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X-ray, optical, and radio follow-up of five thermally emitting isolated neutron star candidates
No full textWe report on follow-up observations with XMM-Newton, the FORS2 instrument at the ESO-VLT, and FAST, aiming to characterise the nature of five thermally emitting isolated neutron star (INS) candidates recently discovered from searches in the footprint of the Spectrum Roentgen Gamma (SRG)/eROSITA All-sky Survey. We find that the X-ray spectra are predominantly thermal and can be described by low-absorbed blackbody models with effective temperatures ranging from 50 to 210 eV. In two sources, the spectra also show narrow absorption features at 300–400 eV. Additional non-thermal emission components are not detected in any of the five candidates. The soft X-ray emission, the absence of optical counterparts in four sources, and the consequent large X-ray-to-optical flux ratios > 3000 − 5400 confirm their INS nature. For the remaining source, eRASSU J144516.0–37442
A decade of solar high-fidelity spectroscopy and precise radial velocities from HARPS-N
No full textContext. The HARPS-N solar telescope has been observing the Sun every possible day since the summer of 2015. We have recently released 10 years of these data, which are available online.
Aims. The goal of this paper is to present the different optimisations made to the ESPRESSO data reduction software used to extract the published HARPS-N solar spectra, describe the data curation, and perform some analyses that demonstrate the extreme radial velocity (RV) precision of those data.
Methods. By analysing all of the HARPS-N wavelength solutions over 13 years, we brought to light instrumental systematics at the 1 m s−1 level. We mitigated those systematics by curating the thorium line list used to derive the wavelength solution and applying a correction to the drift of thorium lines induced by the aging of thorium-argon hollow cathode lamps. After optimisation, we demonstrated a peak-to-peak precision on the HARPS-N wavelength solution better than 0.75 m s−1 over 13 years. We then carefully curated the decade of HARPS-N re-reduced solar observations by rejecting 30% of the data affected either by clouds, bad atmospheric conditions, or well-understood instrumental systematics. Finally, we corrected the curated data for spurious sub-meter-per-second RV effects caused by erroneous instrumental drift measurements and by changes in the spectral blaze function over time.
Results. After curation and correction, a total of 109,466 HARPS-N solar spectra and respective RVs over a decade were made available. The median photon-noise precision of the RV data is 0.28 m s−1, and on daily timescales, the median RV rms is 0.49 m s−1, which is similar to the level imposed by stellar granulation signals. On 10 year timescales, the large RV rms of 2.95 m s−1 results from the RV signature of the Sun’s magnetic cycle. Through modelling of this long-term effect using the Bremen composite magnesium II activity index, we demonstrate a long-term RV precision of 0.41 m s−1. We also analysed contemporaneous HARPS-N and NEID solar RVs and found the data from both instruments to be of similar quality and precision. However, an analysis of the RV difference between these two RV datasets over the three available years gave a surprisingly large RV rms of 1.3 m s−1. This variation is dominated by an unexplained trend that could be caused by a different sensitivity to stellar activity of the two datasets. Once this trend was modelled, the overall RV rms for three years reached 0.79 m s−1, and the RV rms during the low-activity phase decreased to 0.6 m s−1, compatible with what is expected from supergranulation.
Conclusions. This decade of high-cadence HARPS-N solar observations with short- and long-term precision below one m s−1 represents a crucial dataset in the pursuit of further understanding the stellar activity signals in solar-type stars and advancing other science cases requiring such extreme precision
Emission-line and continuum reverberation mapping of the NLS1 galaxy WPVS 48
No full textContext. WPVS 48 is a nearby narrow-line Seyfert 1 galaxy without previous analysis of the broad-line region (BLR) by means of optical spectroscopic reverberation mapping.
Aims. By studying the continuum and emission line variability of WPVS 48, our aim was to infer the BLR size as well as the mass of the central supermassive black hole (SMBH).
Methods. We analysed data from a dedicated optical spectroscopic reverberation mapping campaign of WPVS 48 taken with the 10 m Southern African Large Telescope (SALT) at 24 epochs over a period of seven months between December 2013 and June 2014.
