatures on active stars using multiband photometry, with results indicating penumbral-like temperatures on CoRoT-2. The methodology enhances precision in starspot temperature estimation, beneficial for studies of stellar activity and exoplanet characterization.

Keywords: Starspots, Stellar activity, 1572, 1580, Solar and Stellar Astrophysics, Earth and Planetary Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2025ApJ...992..174V

Bibcode: 2025ApJ...992..174V

Abstract: Neutron star-black hole (NSBH) mergers, detectable via their gravitational-wave (GW) emission, are expected to produce kilonovae (KNe). Four NSBH candidates have been identified and followed-up by more than fifty instruments since the start of the fourth GW observing run (O4), in May 2023, up to July 2024; however, no confirmed associated KN has been detected. This study evaluates ejecta properties from multimessenger observations to understand the absence of detectable KN: we use GW public information and joint observations taken from 05.2023 to 07.2024 (LVK, ATLAS, DECam, GECKO, GOTO, GRANDMA, SAGUARO, TESS, WINTER, ZTF). First, our analysis on follow-up observation strategies shows that, on average, more than 50% of the simulated KNe associated with NSBH mergers reach their peak luminosity around one day after merger in the g, r, i- bands, which is not necessarily covered for each NSBH GW candidate. We also analyze the trade-off between observation efficiency and the intrinsic properties of the KN emission, to understand the impact on how these constraints affect our ability to detect the KN, and underlying ejecta properties for each GW candidate. In particular, we can only confirm the kilonova was not missed for 1% of the GW230529 and S230627c sky localization region, given the large sky localization error of GW230529 and the large distance for S230627c and, their respective KN faint luminosities. More constraining, for S230518h, we infer the dynamical ejecta and postmerger disk wind ejecta mdyn,mwind0.03M☉ and the viewing angle >25°. Similarly, the nonastrophysical origin of S240422ed is likely further confirmed by the fact that we would have detected even a faint KN at the time and presumed distance of the S240422ed event candidate, within a minimum 45% credible region of the sky area, that can be larger depending on the KN scenario.

Keywords: Astrophysics and astroparticle physics, High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology

ADS: https://ui.adsabs.harvard.edu/abs/2025PhRvD.112h3002P

Bibcode: 2025PhRvD.112h3002P

Abstract: We present observations and analyses of three high-magnification microlensing events: KMT-2022-BLG-0954, KMT-2024-BLG-0697, and MOA-2024-BLG-018. All three exhibit the 'Planet/Binary' degeneracy, with planetary solutions corresponding to mass ratios in the range , while the binary solutions yield . For KMT-2022-BLG-0954, we identify a previously unrecognized degeneracy among planetary solutions, involving different mass ratios and normalized source radii. In all three cases, single- lens binary-source models are excluded. Bayesian analyses suggest that the planetary solutions correspond to gas giants orbiting M/K dwarfs beyond the snow line, while KMT-2022-BLG-0954 also admits an alternative interpretation as a super-Earth orbiting a late-type M dwarf. The binary solutions imply a diverse set of systems, including M-dwarf pairs and M-dwarf─brown-dwarf binaries. A review of known events subject to the 'Planet/Binary' degeneracy shows that in most cases the degeneracy cannot be resolved through follow-up high-resolution imaging, particularly in the presence of the newly identified degeneracy.

Keywords: gravitational lensing: micro, planets and satellites: detection, Earth and Planetary Astrophysics, Astrophysics of Galaxies, Instrumentation and Methods for Astrophysics, Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2026MNRAS.545f1893Z

Bibcode: 2026MNRAS.545f1893Z

Abstract: The current studies of microlensing planets are limited by small number statistics. Follow-up observations of high-magnification microlensing events can efficiently form a statistical planetary sample. Since 2020, the Korea Microlensing Telescope Network (KMTNet) and the Las Cumbres Observatory (LCO) global network have been conducting a follow-up program for high-magnification KMTNet events. Here, we report the detection and analysis of a microlensing planetary event, KMT-2023-BLG-1431, for which the subtle (0.05 mag) and short-lived (5 hr) planetary signature was characterized by the follow-up from KMTNet and LCO. A binary- lens single-source (2L1S) analysis reveals a planet/host mass ratio of q = (0.72 0.07) × 10$^-4$, and the single-lens binary-source (1L2S) model is excluded by $^2$ = 80. A Bayesian analysis using a Galactic model yields estimates of the host star mass of , the planetary mass of , and the lens distance of kpc. The projected planet-host separation of au or au, subject to the close/wide degeneracy. We also find that without the follow-up data, the survey-only data cannot break the degeneracy of central/resonant caustics and the degeneracy of 2L1S/1L2S models, showing the importance of follow-up observations for current microlensing surveys.

Keywords: Gravitational microlensing, Gravitational microlensing exoplanet detection, 672, 2147, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2024PASP..136e4402B

Bibcode: 2024PASP..136e4402B

Abstract: We report discovering an exoplanet from following up a microlensing event alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the traditional bulge microlensing fields. Our primary analysis yields a Jovian planet with at a projected orbital separation au, and the host is a 1.1 M $_☉$ turnoff star at 1.3 kpc. At , the host is far brighter than any previously discovered microlensing planet host, opening up the opportunity to test the microlensing model with radial velocity (RV) observations. RV data can be used to measure the planet's orbital period and eccentricity, and they also enable searching for inner planets of the microlensing cold Jupiter, as expected from the ``inner─outer correlation'' inferred from Kepler and RV discoveries. Furthermore, we show that Gaia astrometric microlensing will not only allow precise measurements of its angular Einstein radius $_E$ but also directly measure the microlens parallax vector and unambiguously break a geometric light-curve degeneracy, leading to the definitive characterization of the lens system.

