adsabs/SciX_UAT_keywords huggingface dataset:
Toward a Spectrophotometric Characterization of the Chilean Night Sky. A First Quantitative Assessment of ALAN across the Coquimbo Region

Light pollution is recognized as a global issue that, like other forms of anthropogenic pollution, has a significant impact on ecosystems and adverse effects on living organisms. Plentiful evidence suggests that it has been increasing at an unprecedented rate at all spatial scales. Chile-which, thanks to its unique environmental conditions, has become one of the most prominent astronomical hubs of the world-seems to be no exception. In this paper we present the results of the first observing campaign aimed at quantifying the effects of artificial lights at night on the brightness and colors of the Chilean sky. Through the analysis of photometrically calibrated all-sky images captured at four representative sites with an increasing degree of anthropization, and the comparison with state-of-the-art numerical models, we show that significant levels of light pollution have already altered the appearance of the natural sky even in remote areas. Our observations reveal that the light pollution level recorded in a small town of the Coquimbo Region is comparable with that of Flagstaff, Arizona, a ten times larger Dark Sky city, and that a mid-size urban area that is a gateway to the Atacama Desert displays photometric indicators of night sky quality that are typical of the most densely populated regions of Europe. Our results suggest that there is still much to be done in Chile to keep light pollution under control and thus preserve the darkness of its night sky-a natural and cultural heritage that it is our responsibility to protect.

Keywords: light pollution; night sky brightness; all-sky cameras; photometer; observational astronomy
Optimal Frequency-domain Analysis for Spacecraft Time Series: Introducing the Missing-data Multitaper Power Spectrum Estimator

While the Lomb-Scargle periodogram is foundational to astronomy, it has a significant shortcoming: the variance in the estimated power spectrum does not decrease as more data are acquired. Statisticians have a 60 yr history of developing variance-suppressing power spectrum estimators, but most are not used in astronomy because they are formulated for time series with uniform observing cadence and without seasonal or daily gaps. Here we demonstrate how to apply the missing-data multitaper power spectrum estimator to spacecraft data with uniform time intervals between observations but missing data during thruster fires or momentum dumps. The F-test for harmonic components may be applied to multitaper power spectrum estimates to identify statistically significant oscillations that would not rise above a white noise-based false alarm probability. Multitapering improves the dynamic range of the power spectrum estimate and suppresses spectral window artifacts. We show that the multitaper-F-test combination applied to Kepler observations of KIC 6102338 detects differential rotation without requiring iterative sinusoid fitting and subtraction. Significant signals reside at harmonics of both fundamental rotation frequencies and suggest an antisolar rotation profile. Next we use the missing-data multitaper power spectrum estimator to identify the oscillation modes responsible for the complex "scallop-shell" shape of the K2 light curve of EPIC 203354381. We argue that multitaper power spectrum estimators should be used for all time series with regular observing cadence.

Keywords: time series analysis; astrostatistics techniques; period search; lomb-scargle periodogram; stellar rotation; light curves
TIC 5724661: A Long-period Binary with a Pulsating sdB Star and δ Scuti Variable

Using TESS 20 s cadence data, we have discovered an unusual combination of pulsating stars in what we infer to be a binary system. The binary consists of a standard δ Scuti star with pulsations over the range 32-41 day-1; this is in a likely wide orbit with a hot subdwarf-B (sdB) star, which itself has a large-amplitude p-mode pulsation at 524 day-1. We establish constraints on the period of the putative binary by using radial velocity measurements of the δ Scuti star and show that any sdB companion star must orbit with a period greater than approximately thirty days. Our identification of this sdB binary serves as an important addition to the relatively small number of sdB binaries known to have orbital periods longer than a few days. We model such a binary using MESA and find that this system could be formed through stable, nonconservative mass transfer from either a low-mass or an intermediate-mass progenitor, without undergoing a common-envelope phase.

