A flare from the TeV blazar Mrk 421, occurring in March 2010, was observed for 13 consecutive days from radio to very high energy (VHE; E>100GeV) gamma-rays with MAGIC, VERITAS, Whipple, FermiLAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We model the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigate the physical parameters, and evaluate whether the observed broadband SED variability can be associated to variations in the relativistic particle population. Flux variability was remarkable in the X-ray and VHE bands while it was minor or not significant in the other bands. The one-zone SSC model can describe reasonably well the SED of each day for the 13 consecutive days. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission while the other smaller zone, which is spatially separated from the first one, contributes to the daily-variable emission occurring in X-rays and VHE gamma-rays. Both the one-zone SSC and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly to the underlying particle population. This shows that the particle acceleration and cooling mechanism producing the radiating particles could be the main one responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement to the observed SED at the narrow peaks of the low- and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by the variation of the parameters related to the emitting region itself ({delta}, B and R), in addition to the parameters related to the particle population.
The stellar winds of asymptotic giant branch (AGB) stars are commonly attributed to radiation pressure on dust grains, formed in the wake of shock waves that arise in the stellar atmospheres. The mass loss due to these outflows is substantial, and modelling the dynamical properties of the winds is essential both for studies of individual stars and for understanding the evolution of stellar populations with low to intermediate mass. The purpose of this work is to present an extensive grid of dynamical atmosphere and wind models for M-type AGB stars, covering a wide range of relevant stellar parameters. We used the DARWIN code, which includes frequency-dependent radiation-hydrodynamics and a time-dependent description of dust condensation and evaporation, to simulate the dynamical atmosphere. The wind-driving mechanism is photon scattering on submicron-sized Mg2SiO4 grains. The grid consists of ~4000 models, with luminosities from L*=890L_{sun}_ to L*=40000 L_{sun}_ and effective temperatures from 2200 to 3400K. For the first time different current stellar masses are explored with M-type DARWIN models, ranging from 0.75M_{sun}_ to 3 M_{sun}_. The modelling results are radial atmospheric structures, dynamical properties such as mass-loss rates and wind velocities, and dust properties (e.g. grain sizes, dust-to-gas ratios, and degree of condensed Si). We find that the mass-loss rates of the models correlate strongly with luminosity. They also correlate with the ratio L*/M*: increasing L*/M* by an order of magnitude increases the mass-loss rates by about three orders of magnitude, which may naturally create a superwind regime in evolution models. There is, however, no discernible trend of mass-loss rate with effective temperature, in contrast to what is found for C-type AGB stars. We also find that the mass-loss rates level off at luminosities higher than ~14000L_{sun}_, and consequently at pulsation periods longer than ~800 days. The final grain radii range from 0.25 to 0.6um. The amount of condensed Si is typically between 10 and 40%, with gas-to-dust mass ratios between 500 and 4000.
The paper is devoted to the study of the underlying stellar population of a sample of 62 nearby early-type galaxies, predominantly located in low density environments, a large fraction of which showing emission lines. Ages, metallicities and [{alpha}/Fe] ratios have been derived through the comparison of Lick indices measured at different galacto-centric distances (7 apertures and 4 gradients) with new Simple Stellar Population (SSP) models which account for the presence of alpha/Fe-enhancement. The SSPs cover a wide range of ages (10^8^-16x10^9^yr), metallicities (0.0004<=Z<=0.05) and [{alpha}/Fe] ratios (0-0.8). To derive the stellar population parameters we use an algorithm that provides, together with the most likely solution in the (age, Z, [{alpha}/Fe]) space, also the probability density function along the age-metallicity degeneracy. We derive a large spread in age, with SSP-equivalent ages ranging from a few to 15Gyrs. Age does not show any significant trend with central velocity dispersion sigma_c_ but E galaxies appear on average older than lenticulars.
Near-resonance in a system of sub-Neptunes from TESS
Short Name:
J/AJ/158/177
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the Transiting Exoplanet Survey Satellite detection of a multi-planet system orbiting the V=10.9 K0 dwarf TOI-125. We find evidence for up to five planets, with varying confidence. Three transit signals with high signal-to-noise ratio correspond to sub-Neptune-sized planets (2.76, 2.79, and 2.94 R_{Earth}_), and we statistically validate the planetary nature of the two inner planets (P_b_=4.65 days, P_c_=9.15 days). With only two transits observed, we report the outer object (P_.03_=19.98 days) as a planet candidate with high signal-to-noise ratio. We also detect a candidate transiting super-Earth (1.4 R_{Earth}_) with an orbital period of only 12.7 hr and a candidate Neptune-sized planet (4.2 R_{Earth}_) with a period of 13.28 days, both at low signal-to-noise ratio. This system is amenable to mass determination via radial velocities and transit-timing variations, and provides an opportunity to study planets of similar size while controlling for age and environment. The ratio of orbital periods between TOI-125 b and c (P_c_/P_b_=1.97) is slightly lower than an exact 2:1 commensurability and is atypical of multiple planet systems from Kepler, which show a preference for period ratios just wide of first-order period ratios. A dynamical analysis refines the allowed parameter space through stability arguments and suggests that despite the nearly commensurate periods, the system is unlikely to be in resonance.