Keywords: Gravitational microlensing exoplanet detection, 2147, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2024AJ....168...62W

Bibcode: 2024AJ....168...62W

Abstract: Context. Young planetary systems represent an opportunity to investigate the early stages of (exo)planetary formation because the gravitational interactions have not yet significantly changed the initial configuration of the system. Aims. TOI-4562 b is a highly eccentric temperate Jupiter analogue orbiting a young F7V-type star of < 700 Myr in age with an orbital period of P$_orb$ 225 days and an eccentricity of e = 0.76, and is one of the largest known exoplanets to have formed in situ. Methods. We observed a new transit of TOI-4562 b using the 0.6-m Zeiss telescope at the Pico dos Dias Observatory (OPD/LNA) in Minas Gerais, Brazil, and combine our data with Transiting Exoplanet Survey Satellite (TESS) and archive data, with the aim being to improve the ephemerides of this interesting system. Results. The O - C diagram for the new ephemeris is consistent with the presence of a giant planet in an outer orbit around TOI-4562. TOI-4562 c is a planet with a mass of M = 5.77 M$_Jup$, an orbital period of P$_orb$ = 3990 days, and a semi-major axis of a = 5.219 AU. Conclusions. We report the discovery of TOI-4562 c, the exoplanet with the longest orbital period discovered to date via the transit timing variation (TTV) method. The TOI-4562 system is in the process of violent evolution with intense dynamical changes ─ judging by its young age and high eccentricity ─ and is therefore a prime target for studies of formation and evolution of planetary systems.

Keywords: planets and satellites: dynamical evolution and stability, planets and satellites: formation, stars: activity, Astrophysics - Earth and Planetary Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2024A&A...690L...7F

Bibcode: 2024A&A...690L...7F

Abstract: The sub-Jovian desert is a region in the mass-period and radius-period parameter space that typically encompasses short-period ranges between super-Earths and hot Jupiters, and exhibits an intrinsic dearth of planets. This scarcity is likely shaped by photoevaporation caused by the stellar irradiation received by giant planets that have migrated inward. We report the detection and characterization of TOI-3568 b, a transiting super-Neptune with a mass of 26.4 1.0 M$_$, a radius of 5.30 0.27 R$_$, a bulk density of 0.98 0.15 g cm$^-3$, and an orbital period of 4.417965 (5) d situated in the vicinity of the sub-Jovian desert. This planet orbiting a K dwarf star with solar metallicity was identified photometrically by the Transiting Exoplanet Survey Satellite (TESS). It was characterized as a planet by our high-precision radial-velocity (RV) monitoring program using MAROON-X at Gemini North, supplemented with additional observations from the SPICE large program with SPIRou at CFHT. We performed a Bayesian MCMC joint analysis of the TESS and ground-based photometry, and MAROON-X and SPIRou RVs, to measure the orbit, radius, and mass of the planet, as well as a detailed analysis of the high-resolution flux and polarimetric spectra to determine the physical parameters and elemental abundances of the host star. Our results reveal TOI-3568 b to be a hot super-Neptune rich in hydrogen and helium, with a core of heavier elements of between 10 and 25 M$_$ in mass. We analyzed the photoevaporation status of TOI-3568 b and find that it experiences one of the highest extreme-ultraviolet (EUV) luminosities among planets with a mass of M$_p$ < 2 M$_Nep$, yet it has an evaporation lifetime exceeding 5 Gyr. Positioned in the transition between two significant populations of exoplanets on the mass-period and energy diagrams, this planet presents an opportunity to test theories concerning the origin of the sub-Jovian desert.

Keywords: techniques: photometric, techniques: radial velocities, planetary systems, stars: individual: TOI-3568, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2024A&A...690A.312M

Bibcode: 2024A&A...690A.312M

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Abstract: First detected on 2023 November 4 by the Gravitational-wave Optical Transient Observer, SN 2023wrk is a Type Ia Supernova at 40 Mpc, with significant unburned carbon in the outer ejecta. In this note, we present photometric and spectroscopic observations and analysis conducted by the Global Rapid Advanced Network Devoted to the Multi-messenger Addict over a 115 days period, which includes 78 days of measurements. The observations were contributed by both amateur and professional astronomers. J. Liu et al. analyzed the physical processes involved, and compared the evolution of color and spectral lines. We conclude that SN 2023wrk is the second 1999aa-like object with strong carbon absorption lines that has ever been found, which enriches our understanding of the subclass of 1999aa-like SNe.

Keywords: Time domain astronomy, Amateur astronomers, Amateur astronomy, Supernovae, Type Ia supernovae, Gravitational wave astronomy, Gravitational waves, White dwarf stars, High energy astrophysics, Transient detection, Transient sources, Ejecta, 2109, 34, 35, 1668, 1728, 675, 678, 1799, 739, 1957, 1851, 453

ADS: https://ui.adsabs.harvard.edu/abs/2024RNAAS...8..273A

Bibcode: 2024RNAAS...8..273A

Abstract: TOI-1695 is a V-mag = 13 M-dwarf star from the northern hemisphere at 45 pc from the Sun, around which a 3.134-day periodic transit signal from a super-Earth candidate was identified in TESS photometry. With a transit depth of 1.3 mmag, the radius of candidate TOI-1695.01 was estimated by the TESS pipeline to be 1.82 R$_$ with an equilibrium temperature of ~620 K. We successfully detected a reflex motion of the star and establish that it is due to a planetary companion at an orbital period consistent with the photometric transit period, thanks to a year-long radial-velocity monitoring of TOI-1695 by the SPIRou infrared spectropolarimeter. We used and compared different methods to reduce and analyze those data. We report a 5.5 detection of the planetary signal, giving a mass of 5.51.0 M$_$ and a radius of 2.030.18 R$_$. We derive a mean equilibrium planet temperature of 59090 K. The mean density of this small planet of 3.61.1 g cm$^‒3$ is similar (1.7 lower) than that of the Earth. It leads to a nonnegligible fraction of volatiles in its atmosphere with f$_H,He$ = 0.28$_‒0.23$$^+0.46$% or f$_water$ = 2312%. TOI-1695 b is a new sub-Neptune planet at the border of the M-dwarf radius valley that can help test formation scenarios for super-Earth and sub-Neptune-like planets.

