The problem on heating the atmospheres of T Tauri stars by radiation from an accretion shock has been solved. The structure and radiation spectrum of the emerging so-called hot spot have been calculated in the LTE approximation. The emission not only in continuum but also in lines has been taken into account for the first time when calculating the spot spectrum. Comparison with observations has shown that the strongest of these lines manifest themselves as narrow components of helium and metal emission lines, while the weaker ones decrease significantly the depth of photospheric absorption lines, although until now, this effect has been thought to be due to the emission continuum alone. The veiling by lines changes the depth of different photospheric lines to a very different degree even within a narrow spectral range. Therefore, the nonmonotonic wavelength dependence of the degree of veiling r found for some CTTS does not suggest a nontrivial spectral energy distribution of the veiling continuum. In general, it makes sense to specify the degree of veiling r only by providing the set of photospheric lines from which this quantity was determined. We show that taking into account the contribution of lines to the veiling of the photospheric spectrum can cause the existing estimates of the accretion rate onto T Tauri stars to decrease by several times, with this being also true for stars with a comparatively weakly veiled spectrum. Neglecting the contribution of lines to the veiling can also lead to appreciable errors in determining the effective temperature, interstellar extinction, radial velocity, and v sin i.

We present results from applying the SNAD anomaly detection pipeline to the third public data release of the Zwicky Transient Facility (ZTF DR3). The pipeline is composed of 3 stages: feature extraction, search of outliers with machine learning algorithms and anomaly identification with followup by human experts. Our analysis concentrates in three ZTF fields, comprising more than 2.25 million objects. A set of 4 automatic learning algorithms was used to identify 277 outliers, which were subsequently scrutinised by an expert. From these, 188 (68%) were found to be bogus light curves – including effects from the image subtraction pipeline as well as overlapping between a star and a known asteroid, 66 (24%) were previously reported sources whereas 23 (8%) correspond to non-catalogued objects, with the two latter cases of potential scientific interest (e. g. 1 spectroscopically confirmed RS Canum Venaticorum star, 4 supernovae candidates, 1 red dwarf flare). Moreover, using results from the expert analysis, we were able to identify a simple bi-dimensional relation which can be used to aid filtering potentially bogus light curves in future studies. We provide a complete list of objects with potential scientific application so they can be further scrutinised by the community. These results confirm the importance of combining automatic machine learning algorithms with domain knowledge in the construction of recommendation systems for astronomy. Our code is publicly available*.

Speckle interferometry of the young binary system RW Aur was performed with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences using filters with central wavelengths of 550 nm and 800 nm and passband halfwidths of 20 nm and 100 nm, respectively. The angular separation of the binary components was 1.448 ′′ ± 0.005 and the position angle of the system was 255.9 o ± 0.3. at the observation epoch (JD 2 454 255.9). We find using published data that these values have been changing with mean rates of +0.002 ′′ /yr and +0.02 o /yr, respectively, over the past 70 years. This implies that the direction of the orbital motion of the binary system is opposite to the direction of the disk rotation in RW Aur A. We propose a physical model to explain the formation of circumstellar accretion disks rotating in the reverse direction relative to young binary stars surrounded by protoplanetary disks. Our model can explain the characteristic features of the matter flow in RW Aur A: the high accretion rate, small size of the disk around the massive component, and reverse direction of rotation.

The paper describes the modelling of the structure and spectra of the hot accretion spots on the surface of young stars with taking into account departures from LTE for hydrogen and helium. It has been found that the existence of the ram pressure of the in-falling gas at the outer boundary of the hot spot leads to the Stark broadening of the hydrogen line profiles up to FWHM∼1000 km s −1 at the considered accretion parameters. It is shown that taking into account departures from LTE for atoms and ions of carbon and oxygen does not lead to noticeable changes in the structure of the hot spot.

Results of longitudinal magnetic field B z measurements for young star RW Aur A are presented. We found that B z in the formation region of He I 5876 line's narrow component varies from −1.47 ± 0.15 kG to +1.10 ± 0.15 kG. Our data are consistent with a stellar rotational period of ≃ 5.6d and with a model of two hotspots with an opposite polarity of magnetic field and with a difference in a longitude about 180o . The spot with B z < 0 is located at the hemisphere above the midplane of RW Aur's accretion disc and the spot with B z > 0 is below the midplane.The following upper limits for B z (at 3σ level) were found after averaging of all our observations: 180 G for photosperic lines, 220 G and 230 G for formation regions of H α and [OI] 6300 lines respectively. Upper limit 600 G were found in the region where broad components of emisson lines form.For two cases out of 11 we observed the field in a formation region of a blue absorption wing of Na I D lines i.e. in an outflow: B z = −180 ± 50 G and −810 ± 80 G.Radial velocity of RW Aur's photospheric lines averaged over all our observations is ≃ +10.5 km s −1 what is 5.5 km s −1 less than value derived ten years earlier by Petrov et al. (2001). In this connection, we discuss a possibility that RW Aur is not a binary but a triple system.