Results. WPVS 48 shows variability throughout the campaign. We find a stratified BLR, where the variability amplitude of the integrated emission lines decreases with distance to the ionising continuum source. Specifically, the variable emission of Hα, Hβ, Hγ, and He
The
No full textThe recent discovery of five massive stellar clusters at z = 9.625 in the Cosmic Gems galaxy has raised the question about the formation mechanism of star clusters in the first 500 Myr after the Big Bang. We inferred the total stellar mass in clusters by normalizing and integrating the stellar cluster mass function (SCMF, dn(M)/dM = n0Mβ), assuming three different slopes (β = −1.5, −2.0, and −2.5) and different lower-mass limits between 102 and 105 M⊙. We compared the total integrated cluster stellar mass to the stellar mass inferred from the counter image of the Cosmic Gems, which provides the best modestly magnified (μ = 1.84 ± 0.05) representation of the entire galaxy. The delensed stellar mass of the Cosmic Gems galaxy was estimated as M⊙, with an effective radius of parsecs and a stellar surface mass density of M⊙ pc−2. Accounting for normalization uncertainties – including different lensing magnification scenarios for the arc – a modified SCMF, combined with a significantly high star cluster formation efficiency (approaching 100%), appears to be a necessary condition to explain the relatively short formation timescale of both the star clusters and the counter image, without exceeding the galaxy’s stellar mass. By extrapolating the physical properties at the peak of the burst, we found that in its recent past (≲30 Myr) the Cosmic Gems galaxy likely experienced a specific star formation rate exceeding 25 Gyr−1 and luminosity approaching the “blue monster” regime (MUV < −20). Our study provides insights into the extreme clustered nature of star formation in early galaxies and sheds light on the formation of bound star clusters that might survive to z = 0 as globular clusters older than 13 Gyr
Shock-type inference of L1157 B2 using methanol desorption
No full textContext. Shock types of low-velocity molecular outflows are not always well constrained. Astrochemical comparisons are often made between low-velocity and high-velocity outflows, but without considering the question of the shock type.
Aims. We investigated molecular abundances of post-shock regions to determine whether strong differences between non-irradiated C-type and J-type shocks can be highlighted. One of the main application goals is to diagnose the shock type of the protostellar object L1157 B2 through the use of molecular tracers.
Methods. We simulated grid sets of shock models with the Paris-Durham Shock code with velocities ranging from 5 to 19 km/s and low densities from 102 to 105 cm−3. We computed the desorption percentage of methanol in these simulations and estimated it at higher velocities. We compared our results to observational measurements of L1157 B2 and with a benchmark of four already identified shocks.
Results. L1157 B2 has been diagnosed as a non-irradiated C-type shock, and the method showed a good applicability through the benchmark. Methanol formed in the icy mantle of grains can serve to trace the differences between shock types, at least in non-irradiated conditions. A requirement for the applicability of a species as a shock-type tracer is that it does not undergo significant enhancement or destruction, but is mainly impacted by desorption processes under shocked conditions.
Conclusions. The desorption percentage of methanol is a good criterion in characterizing the shock type of L1157 B2 and should be investigated as a general method to diagnose the shock type in non-irradiated regions. We identify L1157 B2 as a non-irradiated C-type shock with velocities and densities fitting with previous studies
Chemodynamic evidence of pristine gas accretion in the void galaxy VGS 12
No full textContext. Accretion of metal-poor gas is expected to be an important channel of gas replenishment in galaxy evolution studies. However, observational evidence of this process is still relatively scarce.
Aims. The unusual polar disk galaxy VGS 12 was found in the Void Galaxy Survey. It appears to be isolated and resides in the cosmological wall between two large voids. The suggested formation scenario for this peculiar system is accretion of metal-poor gas from the void interior. To confirm or refute the accretion scenario, information on the chemical properties of VGS 12 is crucial and provides novel insights into gas accretion mechanisms when combined with kinematic constraints on the polar material.
Methods. We present for the first time the data on the gas-phase chemical abundance of VGS 12 obtained with the Russian 6m telescope BTA. We complement our analysis with HI data obtained with VLA and the data on the kinematics of the ionized gas.
Results. VGS 12 appears to be a strong outlier from the “metallicity–luminosity” relation, with gas oxygen abundance ∼0.7 dex lower than expected for its luminosity. The nitrogen abundance, on the other hand, is higher than what is typically observed in galaxies with similar metallicity, but is consistent with the metallicity expected given its luminosity. Such behavior is what is expected in the case of metal-poor gas accretion. The H
Astrometric view of companions in the inner dust cavities of protoplanetary discs
No full textContext. Protoplanetary discs with inner dust cavities (often referred to as ‘transition discs’) are potential signposts of planet formation. However, few companions have been identified within these cavities, and the role of companions in shaping them remains unclear.
Aims. We used Gaia astrometry to search for planetary and stellar companions in a sample of 98 transition discs, assessing the occurrence rate of such companions and their potential influence on cavity formation.
Methods. For the 98 young stellar objects (YSOs) with inner dust cavities, we computed Gaia proper motion anomalies, which together with the renormalised unit weight error (RUWE), identify companions with mass ratios q ≳0.01 at ∼0.1−30 au. We assessed the impact of disc gravity, accretion, disc-scattered light, dippers, starspots, jets, and outflows on the measured proper motion anomalies, concluding that these effects are unlikely to affect our analyses and that astrometric techniques such as the one of this work can be robustly applied to YSOs.
