Prominent Lines Research Articles

Gleeok’s Fire-breathing: Triple Flares of AT 2021aeuk within Five Years from the Active Galaxy SDSS J161259.83+421940.3

We present a noteworthy transient AT 2021aeuk exhibiting three distinct optical flares between 2018 and 2023. It is hosted in a radio-loud narrow-line Seyfert 1 galaxy, with an optical image showing a minor tidal morphology and a red mid-infrared color (W1 − W2 = 1.1). Flares II and III exhibit rapid rises, and long-term decays (≳1000 days) with recurring after-peak bumps. The g − r color after subtracting the reference magnitude exhibited a rapid drop and recovery during Flare II, followed by a minor after-peak evolution in blue colors. We applied a canonical tidal disruption event (TDE) fitting on the light curves, which gives a decay index p of −2.99−0.14+0.13 for Flare II and −1.61−0.65+0.34 for Flare III. The blackbody fitting shows lower temperatures (∼103.8 K) with minor after-peak evolution. The blackbody radius (≳1016 cm) and luminosity (∼1045 erg s−1) are larger than the typical TDE sample’s. The time lag (in rest frame) between the ZTF g and r bands ( τg,r=3.4−0.9+1.0 days) significantly exceeds the prediction from the standard accretion disk. Pre-burst spectra reveal prominent Bowen fluorescence lines, indicating a vigorous or potentially long-lasting process that enriches the local metallicity. Additionally, we derived black hole masses of logM•=7.09−0.31+0.18M⊙ and logM•=7.52−0.10+0.08M⊙ using Hβ and Hα emission lines. The variation and recurring features of AT 2021aeuk are not likely induced by the radio-beaming effect or Type II superluminous supernova; however, we cannot rule out the possibility of TDE or enhanced active galactic nuclei accretion process. The unusually high occurrence of three flares within 5 yr may also induced by the complex local environment.

A Spectroscopic and Interferometric Study of W Serpentis Stars. I. Circumbinary Outflow in the Interacting Binary W Serpentis

W Serpentis is an eclipsing binary system and the prototype of the Serpentid class of variable stars. These are interacting binaries experiencing intense mass transfer and mass loss. However, the identities and properties of both stars in W Ser remain a mystery. Here, we present an observational analysis of high-quality, visible-band spectroscopy made with the Apache Point Observatory 3.5 m telescope and Astrophysical Research Consortium Echelle Spectrograph spectrograph plus the first near-IR, long-baseline interferometric observations obtained with the Center for High Angular Resolution Astronomy Array. We present examples of the appearance and radial velocities of the main spectral components: prominent emission lines, strong shell absorption lines, and weak absorption lines. We show that some of the weak absorption features are associated with the cool mass donor, and we present the first radial velocity curve for the donor star. The donor’s absorption lines are rotationally broadened, and we derive a ratio of donor to gainer mass of 0.36 ± 0.09 based on the assumptions that the donor fills its Roche lobe and that it rotates synchronously with the orbit. We use a fit of the All-Sky Automated Survey light curve to determine the orbital inclination and mass estimates of 2.0M ⊙ and 5.7M ⊙ for the donor and gainer, respectively. The partially resolved interferometric measurements of orbital motion are consistent with our derived orbital properties and the distance from Gaia EDR3. Spectroscopic evidence indicates that the gainer is enshrouded in an opaque disk that channels the mass transfer stream into an outflow through the L3 region and into a circumbinary disk.

