Photometric activity of the Herbig Be star MWC 297 over 25 years     

O. Yu. Barsunova  S. Yu. Mel’nikov  V. P. Grinin  N. A. Katysheva  S. Yu. Shugarov 《Astronomy Reports》2013,57(2):89-94

The photometric behavior of the hot, young Herbig Be starMWC 297 on various time scales is studied using published data, as well as new observations. The series of photometric observations covers about 25 years. Over this time, the star showed low-amplitude (ΔV ≈ 0.3 ^m ) irregular variabilitymodulated by large-scale cyclic variabilitywith an amplitude close to 0.2 ^m and a period (or quasi-period) of 5.4±0.1 yr. A detailed seasonal analysis of the data shows that the light curve of MWC 297 displays two types of photometric features: low-amplitude Algol-like fading with an amplitude close to 0.2 ^m and low-amplitude flares resembling the flares of UV Ceti stars, but being more powerful and having longer durations. The variations of the stellar brightness are accompanied by variations of the B-V and V -R colors: when the brightness decreases, B-V decreases, while V -R increases (the star reddens). The reddening law is close to the standard interstellar reddening law. Although the character of the brightness variability ofMWC 297 resembles the photometric activity of UX Ori type stars, which is due to variations of their circumstellar extinction, its scale is very far from the scales observed for UX Ori stars. It is difficult to reconcile the level of photometric activity with the idea that MWC 297 is observed through its own gas-dust disk viewed almost edge-on, as has been suggested in several studies.  相似文献   

Photometric activity and rotational velocities of ux ori stars and related objects     

V. P. Grinin  O. V. Kozlova 《Astrophysics》2000,43(3):239-244

The rotational velocities of young stars of the UX Ori type and related objects are analyzed. It is shown that there is a weak but statistically significant correlation between υsin i and the amplitudes of photometric variability of these stars. It reflects the fact that the brightness variability of this type of star is determined mainly by variations in the column density of circumstellar dust along the line of sight. The latter depends, in turn, on the orientation of the circumstellar disk and is greatest when the disk is oriented edgeon to the observer or at a small angle to the line of sight. Translated from Astrofizika, Vol. 43, No. 3, pp. 329-337, July– September, 2000.  相似文献   

The Stark effect in stellar flares     

V. V. Sobolev  V. P. Grinin 《Astrophysics》1995,38(1):15-21

The formation of the Stark wings of hydrogen lines is considered on the basis of theoretical models of flares in type UV Cetus stars. It is shown that, under certain conditions (depending on the power of the beam of charged particles and their energy spectrum), very broad wings may be formed, extending 20 and more angstroms from the center of the line. Observations of such wings may provide valuable information concerning the energy spectra of the particles inducing the flare.Translated from Astrofizika, Vol. 38, No. 1, pp. 33–44, January–March, 1995.  相似文献   

Dust around young stars. Observations of the polarization of UX Ori in deep minima     

N. V. Voshchinnikov  V. P. Grinin  N. N. Kiselev  N. Kh. Minikulov 《Astrophysics》1988,28(2):182-193

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The Intermittently Embedded Herbig Ae/Be Stars ISO and Ground-Based IR Observations     

C.A. Grady  M.R. Pérez  K.S. Bjorkman  M.L. Sitko  P.S. Thé  D. De Winter  V.P. Grinin  R.W. Russell  D.K. Lynch  M.S. Hanner 《Astrophysics and Space Science》1997,255(1-2):35-41

We discuss silicate emission profiles observed with the ISO SWS and ground-based IR observations in a population of intermittently embedded Herbig Ae/Be stars which are viewed edge-on to their polarimetrically identified dust and gas disks. The ISO SWS observations confirm the lack of a simple correlation between system age and the profile shape. Comparison with laboratory silicates suggests that much of the observed variation is due to different annealing histories of the grains. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

The investigations of ‘zodiacal light’ of isolated AE-Herbig stars with non-periodic Algol-type minima     

V. P. Grinin  N. N. Kiselev  N. Kh. Minikulov  G. P. Chernova  N. V. Voshchinnikov 《Astrophysics and Space Science》1991,186(2):283-298