Keywords: planets and satellites: detection, planets and satellites: fundamental parameters, planets and satellites: individual: TOI-1695 b, techniques: photometric, techniques: radial velocities, Astrophysics - Earth and Planetary Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2023A&A...670A.136K

Bibcode: 2023A&A...670A.136K

Abstract: Characterizing the cyclic magnetic activity of stars that are close approximations of our Sun offers our best hope for understanding our Sun's current and past magnetism, the space weather around solar-type stars, and more generally, the dynamos of other cool stars. The nearest current approximation to the Sun is the solar twin 18 Scorpii, a naked-eye Sun-like star of spectral type G2 Va. However, while 18 Scorpii's physical parameters closely match those of the Sun, its activity cycle is about 7 yr, and shorter than the solar cycle. We report the measurement of a periodicity of 15 yr that corresponds to a longer activity cycle for 18 Scorpii based on observations extending to the last three decades. The global magnetic geometry of 18 Scorpii changes with this 15 yr cycle and appears to be equivalent to the solar 22 yr magnetic polarity cycle. These results suggest that 18 Scorpii is also a magnetic proxy for a younger Sun, adding an important new datum for testing dynamo theory and magnetic evolution of low-mass stars. The results perturb our understanding of the relationship between cycle and rotation, constrain the Sun's magnetism and the Sun-Earth connection over the past billion years, and suggest that solar Schwabe and Hale cycle periods have increased over that time span.

Keywords: Solar cycle, Stellar evolution, Stellar magnetic fields, Solar analogs, Spectropolarimetry, 1487, 1599, 1610, 1941, 1973

ADS: https://ui.adsabs.harvard.edu/abs/2023ApJ...958...57D

Bibcode: 2023ApJ...958...57D

Abstract: Planetary systems around solar analogs inform us about how planets form and evolve in Solar System-like environments. We report the detection and characterization of two planetary systems around the solar analogs TOI-1736 and TOI-2141 using TESS photometry data and spectroscopic data obtained with the SOPHIE instrument on the 1.93 m telescope at the Observatoire de Haute-Provence (OHP). We performed a detailed spectroscopic analysis of these systems to obtain the precise radial velocities (RV) and physical properties of their host stars. TOI-1736 and TOI-2141 each host a transiting sub-Neptune with radii of 2.44 0.18 R$_$ and 3.05 0.23 R$_$, orbital periods of 7.073088(7) days and 18.26157(6) days, and masses of 12.8 1.8 M$_$ and 24 4 M$_$, respectively. TOI-1736 shows long-term RV variations that are consistent with a two-planet solution plus a linear trend of ‒0.177 m s$^‒1$ day$^‒1$. We measured an RV semi-amplitude of 201.1 0.7 m s$^‒1$ for the outer companion, TOI-1736 c, implying aprojected mass of m$_c$sin i = 8.09 0.20 M$_Jup$. From the Gaia DR3 astrometric excess noise, we constrained the mass of TOI-1736 c at 8.7$_‒0.6$$^+1.5$ M$_Jup$. This planet is in an orbit of 570.2 0.6 days with an eccentricity of 0.362 0.003 and a semi-major axis of 1.381 0.017 au, where it receives a flux of 0.71 0.08 times the bolometric flux incident on Earth, making it an interesting case of a supergiant planet that has settled into an eccentric orbit in the habitable zone of a solar analog. Our analysis of the mass-radius relation for the transiting sub-Neptunes shows that both TOI-1736 b and TOI-2141 b likely have an Earth-like dense rocky core and a water-rich envelope. Tables A.1 and A.2 data are available at the CDS via anonymous ftp to <A href=``htt ps://cdsarc.cds.unistra.fr/''>cdsarc.cds.unistra.fr</A> (ftp://130.79.128.5) or via <A href=``https://cdsarc.cds.unistra.fr/viz- bin/cat/J/A+A/680/A84''>https://cdsarc.cds.unistra.fr/viz- bin/cat/J/A+A/680/A84</A>

Keywords: planetary systems, stars: individual: TOI-1736, stars: individual: TOI-2141, stars: solar-type, techniques: photometric, techniques: radial velocities, Astrophysics - Earth and Planetary Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2023A&A...680A..84M

Bibcode: 2023A&A...680A..84M

Abstract: We report the detection and characterization of the transiting sub- Neptune TOI-1759 b, using photometric time series from the Transiting Exoplanet Survey Satellite (TESS) and near-infrared spectropolarimetric data from the Spectro-Polarimètre Infra Rouge (SPIRou) on the Canada-France-Hawaii Telescope. TOI-1759 b orbits a moderately active M0V star with an orbital period of 18.849975 0.000006 days, and we measured a planetary radius and mass of 3.06 0.22 R$_$ and 6.8 2.0 M$_$. Radial velocities were extracted from the SPIRou spectra using both the cross-correlation function and the line-by-line methods, optimizing the velocity measurements in the near-infrared domain. We analyzed the broadband spectral energy distribution of the star and the high- resolution SPIRou spectra to constrain the stellar parameters and thus improve the accuracy of the derived planet parameters. A least squares deconvolution analysis of the SPIRou Stokes V polarized spectra detects Zeeman signatures in TOI-1759. We modeled the rotational modulation of the magnetic stellar activity using a Gaussian process regression with a quasi- periodic covariance function and find a rotation period of 35.65$_‒0.15$$^+0.17$ days. We reconstructed the large-scale surface magnetic field of the star using Zeeman-Doppler imaging, which gives a predominantly poloidal field with a mean strength of 18 4 G. Finally, we performed a joint Bayesian Markov chain Monte Carlo analysis of the TESS photometry and SPIRou radial velocities to optimally constrain the system parameters. At 0.1176 0.0013 au from the star, the planet receives 6.4 times the bolometric flux incident on Earth, and its equilibrium temperature is estimated at 433 14 K. TOI-1759 b is a likely gas- dominated sub-Neptune with an expected high rate of photoevaporation. Therefore, it is an interesting target to search for neutral hydrogen escape, which may provide important constraints on the planetary formation mechanisms responsible for the observed sub-Neptune radius desert. F.1-F.3 are also available at the CDS via anonymous ftp to <A href=``http://cdsarc.u-strasbg.fr''>cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href=``http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/660/A86''>http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/660/A86</A> on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated from the summit of Maunakea by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based on observations obtained with SPIRou, an international project led by Institut de Recherche en Astrophysique et Planétologie, Toulouse, France.