Spectral and timing properties of the accreting millisecond X-ray pulsar IGR J17498−2921 during its 2023 outburst

We present a comprehensive study of the spectral properties of the accreting millisecond X-ray pulsar IGR J17498−2921 during its 2023 outburst. Similar to other accreting millisecond X-ray pulsars, the broadband spectral emission observed quasi-simultaneously by NICER and NuSTAR is well described by an absorbed Comptonized emission with an electron temperature of ∼17 keV plus a disk reflection component. The broadening of the disk reflection spectral features, such as a prominent iron emission line at 6.4–6.7 keV, is consistent with the relativistic motion of matter in a disk truncated at ∼21 Rg from the source, near the Keplerian corotation radius. From the high-cadence monitoring data obtained with NICER, we observed that the evolution of the photon index and the temperature of seed photons tracks variations in the X-ray flux. This is particularly evident close to a sudden ∼–0.25 cycle jump in the pulse phase, which occurs immediately following an X-ray flux flare and a drop in the pulse amplitude below the 3σ detection threshold. We also report on the non-detection of optical pulsations with TNG/SiFAP2 from the highly absorbed optical counterpart.

The fast rise of the unusual type IIL/IIb SN 2018ivc

We present an analysis of the photometric and spectroscopic dataset of the type II supernova (SN) 2018ivc in the nearby (10 Mpc) galaxy Messier 77. Thanks to our high-cadence data, we observed the SN rising very rapidly by nearly three magnitudes in five hours (or 18 mag d$^ $). The $r$-band light curve presents four distinct phases: the maximum light, which was reached in just one day, followed by a first, rapid linear decline and a short-duration plateau. Finally, the long, slower linear decline lasted for one year. Thanks to the ensuing radio re-brightening, we were able to detect SN 2018ivc four years after the explosion. The early spectra show a blue, nearly featureless continuum, but the spectra go on to evolve rapidly; after about ten days, a prominent Halpha line starts to emerge, characterised by a peculiar profile. However, the spectra are heavily contaminated by emission lines from the host galaxy. The He I lines, namely $ are also strong. In addition, strong absorption from the Na I doublet is evident and indicative of a non-negligible internal reddening. From its equivalent width, we derived a lower limit on the host reddening of $A_V mag. From the Balmer decrement and a match of the $B-V$ colour curve of SN 2018ivc to that of the comparison objects, we obtained a host reddening of $A_V mag. The spectra are similar to those of SNe II, but with strong He lines. Given the peculiar light curve and spectral features, we suggest SN 2018ivc could be a transitional object between the type IIL and type IIb SNe classes. In addition, we found signs of an interaction with the circum-stellar medium (CSM) in the light curve, also making SN 2018ivc an interacting event. Finally, we modelled the early multi-band light curves and photospheric velocity of SN 2018ivc to estimate the physical parameters of the explosion and CSM.

On detection of BaO molecular lines in sunspot spectrum

ContextSpectral lines of diatomic molecules are perfect tools for studying the structure of sunspots and their temperature layers and magnetic sensitive absorption features, which are typically higher than in atomic lines. The integrated intensities of a few bands in the rotational structure of the astrophysically significant A1Σ+−X1Σ+and A′1Π−X1Σ+ systems of barium monoxide (BaO) have been measured experimentally using band spectra. An analysis of the prominent lines of (0, 0; 1, 1; 2, 2) bands of A1Σ+−X1Σ+transition and (0, 0; 1, 1; 2, 2) bands of A′1Π−X1Σ+transition with those of sunspot umbral spectrum. The effective rotational temperatures of the A′1Π−X1Σ+transition of BaO in the sunspot umbral spectrum are found to be in the range of 1600 K to 3200 K. AimsAn analysis of BaO prominent rotational molecular lines of A1Σ+−X1Σ+and A′1Π−X1Σ+transition with those of sunspot umbral spectral lines. To find the significant values of radiative transition parameters, vibrational temperature and the effective rotational temperature of the molecule in celestial objects. MethodsCalibrated the rotational structure of molecular band heads and lines for and A1Σ+−X1Σ+and A′1Π−X1Σ+ransitions in laboratory spectrum using most precise Hartmann's technique. High resolution FTS sunspot umbral spectra from NSO/Kitt Peak were used to detect rotational molecular lines due to the A′1Π−X1Σ+transition of the BaO molecule using the method of line coincidence. The effective rotational temperature was derived from the variation of equivalent width (W) with rotational quantum number (J) of spectrally well resolved rotational lines of a band in umbral spectrum. The triangular profile approximation method was used to estimate the equivalent width of the well resolved spectral lines. ResultsThe effective rotational temperatures of the A′1Π−X1Σ+transition of BaO in the sunspot umbral spectrum are found to be in the range of 1600 K to 3200 K. It is compared with other results with a view to obtaining useful physical parameters. This is an evidence to ascertain the possible presence of BaO molecule in solar spectrum in different layers. ConclusionsUnblended rotational lines due to the band of BaO, provide a good range of temperatures for the study of absorbing layers in umbral spectra. The A′1Π−X1Σ+transition of BaO molecular lines is found to be very sensitive to effective temperature. Radiative transition parameters data of these lines, in contrast to intensity measurements, provide us with more direct and detailed information to study the coolest parts of sunspot umbrae.

