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We present AspGap, a new approach to infer stellar labels from low-resolution Gaia XP spectra, including precise [$\alpha$/M] estimates for the first time. AspGap is a neural-network based regression model trained on APOGEE spectra. |
We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the cor... |
We present a new set of zero metallicity models in the range 13-80 $\rm M_\odot$ together to the associated explosive nucleosynthesis. These models are fully homogeneous with the solar metallicity set we published in Limongi & Chieffi (2006) and will be freely available at the web site <a href="http://www.iasf-rom... |
Projected rotational velocities (vsini) are presented for a sample of 350 early B-type main sequence stars in the nearby Galactic disk. The stars are located within ~1.5 kpc from the Sun, and the great majority within 700 pc. |
We present a multiwavelength study of the iconic Bubble Nebula (NGC 7635) and its ionising star BD$+$60$^{\circ}$2522. We obtained XMM-Newton EPIC X-ray observations to search for extended X-ray emission as in other similar wind-blown bubbles around massive stars. |
In this study we combine the multiwavelength ultraviolet -- optical (Solar Dynamics Observatory, SDO) and radio (Nobeyama Radioheliograph, NoRH) observations to get further insight into space-frequency distribution of oscillations at different atmospheric levels of the Sun. We processed the observational data on NOAA ... |
Astrometry from {\it Gaia} DR3 has enabled the discovery of a sample of 3000+ binaries containing white dwarfs (WD) and main-sequence (MS) stars in relatively wide orbits, with orbital periods $P_{\rm orb} = (100-1000)$ d. This population was not predicted by binary population synthesis models before {\it Gaia} and --... |
Observations indicate that outflows from massive young stars are more collimated during their early evolution compared to later stages. Our paper investigates various physical processes that impacts the outflow dynamics, i.e. its acceleration and collimation. |
This Letter investigates the spectral characteristics of the interplanetary magnetic field fluctuations at proton scales during several time intervals chosen along the speed profile of a fast stream. The character of the fluctuations within the first frequency decade, beyond the high frequency break located between th... |
We present stellar parameters of 19 K-type giants and their abundances of 13 chemical elements (Al, Ba, Ca, Fe, K, Mg, Mn, Na, Ni, Sc, Si, Ti and V), selected from two moving groups, covering the metallicity range of -0.6 < [Fe/H] < 0.2, based on high resolution spectra. Most elemental abundances show similar tr... |
(abbreviated) We aim to study the inner wind of the well-known AGB star CW Leo. |
Accurate parallax measurements allow us to determine physical properties of brown dwarfs, and help us to constrain evolutionary and atmospheric models, break the age-mass degeneracy and reveal unresolved binaries. <br>We measured absolute trigonometric parallaxes and proper motions of 6 cool brown dwarfs using backgro... |
This chapter presents a review on the latest advances in the computation of physical conditions and chemical abundances of elements present in photoionized gas H II regions and planetary nebulae). The arrival of highly sensitive spectrographs attached to large telescopes and the development of more sophisticated and d... |
Even though only a handful of sub-stellar companions have been found via direct imaging, each of these discoveries has had a tremendous impact on our understanding of the star formation process and the physics of cool atmospheres. Young stars are prime targets for direct imaging searches for planets and brown dwarfs, ... |
We present an improved spectroscopic and photometric analysis of hydrogen-line DA white dwarfs from the Sloan Digital Sky Survey Data Release 4 based on model atmospheres that include improved Stark broadening profiles with non-ideal gas effects. We also perform a careful visual inspection of all spectroscopic fits wi... |
We discuss the basic physics of hot-star winds and we provide mass-loss rates for (very) massive stars. Whilst the emphasis is on theoretical concepts and line-force modelling, we also discuss the current state of observations and empirical modelling, and address the issue of wind clumping. |
Recent studies suggest that the helium content of multiple stellar populations in globular clusters (GCs) is not uniform. The range of helium varies from cluster to cluster with more massive GCs having, preferentially, large helium spread. |
We present the results of a spectroscopic investigation of two Large Magellanic Cloud globular clusters, NGC 1953 and NGC 1856. Both clusters have similar ages (250 and 300 Myr, respectively). |