Keywords: planetary systems, stars: individual: TOI-1759, techniques: photometric, techniques: radial velocities, stars: magnetic field, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2022A&A...660A..86M

Bibcode: 2022A&A...660A..86M

Abstract: Context. Brown dwarfs are transition objects between stars and planets that are still poorly understood, for which several competing mechanisms have been proposed to describe their formation. Mass measurements are generally difficult to carry out for isolated objects as well as for brown dwarfs orbiting low-mass stars, which are often too faint for a spectroscopic follow-up. Aims: Microlensing provides an alternative tool for the discovery and investigation of such faint systems. Here, we present an analysis of the microlensing event OGLE-2019-BLG-0033/MOA-2019-BLG-035, which is caused by a binary system composed of a brown dwarf orbiting a red dwarf. Methods: Thanks to extensive ground observations and the availability of space observations from Spitzer, it has been possible to obtain accurate estimates of all microlensing parameters, including the parallax, source radius, and orbital motion of the binary lens. Results: Following an accurate modeling process, we found that the lens is composed of a red dwarf with a mass of M$_1$ = 0.149 0.010 M$_☉$ and a brown dwarf with a mass of M$_2$ = 0.0463 0.0031 M$_☉$ at a projected separation of a$_⊥$ = 0.585 au. The system has a peculiar velocity that is typical of old metal-poor populations in the thick disk. A percent-level precision in the mass measurement of brown dwarfs has been achieved only in a few microlensing events up to now, but will likely become more common in the future thanks to the Roman space telescope. lightcurves are only available at the CDS via anonymous ftp to <A href=``http://cdsarc.u-strasbg.fr''>cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href=``http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/663/A100''>http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/663/A100</A>

Keywords: gravitational lensing: micro, binaries: general, brown dwarfs, stars: low-mass, Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies

ADS: https://ui.adsabs.harvard.edu/abs/2022A&A...663A.100H

Bibcode: 2022A&A...663A.100H

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Abstract: We report the discovery of KMT-2020-BLG-0414Lb, with a planet-to-host mass ratio q $_2$ = 0.9─1.2 × 10$^-5$ = 3─4 at 1, which is the lowest mass-ratio microlensing planet to date. Together with two other recent discoveries (4 łesssim q/q $_$ łesssim 6), it fills out the previous empty sector at the bottom of the triangular (log s, log q) diagram, where s is the planet-host separation in units of the angular Einstein radius . Hence, these discoveries call into question the existence, or at least the strength, of the break in the mass-ratio function that was previously suggested to account for the paucity of very low-q planets. Due to the extreme magnification of the event, A $_max$ 1450 for the underlying single-lens event, its light curve revealed a second companion with q $_3$ 0.05 and |log s $_3$| 1, i.e., a factor 10 closer to or farther from the host in projection. The measurements of the microlens parallax $_E$ and the angular Einstein radius allow estimates of the host, planet and second companion masses, (M $_1$, M $_2$, M $_3$) (0.3 M $_☉$, 1.0 M $_$, 17 M$_J$ ), the planet and second companion projected separations, (a $_⊥,2$, a $_⊥,3$) (1.5, 0.15 or 15) au, and system distance D $_L$ 1 kpc. The lens could account for most or all of the blended light (I 19.3) and so can be studied immediately with high-resolution photometric and spectroscopic observations that can further clarify the nature of the system. The planet was found as part of a new program of high-cadence follow-up observations of high- magnification events. The detection of this planet, despite the considerable difficulties imposed by COVID-19 (two KMT sites and OGLE were shut down), illustrates the potential utility of this program.

Keywords: gravitational lensing: micro, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena

ADS: https://ui.adsabs.harvard.edu/abs/2021RAA....21..239Z

Bibcode: 2021RAA....21..239Z

Abstract: In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the High Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.

Keywords: Stellar abundances, High resolution spectroscopy, Red giant clump, Asteroseismology, 1577, 2096, 1370, 73, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2020ApJ...894...67D

