Related papers: Radiative Transfer Effects in He I Emission Lines
Symbiotic binaries are comprised of nebulae, whose densest portions have electron concentrations of 1E+8 - 1E+12 cm-3 and extend to a few AU. They are optically thick enough to cause a measurable effect of the scattering of photons on free…
Interpretation of precision measurements of the cosmic microwave background (CMB) will require a detailed understanding of the recombination era, which determines such quantities as the acoustic oscillation scale and the Silk damping scale.…
We present Cloudy calculations for the intensity of coronal hyperfine lines in various environments. We model indirect collisional and radiative transitions, and quantify the collisionally-excited line emissivity in the density-temperature…
Featureless optical and ultraviolet (UV) spectra are a puzzling signature to emerge from recent observations of luminous fast blue optical transients (LFBOTs) and some tidal disruption events (TDEs). We describe the landscape of source and…
Nebular emission lines are critical to measure physical properties in the ionized gas (e.g., metallicity, the SFR, or dust attenuation). They also account for a significant fraction of broadband fluxes, in particular at the highest…
We have calculated X-ray and UV spectra of Be-like Fe (FeXXIII) ion in collisional-radiative model including all fine-structure transitions among the 2s^2, 2s2p, 2p^2, 2snl, and 2pnl levels where n=3 and 4, adopting data for the collision…
We estimate the He II to H I column density ratio, \eta = N(He II)/N(H I), in the intergalactic medium towards the high redshift (z_{em} = 2.885) bright quasar QSO HE 2347-4342 using Voigt-profile fitting of the H I transitions in the Lyman…
The long-standing difference in chemical abundances determined from optical recombination lines and collisionally excited lines raises questions about our understanding of atomic physics, as well as the assumptions made when determining…
We present the results of our new low-resolution spectroscopic observations of the young compact planetary nebula Hb 12 performed in 2011-2020 with SAI MSU telescopes. We have measured the intensities of more than 50 nebular emission lines…
We present a new model of the optical nebular emission from HII regions by combin- ing the results of the Binary Population and Spectral Synthesis (bpass) code with the photoion- ization code cloudy (Ferland et al. 1998). We explore a…
Thirteen transitions within the ground 3d^2 configuration of Fe VII are identified in ultraviolet and optical spectra of the symbiotic star RR Telescopii obtained with the STIS instrument of the Hubble Space Telescope. The line fluxes are…
We present a reanalysis of the HeII Lyman alpha absorption towards the quasars HS1700+6416 and HE2347-4342 using new high S/N, optical observations. An alternative analysis method is applied, which fits the high quality, optical HI data…
A low-dispersion Keck I spectrum of SN 1980K taken in August 1995 (t = 14.8 yr after explosion) and a November 1997 MDM spectrum (t = 17.0 yr) show broad 5500 km s^{-1} emission lines of H\alpha, [O I] 6300,6364 A, and [O II] 7319,7330 A.…
The shape of the UV ionizing background is reconstructed from optically thin metal absorption-line systems identified in spectra of HE2347-4342, Q1157+3143, and HS1700+6416 in the redshift interval 1.8 < z < 2.9. The systems are analyzed by…
Interpretation of He II Ly{\alpha} absorption spectra after the epoch of He II reionization requires knowledge of the He II ionizing background. While past work has modelled the evolution of the average background, the standard cosmological…
We present a radiative transfer code to model the nebular phase spectra of supernovae (SNe) in non-local thermodynamic equilibrium (NLTE). We apply it to a systematic study of Type Ia SNe using parameterized 1D models and show how nebular…
We have obtained with the LBT Telescope AO system Near-Infrared camera PISCES images of the inner-shell of the nebula around the luminous blue variable star P Cygni in the [Fe II] emission line at 1.6435 {\mu}m. We have combined the images…
The optical and near-infrared late-time spectrum of the under-luminous Type Ia supernova 2003hv is analysed with a code that computes nebular emission from a supernova nebula. Synthetic spectra based on the classical explosion model W7 are…
We present an extended grid of multi-epoch 1D nonlocal thermodynamic equilibrium radiative transfer calculations for nebular-phase Type Ibc supernovae (SNe) from He-star explosions. Compared to Dessart+21, we study the spectral evolution…
This paper presents a study of the dependence of the simulated intensities of recombination lines from hydrogen and helium atoms on the number of $n\ell$-resolved principal quantum numbers included in the calculations. We simulate hydrogen…