Results. Significant proper motion anomalies are found in 31 transition discs (32% of the sample), indicative of companions. We recovered 85% of the known companions within our sensitivity range. Assuming that the astrometry of each system is dominated by a single companion, we modelled the semi-major axis and mass required to reproduce the observed astrometric signals. Most inferred companions have M>30 MJ, placing many within or near the stellar mass regime. Seven sources host companions compatible with a planetary mass (M<13 MJ, HD 100453, J04343128+1722201, J16102955-3922144, MHO6, MP Mus, PDS 70, and Sz 76). For the non-detections, we provide the companion masses and semi-major axes that can be excluded in future searches. About half (53%) of detected companions cannot be reconciled with having carved the observed dust cavities.
Conclusions. We have gathered evidence of the presence of companions in a large sample of transition discs. However, we find that the population of transition discs cannot be fully described as a circumbinary population. Transition discs host as many companions within our sensitivity range as do randomly sampled groups of YSOs and main-sequence stars. If dust cavities are shaped by companions, such companions must reside at larger orbital separations than those of the companions detected here, and we predict them to be of planetary mass
Integrating Coral Reef and Reef Fish Community Data to Support Sustainable Ecotourism Management in Lihaga Island, North Sulawesi, Indonesia
No full textCoral reef ecosystems and reef-fish communities underpin essential ecosystem services in tropical seas, particularly for small-island ecotourism. Lihaga Island in North Sulawesi, Indonesia, is experiencing increasing ecological pressure as marine ecotourism expands, highlighting the need for integrated ecological assessments to support sustainable management. This study evaluates coral reef condition, reef-fish assemblages, and the presence of hawksbill turtles to assess their implications for sustainable ecotourism management. Field surveys were conducted from August to September 2023 at two marine stations surrounding the approximately 8-hectare island, quantifying live and dead coral cover, coral life-form composition, and reef-fish species richness and abundance using underwater visual census and benthic surveys, supported by multivariate analyses and spatial visualization. The coral reefs exhibited moderate overall condition, with mean live coral cover of 38.58 percent and dead coral cover of 40.32 percent. A total of 1,152 reef fishes representing 15 families and 72 species were recorded, dominated by Pomacentridae, Labridae, and Chaetodontidae. The presence of the Critically Endangered hawksbill turtle (Eretmochelys imbricata) indicated the persistence of functional nesting habitat. Sites with higher live coral cover supported greater reef-fish diversity, demonstrating strong ecological coupling between habitat complexity and community structure. The findings indicate that habitat degradation, shifts in trophic composition, and spatial overlap between tourism activities and turtle nesting zones pose risks to long-term ecosystem stability. Adaptive spatial zoning, visitor regulation, and ecologically informed governance are therefore essential to support sustainable small-island ecotourism at Lihaga Island
Effect of Black Rice Enrichment on the Quality of Fermented Milk Produced with
No full textThe incorporation of plant-based ingredients into fermented dairy products can enhance their functional value while maintaining product quality. This study investigated the effects of black rice powder enrichment (0-12% w/v) on the key characteristics of fermented milk produced using Lactiplantibacillus plantarum. Increasing the black rice concentration resulted in a significant decrease in pH from 4.98 to 3.81, indicating enhanced acidification. Viscosity and water-holding capacity showed a significant decrease from 2869.33 to 241.33 cP and from 100% to 50%, respectively, reflecting the disruption of the milk protein gel structure. Colour attributes were significantly affected, with lightness (L*) decreasing from 84.09 to 38.15 and a shift toward reddish-purple hues associated with anthocyanin pigments. The probiotic viability remained consistently high across all formulations (8.45-8.81 log CFU/mL), confirming successful fermentation. Sensory evaluation revealed significant differences among treatments, with moderate black rice enrichment (3-6% w/v) achieving the highest overall acceptability, whereas higher substitution levels negatively affected texture and flavour. These findings demonstrate, for the first time, that black rice powder can be effectively incorporated into fermented milk to enhance its functional properties while preserving probiotic viability and consumer acceptance
Impact of Climate Change on the Hydrological Conditions of The Noelmina Watershed, East Nusa Tenggara, Indonesia
No full textClimate change is a phenomenon that has become a real threat to human life and the environment. Over the past 40 years, climate parameters in the Noelmina River Watershed, East Nusa Tenggara, have undergone changes. This has undoubtedly caused significant changes in the hydrological conditions of the watershed, which covers an area of 1,965,71.39 hectares. Due to the limited climate data available from the Meteorology, Climatology, and Geophysics Agency (BMKG) at the study site, Climate data from the National Aeronautics and Space Administration Prediction of Worldwide Energy Resources (POWER NASA) were used. In the last 40 years, the average air temperature at the study site has increased by 0.19 0C, relative air humidity has increased by 2.1 %, and annual rainfall has increased by 430 mm.There has also been a shift in the climate types in the watershed. Based on the criteria of Smith and Ferguson, Oldeman, and Mohr. Changes in watershed water balance were observed using the Thornwaite-Matter method. The water surplus in the Noelmina sub-watershed increased by 51.06%. The surplus period occurred between December and March. The base flow also increased by 45.8%