Miracle-dz/UniFAR-FTUs huggingface dataset:
Color-Magnitude Diagram and Luminosity Function of M4 near the Hydrogen-burning Limit

A proper-motion separation of M4 members from field stars, using deep Hubble Space Telescope observations separated by a time baseline of 5 yr, allows us to study a pure sample of cluster main-sequence stars almost to the minimum mass for hydrogen burning. High-precision photometry shows how badly current theoretical models fail to reproduce the color-magnitude diagram of low-mass stars of moderate metallicity ([M/H] ≃ -1). This inability of theory to reproduce the luminosity-color relation casts doubt on the theoretical mass-luminosity relation, which is needed to convert the observed luminosity function (LF) into a mass function (MF) as well as to convert our locally determined LF into a global MF. To the extent that we trust theoretical M-L relations for such transformations, we obtain a flat MF from the LF, and some indication that theoretical masses might be too low at a given luminosity, near the H-burning limit.
amico galaxy clusters in KiDS-DR3: sample properties and selection function

We present the first catalogue of galaxy cluster candidates derived from the third data release of the Kilo Degree Survey (KiDS-DR3). The sample of clusters has been produced using the Adaptive Matched Identifier of Clustered Objects (AMICO) algorithm. In this analysis AMICO takes advantage of the luminosity and spatial distribution of galaxies only, not considering colours. In this way, we prevent any selection effect related to the presence or absence of the red-sequence in the clusters. The catalogue contains 7988 candidate galaxy clusters in the redshift range 0.1 3.5 with a purity approaching 95% over the entire redshift range. In addition to the catalogue of galaxy clusters we also provide a catalogue of galaxies with their probabilistic association to galaxy clusters. We quantify the sample purity, completeness and the uncertainties of the detection properties, such as richness, redshift, and position, by means of mock galaxy catalogues derived directly from the data. This preserves their statistical properties including photo-z uncertainties, unknown absorption across the survey, missing data, spatial correlation of galaxies and galaxy clusters. Being based on the real data, such mock catalogues do not have to rely on the assumptions on which numerical simulations and semi-analytic models are based on. This paper is the first of a series of papers in which we discuss the details and physical properties of the sample presented in this work.
The optical/UV excess of X-ray-dim isolated neutron star II. Nonuniformity of plasma on a strangeon star surface

Several X-ray-dim isolated neutron stars (XDINSs), also known as the Magnificent Seven, exhibit a Planck-like soft X-ray spectrum. In the optical/ultraviolet (UV) band, there is an excess of radiation compared to an extrapolation from the X-ray spectrum. However, the majority exhibits “spectral deviations”: the fact that there is more flux at longer wavelengths makes spectra deviate from the Rayleigh-Jeans law. A model of bremsstrahlung emission from a nonuniform plasma atmosphere is proposed in the regime of a strangeon star to explain the optical/UV excess and its spectral deviation as well as X-ray pulsation. The atmosphere is on the surface of strangeon matter, which has negligible emission, and is formed by the accretion of ISM-fed debris disk matter moving along the magnetic field lines to near the polar caps. These particles may spread out of the polar regions which makes the atmosphere non-uniform. The modeled electron temperatures are ∼ 100 − 200 eV with radiation radii R opt ∞ ∼ 5 − 14 km . The spectra of five sources (RX J0720.4–3125, RX J0806.4–4123, RX J1308.6+2127, RX J1605.3+3249, RX J1856.5–3754) from optical/UV to X-ray bands can be fitted well by the radiative model, and exhibit Gaussian absorption lines at ∼ 100 − 500 eV as would be expected. Furthermore, the surroundings (i.e., fallback disks or dusty belts) of XDINSs could be tested by future infrared/submillimeter observations.
Polarization light curve modelling of corotating interaction regions in the wind of the Wolf–Rayet star WR 6

