February 2025
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4 Reads
Astronomy Letters
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Publications (258)
February 2025
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3 Reads
UX Orionis stars are the most active young stars; they undergo sporadic fadings of 2 - 4 magnitudes in the V-band, due to variable circumstellar extinction caused by a nearly edge-on star-disc system. The long-lasting monitoring of a number of stars of this type with the Nordic Optical Telescope from 2019 to 2024 has given a rich collection of material of high-resolution (R ~ 25000) spectra obtained during different brightness states of the stars. In this paper, we present the results of observations for UX Ori itself. Until now only one spectrum of high resolution had been obtained for this star during brightness minimum, making it difficult to do a comprehensive analysis. Our aim is to analyse how different spectral lines change during such irregular fading events, when the star is going in and out of eclipses, obscured by dust along the line of sight. For this purpose we provide a comparative analysis of the profiles and equivalent widths of the spectral lines belonging to the different atoms and ions. In addition we compare the results for UX Ori with those made for another target in our sample: RR Tau. Common features of variability are revealed: 1) a strengthening of the H-alpha line relatively to the continuum during eclipses; 2) the appearance of additional emission on the frequencies of photospheric lines (e.g. Fe II, Ca II, Si II). The different behaviour of the spectral lines during fading found for UX Ori and RR Tau may be caused by two effects: a different contribution of the scattered light to the stellar flux during eclipses or a less intense disc wind of UX Ori.
January 2025
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12 Reads
Astronomy and Astrophysics
Context . UX Orionis stars are the most active young stars; they undergo sporadic fadings of 2–4 magnitudes in the V -band, due to variable circumstellar extinction caused by a nearly edge-on star–disc system. The long-lasting monitoring of a number of stars of this type with the Nordic Optical Telescope from 2019 to 2024 has given a rich collection of material of high-resolution (R ∼ 25 000) spectra obtained during different brightness states of the stars. In this paper, we present the results of observations for UX Ori itself. Until now only one spectrum of high resolution had been obtained for this star during brightness minimum, making it difficult to do a comprehensive analysis. Aims . Our aim is to analyse how different spectral lines change during such irregular fading events, when the star is going in and out of eclipses, obscured by dust along the line of sight. Methods . For this purpose we provide a comparative analysis of the profiles and equivalent widths of the spectral lines belonging to the different atoms and ions. In addition we compare the results for UX Ori with those made for another target in our sample: RR Tau. Results . Common features of variability are revealed: (1) a strengthening of the Hα line relatively to the continuum during eclipses; (2) the appearance of additional emission on the frequencies of photospheric lines (e.g. FeII, CaII, SiII). The different behaviour of the spectral lines during fading found for UX Ori and RR Tau may be caused by two effects: a different contribution of the scattered light to the stellar flux during eclipses or a less intense disc wind of UX Ori.
December 2024
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4 Reads
Astronomy Reports
December 2024
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2 Reads
Письма в астрономический журнал Астрономия и космическая астрофизика
Представлены новые результаты фотометрического и спектрального мониторинга WTTS звезды V715 Per, расположенной в молодом скоплении IC 348 и демонстрирующей комплексный характер переменности. Показано, что переменность эквивалентной ширины эмиссионной линии На модулирована с периодом осевого вращения звезды и находится в противофазе с изменениями блеска. Это служит подтверждением ранее предложенной модели фотометрической переменности V715 Per, основанной на переменной околозвездной экстинкции во внутреннем диске на радиусе коротации. По нашим оценкам, радикальная смена характера переменности, произошедшая после 2010 г., с большой вероятностью обусловлена изменениями темпа аккреции в системе. Новые данные фотометрии показали завершение продолжительного ослабления блеска, наблюдавшегося у звезды в период 2017—2023 гг. и вызванного затмением протяженной пылевой структурой во внешних областях диска. Уточненный период малоамплитудной компоненты переменности составил 5.22d и показал стабильность на протяжении всего ряда наблюдений.