Keywords: b subdwarf stars; asteroseismology; pulsating variable stars; stellar pulsations; delta scuti variable stars; binary stars
Apsidal Motion and Physical Parameters in the Eclipsing System V490 Sct

We report long-term UBVRIR c I c photometry of the highly eccentric 12.04 day detached eclipsing binary V490 Sct (V = 13.1, B9.5+A0, e = 0.40), which we use to determine its relative and absolute parameters. The absolute masses, radii, and temperatures are M A = 2.33 ± 0.07 M⊙, R A = 1.90 ± 0.04 R ⊙, and T A = 9960 ± 60 K for the primary and M B = 2.23±0.07 M⊙, R B = 1.86 ± 0.04 R ⊙, and T B = 9700 ± 80 K for the secondary. The system displays a slow periastron advance that is dominated by General Relativity (GR). Our measurement, $\dot{\omega }=0.86$ deg century-1, is 32% less then the expected rate, $\dot{\omega }\,=\,1.24$ deg century-1, which has an 83% contribution from GR. A comparison with current stellar evolution models shows a good match to the measured properties at an age of about 130 Myr and Solar abundance. The photometric parallax of the system π = 0.73 ± 0.04 mas, matches the GAIA DR2 value, π = 0.76 ± 0.04 mas.

Keywords: apsidal motion; stellar masses; eclipsing binary stars; stellar radii; stellar effective temperatures
A Dataset for Exploring Stellar Activity in Astrometric Measurements from SDO Images of the Sun

We present a data set for investigating the impact of stellar activity on astrometric measurements using NASA's Solar Dynamics Observatory (SDO) images of the Sun. The sensitivity of astrometry for detecting exoplanets is limited by stellar activity (e.g., starspots), which causes the measured "center of flux" of the star to deviate from the true, geometric, center, producing false positive detections. We analyze Helioseismic and Magnetic Imager continuum image data obtained from SDO between 2015 July and 2022 December to examine this "astrometric jitter" phenomenon for the Sun. We employ data processing procedures to clean the images and compute the time series of the sunspot-induced shift between the center of flux and the geometric center. The resulting time series show quasiperiodic variations up to 0.05% of the Sun's radius at its rotation period.

Keywords: astrometry; astrometric exoplanet detection; exoplanet astronomy; sunspots; solar physics; the sun
Identifying Diffuse Spatial Structures in High-energy Photon Lists

Data from high-energy observations are usually obtained as lists of photon events. A common analysis task for such data is to identify whether diffuse emission exists, and to estimate its surface brightness, even in the presence of point sources that may be superposed. We have developed a novel nonparametric event list segmentation algorithm to divide up the field of view into distinct emission components. We use photon location data directly, without binning them into an image. We first construct a graph from the Voronoi tessellation of the observed photon locations and then grow segments using a new adaptation of seeded region growing that we call Seeded Region Growing on Graph, after which the overall method is named SRGonG. Starting with a set of seed locations, this results in an oversegmented data set, which SRGonG then coalesces using a greedy algorithm where adjacent segments are merged to minimize a model comparison statistic; we use the Bayesian Information Criterion. Using SRGonG we are able to identify point-like and diffuse extended sources in the data with equal facility. We validate SRGonG using simulations, demonstrating that it is capable of discerning irregularly shaped low-surface-brightness emission structures as well as point-like sources with strengths comparable to that seen in typical X-ray data. We demonstrate SRGonG's use on the Chandra data of the Antennae galaxies and show that it segments the complex structures appropriately.

Keywords: spatial point processes; astrostatistics techniques; voronoi tessellation; astronomy data modeling
X-Ray Detection of the Galaxy's Missing Baryons in the Circumgalactic Medium of L* Galaxies

The number of baryons hosted in the disks of galaxies is lower than expected based on the mass of their dark matter halos and the fraction of baryon-to-total matter in the Universe, giving rise to the so-called galaxy missing-baryon problem. The presence of cool circumgalactic matter gravitationally bound to its galaxy's halo up to distances of at least 10 times the size of the galaxy's disk mitigates the problem but is far from being sufficient for its solution. It has instead been suggested that the galaxy's missing baryons may hide in a much hotter gaseous phase of the circumgalactic medium, possibly near the halo virial temperature and coexisting with the cool phase. Here we exploit the best available X-ray spectra of known cool circumgalactic absorbers of L* galaxies to report the first direct high statistical significance (best estimates ranging from 4.2σ to 5.6σ, depending on fitting methodology) detection of associated O VII absorption in the stacked XMM-Newton and Chandra spectra of three quasars. We show that these absorbers trace the hot medium in the X-ray halo of these systems at logT(in K) ≃ 5.8-6.3 (comprising the halo virial temperature T vir ≃ 106 K). We estimate masses of the X-ray halo within one virial radius within the interval ${M}_{\mathrm{hot}-\mathrm{CGM}}\simeq {(1\mbox{--}1.7)\times {10}^{11}(Z/0.3{Z}_{\odot })}^{-1}$ M ⊙. For these systems, this corresponds to galaxy missing-baryon fractions in the range ${\xi }_{b}={M}_{\mathrm{hot}-\mathrm{CGM}}/{M}_{\mathrm{missing}}\simeq {(0.7\mbox{--}1.2)(Z/0.3{Z}_{\odot })}^{-1}$ , thus potentially closing the galaxy baryon census in typical L* galaxies. Our measurements contribute significantly to the solution of the long-standing galaxy missing-baryon problem and to the understanding of the continuous cycle of baryons in-and-out of galaxies throughout the life of the Universe.