On the implausible physical implications of a claimed lensed neutral hydrogen detection at redshift z = 1.3

Abstract The Square Kilometre Array mid-frequency array will enable high-redshift detections of neutral hydrogen (H i) emission in galaxies, providing important constraints on the evolution of cold gas in galaxies over cosmic time. Strong gravitational lensing will push back the H i emission frontier towards cosmic noon (z ∼ 2), as has been done for all prominent spectral lines in the interstellar medium of galaxies. Chakraborty & Roy (2023, MNRAS, 519, 4074) report a z = 1.3 H i emission detection towards the well-modelled, galaxy-scale gravitational lens, SDSS J0826+5630. We carry out H i source modelling of the system and find that their claimed H i magnification, μHI = 29 ± 6, requires an H i disk radius of ≲ 1.5 kpc, which implies an implausible mean H i surface mass density in excess of ΣHI > 2000 M⊙ pc−2. This is several orders of magnitude above the highest measured peak values (ΣHI ∼ 10 M⊙ pc−2), above which H i is converted into molecular hydrogen. Our re-analysis requires this to be the highest H i mass galaxy known (MHI ∼ 1011 M⊙), as well as strongly lensed, the latter having a typical probability of order 1 in 103 − 4. We conclude that the claimed detection is spurious.

A new species of Craterium (Myxomycetes, Physarales, Physaraceae) with a mottled peridium

A new species of Craterium, described herein as С. guttatum, was recovered in Russia, during intensive field work in the Kaluzhskiye Zaseki Nature Reserve (Kaluga Oblast’) and in the Sudogodskiy District of the Vladimir Oblast’. Morphological details of sporocarps and spores were examined by light and scanning electron microscopy. The new species is characterized by a unique combination of morphological characters, such as a beaker-shaped sporotheca with a mottled peridium and a prominent line of dehiscence separating the upper part of the sporotheca in the form of a convex white lid, as well as spores densely ornamented with small warts grouped in clusters. The partial sequences of the 18S rRNA, EF1α and mtSSU genes of C. guttatum differ significantly from all Craterium species sequences available to date.

Exploring various extracts and compounds of Grewia velutina as potential anticancer agents: An in vitro and in silico investigations

This study presents a comprehensive investigation into the potential anticancer properties and chemical constituents of an unexplored plant (Grewia velutina) extracts. Three distinct extracts of hexane (GVH), chloroform (GVC) and methanol(GVM) of the plant were used to check their anticancer activity against four prominent cancer cell lines (HepG2, DU145, Hela, A549), and the results were compared with the standard chemotherapeutic agent doxorubicin. Anticancer assays revealed that the GVC extract exhibited highest activity than others, with IC50 values of 61.06 µg/mL, 47.87 µg/mL, 88.76 µg/mL, and 87.99 µg/mL against HepG2, DU145, Hela, and A549 cell lines, respectively and reflected a comparable activity to doxorubicin, highlighting its potential as an effective anticancer agent. With the help of chemical profiling data, molecular docking studies were performed and this study suggested that ionol, present in GVC extract is the most active compound against all the cancerous cells.

