Absolute Magnitude Research Articles

Comparison of the Physical Trace of Global Luminosity Emission at Multiwavelength and Star Formation Rates of Luminous Infrared Galaxies Using Extragalactic Distance Scale Techniques

This paper aims to study the rate of star formation (SFR) in luminous infrared galaxies at different wavelengths using distance measurement techniques (dl, dm) and to know which methods are the most accurate to determine the rate of star formation as we present through this research the results of the statistical analysis (descriptive statistics) for a sample of luminous infrared galaxies. The data used in this research were collected from the NASA Extragalactic Database (NED) and HYPERLEDA, then used to calculate the star formation rate and indicate the accuracy of the distance methods used (dl, dm). Two methods were tested on Hα, OII, FIR, radio continuum at 1.4 GHz, FUV, NUV, and total (FUV + FIR). The results showed that the dl measurement method has the most accuracy in calculating SFR as it depends on the redshift where the relationship between them is direct. while the other distance method (dm) depends on absolute blue magnitude (MB), it was somewhat less accurate, but the two methods are helpful for this type of calculation.

The association between the type of offline social participation and digital literacy among Korean older adults: a cross-sectional study.

Poor social connections are associated with poor digital literacy. Poor digital literacy could induce poor outcomes in daily life or health status, especially among older adults. This study aimed to investigate the effect of social participation based on its absolute magnitude on digital literacy and to confirm the well-known fact that social participations are good for digital literacy is applicable regardless of activity types in a sample of older Korean adults. A total of 9,297 adults aged 65 years or older from the 2020 National Survey of Older Koreans were analyzed. All data were self-reported. Poor digital literacy was defined by limited usage of digital devices. Offline social participation was evaluated using seven different social activities: senior community activities, learning activities, religious activities, volunteer work, leisure, political groups, and club activities. Multivariable logistic regression analysis with covariate adjustment was used for the analysis. Engaging in more than two types of social participation was associated with higher digital literacy: adjusted odds ratio (aOR) 1.965, 95% confidence interval (CI) 1.567-2.465 for two types of participation, and aOR 2.558, 95% CI 2.040-3.208 for more than three types of participation. Additionally, social participation occurring less than once a month and most types of offline activities were associated with improved digital literacy. However, senior community activities were negatively associated with digital literacy (aOR 0.762; 95% CI 0.681-0.852). In this sample of older Korean adults, it was found that the lower the social participation, the poorer the digital literacy. This association may induce the isolation of older adults from societies especially for older adults with senior community activities.

Development and Validation of Sensitivity for Needs of Elderly Scale Among Caregivers Based on Maslow’s Theory

The world currently lives in an aging society. Demand for elderly caregivers and services is rapidly rising. Elderly care encompasses not only medical care, but also the art of human care. Love and respect are usually considered the backbone of the modality of caregivers. This study aimed at developing a sensitivity for needs of elderly scale (SNES) among caregivers. Maslow’s theory of hierarchical needs, especially stage 3 (love and belongingness needs) and stage 4 (esteem needs), was used as a conceptual framework. This study consisted of four steps. The sample groups for the first two steps of item quality and exploratory factory analysis were 420 nursing students. A three-factor model emerged, which includes the sensitivity of needs for love and empathy, the sensitivity of needs for respect, and the sensitivity of needs for honor and dignity. The newly constructed measure consisted of 10 items, which explained the variance by 52.18%. The third step of confirmatory factor analysis, using a new group of 384 nursing students, indicated the model fit. In the final step, the scale was validated using 171 elderly caregivers. Moderate to strong absolute magnitudes of correlations between the new scale and psycho-moral strength, core self-evaluation, future orientation and self-control, moral disengagement, and caring behavior were found. Incremental validity was tested. Discussion and recommendations for further research and implications of the newly constructed measure were offered.