The intriguing WN4b star WR6 has been known to display epoch-dependent spectroscopic, photometric and polarimetric variability for several decades. In this paper, we set out to verify if a simplified analytical model in which Corotating Interaction Regions (CIRs) threading an otherwise spherical wind is able to reproduce the many broadband continuum light curves from the literature with a reasonable set of parameters. We modified the optically thin model we developed in Ignace, St-Louis & Proulx-Giraldeau (2015) to approximately account for multiple scattering and used it to fit 13 separate datasets of this star. By including two CIRs in the wind, we obtained reasonable fits for all datasets with coherent values for the inclination of the rotation axis ($i_0=166^{\circ}$) and for its orientation in the plane of the sky, although in the latter case we obtained two equally acceptable values ($\psi=63^{\circ}$ and $\psi=152^{\circ}$) from the polarimetry. Additional line profile variation simulations using the Sobolev approximation for the line transfer allowed us to eliminate the $\psi=152^{\circ}$ solution. With the adopted configuration ($i_0=166^{\circ}$ and $\psi=63^{\circ}$), we were able to reproduce all datasets relatively well with two CIRs located near the stellar equator and always separated by $\sim 90^{\circ}$ in longitude. The epoch-dependency comes from the fact that these CIRs migrate along the surface of the star. Density contrasts smaller than a factor of two and large opening angles for the CIR ($\beta \geq 35^{\circ}$) were found to best reproduce the type of spectroscopic variability reported in the literature.
The Collimation-corrected Gamma-Ray Burst Energies Correlate with the Peak Energy of Their νFν Spectrum

We consider all bursts with known redshift and νFν peak energy, E. For a good fraction of them an estimate of the jet opening angle is available from the achromatic break of their afterglow light curve. This allows the derivation of the collimation-corrected energy of the bursts, Eγ. The distribution of the values of Eγ is more spread out than in previous findings, covering about 2 orders of magnitude. We find a surprisingly tight correlation between Eγ and the source frame Epeak: E(1 + z) ∝ E. This correlation can shed light on the still uncertain radiation processes for the prompt GRB emission. More importantly, if the small scatter of this newly found correlation could be confirmed by forthcoming data, it would be possible to use it for cosmological purposes.
Identifications of faintChandrasources in the globular cluster M3

We report a $30~\mathrm{ks}$ $Chandra$ ACIS-S survey of the globular cluster M3. Sixteen X-ray sources were detected within the half-light radius ($2.3'$) with $L_X \gtrsim 2.3 \times 10^{31}~\mathrm{erg~s^{-1}}$. We used $Hubble~Space~Telescope$ WFC3/UVIS and ACS/WFC images to find 10 plausible optical/UV counterparts. We fit the spectral energy distribution of the known cataclysmic variable 1E1339.8+2837 with a blue ($T_\mathrm{eff} = 2.10^{+1.96}_{-0.58}\times 10^4~\mathrm{K}$, 90% conf.) spectral component from an accretion disc, plus a red component ($T_\mathrm{eff} = 3.75_{-0.15}^{+1.05}\times 10^3~\mathrm{K}$) potentially from a subgiant donor. The second brightest source (CX2) has a soft blackbody-like spectrum suggesting a quiescent low-mass X-ray binary (qLMXB) containing a neutron star. Six new counterparts have obvious UV and/or blue excesses, suggesting a cataclysmic variable (CV) or background active galactic nucleus (AGN) nature. Two (CX6 and CX8) have proper motions indicating cluster membership, suggesting a CV nature. CX6 is blue in UV filters but red in V-I, which is difficult to interpret. Two CV candidates, CX7 and CX13, show blue excesses in B-V colour but were not detected in the UV. The other two CV candidates were only detected in the two UV bands ($\mathrm{UV_{275}}$ and $\mathrm{NUV_{336}}$), so do not have proper motion measurements, and may well be AGNs. One $Chandra$ source can be confidently identified with a red straggler (a star redward of the giant branch). The observed X-ray source population of M3 appears consistent with its predicted stellar interaction rate.
Massive Stars: Their Environment and Formation

Cloud environment is thought to play a critical role in determining the mechanism of formation of massive stars. In this contribution we review the physical characteristics of the environment around recently formed massive stars. Particular emphasis is given to recent high angular resolution observations which have improved our knowledge of the physical conditions and kinematics of compact regions of ionized gas and of dense and hot molecular cores associated with luminous O and B stars. We will show that this large body of data, gathered during the last decade, has allowed significant progress in the understanding of the physical processes that take place during the formation and early evolution of massive stars.
Local virial relation and velocity anisotropy in self-gravitating system