In the recent years, global coronal models have experienced an ongoing increase in popularity as tools for forecasting solar weather. Within the domain of up to 21.5Rsun, magnetohydrodynamics (MHD) is used to resolve the coronal structure using magnetograms as inputs at the solar surface. |
Angular Momentum Loss is important for understanding astrophysical phenomena such as stellar rotation, magnetic activity, close binaries, and cataclysmic variables. Magnetic breaking is the dominant mechanism in the spin down of young late-type stars. |
Solar meridian observations have been used to evaluate the solar activity of the past. Some important examples are the solar meridian observations made at the Basilica of San Petronio in Bologna by several astronomers and the observations made by Hevelius published in his book Machina Coelestis. |
Massive (>~ 8 solar masses) stars are the progenitors of many astrophysical systems, yet key aspects of their structure and evolution are poorly understood. Asteroseismology has the potential to solve these open puzzles, however, sampling both the short period pulsations and long period beat patterns of massive sta... |
For understanding magnetic effects on dynamical tides, we study the rotating magneto-hydrodynamic (MHD) flow driven by harmonic forcing. The linear responses are analytically derived in a periodic box under the local WKB approximation. |
The Wolf-Rayet (WR) binary system WR140 is a close (0.9-16.7 mas) binary star consisting of an O5 primary and WC7 companion and is known as the archetype of episodic dust-producing WRs. Dust in WR binaries is known to form in a confined stream originating from the collision of the two stellar winds, with orbital motio... |
We report the detection of X-ray emission from the jet-driving symbiotic star MWC 560. We observed MWC 560 with XMM-Newton for 36 ks. |
Solar and heliospheric parameters can depict notable differences between the northern and southern hemisphere. Although hemispheric asymmetries of some heliospheric parameters vary systematically with Hale cycle, this is not common for solar parameters. |
The stellar Rotation $vs. $ Age relation is commonly considered as a useful tool to derive reliable ages for Sun-like stars. |
We present late-time HST images of the site of supernova (SN) 2009ip taken almost 3 yr after its bright 2012 luminosity peak. SN 2009ip is now slightly fainter in broad filters than the progenitor candidate detected by HST in 1999. |
We derive atmospheric parameters and lithium abundances for 671 stars and include our measurements in a literature compilation of 1381 dwarf and subgiant stars. First, a "lithium desert" in the effective temperature (Teff) versus lithium abundance (A_Li) plane is observed such that no stars with Teff~6075 K an... |
The kinematic properties of coronal mass ejections (CMEs) suffer from the projection effects, and it is expected that the real velocity should be larger and the real angular width should be smaller than the apparent values. Several attempts have been tried to correct the projection effects, which however led to a too ... |
We have shown previously that the Murchison Widefield Array (MWA), can detect hundreds of Interplanetary Scintillation (IPS) sources simultaneously across a field of view $\sim30^\circ$ in extent. To test if we can use this capability to track heliospheric structures, we undertook a search of 88 hours of MWA IPS data,... |
We explore the effects of rotation on convective carbon, oxygen, and silicon shell burning during the late stages of evolution in a 20Msun star. Using the Modules for Experiments in Stellar Astrophysics (MESA) we construct 1D stellar models both with no rotation and with an initial rigid rotation of 50% of critical. |
Novalike cataclysmic variables have persistently high mass transfer rates and prominent steady state accretion disks. We present an analysis of infrared observations of twelve novalikes obtained from the Two Micron All Sky Survey, the Spitzer Space Telescope, and the Wide-field Infrared Survey Explorer All Sky Survey.... |
Grids of stellar evolution models with rotation using the Geneva stellar evolution code (Genec) have been published for a wide range of metallicities. We introduce the last remaining grid of Genec models, with a metallicity of $Z=10^{-5}$. |
We present 2 to 2.4 micron integral field spectroscopy of a sample of hot post-AGB stars with early-B spectral types, using the NIFS instrument on Gemini North. These stars are just beginning to ionize their immediate environments and turn into planetary nebulae (PNe). |