Spectral analysis of three hot subdwarf stars: EC 11481-2303, Feige 110, and PG 0909+276

Context. For the precise spectral analysis of hot stars, advanced stellar-atmosphere models that consider deviations from the local thermodynamic equilibrium are mandatory. This requires accurate atomic data to calculate all transition rates and occupation numbers for atomic levels in the considered model atoms, not only for a few prominent lines exhibited in an observation. The critical evaluation of atomic data is a challenge because it requires precise laboratory measurements. Ultraviolet spectroscopy of hot stars with high resolving power provide such “laboratory” spectra. Aims. We compare observed, isolated lines of the iron group (here calcium to nickel) with our synthetic line profiles to judge the accuracy of the respective oscillator strengths. This will verify them or yield individual correction values to improve the spectral analysis, that is the determination of, for example, effective temperature (Teff) and abundances. Methods. To minimize the error propagation from uncertainties in Teff, surface gravity (𝑔), and abundance determination, we start with a precise reanalysis of three hot subdwarf stars, namely EC 11481-2303, Feige 110, and PG0909+276. Then, we measure the abundances of the iron-group elements individually. Based on identified, isolated lines of these elements, we compare observation and models to measure their deviation in strength (equivalent width). Results. For EC 11481–2303 and Feige 110, we confirmed the previously determined Teff and log 𝑔 values within their error limits. For all three stars, we fine-tuned all metal abundances to achieve the best reproduction of the observation. For more than 450 isolated absorption lines of the iron group, we compared modeled and observed line strengths. Considering the uncertainty of the analysis and evaluation procedure, an upper limit for the uncertainty of the underlying atomic data was established. Conclusions. We selected strong, reliable isolated absorption lines, which we recommend to use as reference lines for abundance determinations in related objects.

EROSITA narrowband maps at the energies of soft X-ray emission lines

Hot plasma plays a crucial role in regulating the baryon cycle within the Milky Way, flowing from the energetic sources in the Galactic center and plane, to the corona and the halo. This hot plasma represents an important fraction of the Galactic baryons, plays a key role in galactic outflows and is an important ingredient in galaxy evolution models. Taking advantage of the Spectrum-Roentgen-Gamma (SRG first all-sky survey (eRASS1), in this work our aim is to provide a panoramic view of the hot circumgalactic medium (CGM) of the Milky Way. Compared to the previous all-sky X-ray survey performed by ROSAT, the improved energy resolution of enabled us to map, for the first time, the sky within the narrow energy bands characteristic of soft X-ray emission lines. These lines provide essential information on the physical properties of the hot plasma. Here we present the eRASS1\ half sky maps in narrow energy bands corresponding to the most prominent soft X-ray lines and which allowed us to constrain the distribution of the hot plasma within and surrounding the Milky Way. We corrected the maps by removing the expected contribution associated with the cosmic X-ray background, the time-variable solar wind charge exchange, and the local hot bubble. We applied corrections to mitigate the effect of absorption, therefore highlighting the emission from the CGM of the Milky Way. We used the line ratio of the oxygen lines as a proxy to constrain the temperature of the warm-hot CGM, and we defined a pseudo-temperature $ T $ map. The map highlights how different regions are dominated by different thermal components. Toward the outer halo, the temperature distribution of the CGM on angular scales of 2--20 deg is consistent with being constant $ T T 4<!PCT!>$ with a marginal detection of $ T T = 2.7 <!PCT!> 0.2<!PCT!>$ (statistical) $ 0.6<!PCT!>$ (systematic) in the southern hemisphere. Instead significant variations of $ 12<!PCT!>$ are observed on scales of many tens of degrees when comparing the northern and southern hemispheres. The pseudo-temperature map shows significant variations across the borders of the bubbles, suggesting temperature variations, possibly linked to shocks, between the interior of the Galactic outflow and the unperturbed CGM. In particular, a shell characterized by a lower line ratio appears close to the edge of the bubbles.