Communicating Probabilities of Cervical Cancer Screening Results with Icon Arrays or Tree Diagrams: A Longitudinal Experiment

ABSTRACT Simple graphical displays such as icon arrays and tree diagrams have been proposed for communicating health risks and supporting informed decisions. The UK’s National Health Service (NHS) uses tree diagrams to communicate the chances of different cervical cancer screening results, but their effectiveness has not been compared to icon arrays. We conducted a well-powered longitudinal experiment involving 3,100 UK women eligible for cervical screening (25–64 years) to examine the effectiveness of icon arrays to communicate possible cervical screening results, relative to the UK NHS’s tree diagram and to a numerical-only format. We also examined whether the presence (vs. absence) of explanatory text referring to different types of results (i.e. distinguishing between HPV positive results with vs. without abnormal cervical cells) moderated effects of presentation format. Presentation format did not affect verbatim or gist knowledge of probabilities at initial assessment (i.e. immediately after participants viewed the displays), but icon arrays were associated with better gist knowledge of absolute magnitudes than tree diagrams and numerical-only formats at 1-month follow-up. Participants exposed to icon arrays also perceived lower likelihood of adverse screening results and reported stronger screening intentions at initial assessment. For displays without explanatory text, icon arrays were also associated with more positive user evaluations and less negative affective reactions than tree diagrams at initial assessment. Overall, our findings suggest that icon arrays support enduring knowledge of approximate magnitudes of probabilities and are better suited than tree diagrams for communicating possible screening results.

The ultraviolet luminosity function of star-forming galaxies between redshifts of 0.4 and 0.6

Abstract We combine ultraviolet imaging of the 13H survey field, taken with the XMM-Newton Optical Monitor telescope (XMM-OM) and the Neil Gehrels Swift Observatory Ultraviolet and Optical Telescope (UVOT) in the UVM2 band, to measure rest-frame ultraviolet 1,500 Å luminosity functions of star-forming galaxies with redshifts z between 0.4 and 0.6. In total the UVM2 imaging covers a sky area of 641 arcmin2, and we detect 273 galaxies in the UVM2 image with 0.4 < z < 0.6. The luminosity function is fit by a Schechter function with best-fit values for the faint end slope $\alpha =-1.8^{+0.4}_{-0.3}$ and characteristic absolute magnitude $M^{*} = -19.1^{+0.3}_{-0.4}$. In common with XMM-OM based studies at higher redshifts, our best-fitting value for M* is fainter than previous measurements. We argue that the purging of active galactic nuclei from the sample, facilitated by the co-spatial X-ray survey carried out with XMM-Newton is important for the determination of M*. At the brightest absolute magnitudes (M1500 < −18.5) the average UV colour of our galaxies is consistent with that of minimal-extinction local analogues, but the average UV colour is redder for galaxies at fainter absolute magnitudes, suggesting that higher levels of dust attenuation enter the sample at absolute magnitudes somewhat fainter than M*.

Confirmation of Recurrent Activity of Main-Belt Comet 456P/PANSTARRS (P/2021 L4)

Abstract We report observations from the Magellan Baade Telescope and Lowell Discovery Telescope on UT 2024 October 3 and 26, respectively, confirming for the first time that active asteroid 456P/PANSTARRS is recurrently active (exhibiting a short anti-solar tail on both dates, following previous observations of activity in 2021 when it was discovered), indicating that its activity is likely driven by the sublimation of volatile ice, leading us to consider it a main-belt comet (MBC). We also report observations from the Gemini South Observatory on UT 2023 June 15 in which the object appears inactive, where we measure an absolute magnitude of H V = ( 17.5 ± 0.1 ) mag for the nucleus (assuming G V = 0.15), corresponding to an effective nucleus radius of r n = ( 1.0 ± 0.2 ) km (assuming an albedo of p V = 0.05 ) . 456P is now the 14th MBC for which recurrent activity has been observationally confirmed.

The physical properties of two potential targets for space missions: (155140) 2005 UD and (612267) 2001 SG286

Abstract The ground-based characterization of asteroids is a key step for planning their exploration. The near-earth asteroid 155140 (2005 UD) is a potential flyby target of JAXA’s DESTINIY+ mission, while (612267) 2001 SG286 has been considered as a possible target for in-situ exploration. We aim to determine their physical properties using the observations obtained with various telescopes from Canary Islands Observatory. For 2005 UD we confirmed the two peak lightcurve, a rotation period of 5.224 ± 0.003 h and an amplitude of 0.34 mag. However, a three peak solution seemed also to fit the light-curve, but this was discarded as implausible. Using the obtained visible to near-infrared spectrum we classified it as a Cb-type, and we found a spectral matching with heated carbonaceous chondrite meteorites of CM2 type. The thermal emission flux at 2.2 μm points to an albedo of pV = 0.06 ± 0.02. There are significant differences in the spectrum of 2005 UD compared to that of (3200) Phaeton, hypothesized as its parent body. The accurate visible spectrum obtained with the GTC indicate that 2001 SG286 is an S-type asteroid. The photometric data obtained with INT suggests a rotation period of 12.30 ± 0.01 h and an amplitude of 0.64 mag. With these observations we found its absolute magnitude H = 21.4 ± 0.3, and estimate its size as 160 ± 45 m.