Accurate line lists are crucial for correctly modelling a variety of astrophysical phenomena, including stellar photospheres and the atmospheres of extra-solar planets. This paper presents a new line database Toto for the main isotopologues of titanium oxide (TiO): $^{46}$Ti$^{16}$O, $^{47}$Ti$^{16}$O, $^{48}$Ti$^{16}... |
In this paper we present a new catalogue of Chemically Peculiar (CP) stars obtained by compiling publications in which abundances of metals are provided. Our catalogue includes 428 stars for which the data were obtained through spectroscopic observations. |
Abridged. The 12CO/13CO ratio in the circumstellar envelope (CSE) of asymptotic giant branch (AGB) stars has been extensively used as the tracer of the photospheric 12C/13C ratio. |
We present a deep and wide field-of-view (4'x 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 micron H2 v=1-0 S(1) line. The excellent seeing (0.4'') at the Subaru Telescope, allows the details of cometary knots to be examined. |
We analyze the magnetic evolution of solar active region (AR) NOAA 11476 that, between 9 and 10 May 2012, produced a series of surge-type eruptions accompanied by GOES X-ray class M flares. Using force-free models of the AR coronal structure and observations in several wavelengths, in previous works we studied the det... |
Using the ULTRASPEC instrument mounted on the 2.4-m Thai National Telescope, we observed two large flares, each with a total energy close to 10^34 erg with sub-second cadence. A combination of a wavelet analysis, a Fourier transform plus an empirical mode decomposition, reveals quasi-period pulsations (QPP) which exhi... |
Although high energetic radiation from flares is a potential threat to exoplanet atmospheres and may lead to surface sterilization, it might also provide the extra energy for low-mass stars needed to trigger and sustain prebiotic chemistry. We investigate two flares on TRAPPIST-1, an ultra-cool dwarf star that hosts s... |
For the observational modeling of horizontal abundance distributions and of magnetic geometries in chemically peculiar (CP) stars, Zeeman Doppler mapping (ZDM) has become the method of choice. Comparisons between abundance maps obtained for CP stars and predictions from numerical simulations of atomic diffusion have a... |
In this work, we present SoFT: Solar Feature Tracking, a novel feature-tracking tool developed in Python and designed to detect, identify, and track magnetic elements in the solar atmosphere. It relies on a watershed segmentation algorithm to effectively detect magnetic clumps within magnetograms, which are then assoc... |
The study of long-term evolution of neutron star (NS) magnetic fields is key to understanding the rich diversity of NS observations, and to unifying their nature despite the different emission mechanisms and observed properties. Such studies in principle permit a deeper understanding of the most important parameters d... |
High-resolution spectroscopy of strong chromospheric absorption lines delivers nowadays several millions of spectra per observing day, when using fast scanning devices to cover large regions on the solar surface. Therefore, fast and robust inversion schemes are needed to explore the large data volume. |
We have performed a search for flares and Quasi-Periodic Pulsations (QPPs) from low mass M dwarf stars using TESS 2 min cadence data. We find seven stars which show evidence of QPPs. |
The work reported in this dissertation will concern the study of kinetics, cycles and quantum mechanic processes of nuclear reactions involved in massive stars together with explosive nucleosynthesis phenomena having a key role in supernovae explosion. Four main fields will be explored: physics of nuclear reaction, hy... |
We present recent progress in our understanding of the physical interaction mechanisms at work in evolved binaries of low-to-intermediate initial mass, which are surrounded by a stable disc of gas and dust. These systems are known as post-asymptotic giant-branch (post-AGB) binaries, but recently, it has been shown tha... |
We report the discovery of eclipses and the first orbital period measurements for four cataclysmic variables, plus the first orbital period measurements for one known eclipsing and two magnetic systems. SDSS J093537.46+161950.8 exhibits 1-mag deep eclipses with a period of 92.245 min. |
While the presence of magnetic fields on low-mass stars is attributed to a dynamo process essentially driven by convective motions, the existence of magnetic fields on intermediate-mass stars has very likely other reasons. Presuming that the fields we see are nearly constant in time, the paper focuses on the generatio... |