Bibcode: 2020ApJ...894...67D

Abstract: Context. One of the most enigmatic phenomena related to solar activity is the so-called Maunder minimum phase. It consists in the lowest sunspot count ever registered for the Sun and has not been confirmed for other stars to date. Since the spectroscopic observations of stellar activity at the Mount Wilson Observatory, the solar analog HD 43587 has shown a very low and apparently invariant activity level, which makes it a Maunder minimum candidate. Aims: We aim to analyze the chromospheric activity evolution of HD 43587 and its evolutive status, with the intention of unraveling the reasons for this low and flat activity. Methods: We used an activity measurements dataset available in the literature, and computed the S-index from HARPS and NARVAL spectra to infer a cycle period. Additionally, we analyzed the CoRoT light curve of HD 43587, and applied gyrochronology and activity calibrations to determine its rotation period. Finally, based on an evolutionary model and the inferred rotation period, we used the EULAG-MHD code to perform global MHD simulations of HD 43587 to get some insight into its dynamo process. Results: We confirm the almost flat activity profile, with a cycle period P$_cyc$ = 10.44 3.03 yr deduced from the S-index time series, and a long-term trend that might be a period of more than 50 yr. It was impossible to define a rotation period from the light curve, however gyrochronology and activity calibrations allow us to infer an indirect estimate of $^̄$P$_rot$ = 22.6 1.9 d. Furthermore, the MHD simulations confirm an oscillatory dynamo with a cycle period in good agreement with the observations and a low level of surface magnetic activity. Conclusions: We conclude that this object might be experiencing a ``natural'' decrease in magnetic activity as a consequence of its age. Nevertheless, the possibility that HD 43587 is in a Maunder minimum phase cannot be ruled out.

Keywords: stars: activity, dynamo, stars: chromospheres, stars: rotation, stars: solar-type, stars: magnetic field, Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2020A&A...640A..46F

Bibcode: 2020A&A...640A..46F

Abstract: A major obstacle to interpreting the rotation period distribution for main-sequence stars from Kepler mission data has been the lack of a precise evolutionary status for these objects. We address this by investigating the evolutionary status based on Gaia Data Release 2 parallaxes and photometry for more than 30,000 Kepler stars with rotation period measurements. Many of these are subgiants and should be excluded in future work on dwarfs. We particularly investigate a 193-star sample of solar analogs and report newly determined rotation periods for 125 of these. These include 54 stars from a prior sample, of which we can confirm the periods for 50. The remainder are new, and 10 of them longer than a solar rotation period, suggesting that Sun-like stars continue to spin down on the main sequence past solar age. Our sample of solar analogs could potentially serve as a benchmark for future missions, such as PLAnetary Transits and Oscillations of stars, and emphasizes the need for additional astrometric, photometric, and spectroscopic information before interpreting the stellar populations and results from time series surveys.

Keywords: Fundamental parameters of stars, Stellar rotation, Stellar activity, Stellar photometry, Stellar evolution, Starspots, 555, 1629, 1580, 1620, 1599, 1572, Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2020ApJ...898..173D

Bibcode: 2020ApJ...898..173D

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ADS: https://ui.adsabs.harvard.edu/abs/2020PLoSO..1537627L

Bibcode: 2020PLoSO..1537627L

Abstract: We present a study of the evolutionary state of a few lithium-rich giant stars based on the Gaia Data Release 2 (DR2) parallaxes and photometry. We also investigate the chromospheric activity, the presence of a surface magnetic field, and the radial velocity for our sample stars. We analysed both archive and new data. We gathered archive spectra from several instruments, mainly ELODIE and NARVAL, and we added new data acquired with the spectrograph MUSICOS. We applied the least-squares deconvolution technique to obtain Stokes V and I mean profiles to compute longitudinal magnetic field for a subset. Moreover, for the same subset, we analysed the Ca II H&K emission lines to calculate the S-index. We also derived atmospheric parameters and Li abundances for all 18 stars of our sample. We found that stars previously classified as red giant branch (RGB) may actually be at a different evolutionary state. Furthermore, we identified that most stars in our sample with detection of surface magnetic field show at least moderate rotation velocities, but none the less, we could not detect a magnetic field in two fast rotators. Because of our small sample of magnetic giants, it is difficult to determine if the presence of surface magnetic field and the Li-rich giant phenomena could be somehow linked. The large variation of the radial velocity of part of our sample indicates that some of them might have a binary companion, which may change the way we look at the Li problem in giant stars.

Keywords: techniques: radial velocities, techniques: spectroscopic, stars: abundances, stars: evolution, stars: late-type, stars: magnetic field, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2020MNRAS.498.2295G

Bibcode: 2020MNRAS.498.2295G

Abstract: We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of M$_P$ = 0.138 0.023 $ M_J$ (43.9 7.3 $\, M_ $ ), a radius of R$_P$ = 0.639 0.013 $ R_J$ (7.16 0.15 $\, R_ $ ), bulk density of $0.65^+0.12_-0.11$ (cgs), and period $18.38818^+0.00085_-0.00084$ $ days$ . TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M$_*$ = 1.390 0.046 $ M_sun$ , R$_*$ = 1.888 0.033 $ R_sun$ , T$_eff$ = 6075 90 $ K$ , and vsin i = 11.3 0.5 km s$^-1$. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a 71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems.

Keywords: asteroseismology, techniques: photometric, techniques: radial velocities, techniques: spectroscopic, planetary systems, stars: individual (TIC 200723869/TOI-257), Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2021MNRAS.502.3704A

Bibcode: 2021MNRAS.502.3704A

Abstract: In recent years, several close post-common-envelope eclipsing binaries have been found to show cyclic eclipse timing variations (ETVs). This effect is usually interpreted either as the gravitational interaction among circumbinary bodies and the host binary—known as the light travel time (LTT) effect—or as the quadrupole moment variations in one magnetic active component—known as the Applegate mechanism. In this study, we present an analysis of the ETV and the magnetic cycle of the close binary KIC 10544976. This system is composed of a white dwarf and a red dwarf in a short orbital period (0.35 days) and was monitored by ground-based telescopes between 2005 and 2017 and by the Kepler satellite between 2009 and 2013. Using the Kepler data, we derived the magnetic cycle of the red dwarf by two ways: the rate and energy of flares and the variability due to spots. Both methods resulted in a cycle of 600 days, which is in agreement with magnetic cycles measured for single low-mass stars. The orbital period of KIC 10544976 shows only one long-term variation which can be fitted by an LTT effect with period of 16.8 yr. Hence, one possible explanation for the ETVs is the presence of a circumbinary body with a minimal mass of 13.4 M $_Jup$. In the particular scenario of coplanarity between the external body and the inner binary, the third body mass is also 13.4 M $_Jup$. In this case, the circumbinary planet must either have survived the evolution of the host binary or have been formed as a consequence of its evolution.