How Meteor Showers Can Guide the Search for Long-period Comets

With orbital periods longer than 200 yr, most long-period comets (LPCs) remain undiscovered until they are in-bound toward perihelion. The comets that pass close to Earth’s orbit are potentially hazardous objects. Those with orbital periods up to ∼4000 yr tend to have passed close to Earth’s orbit in a previous orbit and produced a meteoroid stream dense enough to be detected at Earth as a meteor shower. In anticipation of Rubin Observatory’s Legacy Survey of Space and Time (LSST), we investigate how these meteor showers can guide dedicated searches for their parent comets. Assuming search parameters informed by LSST, we calculated where the 17 known parent bodies of LPC meteor showers would have been discovered based on a cloud of synthetic comets generated from the shower properties as measured at Earth. We find that the synthetic comets predict the on-sky location of the parent comets at the time of their discovery. The parent comet’s location on average would have been 1.°51 ± 1.°19 from a line fit through the synthetic comet cloud. The difference between the heliocentric distance of the parent and mean heliocentric distance of synthetic comets on the line was 2.09 ± 1.89 au for comets with unknown absolute nuclear magnitudes and 0.96 ± 0.80 au for comets with known absolute nuclear magnitudes. We applied this method to the σ-Hydrids, the proposed meteor shower of comet Nishimura, and found that it successfully matched the pre-covery location of this comet 8 months prior to Nishimura’s discovery.

Debiasing astro-photometric observations with corrections using statistics (DePhOCUS)

Photometric measurements allow the determination of an asteroid’s absolute magnitude, which often represents the sole means to infer its size. Photometric observations can be obtained in a variety of filters that can be unique to a specific observatory. Those observations are then calibrated into specific bands with respect to reference star catalogs. In order to combine all the different measurements for evaluation, photometric observations need to be converted to a common band, typically V-band. Current band-correction schemes in use by IAU’s Minor Planet Center (MPC), JPL’s Center for Near Earth Object Studies (CNEOS) and ESA’s NEO Coordination Centre (NEOCC) use average correction values for the apparent magnitude derived from photometry of asteroids as the corrections are dependent on the typically unknown spectrum of the object to be corrected. By statistically analyzing the photometric residuals of asteroids, we develop a new photometric correction scheme that does not only consider the band, but also accounts for reference catalog and observatory. We analyzed nearly 500000 observations submitted to the MPC from 468 asteroids with published and independently determined high confidence H and G values. We describe a new statistical photometry correction scheme for asteroid observations with debiased corrections. Testing this scheme on a reference group of asteroids, we see a 36% reduction in the photometric residuals. Moreover, the new scheme leads to a more accurate and debiased determination of the H-G magnitude system and, in turn, to more reliable inferred sizes. We discuss the significant shift in the corrections with this “DePhOCUS” debiasing system, its limitations, and the impact for photometric and physical properties of all asteroids, especially Near-Earth Objects.

Optical and Radio Analysis of Systematically Classified Broad-lined Type Ic Supernovae from the Zwicky Transient Facility