We investigate the merging process in N-body self-gravitating system from the viewpoints of the local virial relation which is the relation between the local kinetic energy and the local potential. We compare both the density profile and the phase space density profile in cosmological simulations with the critical solutions of collisionless static state satisfying the local virial (LV) relation. We got the results that the critical solution can explain the characteristic density profile with the appropriate value of anisotropy parameter β ∼ 0.5. It can also explain the power law of the phase space density profile in the outer part of a bound state. However, it fails in explaining the central low temperature part which is connected to the scale invariant phase space density. It can be well fitted to the critical solution with the higher value of β ∼ 0.75. These results indicate that the LV relation is not compatible with the scale invariant phase space density in cosmological simulation.
Witten-Veneziano relation, quenched QCD, and overlap fermions

The quarks in quenched QCD have an anomalous self-interaction in the flavor singlet Goldstone boson channel. This coupling is extracted from a graph with disconnected quark lines, and is used to infer the mass of the eta-prime meson in full QCD. When the fermions are described by an overlap action, the Witten-Veneziano relation is an exact relation between the topological susceptibility (as defined through fermionic zero modes) and the inferred value of the eta-prime mass. Using an overlap action we compute the hairpin amplitude and determine the fermion zero-mode susceptibility, the inferred eta-prime mass and other parameters characterizing the low energy chiral properties of quenched QCD.
Breakup of a laminar capillary jet of a viscoelastic fluid

The stability of non-Newtonian jets was investigated. A linearized stability analysis shows that a liquid column of a viscoelastic fluid exhibits more rapid growth of axisymmetric wave disturbances than a Newtonian fluid of the same zero shear viscosity. This result is independent of the form of constitutive equation chosen. Experiments in weakly elastic fluids confirm this expectation, whereas data on fluids with more pronounced elastic properties indicate that non-linear phenomena are dominating. The disturbances appear as a series of droplets connected by random lengths of threads, which thin with distance and eventually lead to jet breakup. Even in dilute viscoelastic solutions, jet breakup does not occur by the growth of clearly defined waves.
GS242-03+37: a lucky survivor in the galactic gravitational field

Context. HI shells and supershells, found in discs of many galaxies including our own, are formed by the activity of young and massive stars (supernova explosions and stellar winds), but the formation of these structures may be linked to other energetic events, such as interactions of high-velocity clouds with the galactic disc. The larger structures in particular significantly influence their surroundings; their walls are often places where molecular clouds reside and where star formation happens. Aims. We explore the HI supershell GS242-03+37, a large structure in the outer Milky Way. Its size and position make it a good case for studying the effects of large shells on their surrounding. Methods. We perform numerical simulations of the structure with the simplified hydrodynamical code RING, which uses the thin-shell approximation. The best fit is found by a comparison with the HI data and then we compare our model with the distribution of star clusters near this supershell. Results. The best model of GS242-03+37 requires, contrary to previous estimates, a relatively low amount of energy, and it has an old age of ∼100 Myr. We also find that the distribution of young star clusters (with ages <120 Myr) is correlated with walls of the supershell, while the distribution of older clusters is not. Clusters that have the highest probability of being born in the wall of the supershell show an age sequence along the wall. Conclusions. GS242-03+37 is a relatively old structure, shaped by the differential rotation, and its wall is a birthplace of several star clusters. The star formation started at a time when the supershell was not already supersonically expanding; it was a result of the density increase due to the galactic shear and oscillations perpendicular to the disc of the Milky Way.
Ising and dimer models in two and three dimensions

Motivated by recent interest in 2+1 dimensional quantum dimer models, we revisit Fisher's mapping of two-dimensional Ising models to hardcore dimer models. First, we note that the symmetry breaking transition of the ferromagnetic Ising model maps onto a non-symmetry breaking transition in dimer language-instead it becomes a deconfinement transition for test monomers. Next, we introduce a modification of Fisher's mapping in which a second dimer model, also equivalent to the Ising model, is defined on a generically different lattice derived from the dual. In contrast to Fisher's original mapping, this enables us to reformulate frustrated Ising models as dimer models with positive weights and we illustrate this by providing a new solution of the fully frustrated Ising model on the square lattice. Finally, by means of the modified mapping we show that a large class of three-dimensional Ising models are precisely equivalent, in the time continuum limit, to particular quantum dimer models. As Ising models in three dimensions are dual to Ising gauge theories, this further yields an exact map between the latter and the quantum dimer models. The paramagnetic phase in Ising language maps onto a deconfined, topologically ordered phase in the dimer models. Using this set of ideas, we also construct an exactly soluble quantum eight vertex model.
The Dynamical Stability of a Fat Disk with Constant Specific Angular Momentum