We present optical and infrared spectroscopy of V1309 Sco, an object that erupted in 2008 in a stellar-merger event. During the outburst, V1309 Sco displayed characteristics typical of red transients, a class of objects similar to V838 Mon. |
We study the high-quality CMDs of three star clusters, NGC 1831, NGC 1868 and NGC 2249 in detail, via the two most likely causes (stellar rotation and age spread) for CMDs with extended main-sequence turn-offs. The results show evident failure of stellar rotation (including resolved and unresolved binary stars) to int... |
Motivated by the observational results of Braun (1995), we extend the model of Hanson & Cally (2014) to address the effect of multiple scattering of f and p-modes by an ensemble of thin vertical magnetic flux tubes in the surface layers of the Sun. As in observational Hankel analysis we measure the scatter and pha... |
Obtaining the magnetic field vector accurately in the solar atmosphere is essential for studying changes in field topology during flares and to reliably model space weather. We tackle this problem by applying various inversion methods to a confined X2.2 flare in NOAA AR 12673 on September 6, 2017, comparing the photos... |
With the aim of studying AR fan loops using Hinode/EIS and SDO/AIA, we investigate a number of inconsistencies in modeling the absolute intensities of Fe VIII and Si VII lines, and address why their images look very similar despite the fact that they have significantly different formation temperatures in ionization equ... |
The solar physics community is entering a golden era that is ripe with next-generation ground- and space-based facilities. With ever-increasing resolving power stemming from the newest observational telescopes, it becomes more challenging to obtain (near-)simultaneous measurements at high spatial, temporal and spectra... |
TWA 3A is the most recent addition to a small group of young binary systems that both actively accrete from a circumbinary disk and have spectroscopic orbital solutions. As such, it provides a unique opportunity to test binary accretion theory in a well-constrained setting. |
It has been shown recently that magnetic twist and axisymmetric MHD modes are ubiquitous in the solar atmosphere and therefore, the study of resonant absorption for these modes have become a pressing issue as it can have important consequences for heating magnetic flux tubes in the solar atmosphere and the observed dam... |
We review observations of solar activity, geomagnetic variation, and auroral visibility for the extreme geomagnetic storm on 1872 February 4. The extreme storm (referred to here as the Chapman-Silverman storm) apparently originated from a complex active region of moderate area (\approx 500 {\mu}sh) that was favorably ... |
The first four gravitational wave events detected by LIGO were all interpreted as merging black hole binaries (BHBs), opening a new perspective on the study of such systems. Here we use our new population-synthesis code MOBSE, an upgraded version of BSE (Hurley et al. 2002), to investigate the demography of merging BH... |
Spectropolarimetric observations of a sunspot were carried out with the Tenerife Infrared Polarimeter at Observatorio del Teide, Tenerife, Spain. Maps of the physical parameters were obtained from an inversion of the Stokes profiles observed in the infrared Fe i line at 15648 angstrom. |
Massive stars in their late stages of evolution as Red Supergiants experience mass loss. The resulting winds show various degrees of dynamical and chemical complexity and produce molecules and dust grains. |
The accretion luminosity of an FU Ori disk is a fundamental system parameter, but a challenging one to estimate for all but the most well-studied systems. FU Ori objects are dynamically evolving accretion disks, especially close in time to the outburst epoch. |
The obvious lack of the binary stellar systems that contain neutron stars (NS) is observed at present. Partly it is caused by the fact that it is very difficult to detect neutron star in a binary system if this relativistic component does not manifest itself as a radio pulsar. |
Results of the three-colour photoelectric observation of the close binary system XZ Cep, obtained at the Abastumani Astrophysical observatory, are presented. |
Post-AGB stars are exquisite probes of AGB nucleosynthesis. However, the previous lack of accurate distances jeopardised comparison with theoretical AGB models. |
We present a new technique to quantify cluster-to-cluster variations in the observed present-day stellar mass functions of a large sample of star clusters. Our method quantifies these differences as a function of both the stellar mass and the total cluster mass, and offers the advantage that it is insensitive to the p... |
