Sazuna/UAT_keywords huggingface dataset:
Detectability of Solar Rotation Period across Various Wavelengths. The light curves of old G dwarfs obtained in the visible and near-infrared wavelength ranges are highly irregular. This significantly complicates the detectability of the rotation periods of stars similar to the Sun in large photometric surveys, such as Kepler and TESS. In this study, we show that light curves collected in the ultraviolet (UV) wavelength range are much more suitable for measuring rotation periods. Motivated by the observation that the Sun's rotational period is clearly discernible in the UV part of the spectrum, we study the wavelength dependence of the rotational period detectability. We employ the Spectral and Total Irradiance Reconstructions model to characterize the detectability of the solar rotation period across various wavelengths using the autocorrelation technique. We find that at wavelengths above 400 nm, the probability of detecting the rotation period of the Sun observed at a random phase of its activity cycle is approximately 20%. The probability increases to 80% at wavelengths shorter than 400 nm. These findings underscore the importance of UV stellar photometry.

Keywords: Solar cycle, Detection, Solar rotation, Solar ultraviolet emission, Space telescopes, Sunspots, Stellar activity, Solar faculae, Space observatories, Ultraviolet astronomy, Solar activity, Stellar rotation
A Diverse, Overlooked Population of Type Ia Supernovae Exhibiting Mid-infrared Signatures of Delayed Circumstellar Interaction. Type Ia supernovae (SNe Ia) arise from the thermonuclear explosions of white dwarfs in multiple-star systems. A rare subclass of SNe Ia exhibit signatures of interaction with circumstellar material (CSM), allowing for direct constraints on companion material. While most known events show evidence for dense nearby CSM identified via peak-light spectroscopy (as SNe Ia-CSM), targeted late-time searches have revealed a handful of cases exhibiting delayed CSM interaction with detached shells. Here we present the first all-sky search for late CSM interaction in SNe Ia using a new image subtraction pipeline for mid-infrared data from the NEOWISE space telescope. Analyzing a sample of ≍8500 SNe Ia, we report evidence for late-time mid-infrared brightening in five previously overlooked events spanning subtypes SNe Iax, SNe Ia-91T, and super-Chandra SNe Ia. Our systematic search doubles the known sample and suggests that ≳0.05% of SNe Ia exhibit mid-infrared signatures of delayed CSM interaction. The mid-infrared light curves ubiquitously indicate the presence of multiple (or extended) detached CSM shells located at ≳1016─1017 cm, containing 10−6 to 10−4 M⊙ of dust, with some sources showing evidence for new dust formation, possibly within the cold, dense shell of the ejecta. We do not detect interaction signatures in spectroscopic and radio follow-up; however, the limits are largely consistent with previously confirmed events given the sensitivity and observation phase. Our results highlight that CSM interaction is more prevalent than previously estimated from optical and ultraviolet searches and that mid-infrared synoptic surveys provide a unique window into this phenomenon.

Keywords: Interacting binary stars, Infrared excess, Type Ia supernovae, Supernovae, Common envelope binary stars
Discovery of Local Analogs to JWST's Little Red Dots. Recently, the James Webb Space Telescope has revealed a new class of high-redshift (high-z, z &gt; 4) compact galaxies that are red in the rest-frame optical and blue in the rest-frame UV with V-shaped spectral energy distributions (SEDs), referred to as "little red dots" (LRDs). It is very likely that LRDs host obscured broad-line active galactic nuclei (AGNs). In the meanwhile, Green Pea galaxies (GPs), which are compact dwarf galaxies at low redshift, share various similar properties with high-redshift star-forming galaxies. Here, we aim to find the connection between the LRDs and GPs hosting broad-line AGNs (BLGPs). With a sample of 19 BLGPs obtained from our previous work, we further identify seven GPs with V-shaped rest-frame UV-to-optical SEDs that are likely local analogs to LRDs. These V-shaped BLGPs exhibit faint UV absolute magnitudes and sub-Eddington rates similar to those of LRDs. Three of them occupy a similar region to LRDs in the Baldwin–Philips–Terlevich diagram, suggesting they have similar ionization conditions and gas-phase metallicities to LRDs. These similarities suggest that V-shaped BLGPs can be taken as local analogs of high-redshift LRDs. In addition, most (16/19) BLGPs, including six V-shaped BLGPs, host overmassive black holes (BHs) above the local MBH–M* relation, making it the first sample of galaxies hosting overmassive BHs at z &lt; 0.4. These findings will help us learn more about the formation and coevolution of early galaxies and BHs.