Keywords: binaries: eclipsing, planetary systems, stars: activity, stars: flare, stars: individual: KIC 10544976, starspots, Astrophysics - Solar and Stellar Astrophysics

ADS: https://ui.adsabs.harvard.edu/abs/2019AJ....157..150A

Bibcode: 2019AJ....157..150A

Abstract: This study investigates the polarization of Novae stars, focusing on the targets V1723 Sco and V572 Vel. Observations were conducted at the Observatório do Pico dos Dias using IAGPOL and SPARC4 polarimetric instruments. The main objective is to evaluate whether these Novae exhibit intrinsic polarization rather than polarization originating from the interstellar medium. Polarimetric measurements often reflect a combination of signals from both the source and the interstellar medium. Therefore, a crucial step in the analysis is to disentangle these contributions in order to confirm whether the observed polarization truly originates from the Nova itself. Such polarization can provide insights into the system, for example by revealing asymmetries in the geometry of the ejected material or by indicating whether the scattering within the ejecta is caused by dust or by electrons, as suggested by the spectral dependence of the polarization.

Keywords: novae, cataclysmic variables, Techniques: polarimetric

ADS: https://ui.adsabs.harvard.edu/abs/2026asab.confE...1M

Bibcode: 2026asab.confE...1M

Abstract: We introduce the SPARC4 Pipeline, an automated data reduction software package designed to process photometric and polarimetric data in four photometric bands (g, r, i, z), obtained with the new instrument SPARC4 installed on the 1.6 m telescope at the Pico dos Dias Observatory. The software is open source, written in Python, based on the ASTROPOP package and other widely used astronomical packages. We present the main strategies and techniques used for calibrating the images and obtaining aperture photometry and dual-beam polarimetry of point-like sources. Science-grade reduction products for observations obtained during commissioning and science verification runs are presented, covering a broad range of scientific applications. Specifically, we present the following results: astrometric and photometric calibration of a crowded field; high-precision, high-cadence photometric and polarimetric time series for a delta-Scuti variable star and a transit of the exoplanet WASP-78 b; polarimetric results from a standard star in the Flame Nebula; and a deep image of an extended object -- the spiral galaxy pair NGC-4045.

Keywords: SPARC4, Data reduction software, Photometry, Polarimetry

ADS: https://ui.adsabs.harvard.edu/abs/2025BASBr..36...65M

Bibcode: 2025BASBr..36...65M

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Abstract: The instrument Simultaneous Polarimeter and Rapid Camera in Four Bands (SPARC4) is being commissioned in the 1.6 m telescope of the Pico dos Dias Observatory (OPD). It is the result of a partnership between Instituto Nacional de Pesquisas Espaciais (INPE) and Laboratório Nacional de Astrofísica (LNA). In this work, we present the photometric characterization of SPARC4, such as its field distortions and signal-to-noise ratio. We will also discuss the photometric calibration procedure done through astronomical catalogs (e.g. Gaia DR3). Finally, we discuss the quality and consistency of the transformations of the natural system to the Sloan Sky Digital Survey (SDSS) griz standard system, given that the SPARC4 bands were designed to be similar to those of SDSS.

Keywords: Instrumentation: photometers, Techniques: photometric, Methods: observational

ADS: https://ui.adsabs.harvard.edu/abs/2024BASBr..35..313S

Bibcode: 2024BASBr..35..313S

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ADS: https://ui.adsabs.harvard.edu/abs/2023BASBr..34...84F

Bibcode: 2023BASBr..34...84F

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ADS: https://ui.adsabs.harvard.edu/abs/2023BASBr..34..281S

Bibcode: 2023BASBr..34..281S

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ADS: https://ui.adsabs.harvard.edu/abs/2023BASBr..34..300B

Bibcode: 2023BASBr..34..300B

Abstract: We performed a validation exercise to recover the rotational modulation for 1,000 simulated PLATO light curves. We created a powerful simulation tool built upon the PLATO Solar-like Light-curve Simulator combining astrophysical (starspot rotation and evolution, planetary transits, oscillations, and granulations) and systematic instrumental effects. The simulated light curves follow specifications from the PLATO telescope in order to closely reproduce the expected raw data. We present a method of stitching and detrending to recover the original signal while also separating the rotational signal from the transit/eclipsing one. We find that a precise determination of rotation periods using this pre-processing pipeline is possible at every level of activity. From the stars with clear rotation determination, 92% of the values we recover are within the 10% confidence interval of the inputs.

Keywords: Rotation modulation, Transits, Light Curve, Zenodo community plato2021

ADS: https://ui.adsabs.harvard.edu/abs/2021plat.confE..60D

Bibcode: 2021plat.confE..60D

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Abstract: Here we report the following limiting magnitudes, uncorrected for Galactic extinction: Filter | Mag (AB) r | > 22.53 This result is in agreement with the analysis of DECam GW-MMADS (GCN 41197). We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (http://grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518).

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ADS: https://ui.adsabs.harvard.edu/abs/2025GCN.41216....1C

Bibcode: 2025GCN.41216....1C

Abstract: Based on the coordinates of the field center (RA=10:25:19.48, DEC=-27:41:54.00), we obtained 12 frames of 300 seconds each using the 0.6m telescope of OPD, starting on 2025-02-16 at 02:30:42.23 and ending at 07:43:29.39 UTC. The FOV of the stacked image is 10.5x10.5 arcmin with a pixel scale of 0.614 arcsec/pixel. We did not detect any candidate in our stacked images with an upper limit of I > 21.34 mag at 5-sigma, calibrated against several stars of the I/339 catalog (HSOY, Altmann et al, 2017). Our non-detection upper limit is similar to the results of Ducoin et al. (GCN 39344) with nothing brighter than 22.7 mag detected in r. Our results are also in slight discrepancy with the findings of Malesani et al. (GCN 39341). GRANDMA is a worldwide telescope network (http://grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518).