On etudie la stabilite de tores en rotation, stationnaires, axisymetriques de moment angulaire specifique constant et d'entropie uniforme. A l'aide d'une equation de perturbation linearisee, on resout numeriquement le probleme aux valeurs propres a 2 dimensions. On trouve que de tels tores sont instables
Self-gravity and dissipation in polar rings

Studies of inclined rings inside galaxy potentials have mostly considered the influence of self-gravity and viscous dissipation separately. In this study, we construct models of highly inclined ('polar') rings in an external potential including both self-gravity and dissipation due to a drag force. We do not include pressure forces and thus ignore shock heating that dominates the evolution of gaseous rings inside strongly nonspherical potentials. We adopt an oblate spheroidal scale-free logarithmic potential with axis ratio q = 0.85 and an initial inclination of 80 deg for the self-gravitating rings. We find that stellar (dissipationless) rings suffer from mass loss during their evolution. Mass loss also drives a secular change of the mean inclination toward the poles of the potential. As much as half of the ring mass escapes in the process and forms an inner and an outer shell of precessing orbits. If the remaining mass is more than approximately 0.02 of the enclosed galaxy mass, rings remain bound and do not fall apart from differential precession. The rings precess at a constant rate for more than a precession period tau(sub p) finding the configuration predicted by Sparke in 1986 which warps at larger radii toward the poles of the potential. We model shear viscosity with a velocity-dependent drag force and find that nuclear inflow dominates over self-gravity if the characteristic viscous inflow time scale tau(sub vi) is shorter than approximately 25(tau(sub p)). Rings with (tau(sub vi))/(tau(sub p)) less than or approximately equal to 25 collapse toward the nucleus of the potential within one precession period independent of the amount of self-gravity. Our results imply that stars and gas in real polar rings exhibit markedly different dynamical evolutions.
The Position of Sagittarius A*. III. Motion of the Stellar Cusp

In the first two papers of this series, we determined the position of Sgr A* on infrared images by aligning the positions of red giant stars with positions measured at radio wavelengths for their circumstellar SiO masers. In this paper, we report the detections of five new stellar SiO masers within 50'' (2 pc) of Sgr A* and new and/or improved positions and proper motions of 15 stellar SiO masers. The current accuracies are ≈1 mas in position and ≈0.3 mas yr-1 in proper motion. We find that the proper motion of the central stellar cluster with respect to Sgr A* is less than 45 km s-1. One star, IRS 9, has a three-dimensional speed of ≈370 km s -1 at a projected distance of 0.33 pc from Sgr A*. If IRS 9 is bound to the inner parsec, this requires an enclosed mass that exceeds current estimates of the sum of the mass of Sgr A* and luminous stars in the stellar cusp by ≈0.8 × 106 M☉. Possible explanations include: (1) that IRS 9 is not bound to the central parsec and has "fallen" from a radius greater than 9 pc, (2) that a cluster of dark stellar remnants accounts for some of the excess mass, and/or (3) that R0 is considerably greater than 8 kpc.
The nature of PISN candidates: clues from nebular spectra