Keywords: Extragalactic astronomy, Supermassive black holes, Emission line galaxies
Nonstop Variability of Sgr A* Using JWST at 2.1 and 4.8 μm Wavelengths: Evidence for Distinct Populations of Faint and Bright Variable Emission. We present the first results of JWST Cycle 1 and 2 observations of Sgr A* using NIRCam taken simultaneously at 2.1 and 4.8 μm for a total of ∼48 hr over seven different epochs in 2023 and 2024. We find correlated variability at 2.1 and 4.8 μm in all epochs, continual short-timescale (a few seconds) variability, and epoch-to-epoch variable emission implying long-term (∼days to months) variability of Sgr A*. A highlight of this analysis is the evidence for subminute, horizon-scale time variability of Sgr A*, probing inner accretion disk size scales. The power spectra of the light curves in each observing epoch also indicate long-term variable emission. With continuous observations, JWST data suggest that the flux of Sgr A* is fluctuating constantly. The flux density correlation exhibits a distinct break in the slope at ∼3 mJy at 2.1 μm. The analysis indicates two different processes contributing to the variability of Sgr A*. Brighter emission trends toward shallower spectral indices than the fainter emission. Cross-correlation of the light curves indicates for the first time a time delay of 3–40 s in the 4.8 μm variability with respect to 2.1 μm. This phase shift leads to loops in plots of flux density versus spectral index as the emission rises and falls. Modeling suggests that the synchrotron emission from the evolving, age-stratified electron population reproduces the shape of the observed light curves with a direct estimate of the magnetic field strengths in the range between 40 and 90 G and an upper cutoff energy, Ec, between 420 and 720 MeV.

Keywords: Black hole physics
Einstein Probe Discovery of EP J005245.1−722843: A Rare Be─White Dwarf Binary in the Small Magellanic Cloud?. On 2024 May 27, the Wide-field X-ray Telescope on board the Space Sciences, University of Chinese Academy of Einstein Probe (EP) mission detected enhanced X-ray emission from a new transient source in the Small Magellanic Cloud during its commissioning phase. Prompt follow-up with the EP Follow-up X-ray Telescope, the Swift X-ray Telescope. and NICER have revealed a very soft, thermally emitting source (kT ~ 0.1 keV at the outburst peak) with an X-ray luminosity of L ~ 4 × 1038 erg s−1, labeled EP J005245.1−722843. This supersoft outburst faded very quickly in a week's time. Several emission lines and absorption edges were present in the X-ray spectrum, including deep nitrogen (0.67 keV) and oxygen (0.87 keV) absorption edges. The X-ray emission resembles the supersoft source phase of typical nova outbursts from an accreting white dwarf (WD) in a binary system, despite the X-ray source being historically associated with an O9-B0e massive star exhibiting a 17.55 day periodicity in the optical band. The discovery of this supersoft outburst suggests that EP J005245.1−722843 is a BeWD X-ray binary: an elusive evolutionary stage where two main-sequence massive stars have undergone a common envelope phase and experienced at least two episodes of mass transfer. In addition, the very short duration of the outburst and the presence of Ne features hint at a rather massive, i.e., close to the Chandrasekhar limit, Ne─O WD in the system.

Keywords: Accretion, X-ray binary stars, White dwarf stars, High mass x-ray binary stars, Small Magellanic Cloud
On the Abiotic Origin of Dimethyl Sulfide: Discovery of Dimethyl Sulfide in the Interstellar Medium. Following the discovery of dimethyl sulfide (DMS; CH3SCH3) signatures in comet 67P/Churyumov–Gerasimenko, we report the first detection of this organosulfur species in the interstellar medium during the exploration of an ultradeep molecular line survey performed toward the Galactic center molecular cloud G+0.693-0.027 with the Yebes 40 m and IRAM 30 m telescopes. We derive a molecular column density of N = (2.6 ± 0.3) × 1013 cm‑2, yielding a fractional abundance relative to H2 of ∼1.9 × 10‑10. This implies that DMS is a factor of ∼1.6 times less abundant than its structural isomer CH3CH2SH and ∼30 times less abundant than its O-analog dimethyl ether (CH3OCH3) toward this cloud, in excellent agreement with previous results on various O/S pairs. Furthermore, we find a remarkable resemblance between the relative abundance of DMS/CH3OH in G+0.693-0.027 (∼1.7 × 10‑3) and in the comet (∼1.3 × 10‑3). Although the chemistry of DMS beyond Earth has yet to be fully disclosed, this discovery provides conclusive observational evidence on its efficient abiotic production in the interstellar medium, casting doubt on using DMS as a reliable biomarker in exoplanet science.

