Related papers: Modeling the spectrum of V4334 Sgr (Sakurai's Obje…
Theoretical spectral energy distributions are computed for a grid of hydrogen-deficient and carbon-rich model atmospheres with a range in T(eff) of 4000 - 5500 K and log g of 1.0 - 0.0, using the technique of opacity sampling, and taking…
Theoretical spectral energy distributions computed for a grid of hydrogen-deficient and carbon-rich model atmospheres have been compared with the observed infrared (1--2.5 $\mu$m) spectra of V4334 Sgr (Sakurai's Object) on 1997 April 21 and…
We model the spectra and spectral energy distribution of V838 Mon which were observed in February, March, and November, 2002. Theoretical spectra are calculated using the classical model atmospheres taking into account absorption of atomic…
We present an analysis of the evolution of circumstellar dust and molecules in the environment of the very late thermal pulse object V4334 Sgr (Sakurai's Object) over a $\sim20$-year period, drawing on ground-, airborne- and space-based…
We present a $0.8-2.5\,\mu$m spectrum of the Very Late Thermal Pulse object V4334 Sgr (Sakurai's Object), obtained in 2020 September. The spectrum displays a continuum that rises strongly to longer wavelengths, and is considerably brighter…
We report the results of monitoring of V4334 Sgr (Sakurai's Object) at 450 microns and 850 microns with SCUBA on the James Clerk Maxwell Telescope. The flux density at both wavelengths has increased dramatically since 2001, and is…
Procedure and results of computations of stellar model atmospheres and spectral energy distributions are discussed. Model atmospheres of some chemically peculiar stars are computed taking into account detailed information about their…
We present the results of our analysis of a high resolution (R ~ 30000) infrared spectrum of V4334 Sgr (Sakurai's Object) around the first overtone CO bands, obtained in 1998 July. The 12CO and 13CO bands are well-resolved, and we compute…
We present spectral results from a multi-satellite, broad-band campaign on the Narrow-line Seyfert 1 galaxy Ton S180 performed at the end of 1999. We discuss the spectral-energy distribution of the source, combining simultaneous Chandra,…
We present an observation of the very late thermal pulse object V4334 Sgr (Sakurai's Object) with the Infrared Spectrometer (IRS) on the Spitzer Space Telescope. The emission from 5-38 microns is dominated by the still-cooling dust shell. A…
V4334 Sgr (Sakurai's object) is an enigmatic evolved star that underwent a very late thermal pulse a few years before its discovery in 1996. It ejected a new, hydrogen-deficient nebula in the process. Emission lines from the newly ejected…
We have generated new, self-consistent spectral and atmosphere models for the effective temperature range 600 K to 1300 K thought to encompass the known T dwarfs. For the first time, theoretical models are compared with a {\it family} of…
CCD UBVRi photometry of the final helium flash object V4334 Sgr (Sakurai's Object), carried out during 1997 - 1999, is presented, and the light curve from its pre-discovery rise to the dust obscuration phase is constructed. The optical…
We present a determination of the effective temperatures, iron abundances, and microturbulent velocities for the pseudophotosphere of V838 Mon on 2002 February 25, and March 2 and 26. Physical parameters of the line forming region were…
We carry out 1D hydrodynamical simulations of the evolution of a spherically symmetric supernova remnant (SNR) subject to an external radiation field (ERF) that influences the cooling and heating rates of the gas. We consider homogeneous…
The central star V4334 Sgr (Sakurai's Nova) of the planetary nebula PN G010.4+04.4 underwent in 1995-1996 the rare event of a very late helium flash. It represents only one out of two such events during the era of modern astronomy (the…
The spectral energy distribution (SED) of the TT Ari system, which is well known from published IUE and optical photometric observations, was modeled by a steady-state accretion \alpha-disc around a white dwarf. Parameters of the system…
The spatial-dependent propagation model has been successfully used to explain diverse observational phenomena, including the spectral hardening of cosmic-ray nuclei above $200$ GV, the large-scale dipole anisotropy and the diffusive gamma…
We propose a model where a supernova explodes in some vicinity of our solar system (some tens of parsecs) in the recent past (some tens of thousands years) with the energy release in cosmic rays of order of $ 10 ^ {51} $ erg. The flux from…
V4334 Sgr (a.k.a. Sakurai's object) is the central star of an old planetary nebula that underwent a very late thermal pulse a few years before its discovery in 1996. We have been monitoring the evolution of the optical emission line…