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ADS: https://ui.adsabs.harvard.edu/abs/2025GCN.39353....1D

Bibcode: 2025GCN.39353....1D

Abstract: We observed the field of GRB 241217A / EP241217B, detected by SVOM/ECLAIRs (GCN 38594) and Einstein Probe (GCN 38606), using T1MPicduMidi, starting 5 hours after T0. We obtain the following optical 5-sigma upperlimit at the SVOM/VT position (GCN 38600): | Tstart (UTC) | Telescope | Exposure | Filter | Magnitude | | 2024-12-17T22:09:50 | T1MPicduMidi | 126x60s | r | >21.46 (AB) | We also do not detect any uncatalogued sources within the SVOM/ECLAIRs error region, down to a 5-sigma upper limit of r > 21.35 (AB). All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022), and calibrated with the Pan-STARRS DR1 catalogue. GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518).

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ADS: https://ui.adsabs.harvard.edu/abs/2024GCN.38628....1H

Bibcode: 2024GCN.38628....1H

Abstract: We observed the field of GRB 241217A, detected by SVOM/ECLAIRs (GCN 38594) using TAROT/TRE. Observations (unfiltered) began at 2024-12-17T17:22:00UTC, 19 min after T0 and continued up to 45 min after T0. We did not detect any optical afterglow candidate in our stacked images within a 5-sigma upper limit of r > 18.1 (AB magnitude, calibrated with PanSTARRS). All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518).

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ADS: https://ui.adsabs.harvard.edu/abs/2024GCN.38597....1H

Bibcode: 2024GCN.38597....1H

Abstract: We performed observations with the GRANDMA network on the field of GRB 241006A, detected by Swift-BAT (GCN 37722). The first images were taken at OPD starting from 2024-10-07T01:01:42, 3 hours after the GRB trigger, in the I and R filters. TRT-SBO also observed the field in R and I filters starting from 2024-10-07T09:26:52, 11.5 hours after the trigger. We did not detect any optical counterparts of the Swift-XRT afterglow position (RaDec 304.74263 -40.80500, GCN 37724), with the following 5-sigma upperlimits at its coordinates: +------------- +-------------+--------+----------+-----------+-------------+ | MJD (start) | T-T0 (days) | Filter | Exposure | Telescope | U.L. (Vega) | |-------------+-------------+--------+----------+------ -----+-------------+ | 60590.0429 | 0.1318 | I | 16x360s | OPD | 19.6 | |-------------+-------------+--------+----------+-------- ---+-------------+ | 60590.0556 | 0.1445 | R | 9x360s | OPD | 20.1 | |-------------+-------------+--------+----------+-------- ---+-------------+ | 60590.3937 | 0.4826 | R | 5x300s | TRT-SBO | 21.6 | |-------------+-------------+--------+----------+------ -----+-------------+ | 60590.4079 | 0.4968 | I | 5x300s | TRT- SBO | 20.0 | +-------------+-------------+--------+----------+-- ---------+-------------+ We also searched the Swift-BAT field (RA, Dec 304.794, -40.796, uncertainty 3 arcmin) and did not detect any optical counterpart. The 5-sigma upperlimits on the field are: +-------------+-------------+--------+----------+---- -------+-------------+ | MJD (start) | T-T0 (days) | Filter | Exposure | Telescope | U.L. (Vega) | |-------------+------------ -+--------+----------+-----------+-------------+ | 60590.0429 | 0.1318 | I | 16x360s | OPD | 19.4 | |-------------+------------- +--------+----------+-----------+-------------+ | 60590.0556 | 0.1445 | R | 9x360s | OPD | 20.0 | |-------------+-------------+ --------+----------+-----------+-------------+ | 60590.3937 | 0.4826 | R | 5x300s | TRT-SBO | 21.5 | |-------------+---------- ---+--------+----------+-----------+-------------+ | 60590.4079 | 0.4968 | I | 5x300s | TRT-SBO | 19.9 | +-------------+-------- -----+--------+----------+-----------+-------------+ All the data has been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). We use the SkyPortal application (skyportal.io) to monitor our observational campaign. GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi- messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518)

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ADS: https://ui.adsabs.harvard.edu/abs/2024GCN.37738....1H

Bibcode: 2024GCN.37738....1H

Abstract: We observed the localization region of the neutrino event IceCube-240424A (Zegarelli, GCN 36283; Mand, GCN 36309) primarily at the location of the gamma-ray source Fermi J2151.3+0220 (Garrappa et. al, GCN 36349; RA: 327.83 deg, DEC: 2.34 deg). We considered T0 as 2024-04-24 01:49:26.0 UT. We did not find any optical counterpart in our images within a 10 arcmin radius around the J2151.3+0220 position for the ASO telescope, and within a 5 arcmin radius for the OPD telescope. In the following table, we report a subset of the preliminary photometry of our observations of J2151.3+0220. Upper limits are reported in the Vega system. | T-T0 [day] | MJD | Telescope | Exposure | Filter | Upperlimit (5 sig.) | +------------+-------- --------+-----------+-----------+--------+---------------------+ | 6.07 | 60430.15036744 | ASO | 17x180s | L | 21.8 | | 7.19 | 60431.26727265 | OPD | 10x180s | R | 20.8 | | 7.21 | 60431.28910205 | OPD | 10x200s | R | 21.1 | | 7.24 | 60431.31329227 | OPD | 12x250s | R | 21.4 | ASO and OPD data have been calibrated in V and in R, respectively, using the Gaia DR3 Synphot catalog All the data have been reduced by a single data processing pipeline STDPIPE (Karpov et al., 2022). GRANDMA is a worldwide coordinated telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).