High linear polarization (up to 5–8%) discovered by our group in the deep minima of isolated AE-Herbig stars is discussed in the framework of the model of zodiacal light produced by scattering matter in a circumstellar dust envelope (probably in protoplanetary discs). The numerical simulations of polarizational and colourimetrical properties of the scattered light based on the Mie theory permit to obtain from the observations some important parameters of circumstellar dust: the size distribution of grains, their rough chemical composition (silicate/graphite), the flatness of the dust envelope.Moreover, the position angle of polarization in deep minima may be used for determination of the symmetry axis projection of circumstellar disc on the sky relative to the direction of local interstellar magnetic field. The latest is important in order to understand the role of the magnetic field at the initial phase of gravitational collapse of protostellar clouds.Finally, the component of linear polarization which is due to the alignment of nonspherical circumstellar grains may be separate from the observed polarization under certain conditions.Paper presented at the 12th European Regional Astronomical Meetings of the IAU European Astronomers Look to the Future, held 8–11 October, 1990 in Davos, Switzerland.  相似文献   

Influence of the Disk Wind on the Intrinsic Polarization of Young Stars     

Shulman  S. G.  Grinin  V. P. 《Astronomy Letters》2019,45(6):384-395

The behavior of the linear polarization parameters of UX Ori stars during their eclipses by circumstellar dust clouds is studied. A circumstellar disk with a disk wind creating a puffing in the dust sublimation zone is considered. We show that the disk puffing can strongly affect the degree of polarization and color index of the star during its eclipse. A strong wind can change the orientation of the plane of linear polarization. The scattered radiation from a thin disk is polarized perpendicularly to its plane, but the radiation from a disk with a strong wind can be polarized along the disk plane. A situation where the disk-scattered radiation is not polarized in a certain spectral band is possible owing to the disk puffing. There can be different orientations of the linear polarization of the disk radiation in different spectral bands.

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On the Scattered Radiation Spectrum of Protoplanetary Disks     

Grinin  V. P.  Tambovtseva  L. V.  Dmitriev  D. V. 《Astronomy Reports》2022,66(4):314-320

Astronomy Reports - The deformation of the photospheric radiation of a young star during scattering in the inner regions of the protoplanetary disk has been studied. The distortion of spectral...  相似文献   

Modulation of circumstellar extinction in a young binary system with a low-mass companion in a noncoplanar orbit     

V. P. Grinin  T. V. Demidova  N. Ya. Sotnikova 《Astronomy Letters》2010,36(11):808-815

We consider a model of cyclic brightness variations in a young star with a low-mass (q = M ₂/M ₁ ≤ 0.1) companion that accretes matter from the remnants of a protostellar cloud (circumbinary disk). We assume that the orbit of the companion is circular and that its plane does not coincide with the disk plane. We have computed grids of hydrodynamic models for such a binary by the SPH method based on which we have investigated the circumstellar extinction variations produced by the streams of matter and density waves excited in the circumbinary disk by the orbital motion of the companion. We show that, depending on the inclination and orientation of the binary’s line of nodes relative to the observer, the brightness of the primary component can undergo various (in shape and depth) oscillations with a period equal to the orbital one. In contrast to the models with coplanar circular orbits, the accretion rate onto the components of a binary with a noncoplanar orbit depends on the orbital phase. The results of our computations can be used to study the cyclic activity of UX Ori stars and young eclipsing binaries with anomalously long eclipses.  相似文献   

Bimodal brightness oscillations in models of young binary systems     

T. V. Demidova  N. Ya. Sotnikova  V. P. Grinin 《Astronomy Letters》2010,36(6):422-429

We consider a model for the cyclic activity of young binary stars that accrete matter from the remnants of a protostellar cloud. If the orbit of such a binary system is inclined at a small angle to the line of sight, then the streams of matter and the density waves excited in the circumbinary disk can screen the primary component of the binary from the observer. To study these phenomena by the SPH (smoothed particle hydrodynamics) method, we have computed grids of hydrodynamic models for binary systems based on which we have constructed the light curves as a function of the orbital phase. The main emphasis is on investigating the properties of the brightness oscillations. Therefore, the model parameters were varied within the following ranges: the component mass ratio q = M ₂: M ₁ = 0.2–0.5 and the eccentricity = 0–0.7. The parameter that defined the binary viscosity was also varied. We adopted optical grain characteristics typical of circumstellar dust. Our computations have shown that bimodal oscillations are excited in binaries with eccentric orbits, provided that the binary components do not differ too much in mass. In this case, the ratios of the periods and amplitudes of the bimodal oscillations and their shape depend strongly on the inclination of the binary plane and its orientation relative to the observer. Our analysis shows that the computed light curves can be used in interpreting the cyclic activity of UX Ori stars.  相似文献