A group of superluminous supernovae characterized by broad light curves have been suggested to be pair instability SNe (PISNe). Nebular spectra computed using PISN models have failed to reproduce the broad emission lines observed in these SNe, casting doubts on their true nature. Here, models of both PISNe and the explosion following the collapse of the core of a very massive star (100MΘ) are used to compute nebular spectra, which are compared to the spectrum of the prototypical PISN candidate, SN 2007bi. PISN models are confirmed to produce synthetic spectra showing narrow emission lines, resulting from the confinement of 56Ni to the lowest velocities (≤ 2000 km s-1) and in clear disagreement with the spectrum of SN 2007bi. Spectra more closely resembling SN2007bi are obtained if the PISN models are fully mixed in abundance. Massive core-collapse models produce enough 56Ni to power the light curve of PISN candidates, but their spectra are also not adequate. The nebular spectrum of SN 2007bi can be successfully reproduced if the inner region is artificially filled with oxygenrich, low-velocity ejecta. This most likely requires a grossly aspherical explosion. A major difference between PISN and massive collapse models is that the former emit much more strongly in the NIR. It is concluded that: (a) current PISN candidates, in particular SN 2007bi, are more likely the result of the collapse and explosion of massive stars below the PI limit; (b) significant asymmetry is required to reproduce the late-time spectrum of SN2007bi. © 2019 The Author(s).
The identification of SS73 71 as a new symbiotic star

We report spectroscopic observations of a new symbiotic star. This star is located in our Galaxy in the direction of the bulge and was discovered during a southern spectroscopic survey of H α emission line objects. The star, SS73 71, after Sanduleak & Stephenson (1973), shows characteristics of a symbiotic star: the presence of TiO bands and emission lines of ions of higher ionization such as He ii4686 A and [O iii]5007 A. Here, we present some of the main spectroscopic features, line intensities and, whenever possible, some physical parameters.
Photoemission Spectroscopy from Inhomogeneous Models of Cuprates

We investigate the electronic dynamics in the underdoped cuprates focusing on the effects of one-dimensional charge stripes. We address recent experimental Angular-Resolved Photoemission Spectra results on (La1.28Nd0.6Sr0.12)CuO4. We find that various inhomogeneous models can account for the distribution of quasiparticle weights close to momentum k = (π,0) and symmetry related points. The observed flat dispersion region around the same k point can only be addressed by certain classes of those inhomogeneous models which locally break spin symmetry. Homogeneous models including hopping elements up to second neighbors cannot reproduce the experimental quasiparticle weight, since most of it is centered around k = ( � 2 , � 2 ).
Zero-temperature limit of the supersymmetry-breaking complexity in dilute spin-glass models

We study the SUSY-breaking complexity of the Bethe Lattice Spin-Glass in the zero temperature limit. We consider both the Gaussian and the bimodal distribution of the coupling constants. For $J_{ij}=\pm 1$ the SUSY breaking theory yields fields distributions that concentrate on integer values at low temperatures, at variance with the unbroken SUSY theory. This concentration takes place both in the quenched as well as in the simpler annealed formulation.
Dynamic stability of compact stars

After some historical remarks we discuss diﬀerent criteria of dynamical stability of stars, and properties of the critical states where dynamical stability is lost, leading to collapse with formation of the neutron star or a black hole. At the end some observational and theoretical problems related to quark stars are discussed.
D-branes and Deformation Quantization

In this note we explain how world-volume geometries of D-branes can be reconstructed within the microscopic framework where D-branes are described through boundary conformal field theory. We extract the (non-commutative) world-volume algebras from the operator product expansions of open string vertex operators. For branes in a flat background with constant non-vanishing B-field, the operator products are computed perturbatively to all orders in the field strength. The resulting series coincides with Kontsevich's presentation of the Moyal product. After extending these considerations to fermionic fields we conclude with some remarks on the generalization of our approach to curved backgrounds.
Upper Limits Set by Causality on the Rotation and Mass of Uniformly Rotating Relativistic Stars

Causality alone suffices to set a lower bound on the period of rotation of relativistic stars as a function of their maximum observed mass. That is, by assuming a one-parameter equation of state (EOS) that satisfies vsound < c and that allows stars with masses as large as the largest observed neutron star mass, M, we find P(ms)>0.282+0.196(M/M-1.442). The limit does not assume that the EOS agrees with a known low-density form for ordinary matter, and if one adds that assumption, the minimum period is raised by a few percent: for a match at n = 0.1 fm-3, we find P(ms)>0.295 + 0.203(M/M-1.442). The minimizing EOS yields models with a maximally soft exterior supported by a maximally stiff core. An analogous upper limit set by causality on the maximum mass of rotating neutron stars requires a low-density match, and the limit depends on the matching density, ϵm. We recompute it, obtaining a slightly revised value, M≃6.1(2×1014 g cm-3/ϵm)1/2 M☉.