Keywords: circumgalactic medium; missing mass; x-ray astronomy; galaxies; lyman limit systems; quasar absorption line spectroscopy
Seeking Echoes of Circumstellar Disks in Kepler Light Curves

Light echoes of flares on active stars offer the opportunity for direct detection of circumstellar dust. We revisit the problem of identifying faint echoes in postflare light curves, focusing on debris disks from ongoing planet formation. Starting with simulations, we develop an algorithm for estimating the radial extent and total mass from disk echo profiles. We apply this algorithm to light curves from over 2100 stars observed by NASA's Kepler mission, selected for multiple short-lived flares in either the long-cadence or short-cadence data sets. While flux uncertainties in light curves from individual stars preclude useful mass limits on circumstellar disks, catalog-averaged light curves yield constraints on disk mass that are comparable to estimates from known debris disks. The average mass in micron- to millimeter-sized dust around the Kepler stars cannot exceed 10% of an Earth mass in exo-Kuiper belts or 10% of a lunar mass in the terrestrial zone. We group stars according to IR excess, based on WISE W1-W3 color, as an indicator for the presence of circumstellar dust. The mass limits are greater for stars with strong IR excess, a hint that echoes are lurking not far beneath the noise in postflare light curves. With increased sensitivity, echo detection will let time-domain astronomy complement spectroscopic and direct-imaging studies in mapping how, when, and where planets form.

Keywords: circumstellar disks; debris disks; exozodiacal dust; stellar flares; exoplanet astronomy
Constraining Spatial Densities of Early Ice Formation in Small Dense Molecular Cores from Extinction Maps

Tracing dust in small dense molecular cores is a powerful tool to study the conditions required for ices to form during the prestellar phase. To study these environments, five molecular cores were observed: three with ongoing low-mass star formation (B59, B335, and L483), and two starless collapsing cores (L63 and L694-2). Deep images were taken in the infrared JHK bands with the United Kingdom Infrared Telescope WFCAM (Wide Field Camera) instrument and IRAC channels 1 and 2 on the Spitzer Space Telescope. These five photometric bands were used to calculate extinction along the line of sight toward background stars. After smoothing the data, we produced high spatial resolution extinction maps (~13″-29″). The maps were then projected into the third dimension using the AVIATOR algorithm implementing the inverse Abel transform. The volume densities of the total hydrogen were measured along lines of sight where ices (H2O, CO, and CH3OH) have previously been detected. We find that lines of sight with pure CH3OH or a mixture of CH3OH with CO have maximum volume densities above 1.0 × 105 cm-3. These densities are only reached within a small fraction of each of the cores (~0.3%-2.1%). CH3OH presence may indicate the onset of complex organic molecule formation within dense cores, and thus we can constrain the region where this onset can begin. The maximum volume densities toward star-forming cores in our sample (~(1.2-1.7) × 106 cm-3) are higher than those toward starless cores (~(3.5-9.5) × 105 cm-3).