Why we should not “help bad choosers:” screening, nudging, and epistemic risk

One prominent line of support for nudging in screening programs is the claim that nudging can help ‘bad choosers’ — that is, it can help some patients make choices more in line with their own values and preferences. In this article, I argue that due to the presence of epistemic risk in many screening programs, the argument that nudging can help ‘bad choosers’ should be revised or rejected. Expanding on the work of Biddle, J. B. 2020. Epistemic risks in cancer screening: Implications for ethics and policy. Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences 79: 101200.), I argue that epistemic risk undermines the argument that nudging can help to promote patient autonomy in the context of screening. Specifically, I argue that epistemic risk results in the inclusion of non-patient values and preferences in the screening process, which challenges the claim that nudging can help patients make choices more in line with their own values and preferences. I present four reasons to think epistemic risk undermines the argument in this way: (1) conflicting values; (2) lack of transparency; (3) limited autonomy in opting out; (4) unjustified manipulation. The presence of epistemic risk in screening programs means that nudging may not always be an effective means of promoting patient autonomy and informed consent. As such, epistemic risk poses significant challenges to at least one ethical justification of nudging in screening programs, and raises further questions about the role of nudging in promoting patient decision-making.

Broad absorption line quasars in the Dark Energy Spectroscopic Instrument Early Data Release

ABSTRACT Broad absorption line (BAL) quasars are characterized by gas clouds that absorb flux at the wavelength of common quasar spectral features, although blueshifted by velocities that can exceed $0.1c$. BAL features are interesting as signatures of significant feedback, yet they can also compromise cosmological studies with quasars by distorting the shape of the most prominent quasar emission lines, impacting redshift accuracy and measurements of the matter density distribution traced by the Lyman $\alpha$ forest. We present a catalogue of BAL quasars discovered in the Dark Energy Spectroscopic Instrument (DESI) survey Early Data Release, which were observed as part of DESI Survey Validation, as well as the first two months of the main survey. We describe our method to automatically identify BAL quasars in DESI data, the quantities we measure for each BAL, and investigate the completeness and purity of this method with mock DESI observations. We mask the wavelengths of the BAL features and re-evaluate each BAL quasar redshift, finding new redshifts which are $243\, {\rm km}\, {\rm s}^{-1}$ smaller on average for the BAL quasar sample. These new, more accurate redshifts are important to obtain the best measurements of quasar clustering, especially at small scales. Finally, we present some spectra of rarer classes of BALs that illustrate the potential of DESI data to identify such populations for further study.

Isolated single-photon emitters with low Huang–Rhys factor in hexagonal boron nitride at room temperature

The development of stable room-temperature bright single-photon emitters using atomic defects in hexagonal boron nitride flakes (h-BN) provides significant promise for quantum technologies. However, an outstanding challenge in h-BN is the creation and detection of isolated, stable single-photon emitters with high emission rates and with very low Huang–Rhys (HR) factor. Here, we discuss the quantum photonic properties of a single, isolated, stable quantum emitter that emits single photons with a high emission rate and a low HR value of 0.6 ± 0.2 at room temperature. A scanning confocal image confirms the presence of a deserted, single-quantum emitter with a prominent zero-phonon line at ∼578 nm with a well-separated phonon sideband at 626 nm. The second-order intensity-intensity correlation measurement shows an anti-bunching dip of ∼0.25 with an emission lifetime of 2.46 ± 0.1 ns, reinforcing distinct features of the single-photon emitter. The importance of low-energy electron beam irradiation and subsequent annealing is emphasized to achieve stable, reproducible single-photon emitters.