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ADS: https://ui.adsabs.harvard.edu/abs/2024GCN.36396....1A

Bibcode: 2024GCN.36396....1A

Abstract: We report photometry of Type II SN 2024jlf (TNSTR-2024-1682, TNSCR-2024-1686) gathered with the OAUNI 51cm telescope (arXiv:1512.03104) at Huancayo Observatory, Peru.

Keywords: Supernovae, Transient

ADS: https://ui.adsabs.harvard.edu/abs/2024ATel16921....1P

Bibcode: 2024ATel16921....1P

Abstract: We report photometry of Type Ia SN 2023mkt gathered with the OAUNI 51cm telescope at Huancayo Observatory, Peru. CCD imaging in R filter was performed on two consecutive nights under non-photometric conditions with an airmass lower than 1.7. The integration time was 90x20s=1800s in both nights.

Keywords: Supernovae, Transient

ADS: https://ui.adsabs.harvard.edu/abs/2023ATel16234....1P

Bibcode: 2023ATel16234....1P

Abstract: CCD imaging was performed of the NGC 1640 field using the OAUNI 51cm telescope at Huancayo Observatory, Peru, on 2023-08-19.310 (UT). No source is detected at the position of AT 2023pow (TNSTR-2023-1982) with limiting magnitude R ~ 18.5.

Keywords: Transient

ADS: https://ui.adsabs.harvard.edu/abs/2023ATel16203....1P

Bibcode: 2023ATel16203....1P

Abstract: Photometry of Type II SN 2023ijd (TNSTR-2023-1092, TNSCR-2023-1112) was gathered with the OAUNI 51cm telescope (arXiv:1512.03104) at Huancayo Observatory, Peru.

Keywords: Supernovae, Transient

ADS: https://ui.adsabs.harvard.edu/abs/2023ATel16166....1P

Bibcode: 2023ATel16166....1P

Abstract: We confirm the Nova object in Sgr, designation: TCP J17525020-2024150, first reported by Andrew Pearce on 2023 Jul 15.459 from (CBET 5278). We performed the photometric and spectroscopic analysis of the object observed from Observatorio Pico dos Dias (OPD-LNA- MCTI) - Brazil, at 2023 Jul 16.0-16.2 UTC. The photometry analysis and imaging were obtained using two telescopes: the 0.6m Boller & Chivens telescope along a CCD Andor IKon 14912, FOV: 11.6 arcmin (2023 Jul 16.0121), and the 0.6m Zeiss telescope also with a CCD Andor IKon L13740, FOV: 12.629 arcmin (2023 Jul 16.0497).

Keywords: Nova

ADS: https://ui.adsabs.harvard.edu/abs/2023ATel16143....1D

Bibcode: 2023ATel16143....1D

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ADS: https://ui.adsabs.harvard.edu/abs/2023ATel16157....1D

Bibcode: 2023ATel16157....1D

Abstract: We report additional multiband photometry of Type Ia SN2022hrs (TNSTR-2022-994, TNSCR-2022-997, ATel #15378) on 2022-07-01 (UT) gathered with the OAUNI 51cm telescope (Pereyra et al. 2015; arXiv:1512.03104) at Huancayo Observatory, Peru.

Keywords: Supernovae, Transient

ADS: https://ui.adsabs.harvard.edu/abs/2022ATel15539....1P

Bibcode: 2022ATel15539....1P

Abstract: Multiband photometry of Type Ic SN2022jli (TNSTR-2022-1198, TNSCR-2022-1261) on 2022-07-01 (UT) was gathered with the OAUNI 51cm telescope (arXiv:1512.03104) at Huancayo Observatory, Peru.

Keywords: Supernovae

ADS: https://ui.adsabs.harvard.edu/abs/2022ATel15526....1P

Bibcode: 2022ATel15526....1P

Abstract: We report photometry post 2021 outburst of the recurrent nova RS Oph on 2022-05-02 (UT) gathered with the OAUNI 51cm telescope (Pereyra et al. 2015; arXiv:1512.03104) at Huancayo Observatory, Peru.

Keywords: Cataclysmic Variable, Nova

ADS: https://ui.adsabs.harvard.edu/abs/2022ATel15387....1P

Bibcode: 2022ATel15387....1P

Abstract: We report multiband photometry of Type Ia SN2022hrs (TNSTR-2022-994, TNSCR-2022-997) on 2022-05-02 (UT) gathered with the OAUNI 51cm telescope (Pereyra et al. 2015; arXiv:1512.03104) at Huancayo Observatory, Peru.

Keywords: Supernovae, Transient

ADS: https://ui.adsabs.harvard.edu/abs/2022ATel15378....1P

Bibcode: 2022ATel15378....1P

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ADS: https://ui.adsabs.harvard.edu/abs/2024yCat..36909007F

Bibcode: 2024yCat..36909007F

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ADS: https://ui.adsabs.harvard.edu/abs/2023yCat..36800084M

Bibcode: 2023yCat..36800084M

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ADS: https://ui.adsabs.harvard.edu/abs/2022yCat..36600086M

Bibcode: 2022yCat..36600086M

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ADS: https://ui.adsabs.harvard.edu/abs/2021yCat..18980173D

Bibcode: 2021yCat..18980173D

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ADS: https://ui.adsabs.harvard.edu/abs/2019yCat..51570150A

Bibcode: 2019yCat..51570150A

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ADS: https://ui.adsabs.harvard.edu/abs/2018zndo...1323217L

Bibcode: 2018zndo...1323217L