The surface [C/N] ratios of evolved giants are strongly affected by the first dredge-up (FDU) of nuclear-processed material from stellar cores. C and N also have distinct nucleosynthetic origins and serve as diagnostics of mixing and mass loss. |
The prevalence of substructures in $\sim1-10$ Myr old protoplanetary disks, which are often linked to planet formation, has raised the question of how early such features form, and as a corollary, how early planet formation begins. Here we present observations of seven protostellar disks (aged $\sim0.1-1$ Myr) from th... |
For the well studied halo star HD 122563 and the four stars in the globular cluster NGC 6397, we determine NLTE abundances of iron using classical plane-parallel model atmospheres. Each star reveals a discrepancy in abundances between the Fe I lines arising from the ground state and the other Fe I lines, in qualitativ... |
We have conducted a deep photometric survey of a 0.5 deg x 0.5 deg area of the Galactic Plane using the WFI instrument on the 2.2-m ESO telescope on La Silla, Chile. The dataset comprises a total of 267 R-band images, 204 from a 16 day observation run in 2005, supplemented by 63 images from a six week period in 2002. |
Infrared Dark Clouds (IRDCs) host the initial conditions under which massive stars and stellar clusters form. We have obtained high sensitivity and high spectral resolution observations with the IRAM 30m antenna, which allowed us to perform detailed analysis of the kinematics within one IRDC, G035.39-00.33. |
The Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft observed flare footpoint regions coincident with a surge for a M3.7 flare observed on 25 September 2011 at N12 E33 in active region 11302. The flare was observed in spectral lines of O VI, Fe X, Fe XII, Fe XIV, Fe XV, Fe XVI, Fe XVII, Fe XXIII... |
Remote sensing observations of coronal holes show that heavy ions are hotter than protons and their temperature is anisotropic. In-situ observations of fast solar wind streams provide direct evidence for turbulent Alfvén wave spectrum, left-hand polarized ion-cyclotron waves, and He$^{++}$ -- proton drift in the solar... |
Using a sample of 31 main-sequence OB stars located between galactocentric distances 8.4 - 15.6 kpc, we aim to probe the present-day radial abundance gradients of the Galactic disk. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5-m telescope on Las Campanas... |
The asymptotic giant branch (AGB) star HR3126, associated with the arcminute-scale bipolar Toby Jug Nebula, provides a rare opportunity to study the emergence of bipolar structures at the end of the AGB phase. We carried out long-baseline interferometric observations with AMBER and GRAVITY (2--2.45 micron) at the Very... |
Coronal Mass Ejections (CMEs) are immense eruptions of plasma and magnetic fields that are propelled outward from the Sun, sometimes with velocities greater than 2000 km/s. They are responsible for some of the most severe space weather at Earth, including geomagnetic storms and solar energetic particle (SEP) events. |
Multiple outbursts of type Ia SNe in one galaxy present a unique opportunity to study the homogeneity of these objects. NGC 3147 is only the second known galaxy with three SNe Ia, another one is NGC 1316. |
We present new reddening measurements towards the young supernova remnant Cassiopeia A, using two techniques not previously applied to this object. Our observations of the near-infrared [Fe II] 1.257 micron and 1.644 micron lines show the extinction to be highly variable across the remnant, increasing towards the west... |
The double pulsar system PSR J0737-3039A/B is a double neutron star binary, with a 2.4-hour orbital period, which has allowed measurement of relativistic orbital perturbations to high precision. The low mass of the second-formed neutron star, as well as the low system eccentricity and proper motion, point to a differe... |
In this paper, the period evolution of the rotating chemically peculiar star V473\,Tau is investigated. Even though the star has been observed for more than fifty years, for the first time four consecutive years of space-based data covering between 2007 and 2010 are presented. |
Solar energetic particles (SEPs) are an essential source of space radiation, which are hazards for humans in space, spacecraft, and technology in general. In this paper we propose a deep learning method, specifically a bidirectional long short-term memory (biLSTM) network, to predict if an active region (AR) would pro... |
We have developed a refined and optimized version of the Warsaw Test Particle Model of interstellar neutral gas in the heliosphere, specially tailored for analysis of IBEX-Lo observations. The former version of the model was used in the analysis of neutral He observed by IBEX that resulted in an unexpected conclusion ... |