Probing the Shock Breakout Signal of SN 2024ggi from the Transformation of Early Flash Spectroscopy

We present early-time, hour-to-day cadence spectroscopy of the nearby Type II supernova (SN II) 2024ggi, which was discovered at a phase when the SN shock had just emerged from the red supergiant (RSG) progenitor star. Over the first few days after the first light, SN 2024ggi exhibited prominent narrow emission lines formed through intense and persistent photoionization of the nearby circumstellar material (CSM). In the first 63 hr, spectral lines of He, C, N, and O revealed a rapid rise in ionization as a result of the progressive sweeping up of the CSM by the shock. The duration of the IIn-like spectra indicates a dense and relatively confined CSM distribution extending up to ∼4 × 1014 cm. Spectral modeling reveals that a CSM mass-loss rate at this region exceeding 5 × 10−3 M ⊙ yr−1 is required to reproduce low-ionization emissions, which dramatically exceeds that of an RSG. Analyzing the Hα emission shift implies the velocity of the unshocked outer CSM to be between 20 and 40 km s−1, matching the typical wind velocity of an RSG. The differences between the inner and outer layers of the CSM and an RSG progenitor highlight a complex mass-loss history before the explosion of SN 2024ggi.

PDRs4All

Context. Mid-infrared emission features are important probes of the properties of ionized gas and hot or warm molecular gas, which are difficult to probe at other wavelengths. The Orion Bar photodissociation region (PDR) is a bright, nearby, and frequently studied target containing large amounts of gas under these conditions. Under the “PDRs4All” Early Release Science Program for JWST, a part of the Orion Bar was observed with MIRI integral field unit (IFU) spectroscopy, and these high-sensitivity IR spectroscopic images of very high angular resolution (0.2″) provide a rich observational inventory of the mid-infrared (MIR) emission lines, while resolving the H II region, the ionization front, and multiple dissociation fronts. Aims. We list, identify, and measure the most prominent gas emission lines in the Orion Bar using the new MIRI IFU data. An initial analysis summarizes the physical conditions of the gas and demonstrates the potential of these new data and future IFU observations with JWST. Methods. The MIRI IFU mosaic spatially resolves the substructure of the PDR, its footprint cutting perpendicularly across the ionization front and three dissociation fronts. We performed an up-to-date data reduction, and extracted five spectra that represent the ionized, atomic, and molecular gas layers. We identified the observed lines through a comparison with theoretical line lists derived from atomic data and simulated PDR models. The identified species and transitions are summarized in the main table of this work, with measurements of the line intensities and central wavelengths. Results. We identified around 100 lines and report an additional 18 lines that remain unidentified. The majority consists of H I recombination lines arising from the ionized gas layer bordering the PDR. The H I line ratios are well matched by emissivity coefficients from H recombination theory, but deviate by up to 10% because of contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni. We show how the Ne III/Ne II, S IV/S III, and Ar III/Ar II ratios trace the conditions in the ionized layer bordering the PDR, while Fe III/Fe II and Ni III/Ni II exhibit a different behavior, as there are significant contributions to Fe II and Ni II from the neutral PDR gas. We observe the pure-rotational H2 lines in the vibrational ground state from 0–0 S(1) to 0–0 S (8), and in the first vibrationally excited state from 1–1 S (5) to 1–1 S(9). We derive H2 excitation diagrams, and for the three observed dissociation fronts, the rotational excitation can be approximated with one thermal (~700 K) component representative of an average gas temperature, and one nonthermal component (~2700 K) probing the effect of UV pumping. We compare these results to an existing model of the Orion Bar PDR, and find that the predicted excitation matches the data qualitatively, while adjustments to the parameters of the PDR model are required to reproduce the intensity of the 0–0 S (6) to S (8) lines.