We study a magnitude-limited sample of 36 broad-lined type Ic supernovae (SNe Ic-BL) from the Zwicky Transient Facility Bright Transient Survey (detected between 2018 March and 2021 August), which is the largest systematic study of SNe Ic-BL done in literature thus far. We present the light curves (LCs) for each of the SNe and analyze the shape of the LCs to derive empirical parameters, along with the explosion epochs for every event. The sample has an average absolute peak magnitude in the r band of M¯r,max=−18.51±0.15 mag. Using spectra obtained around peak light, we compute expansion velocities from the Fe ii 5169 Å line for each event with high enough signal-to-noise ratio spectra, and find an average value of vph¯=16,100±1100 km s−1. We also compute bolometric LCs, study the blackbody temperature and radii evolution over time, and derive the explosion properties of the SNe. The explosion properties of the sample have average values of M¯Ni=0.37−0.06+0.08M⊙ , M¯ej=2.45−0.41+0.47M⊙ , and E¯K=(4.02−1.00+1.37)×1051 erg. Thirteen events have radio observations from the Very Large Array, with eight detections and five non-detections. We find that the populations that have radio detections and radio non-detections are indistinct from one another with respect to their optically inferred explosion properties, and there are no statistically significant correlations present between the events’ radio luminosities and optically inferred explosion properties. This provides evidence that the explosion properties derived from optical data alone cannot give inferences about the radio properties of SNe Ic-BL and likely their relativistic jet formation mechanisms.

Searching for Gravitational Wave Optical Counterparts with the Zwicky Transient Facility: Summary of O4a

During the first half of the fourth observing run (O4a) of the International Gravitational Wave Network, the Zwicky Transient Facility (ZTF) conducted a systematic search for kilonova (KN) counterparts to binary neutron star (BNS) and neutron star–black hole (NSBH) merger candidates. Here, we present a comprehensive study of the five high-significance (False Alarm Rate less than 1 yr−1) BNS and NSBH candidates in O4a. Our follow-up campaigns relied on both target-of-opportunity observations and re-weighting of the nominal survey schedule to maximize coverage. We describe the toolkit we have been developing, Fritz, an instance of SkyPortal, instrumental in coordinating and managing our telescope scheduling, candidate vetting, and follow-up observations through a user-friendly interface. ZTF covered a total of 2841 deg2 within the skymaps of the high-significance GW events, reaching a median depth of g ≈ 20.2 mag. We circulated 15 candidates, but found no viable KN counterpart to any of the GW events. Based on the ZTF non-detections of the high-significance events in O4a, we used a Bayesian approach, nimbus, to quantify the posterior probability of KN model parameters that are consistent with our non-detections. Our analysis favors KNe with initial absolute magnitude fainter than −16 mag. The joint posterior probability of a GW170817-like KN associated with all our O4a follow-ups was 64%. Additionally, we use a survey simulation software, simsurvey, to determine that our combined filtered efficiency to detect a GW170817-like KN is 36%, when considering the 5 confirmed astrophysical events in O3 (1 BNS and 4 NSBH events), along with our O4a follow-ups. Following Kasliwal et al., we derived joint constraints on the underlying KN luminosity function based on our O3 and O4a follow-ups, determining that no more than 76% of KNe fading at 1 mag day−1 can peak at a magnitude brighter than −17.5 mag.

QSO MUSEUM

Extended Lyα emission is routinely found around single quasars across cosmic time. However, few studies have investigated how such emission changes in fields with physically associated quasar pairs, which should reside in dense environments and are predicted to be linked through intergalactic filaments. We present VLT/MUSE snapshot observations (45 minutes/source) to unveil extended Lyα emission on scales of the circumgalactic medium (CGM) around the largest sample of physically associated quasar pairs to date, encompassing eight pairs (14 observed quasars) at z ∼ 3 with an i-band magnitude between 18 and 22.75, corresponding to absolute magnitudes Mi(z = 2) between −29.6 and −24.9. The pairs are either at close (∼50–100 kpc, five pairs) or wide (∼450–500 kpc, three pairs) angular separation and have velocity differences of Δv ≤ 2000 km s−1. We detected extended emission around 12 of the 14 targeted quasars and investigated the luminosity, size, kinematics, and morphology of these Lyα nebulae. On average, they span about 90 kpc and are 2.8 × 1043 erg s−1 bright. Irrespective of the quasars’ projected distance, the nebulae often (∼45%) extend toward the other quasar in the pair, leading to asymmetric emission whose flux-weighted centroid is at an offset position from any quasar location. We show that large nebulae are preferentially aligned with the large-scale structure, as traced by the direction between the two quasars, and conclude that the cool gas (104 K) in the CGM traces well the direction of cosmic web filaments. Additionally, the radial profile of the Lyα surface brightness around quasar pairs can be described by a power law with a shallower slope (∼−1.6) with respect to single quasars (∼−2), indicative of increased CGM densities out to large radii and/or an enhanced contribution from the intergalactic medium (IGM) due to the dense environments expected around quasar pairs. The sample presented in this study contains excellent targets for ultra-deep observations to directly study filamentary IGM structures in emission. This work demonstrates that a large snapshot survey of quasar pairs will pave the way to direct statistical study of the IGM.