Keywords: interstellar dust extinction; interstellar extinction; infrared astronomy; infrared photometry; molecular clouds; bok globules; young stellar objects; ice formation
The Relation between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies. III. The Link to the M •-M * Correlation

We continue to explore the relationship between the total number of globular clusters (GCs), N GC, and the central black hole mass, M •, in spiral galaxies. We present here results for the Sab galaxies NGC 3368, NGC 4736 (M94), and NGC 4826 (M64), and the Sm galaxy NGC 4395. The GC candidate selection is based on the (u* - $i^{\prime} $ ) versus ( $i^{\prime} $ - K s ) color-color diagram, and $i^{\prime} $ -band shape parameters. We determine the M • versus N GC correlation for these spirals, plus NGC 4258, NGC 253, M104, M81, M31, and the Milky Way. We also redetermine the correlation for the elliptical sample in Harris et al., with updated galaxy types from Sahu et al. Additionally, we derive the total stellar galaxy mass, M *, from its two-slope correlation with N GC, and fit M • versus M * for both spirals and ellipticals. We obtain log M • ∝ (1.01 ± 0.13) log N GC for ellipticals, and log M • ∝ (1.64 ± 0.24) log N GC for late-type galaxies (LTGs). The linear M • versus N GC correlation in ellipticals could be due to statistical convergence through mergers, unlike the much steeper correlation for LTGs. However, in the M • versus total stellar mass (M *) parameter space, with M * derived from its correlation with N GC, M • ∝ (1.48 ± 0.18) log M * for ellipticals, and M • ∝ (1.21 ± 0.16) log M * for LTGs. The observed agreement between ellipticals and LTGs in this parameter space may imply that black holes and galaxies coevolve through calm accretion, active galactic nuclei feedback, and other secular processes.

Keywords: galaxy formation; galaxy evolution; spiral galaxies; globular star clusters; star clusters; classical black holes; black holes
Morphology of Star-forming Clumps in Ram-pressure Stripped Galaxies as Seen by HST

We characterize the morphological properties of a statistically relevant sample of Hα and UV young star-forming clumps and optical complexes, observed with the Hubble Space Telescope in six galaxies of the GASP sample undergoing ram pressure stripping. The catalogs comprise 2406 (323 in the tails) Hα clumps, 3750 (899) UV clumps, and 424 tail optical complexes. About 15%-20% of the clumps and 50% of the complexes are resolved in size. We find that more than half of the complexes contain no Hα clumps, while most of them contain at least one UV clump. The clump number and size increase with the complex size, while the median complex filling factor is larger for UV clumps (0.27) than that for Hα clumps (0.10) and does not correlate with almost any morphological property. This suggests that the clumps' number and size grow with the complex keeping the filling factor constant. When studying the position of the clumps inside their complexes, Hα clumps, and UV clumps to a lesser extent, show a displacement from the complex center of 0.1-1 kpc, and in ~60% of the cases, they are displaced away from the galactic disk. This is in accordance with the fireball configuration, already observed in the tails of stripped galaxies. Finally, the filling factor and the clump radius increase with the distance from the galactic disk, suggesting that the reciprocal displacement of the different stellar generations increases as a consequence of the velocity gradient caused by ram pressure.

Keywords: galaxy clusters; galaxy evolution; star formation; star forming regions; galaxy structure; galaxy tails
Speckle Interferometry at SOAR Telescope in 2023

Results of the speckle-interferometry observations at the 4.1 m Southern Astrophysical Research Telescope obtained during 2023 are presented: 1913 measurements of 1533 resolved pairs or subsystems (median separation 0.″16) and nonresolutions of 552 targets; 42 pairs are resolved here for the first time. This work continues our long-term effort to monitor orbital motion in close binaries and hierarchical systems. A large number (147) of orbits have been determined for the first time or updated using these measurements. Complementarity of this program with the Gaia mission is highlighted.

Keywords: binary stars; interferometric binary stars; multiple stars
Spectra of Cosmic-Ray Sodium and Aluminum and Unexpected Aluminum Excess

Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, $\bar{p}$ , e ±, and nuclei (H-Si, Fe), which resulted in a number of breakthroughs. The most recent AMS-02 result is the measurement of the spectra of CR sodium and aluminum up to ~2 TV. Given their low solar system abundances, a significant fraction of each element is produced in fragmentations of heavier species, predominantly Ne, Mg, and Si. In this paper, we use precise measurements of the sodium and aluminum spectra by AMS-02 together with ACE-CRIS and Voyager 1 data to test their origin. We show that the sodium spectrum agrees well with the predictions made with the GALPROP-HELMOD framework, while the aluminum spectrum shows a significant excess in the rigidity range from 2-7 GV. In this context, we discuss the origin of other low-energy excesses in Li, F, and Fe found earlier. The observed excesses in Li, F, and Al appear to be consistent with the local Wolf-Rayet stars hypothesis, invoked to reproduce anomalous 22Ne/20Ne, 12C/16O, and 58Fe/56Fe ratios in CRs, while excess in Fe is likely connected with a past supernova activity in the solar neighborhood. We also provide updated local interstellar spectra (LIS) of sodium and aluminum in the rigidity range from a few megavolts to ~2 TV. Our calculations employ the self-consistent GALPROP-HELMOD framework, which has proved to be a reliable tool in deriving the LIS of CR $\bar{p}$ , e -, and nuclei Z ≤ 28.

Keywords: galactic cosmic rays; secondary cosmic rays; heliosphere; interstellar medium; interplanetary medium; galaxy abundances
EDEN: Flare Activity of the Nearby Exoplanet-hosting M Dwarf Wolf 359 Based on K2 and EDEN Light Curves

We report the flare activity of Wolf 359, the fifth closest star to the Sun and a candidate exoplanet-hosting M dwarf. The star was a target of the Kepler/K2 mission and was observed by the EDEN project, a global network of 1-2 m class telescopes for detection and characterization of rocky exoplanets in the habitable zones of late-M dwarfs within 50 light year from the solar system. In the combination of the archived K2 data and our EDEN observations, a total of 872 flares have been detected, 861 with the K2 (860 in the short-cadence and 18 in the long-cadence data, with 17 long-cadence events having short-cadence counterparts) and 11 with EDEN. Wolf 359 has relatively strong flare activity even among flaring M dwarfs, in terms of the flare activity indicator (FA) defined as the integrated flare energy relative to the total stellar bolometric energy, where FA = ∑Ef/∫Lbol dt ∼ 8.93 × 10-5 for the long-cadence flares, whereas for K2 short cadence and EDEN flares, the FA values are somewhat larger, FA ≈ 6.67 × 10-4 and FA ≈ 5.25 × 10-4, respectively. Such a level of activity, in accordance with the rotation period (Prot), suggests the star to be in the saturation phase. The size of the starspots is estimated to be at least 1.87% ± 0.59% of the projected disk area of Wolf 359. We find no correlation of FA with the stellar rotational phase. Our analysis indicates a flare frequency distribution in a power-law form of ${dN}/{dE}\propto {E}^{-\alpha }$ with α = 2.13 ± 0.14, equivalent to an occurrence rate of flares Ef ≥ 1031 erg about once per day and of superflares with Ef ≥ 1033 erg approximately 10 times per year. These superflares may impact the habitability of system in multiple ways, the details of which are topics for future investigations.

Keywords: planet hosting stars; exoplanet systems; exoplanet astronomy; exoplanets; flare stars; stellar flares; stellar phenomena
Powerful Flare Phenomena in Water Vapor Maser Lines in the Emerging Protostellar System with Protoplanetary Disks IRAS 16293-2422

According to the detailed monitoring of the water maser at a frequency of 22.2 GHz from 2019 to 2021 in IRAS 16293-2422, two powerful phenomena that occurred at radial velocities of about 6 and 8 km s-1 were detected. Each flare phenomenon consisted of several separate flares lasting no more than a month. The existence of the several emitting maser spot configurations with very close radial velocities, located in the line of sight of the observer, were confirmed for the first time. This made possible to demonstrate the plausibility of the water maser activation hypothesis based on an increase in the amplification length of the maser due to several maser condensations. In both cases, powerful short flares were located on the top of less powerful, but more prolonged ones. Their radiation initiated the release of more powerful flares. The broad Doppler spectral lines of less powerful flares indicate that their masers are probably in a saturated state, while more powerful masers are in unsaturated state. New important parameters of water masers have been obtained, including flare amplitudes, maser line widths, H2O kinetic temperatures during flares, data on the relaxation time of the maser medium, and the fact of existence of a cascade amplification of the water maser in cases of powerful short flares. The possible localization of water masers at features near 6 and 8 km s-1 within the young gas and dust complex IRAS 16293-2422 is also discussed in this work.

Keywords: star forming regions; interstellar molecules; proplyds