Mapping the Imprints of Stellar and Active Galactic Nucleus Feedback in the Circumgalactic Medium with X-Ray Microcalorimeters

The Astro2020 Decadal Survey has identified the mapping of the circumgalactic medium (CGM; the gaseous plasma around galaxies) as a key objective. We explore the prospects for characterizing the CGM in and around nearby galaxy halos with a future large-grasp X-ray microcalorimeter. We create realistic mock observations from hydrodynamical simulations (EAGLE, IllustrisTNG, and Simba) that demonstrate a wide range of potential measurements, which will address the open questions in galaxy formation and evolution. By including all background and foreground components in our mock observations, we show why it is impossible to perform these measurements with current instruments, such as X-ray CCDs, and why only microcalorimeters will allow us to distinguish the faint CGM emission from the bright Milky Way (MW) foreground emission lines. We find that individual halos of MW mass can, on average and depending on star formation rate, be traced out to large radii, around R 500, and for larger galaxies even out to R 200, using prominent emission lines, such as O vii, or O viii. Furthermore, we show that emission-line ratios for individual halos can reveal the radial temperature structure. Substructure measurements show that it will be possible to relate azimuthal variations to the feedback mode of the galaxy. We demonstrate the ability to construct temperature, velocity, and abundance ratio maps from spectral fitting for individual galaxy halos, which reveal rotation features, active galactic nucleus outbursts, and enrichment.

Identifying type II quasars at intermediate redshift with few-shot learning photometric classification

Context. A sub-population of AGNs where the central engine is obscured are known as type II quasars (QSO2s). These luminous AGNs have a thick and dusty torus that obscures the accretion disc from our line of sight. Thus, their special orientation allows for detailed studies of the AGN-host co-evolution. Increasing the sample size of QSO2 sources in critical redshift ranges is crucial for understanding the interplay of AGN feedback, the AGN-host relationship, and the evolution of active galaxies.Aims. We aim to identify QSO2 candidates in the ‘redshift desert’ using optical and infrared photometry. At this intermediate redshift range (i.e. 1 ≤ ɀ ≤ 2), most of the prominent optical emission lines in QSO2 sources (e.g. CIVλl549; [OIII]λλ4959, 5008) fall either outside the wavelength range of the SDSS optical spectra or in particularly noisy wavelength ranges, making QSO2 identification challenging. Therefore, we adopted a semi-supervised machine learning approach to select candidates in the SDSS galaxy sample.Methods. Recent applications of machine learning in astronomy focus on problems involving large data sets, with small data sets often being overlooked. We developed a ‘few-shot’ learning approach for the identification and classification of rare-object classes using limited training data (200 sources). The new AMELIA pipeline uses a transfer-learning based approach with decision trees, distance-based, and deep learning methods to build a classifier capable of identifying rare objects on the basis of an observational training data set.Results. We validated the performance ofAMELIAby addressing the problem of identifying QSO2s at 1 ≤ ɀ ≤ 2 using SDSS and WISE photometry, obtaining an F1-score above 0.8 in a supervised approach. We then usedAMELIAto select new QSO2 candidates in the ‘redshift desert’ and examined the nature of the candidates using SDSS spectra, when available. In particular, we identified a sub-population of [NeV]λ3426 emitters at ɀ ~ 1.1, which are highly likely to contain obscured AGNs. We used X-ray and radio crossmatching to validate our classification and investigated the performance of photometric criteria from the literature showing that our candidates have an inherent dusty nature. Finally, we derived physical properties for our QSO2 sample using photoionisation models and verified the AGN classification using an SED fitting.Conclusions. Our results demonstrate the potential of few-shot learning applied to small data sets of rare objects, in particular QSO2s, and confirms that optical-IR information can be further explored to search for obscured AGNs. We present a new sample of candidates to be further studied and validated using multi-wavelength observations.