Keywords: Interstellar molecules, Galactic center, Spectral line identification, Astrochemistry, Interstellar clouds
Magnetic Field Amplification during Stellar Collisions between Low-mass Stars. Blue straggler stars in stellar clusters appear younger and bluer than other cluster members, offering a unique opportunity to understand the stellar dynamics and populations within their hosts. In the collisional formation scenario, excessive angular momentum in the collision product poses a challenge, as the consequent significant mass loss during transition to a stable state leads to a star with too low of a mass to be a blue straggler, unless it spins down efficiently. While many proposed spin-down mechanisms require magnetic fields, the existence or strength of these magnetic fields has not been confirmed. Here, we present 3D moving-mesh magnetohydrodynamical simulations of collisions between low-mass main-sequence stars and investigate magnetic field amplification. Magnetic field energy is amplified during collisions by a factor of 108–1010, resulting in the magnetic field strength of 107–108 G at the core of the collision product, independent of collision parameters. The surface magnetic field strengths increase up to 10–104 G. In addition, a distinctly flattened, rotating gas structure appears around the collision products in off-axis collisions, suggesting potential disk formation. These findings indicate that magnetic braking and disk locking could facilitate spin-down, enabling the formation of blue straggler stars.

Keywords: Globular star clusters, Magnetohydrodynamics, Stellar dynamics, Blue straggler stars, Stellar distance
Evidence for Variable Accretion onto PDS 70 c and Implications for Protoplanet Detections. Understanding the processes of planet formation and accretion in young systems is essential to unraveling the initial conditions of planetary systems. The PDS 70 system, which hosts two directly imaged protoplanets, provides a unique laboratory for studying these phenomena, particularly through Hα emission, a commonly used accretion tracer. We present multiepoch observations and examine the variability in accretion signatures within this system, focusing on PDS 70 b and c. Using Hubble Space Telescope narrowband Hα imaging data taken in 2020 and 2024, we achieve high signal-to-noise ratio detections of these planets and reveal significant changes in Hα flux. For PDS 70 c, the Hα flux more than doubled between 2020 and 2024. The trend is consistent with the one identified in recently published MagAO-X data, further confirming that PDS 70 c has become significantly brighter in Hα between 2023 March and 2024 May. The observed variability suggests dynamic accretion processes, possibly modulated by circumplanetary disk properties or transient accretion bursts. High-amplitude variability in PDS 70 c motivates simultaneous monitoring of multiple accretion tracers to probe the mechanisms of mass growth of gas giant planets. We quantify the impact of variability on the detectability of protoplanets in imaging surveys and emphasize the need for continued and regular monitoring to accurately assess the occurrence and characteristics of young, forming planets.

Keywords: Accretion, Exoplanet astronomy, Direct imaging, Time domain astronomy, Planet formation
Carving the Edges of the Rocky Planet Population. Short-period planets provide ideal laboratories for testing star–planet interaction. Planets that are smaller than ∼2 R⊕ are considered to be largely rocky, either having been stripped of or never having acquired the gaseous envelope. Zooming in on this short-period rocky planet population, clear edges appear in the mass–period and radius–period space. Over ∼0.2–20 days and 0.09–1.42 M⊙, the maximum mass of the rocky planets stays below ∼10 M⊕ with a hint of decrease toward ≲1 day, ≳4 days, and ≲0.45 M⊙. In radius–period space, there is a relative deficit of ≲2 R⊕ planets inside ∼1 day. We demonstrate how the edges in the mass–period space can be explained by a combination of tidal decay and photoevaporation, whereas the rocky planet desert in the radius–period space is a signature of magnetic drag on the planet as it orbits within the stellar magnetic field. Currently observed catastrophically evaporating planets may have started their death spiral from ∼1 day with planets of mass up to ∼0.3 M⊕ under the magnetic drag. More discoveries and characterization of small planets around mid- to late M and A stars would be welcome to better constrain the stellar parameters critical in shaping the edges of rocky planet population, including their UV radiation history, tidal effects, and magnetic properties.