The red giant branch tip in the SDSS, PS1, JWST, NGRST, and Euclid photometric systems

We used synthetic photometry from Gaia DR3 BP and RP spectra for a large selected sample of stars in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) to derive the magnitude of the red giant branch (RGB) tip for these two galaxies in several passbands across a range of widely used optical photometric systems, including those of space missions that have not yet started their operations. The RGB tip is estimated by fitting a well motivated model to the RGB luminosity function (LF) within a fully Bayesian framework, allowing for a proper representation of the uncertainties of all the involved parameters and their correlations. By adopting the best available distance and interstellar extinction estimates, we provide a calibration of the RGB tip as a standard candle for the following passbands: Johnson-Kron-Cousins I (mainly used for validation purposes), Hubble Space Telescope F814W, Sloan Digital Sky Survey i and z, PanSTARRS 1 y, James Webb Space Telescope F090W, Nancy Grace Roman Space Telescope Z087, and Euclid IE, with an accuracy within a few per cent, depending on the case. We used theoretical models to explore the trend of the absolute magnitude of the tip as a function of colour in the different passbands (beyond the range spanned by the LMC and SMC), as well as its dependency on age. These calibrations can be very helpful to obtain state-of-the-art RGB tip distance estimates to stellar systems in a very large range of distances directly from data in the natural photometric system of these surveys and/or missions, without recurring to photometric transformations. We have made the photometric catalogues publicly available for calibrations in additional passbands or for different approaches in the estimate of the tip, as well as for stellar populations and stellar astrophysics studies that may take advantage of large and homogeneous datasets of stars with magnitudes in 22 different passbands.

New method for graphing impedance values as an analytical tool suitable for electrochemical impedance spectroscopy

A new method for graphing electrical impedance values named a “differentiation-based Bode plot” is proposed. This method facilitates the analysis procedure and reduces the arbitrariness of the interpretation of electrochemical impedance spectroscopy (EIS) data. Among the various methods for graphing impedance values, Nyquist plots are commonly adopted (primarily in the field of EIS) because of the apparent correlation between their shape and the corresponding equivalent circuit. However, because Nyquist plots do not contain frequency information, Bode phase and magnitude plots are frequently utilized. Although such plots are suitable for determining the absolute magnitude and phase of the impedance, they are not always useful for selecting the structure of an equivalent circuit, which is a hypothetical model for electrochemical cells. In the proposed method, instead of the real (Z’) and imaginary (Z’’) parts, two functions of the impedance derivatives with respect to frequency, i.e., dZ’/d(log f) and dZ’’/d(log f), are plotted. As substitutions for the Bode phase and magnitude plots, arctan{dZ’’/d(log f) ÷ dZ’/d(log f)} and log[sqrt{(dZ’/d(log f))2 + (dZ’’/d(log f))2}] are plotted against log f. Unlike the classical Bode plot, the differentiation-based Bode plot is independent of the lateral shift in the Nyquist plot, which is advantageous for determining an equivalent circuit. To demonstrate this advantage, the impedance values of typical equivalent circuits used in electrochemistry are calculated and plotted to compare differentiation-based Bode plots with Nyquist and classical Bode plots.