γ-Glutamyltranspeptidase fluorescence lifetime response probe for precision tumor detection unveiling A549 cancer cell specificity

γ-Glutamyltranspeptidase (γ-GGT), as a key enzyme, exhibits markedly higher expression levels in tumor cells compared to normal cells. Under normal conditions, γ-GGT activity on the cell membrane is relatively low, but it undergoes a significant upregulation in cancer cells, making it a potential cancer biomarker. Particularly in A549 cells, a prominent cancer cell line, the pronounced upregulation of γ-GGT expression emphasizes its potential as a unique recognition target and a robust marker for A549 cells. This study successfully synthesized a highly selective γ-GGT fluorescent probe, the exhibits commendable sensitivity (LOD = 0.0021U/mL) and selectivity, achieving efficient detection at the cellular level and providing accurate insights into differential expression between normal and cancer cells. The alterations in fluorescence lifetime observed before and after the probe's reaction with γ-GGT serve as a crucial foundation for fluorescence lifetime imaging on living cells. The probe has become a powerful tool for precise localization of tumor cells, particularly demonstrating its capability for specific recognition in A549 cells. Overall, this research highlights the potential of γ-GGT as a target for fluorescent probes, emphasizing its prospects in specific recognition, particularly in A549 cells, with profound implications for advancing early cancer diagnosis and treatment methods.

Unveiling stellar aurorae: simulating auroral emission lines in hot stars induced by high-energy irradiation

ABSTRACT Auroral emission lines result from the interaction between magnetic field and stellar wind, offering valuable insights into physical properties and processes occurring within magnetospheres of celestial bodies. While extensively studied in planetary and exoplanetary atmospheres, in ultracool dwarfs, and as radio emission from early-type stars, the presence of specific auroral emission lines in hot star spectra remains unexplored. In this study, we utilized tlusty code to simulate the auroral lines, while modelling the effect of the interaction between stellar wind and magnetosphere through X-ray irradiation. Utilizing high-resolution synthetic spectra generated from model atmospheres, we identified potential candidate lines indicative of auroral emission, which were absent in non-irradiated spectra. Emission lines in synthetic spectra were present primarily in the infrared domain. The most prominent line generated by irradiation was He ii 69458 Å, which appeared in all our model atmospheres with effective temperatures ranging from 15 kK to 30 kK. We also calculated the minimum irradiation required to detect emission in this most prominent line. The presence of emission lines was interpreted by considering changes in the population of different excited states of given atoms. Besides the appearance of infrared emission lines, high-energy irradiation causes infrared excess. To complement our simulations, we also searched for auroral lines in Far Ultraviolet Spectroscopic Explorer (FUSE) observations, which are deposited in the Multimission Archive at Space Telescope catalogue. The comparison of observed spectra with synthetic spectra did not identify any possible candidate emission lines in FUSE spectra.

On the Origin of the X-Ray Emission in Heavily Obscured Compact Radio Sources

X-ray continuum emission of active galactic nuclei (AGNs) may be reflected by circumnuclear dusty tori, producing prominent fluorescence iron lines at X-ray frequencies. Here, we discuss the broadband emission of three radio-loud AGNs belonging to the class of compact symmetric objects (CSOs), with detected narrow Fe Kα lines. CSOs have newly born radio jets, forming compact radio lobes with projected linear sizes of the order of a few to hundreds of parsecs. We model the radio-to-γ-ray spectra of compact lobes in J1407+2827, J1511+0518, and J2022+6137, which are among the nearest and the youngest CSOs known to date, and are characterized by an intrinsic X-ray absorbing column density of N H > 1023 cm−2. In addition to the archival data, we analyze the newly acquired Chandra X-ray Observatory and Submillimeter Array (SMA) observations, and also refine the γ-ray upper limits from Fermi Large Area Telescope monitoring. The new Chandra data exclude the presence of the extended X-ray emission components on scales larger than 1.″5. The SMA data unveil a correlation between the spectral index of the electron distribution in the lobes and N H, which can explain the γ-ray quietness of heavily obscured CSOs. Based on our modeling, we argue that the inverse-Compton emission of compact radio lobes may account for the intrinsic X-ray continuum in all these sources. Furthermore, we propose that the observed iron lines may be produced by a reflection of the lobes’ continuum from the surrounding cold dust.