Keywords: Exoplanet astronomy, Star-planet interactions, Exoplanet formation
Lunar Ionosphere in the Geotail Region as Observed by Chandrayaan-2 Orbiter Using Two-way Radio Occultation Measurements. The study presents the first electron density profile of the Lunar ionosphere when the Moon is inside the geomagnetic tail region. This observation used S-band telemetry and telecommand radio signals in a two-way radio occultation experiment from Chandrayaan-2 (CH-2) orbiting the Moon. The radio signals were tracked using an 18 m diameter antenna at the Indian Deep Space Network (IDSN). The IDSN served as an active source for generating and receiving the radio signal, while the onboard oscillator on CH-2 was used as a passive receiver and transmitter. The transmitted radio signal passed twice through the lunar plasma medium before reaching the receiver end. The study found a high electron density of approximately ∼2.5 × 104 per cm‑3 close to the surface of the Moon. Three-dimensional lunar ionospheric model simulations show that to achieve such high plasma density, the plasma should be in photochemical equilibrium, which is possible inside the geomagnetic tail only in the presence of lunar crustal magnetic fields. The model also introduced a localized reduction in Ar and Ne neutral density to align with previous observations near the lunar pole.

Keywords: Lunar composition, Radio occultation, Lunar science, Lunar atmosphere, Earth-moon system
The Influence of Stellar Chromospheres and Coronae on Exoplanet Transmission Spectroscopy. A main source of bias in transmission spectroscopy of exoplanet atmospheres is magnetic activity of the host star in the form of stellar spots, faculae, or flares. However, the fact that main-sequence stars have a chromosphere and a corona and that these optically thin layers are dominated by line emission may alter the global interpretation of the planetary spectrum has largely been neglected. Using a JWST NIRISS/SOSS data set of hot Jupiter HAT-P-18 b, we show that even at near-IR and IR wavelengths, the presence of these layers leads to significant changes in the transmission spectrum of the planetary atmosphere. Accounting for these stellar outer layers thus improves the atmospheric fit of HAT-P-18 b and increases its best-fit atmospheric temperature from   K to   K, a value much closer to the predicted equilibrium temperature of ∼852 K. Our analysis also decreases the best-fit abundance of CO2 by almost an order of magnitude. The approach provides a new window to the properties of chromospheres/corona in stars other than our Sun.

Keywords: Exoplanet atmospheres, Stellar atmospheres, Hot Jupiters
The MUSE Ultra Deep Field: A 5 Mpc Stretch of the z ≍ 4 Cosmic Web Revealed in Emission. We detect Lyα emission from a ≍5 Mpc-long (comoving) portion of the cosmic web hosting an overdensity (δ ≍ 25) of 19 Lyα emitters (LAEs) at z ≍ 4 within the MUSE Ultra Deep Field (MUDF), reaching an average surface brightness (SB) of 5 × 10−20 erg s−1 cm−2 arcsec−2. This large-scale structure has an average SB similar to the filament across the two MUDF quasars at z ≍ 3.22. However, deep multiwavelength data do not show a clear presence of active galactic nuclei, suggesting that the emission is mainly regulated by the underlying gas density. We find ≍0.2 dex higher star formation compared to control samples and a remarkable predominance (5/7) of blue-peaked emission lines in the spectra of the embedded LAEs, indicative of favorable conditions for gas accretion. Lastly, we quantify the contribution of intragalactic gas to the Lyα SB profile at large distances from LAEs. By studying samples of filaments detected in emission within diverse environments, we are finally gaining new insight into the physics of gas accretion within the cosmic web.

Keywords: Large-scale structure of the universe, Galactic and extragalactic astronomy, Cosmic web, Galaxy groups, Intergalactic filaments
SN 2023zaw: The Low-energy Explosion of an Ultrastripped Star. Most stripped-envelope supernova progenitors are thought to be formed through binary interaction, losing hydrogen and/or helium from their outer layers. Ultrastripped supernovae are an emerging class of transient that are expected to be produced through envelope stripping by a neutron star companion. However, relatively few examples are known, and the outcomes of such systems can be diverse and are poorly understood at present. Here we present spectroscopic observations and high-cadence, multiband photometry of SN 2023zaw, a rapidly evolving supernova with a low ejecta mass. SN 2023zaw was discovered in a nearby spiral galaxy at D = 39.7 Mpc. It has significant Milky Way extinction, E(B − V)MW = 0.21, and significant (but uncertain) host extinction. Bayesian evidence comparison reveals that nickel is not the only power source and that an additional energy source is required to explain our observations. Our models suggest that an ejecta mass of Mej ∼ 0.07 M⊙ and a synthesised nickel mass of MNi ∼ 0.007 M⊙ are required to explain the observations. We find that additional heating from a central engine, or interaction with circumstellar material, can power the early light curve.