Photometry and kinematics of dwarf galaxies from the Apertif HI survey

Understanding the dwarf galaxy population in low density environments (in the field) is crucial for testing the current Lambda Cold Dark Matter cosmological model. The increase in diversity toward low-mass galaxies is seen as an increase in the scatter of scaling relations, such as the stellar mass--size and the baryonic Tully-Fisher relation (BTFR), and is also demonstrated by recent in-depth studies of an extreme sub-class of dwarf galaxies with low surface brightnesses but large physical sizes called ultra-diffuse galaxies (UDGs). We aim to select dwarf galaxies independent of their stellar content and to make a detailed study of their gas and stellar properties. We selected galaxies from the APERture Tile In Focus (Apertif) survey and applied a constraint on their $i$-band absolute magnitude in order to exclude high-mass systems. The sample consists of 24 galaxies, 22 of which are resolved in by at least three beams, and they span mass ranges of 8.6 $ lesssim 9.7 and a stellar mass range of 8.0 $ lesssim 9.7 (with only three galaxies having log ( msun)>9). We determined the geometrical parameters of the and stellar disks, built kinematic models from the data using and extracted surface brightness profiles in the g-, r- and i- bands from the Pan-STARRS 1 photometric survey. We used these measurements to place our galaxies on the stellar mass--size relation and the BTFR, and we compared them with other samples from the literature. We find that at a fixed stellar mass, our dwarfs have larger optical effective radii than isolated optically selected dwarfs from the literature, and we found misalignments between the optical and morphologies for some of our sample. For most of our galaxies, we used the morphology to determine their kinematics, and we stress that deep optical observations are needed to trace the underlying stellar disks. Standard dwarfs in our sample follow the same BTFR of high-mass galaxies, whereas UDGs are slightly offset toward lower rotational velocities, in qualitative agreement with results from previous studies. Finally, our sample features a fraction (25<!PCT!>) of dwarf galaxies in pairs that is significantly larger with respect to previous estimates based on optical spectroscopic data.

Topological Approach to Void Finding Applied to the SDSS Galaxy Map

The structure of the low redshift Universe is dominated by a multiscale void distribution delineated by filaments and walls of galaxies. The characteristics of voids, such as morphology, average density profile, and correlation function, can be used as cosmological probes. However, their physical properties are difficult to infer due to shot noise and the general lack of tracer particles used to define them. In this work, we construct a robust, topology-based void-finding algorithm that utilizes Persistent Homology to detect persistent features in the data. We apply this approach to a volume-limited subsample of galaxies in the SDSS I/II Main Galaxy catalog with the r-band absolute magnitude brighter than M r = −20.19, and a set of mock catalogs constructed using the Horizon Run 4 cosmological N-body simulation. We measure the size distribution of voids, their averaged radial profile, sphericity, and the centroid nearest neighbor separation, using conservative values for the threshold and persistence. We find 32 topologically robust voids in the SDSS data over the redshift range 0.02 ≤ z ≤ 0.116, with effective radii in the range 21−56 h −1 Mpc. The median nearest neighbor void separation is found to be ∼57 h −1 Mpc, and the median radial void profile is consistent with the expected shape from the mock data.

Physical properties of trans-Neptunian object (143707) 2003 UY117 derived from stellar occultation and photometric observations

Context. Trans-Neptunian objects (TNOs) are considered to be among the most primitive objects in our Solar System. Knowledge of their primary physical properties is essential for understanding their origin and the evolution of the outer Solar System. In this context, stellar occultations are a powerful and sensitive technique for studying these distant and faint objects. Aims. We aim to obtain the size, shape, absolute magnitude, and geometric albedo for TNO (143707) 2003 UY117. Methods. We predicted a stellar occultation by this TNO for 2020 October 23 UT and ran a specific campaign to investigate this event. We derived the projected profile shape and size from the occultation observations by means of an elliptical fit to the occultation chords. We also performed photometric observations of (143707) 2003 UY117 to obtain the absolute magnitude and the rotational period from the observed rotational light curve. Finally, we combined these results to derive the three-dimensional shape, volume-equivalent diameter, and geometric albedo for this TNO. Results. From the stellar occultation, we obtained a projected ellipse with axes of (282 ± 18) × (184 ± 32) km. The area-equivalent diameter for this ellipse is Deq,A = 228 ± 21 km. From our photometric R band observations, we derived an absolute magnitude of HV = 5.97 ± 0.07 mag using V − R = 0.46 ± 0.07 mag, which was derived from a V band subset of these data. The rotational light curve has a peak-to-valley amplitude of ∆m = 0.36 ± 0.13 mag. We find the most likely rotation period to be P = 12.376 ± 0.0033 hours. By combining the occultation with the rotational light curve results and assuming a triaxial ellipsoid, we derived axes of a × b × c = (332 ± 24) km × (216 ± 24) km × (180−24+28) km for this ellipsoid, and therefore a volume-equivalent diameter of Deq,V = 235 ± 25 km. Finally, the values for the absolute magnitude and for the area-equivalent diameter yield a geometric albedo of pV = 0.139 ± 0.027.