The neutrino-nucleus reaction cross sections of ^4^He and ^12^C are evaluated using new shell model Hamiltonians. Branching ratios of various decay channels are calculated to evaluate the yields of Li, Be, and B produced through the {nu}-process in supernova explosions. The new cross sections enhance the yields of ^7^Li and ^11^B produced during the supernova explosion of a 16.2M_{sun}_ star model compared to the case using the conventional cross sections by about 10%. On the other hand, the yield of ^10^B decreases by a factor of 2. The yields of ^6^Li, ^9^Be, and the radioactive nucleus ^10^Be are found at a level of ~10^-11^M_{sun}_. The temperature of {nu}_{mu},{tau}_ - and {nu}{bar}_{mu},{tau}_ - neutrinos inferred from the supernova contribution of ^11^B in Galactic chemical evolution models is constrained to the 4.3-6.5MeV range. The increase in the ^7^Li and ^11^B yields due to neutrino oscillations is demonstrated with the new cross sections.
A search for muon neutrinos in coincidence with gamma-ray bursts with the ANTARES neutrino detector using data from the end of 2007 to 2011 is performed. Expected neutrino fluxes are calculated for each burst individually. The most recent numerical calculations of the spectra using the NeuCosmA code are employed, which include Monte Carlo simulations of the full underlying photohadronic interaction processes. The discovery probability for a selection of 296 gamma-ray bursts in the given period is optimised using an extended maximum-likelihood strategy. No significant excess over background is found in the data, and 90% confidence level upper limits are placed on the total expected flux according to the model.
We study the global properties of neutron stars obtained with the Brussels-Montreal equations of state (EoSs). These EoSs, which provide a unified description of all regions of a neutron star, are based on the generalised Skyrme functionals BSk19, BSk20, and BSk21. The neutron-star properties thus obtained are compared with various astrophysical observations. We find that only the stiffest EoS, based on the functional BSk21, is at least marginally compatible with all the constraints inferred from these observations.
The spectra of B-type and early A-type stars show numerous unidentified lines in the whole optical range, especially in the 5100-5400{AA} interval. Because FeII transitions to high energy levels should be observed in this region, we used semiempirical predicted wavelengths and gf-values of FeII to identify unknown lines. Semiempirical line data for FeII computed by Kurucz are used to synthesize the spectrum of the slow-rotating, Fe - overabundant CP star HR6000.
The infrared (IR) emission of dust heated by stars provides critical information for galaxy evolution studies. Unfortunately, observations are often limited to the mid-IR, making templates a necessity. Previously published templates were based on small samples of luminous galaxies, which are not necessarily representative of normal star-forming galaxies. We constructed new-generation dust templates, including instrument-specific relations and software tools that facilitate the estimation of the total IR (TIR) luminosity as well as obscured and unobscured star formation rate (SFR) based on one or several fluxes up to z=4. For the first time, the templates include a dependence on both TIR luminosity and the specific SFR (sSFR), thereby increasing their reliability and utility for a wide range of galaxies. We also provide formulae for calculating TIR luminosities and SFR from JWST F2100W observations at 0<z<2. Our templates are based on 2584 normal star-forming galaxies spanning a wide range of stellar mass and sSFR, including sSFRs typical at higher redshifts. IR spectra and properties were obtained using cigale and the physically motivated Draine & Li (2007ApJ...657..810D) dust models. The photometry from the GALEX-SDSS-WISE Legacy Catalog was supplemented with 2MASS and Herschel-ATLAS, up to 19 bands from FUV to 500um. The shape of the dust spectrum varies with TIR luminosity, but also independently with sSFR. Remarkably precise estimates of the dust luminosity are possible with a single band over the rest-frame 12-17um and 55-130um. We validate single-band estimates on diverse populations, including local luminous IR galaxies, and find no significant systematic errors. Using two or more bands simultaneously yields the unbiased estimation of the TIR luminosity, even of star-forming dwarfs. We obtain fresh insights regarding the interplay between monochromatic IR luminosities, spectral shapes, and physical properties, and we constructed new templates and estimators of the dust luminosity and SFR. We provide software for generating templates and estimating these quantities based on 1-4 bands from WISE, JWST, Spitzer, and Herschel, up to z=4.
New grids of Atlas9 models have been calculated using revised convection parameters and updated opacity-distribution functions, for chemical compositions intended to be representative of solar, [M/H]=+0.3,+0.5, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC) abundances. The grids cover Teff=3.5-50kK, from logg=5.0 to the effective Eddington limit. Limb-darkening coefficients and synthetic photometry are presented in the UBVRIJHKLM, uvby, ugriz, WFCAM, Hipparcos/Tycho, and Kepler passbands for these models, and for Castelli's comparable 'new-ODF' grids. Flux distributions are given for the new models. The sensitivity of limb-darkening coefficients to the adopted physics is illustrated.