Magnetic fields are important contributers to the dynamics of collapsing molecular cloud cores, and can have a major effect on whether collapse results in a single protostar or fragmentation into a binary or multiple protostar system. New models are presented of the collapse of magnetic cloud cores using the adaptive ... |
A powerful coronal mass ejection (CME) occurred on 2017 September 10 near the end of the declining phase of the historically weak solar cycle 24. We obtain new insights concerning the geometry and kinematics of CME-driven shocks in relation to their heliospheric impacts from the optimal, multi-spacecraft observations ... |
The eruption of the filament/flux rope generates the coronal perturbations, which further form EUV waves. There are two types of EUV waves, including fast-mode magnetosonic waves and slow waves. |
Winds of cool dwarfs are difficult to observe, with only a few M dwarfs presenting observationally-derived mass-loss rates (Mdot), which span several orders of magnitude. Close-in exoplanets are conveniently positioned in the inner regions of stellar winds and can, thus, be used to probe the otherwise-unobservable loc... |
As a byproduct of our search for Galactic stellar systems with gamma-ray emission, we have identified an unrelated cool and evolved star (IRC-10412) that attracted our attention due to its strong radio emission level with a spectral index matching, almost perfectly, the canonical +0.6 value expected from an ionized ste... |
Li et al. (2018a; Li18a) claimed that the young stellar cluster NGC2173 in the Large Magellanic Cloud (LMC) harbours a bifurcated sequence of blue straggler stars (BSSs), similar to those detected in a few dynamically old globular clusters. However, Dalessandro et al. (2019; D19) re-analyzed the data by taking into ac... |
We address the problem of angular momentum transport in stellar radiative interiors with a novel semi-analytic spectral technique, using an eigenfunction series expansion, that can be used to derive benchmark solutions in hydromagnetic regimes with very high Reynolds number (10^7 - 10^8). The error arising from the tr... |
The age-metallicity relation is a fundamental tool for constraining the chemical evolution of the Galactic disc. In this work we analyse the observational properties of this relation using binary stars that have not interacted consisting of a white dwarf - from which we can derive the total age of the system - and a m... |
Photospheric magnetic field not only plays important roles in building up free energy and triggering solar eruptions, but also has been observed to change rapidly and permanently responding to the coronal magnetic field restructuring due to coronal transients. The Helioseismic and Magnetic Imager instrument (HMI) on b... |
Star clusters are interesting laboratories to study star formation, single and binary stellar evolution, and stellar dynamics. We have used the exquisite data from $Gaia$'s data release 3 (DR3) to study 21 relatively rich and nearby open clusters with member numbers ($N_{\rm{cl}}$)$>500$. |
Motivated by the need for a solid state strange quark matter to better explain some observational phenomena, we discussed possibility of color singlet cluster formation in cold strange quark matter by a rough calculation following the excluded volume method proposed by Clark et al (1986) and adopted quark mass density ... |
Predicting nuclear masses is a longstanding challenge. One path forward is machine learning (ML) which trains on experimental data, but can suffer large errors when extrapolating toward neutron-rich species. |
We report the discovery of J1953-1019, the first resolved triple white dwarf system. The triplet consists of an inner white dwarf binary and a wider companion. |
Energetic events on the Sun, particularly coronal mass ejections and high speed streams, regulate the near Earth space environment and give rise to space weather. A major terrestrial manifestation of such events are geomagnetic storms. |
We use Cycle 21 Hubble Space Telescope (HST) observations and HST archival ACS Treasury observations of Galactic Globular Clusters to find and characterize two stellar populations in NGC 5024 (M53), NGC 5272 (M3), and NGC 6352. For these three clusters, both single and double-population analyses are used to determine ... |
Arc- and tail-like structures associated with disks around Herbig stars can be a consequence of infall events occurring after the initial collapse phase of a forming star. An encounter event of gas with a star can lead to the formation of a second-generation disk after the initial protostellar collapse phase. |
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