Keywords: Core-collapse supernovae, Type Ib supernovae, Transient sources, Circumstellar matter, Supernovae
NGDEEP: The Star Formation and Ionization Properties of Galaxies at 1.7 &lt; z &lt; 3.4. We use JWST/NIRISS slitless spectroscopy from the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey to investigate the physical condition of 178 star-forming galaxies at 1.7 &lt; z &lt; 3.4. At these redshifts, the deep NGDEEP NIRISS slitless spectroscopy covers the [O II]λλ3726,3729, [O III]λλ4959,5007, Hβ and Hα emission features for galaxies with stellar masses  , nearly a factor of 100 lower than previous studies. We focus on the [O II]/[O III] (O32) ratio which is primarily sensitive to the ionization state and with a secondary dependence on the gas-phase metallicity of the interstellar medium. We find significant (≳5σ) correlations between the O32 ratio and galaxy properties as O32 increases with decreasing stellar mass, decreasing star formation rate (SFR), increasing specific SFR (sSFR ≡ SFR/M *), and increasing equivalent width (EW) of Hα and Hβ. These trends suggest a tight connection between the ionization parameter and these galaxy properties. Galaxies at z ∼ 2–3 exhibit a higher O32 than local normal galaxies with the same stellar masses and SFRs, indicating that they have a higher ionization parameter and lower metallicity than local normal galaxies. In addition, we observe a mild evolutionary trend in the O32–EW(Hβ) relation from z ∼ 0 to z ≳ 5, where higher redshift galaxies show increased O32 and EW, with possibly higher O32 at fixed EW. We argue that both the enhanced recent star formation activity and the higher star formation surface density may contribute to the increase in O32 and the ionization parameter.

Keywords: Galaxy evolution, Galaxy stellar content, Star formation, High-redshift galaxies
Short-period Small Planets with High Mutual Inclinations are More Common around Metal-rich Stars. We present a correlation between the stellar metallicities and the mutual inclinations of multiplanet systems hosting short-period small planets (a/R⋆ &lt; 12, Rp &lt; 4 R⊕). We analyzed 89 multiplanet systems discovered by Kepler, K2, and TESS, where the innermost planets have periods shorter than 10 days. We found that the mutual inclinations of the innermost two planets are higher and more diverse around metal-rich stars. The mutual inclinations are calculated as the absolute differences between the best-fit inclinations of the innermost two planets from transit modeling, which represent the lower limits of the true mutual inclinations. The mean and variance values of the mutual inclination distribution of the metal-rich systems are 3 1 ± 0.5 and 3 1 ± 0.4, while for the metal-poor systems they are 1 3 ± 0.2 and 1 0 ± 0.2. This finding suggests that inner planetary systems around metal-rich stars are dynamically hotter. We summarized the theories that could plausibly explain this correlation, including the influence of giant planets, higher solid densities in protoplanetary disks around metal-rich stars, or secular chaos coupled with an excess of angular momentum deficits. Planet formation and population synthesis models tracking the mutual inclination evolution would be essential to fully understand this correlation.

Keywords: Exoplanet dynamics, Inclination, Transits, Exoplanets, Metallicity
Coupling of Dynamical Tide and Orbital Motion. The dynamical tide consists of various waves that can resonate with orbital motion. We test this coupling of the dynamical tide and orbital motion using a simple 2D shallow water model, which can be applied to a rocky planet covered with a thin ocean or atmosphere. Then we take the Earth–Moon system as a fiducial model to calculate the tidal resonances and orbital evolution. We find that tidal dissipation can even increase with increasing orbital separation because of the coupling of the dynamical tide and orbital motion. We draw the conclusion that the coupling is not negligible to study the orbital evolution on a secular timescale.

Keywords: Tides, Astrophysical fluid dynamics