arXiv subjects

Miroslav Šlechta

Publications and source records attributed to Miroslav Šlechta.

5 recordsLinked to original sources

arXiv2026

The first hours and days of the 2021 explosion of the recurrent symbiotic nova RS Ophiuchii

The accretion of matter on a massive white dwarf (WD) can lead to repeated nuclear explosions on its surface over a timescale of years to decades. The seventh explosion of the recurrent symbiotic nova RS Ophiuchi (RS Oph) was recorded on August 8, 2021. In this paper, we examine its early evolution, from 9 hours before its optical maximum until day 42. We achieved our goal by modeling the spectral energy distribution (SED) using optical spectroscopy and simultaneous $BVR_{\rm C}I_{\rm C}$ photometry, supplemented by $JHKL$ photometry and ultraviolet spectroscopy from previous explosions in 2006 and 1985. Our SED models revealed an early stage of development of the ejecta bipolar structure, consisting of a flared, density-enhanced equatorial disk and low-density regions in bipolar directions. The comparability of the internal shocks' luminosity in the equatorial outflow, inferred from our model parameters, with the luminosity of the warm WD pseudophotosphere during its presence in the spectrum (until $\sim$day 42) confirmed that a significant part of its radiation originates from reprocessed shock emission. We explain the formation and evolution of the bipolar ejecta structure during RS Oph explosions by the rotation of the accreting WD. Such an ejecta structure provides a natural framework for the generation of strong internal shocks and thus $γ$-ray emission inside the ejecta.

astro-ph.SR↗

arXiv2016

Spectroscopy of close visual binary components of the stable shell star 1 Del

Stable shell stars are ideal objects for studying basic physical principles of the formation of disks in Be stars. If these stars have a close unresolved visual companion, its contribution toward the modelling of the disk cannot be overlooked, as is sometimes done. The study aims to spectroscopically resolve close visual binary Be (shell) star 1 Del, which up to now was only resolved by speckle or micrometric measurements. The integral field spectroscopy obtained by the SINFONI spectrograph at the VLT telescope in the European Southern Observatory (ESO) in the infrared region was used; we supplemented these observations with visual spectroscopy with the Perek Telescope at the Ondrejov Observatory. Spectra of 1 Del were successfully resolved, and, for the first time, spectra of 1 Del B were obtained. We found that 1 Del A is a Be/shell star, while 1 Del B is not an emission-line object.

astro-ph.SR↗

arXiv2015

Spectroscopic survey of emission-line stars. I. B[e] stars

Emission-line stars are typically surrounded by dense circumstellar material, often in form of rings or disc-like structures. Line emission from forbidden transitions trace a diversity of density and temperature regimes. Of particular interest are the forbidden lines of [O I] λλ6300, 6364 and [Ca II] λλ7291, 7324. They arise in complementary, high-density environments, such as the inner-disc regions around B[e] supergiants. To study physical conditions traced by these lines and to investigate how common they are, we initiated a survey of emission-line stars. Here, we focus on a sample of nine B[e] stars in different evolutionary phases. Emission of the [O I] lines is one of the characteristics of B[e] stars. We find that four of the objects display [Ca II] line emission: for the B[e] supergiants V1478 Cyg and 3 Pup the kinematics obtained from the [O I] and [Ca II] line profiles agrees with a Keplerian rotating disc scenario; the forbidden lines of the compact planetary nebula OY Gem display no kinematical broadening beyond spectral resolution; the LBV candidate V1429 Aql shows no [O I] lines, but the profile of its [Ca II] lines suggests that the emission originates in its hot, ionized circumbinary disc. As none of the B[e] stars of lower mass displays [Ca II] line emission, we conclude that these lines are more likely observable in massive stars with dense discs, supporting and strengthening the suggestion that their appearance requires high-density environments.

astro-ph.SR↗

arXiv2010

The O-type eclipsing binary SZ Cam revisited

We analyse new spectra of the multiple system SZ Cam because previous studies found different values of the primary radial velocity amplitude. The older solutions of light curves also have different ratios of secondary to primary luminosity as inferred from the observed equivalent widths of spectral lines. We therefore reanalyse the light curves of the eclipsing pair. Only the light curve derived by Wesselink has a solution that agrees with the observed equivalent width ratio. The resulting parameters of the binary are discussed. Masses of $M_1=16.6$ and $M_2=11.9$ M$_{\odot}$, and radii $R_1=9.4$ and $R_2=5.4$ R$_{\odot}$ are derived. We point out that radial velocities measured with the CCF method can be misleading when the method is applied to multiple systems with complex line blends. New radial velocities are also obtained for the visual component ADS 2984 A (HD 25639).

astro-ph.SR↗

arXiv2010

A new ephemeris and an orbital solution of ε Aurigae

We collected rich series of RV measurements covering last 110 years and photometric observations from the past 6 primary eclipses, complemented them by our new observations and derived a new precise ephemeris and an orbital solution of epsilon Aur.

astro-ph.SR↗