2019 UO14: A Transient Trojan of Saturn

Saturn has long been the only giant planet in our solar system without any known Trojan members. In this Letter, with serendipitous archival observations and refined orbit determination, we report that 2019 UO14 is a Trojan of the gas giant. However, the object is only a transient Trojan currently librating around the leading Lagrange point L 4 of the Sun–Saturn system in a period of ∼0.7 kyr. Our N-body numerical simulation shows that 2019 UO14 was likely captured as a Centaur and became trapped around L 4 ∼ 2 kyr ago from a horseshoe co-orbital. The current Trojan state will be maintained for another millennium or thereabouts before transitioning back to a horseshoe state. Additionally, we characterize the physical properties of 2019 UO14. Assuming a linear phase slope of 0.06 ± 0.01 mag deg−1, the mean r-band absolute magnitude of the object was determined to be H r = 13.11 ± 0.07, with its color measured to be consistent with that of Jupiter and Neptune Trojans and not statistically different from Centaurs. Although the short-lived Saturn Trojan exhibited no compelling evidence of activity in the observations, we favor the possibility that it could be an active Trojan. If confirmed, 2019 UO14 would be marked as the first active Trojan in our solar system. We conservatively determine the optical depth of dust within our photometric aperture to be ≲10−7, corresponding to a dust mass-loss rate to be ≲1 kg s−1, provided that the physical properties of dust grains resemble Centaur 29P/Schwassmann–Wachmann 1.

Light-modulated van der Waals force microscopy

Atomic force microscope generally works by manipulating the absolute magnitude of the van der Waals force between tip and specimen. This force is, however, less sensitive to atom species than to tip-sample separations, making compositional identification difficult, even under multi-modal strategies or other atomic force microscopy variations. Here, we report the phenomenon of a light-modulated tip-sample van der Waals force whose magnitude is found to be material specific, which can be employed to discriminate heterogeneous compositions of materials. We thus establish a near-field microscopic method, named light-modulated van der Waals force microscopy. Experiments discriminating heterogeneous crystalline phases or compositions in typical materials demonstrate a high compositional resolving capability, represented by a 20 dB signal-to-noise ratio on a MoTe2 film under the excitation of a 633 nm laser of 1.2 mW, alongside a sub-10 nm lateral spatial resolution, smaller than the tip size of 20 nm. The simplicity of the light modulation mechanism, minute excitation light power, broadband excitation wavelength, and diversity of the applicable materials imply broad applications of this method on material characterization, particularly on two-dimensional materials that are promising candidates for next-generation chips.

Distance and stellar parameter estimations of solar-like stars from the LAMOST spectroscopic survey

The Gaia mission has opened up a new era for the precise astrometry of stars, thus revolutionizing our understanding of the Milky Way. However, beyond a few kiloparseconds from the Sun, parallax measurements become less reliable, and even within 2 kpc, there still exist stars with large uncertainties. Our aim was to determine the distance and stellar parameters of 521,424 solar-like stars from LAMOST DR9; these stars lacked precise distance measurements (uncertainties higher than 20<!PCT!> or even without any distance estimations) when checked with Gaia. We proposed a convolutional neural network (CNN) model to predict the absolute magnitudes, colors, and stellar parameters ( and directly from low-resolution spectra. For spectra with signal-to-noise ratios at $g$ band ($ S/N_g $) greater than 10, the model achieves a precision of 85 K for 0.07 dex for 0.06 dex for 0.25 mag for and 0.03 mag for The estimated distances have a median fractional error of 4<!PCT!> with a standard deviation of 8<!PCT!>. We applied the trained CNN model to 521,424 solar-like stars to derive the distance and stellar parameters. Compared with other distance estimation studies and spectroscopic surveys, the results show good consistency. Additionally, we investigated the metallicity gradients of the Milky Way from a subsample, and find a radial gradient ranging from $-0.05 < R < 0.0\ dex\ $ and a vertical gradient ranging from $-0.26 < Z < -0.07\ dex\ We conclude that our method is effective in estimating distances and stellar parameters for solar-like stars with limited astrometric data. Our measurements are reliable for Galactic structure studies and hopefully will be useful for exoplanet researches.