October 2024
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1 Read
Астрономический журнал
In this article we analyze the properties of the photometric and spectral variability of the young star V718 Per, a member of the cluster IC 348, in terms of its possible binarity. The most realistic is the model where the main component of the system V718 Per A — with an effective temperature of 5200 K — is periodically shielded by two extended dust periods structures consisting of large particles and moving around the star in resonance with two planets. Their orbital periods are 4.7 years and 213 days. Their ratio with high accuracy is 1:8, and the ratio of the large semi-axes is 1:4. The masses of the planets do not exceed 6 МJup. At the moments of total eclipses of V718 Per A, the radiation of the system is dominated by a colder component with an effective temperature of 4150 ± 100 K, which explains the reddening of the star observed in the brightness minima, as well as its spectral changes during brightness weakening. Speckle interferometric observations performed on the 2.5-m telescope of the CMO of SAI MSU made it possible to estimate the upper limit of the angular distance between the components of the system: 0.1′′, which is equivalent to a projection distance of 30 a.u. The unique feature of this system is that the planes of the planetary orbits practically coincide with the line of sight. Such an orientation of the system is most favorable for measuring fluctuations in the radial velocity of a star caused by the orbital motion of planets, as well as for observing planetary transits along the disk of the main component of the system.
July 2024
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1 Read
Astronomy Letters
July 2024
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3 Reads
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2 Citations
Astronomy Letters
January 2024
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6 Reads
Astronomy Letters
January 2024
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9 Reads
Astronomy Reports
Citations (50)
... Compared to typical accreting protoplanetary disks, the gas accretion rate is low (M M 7 10 yr 12 1 --), as estimated from an empirical magnetospheric accretion model (Potravnov et al. 2017). Optical spectroscopic monitoring shows that the accretion rate is variable without known periodicity and can reach 1 order of magnitude higher during outbursts (Dmitriev et al. 2023). The Galactic motion of RZ Psc calculated with new Gaia DR2 astrometric data suggests a possible membership in the Cas-Tau OB association with an age of 20 3 5 + -Myr (Potravnov et al. 2019). ...
- Citing Article
February 2023
Monthly Notices of the Royal Astronomical Society
... Ho we ver, unlike pre viously de veloped models, our model takes into account adv ectiv e transfer of ionization that can be important in low-density plasma when collisional recombination and ionization processes are slow (see Section 3 ). As it is shown in Dmitriev & Grinin ( 2022 ), this effect can be important at the low accretion rates Ṁ ≤ 10 −9 M yr −1 , like in the case of RZ Psc. ...
- Citing Article
October 2022
Astronomy Letters
... The disc shows asymmetric features such as arms and spirals at least for several thousands years (see the animation associated with Fig. 4 ). The disturbance may evolve into multiple rings after several disc rotations as demonstrated by Demidova & Grinin ( 2022 ). Ho we ver, our model does not include any physical dissipation processes, and long-time evolution is beyond the scope of this paper. ...
- Citing Article
- Full-text available
May 2022
The Astrophysical Journal
... The review [16] is devoted to the scattered radiation of circumstellar protoplanetary disks. In the majority of cases, this contribution to the total optical radiation of young stars is rather small. ...
- Citing Article
- Full-text available
April 2022
... The θ I (I) relation was observed earlier, e.g. in RW Aur A (Dodin et al. . It may result from non-axisymmetric distribution of scattering dust (Grinin et al., , 1994Shulman and Grinin, 2022). However, to substantiate this hypothesis quantitatively, more polarimetric data at different wavelengths are needed. ...
- Citing Article
March 2022
Monthly Notices of the Royal Astronomical Society
... Very seldom are deep eclipses lasting more than a year observed in young stars [23][24][25][26][27]. Their physics apparently differs from the simple model of the CS dust cloud transit across the stellar disk accepted for the UX Ori type stars. ...
- Citing Article
September 2021
Astronomy Reports
... This follows both from observational investigations (Cauley & Johns-Krull 2014, 2015 and from spectroscopic and interferometric modelling of their emission spectra (Garcia Lopez et al. 2015; Caratti o Garatti et al. χ is the airmass, S/N is the measured S/N ratio around 5300 Å, V is the nearest in time V-band photometry and σ V its error, and ∆t gives the time difference between spectroscopy and photometry in fractional days (negative value means photometry was obtained before the spectroscopy). 2015; Kreplin et al. 2018;Tambovtseva et al. 2014Tambovtseva et al. , 2016Tambovtseva et al. , 2020. More information on the current knowledge of Herbig stars (and UXORs) can be found in the recent review by Brittain et al. (2023). ...
- Citing Article
December 2020
Astronomy Reports
... Although simple Keplerian disks are capable of reproducing Brγ spectro-interferometric observations in some HAeBes (Kraus et al. 2012a;Ellerbroek et al. 2015;Mendigutía et al. 2015a), hydrogen emission lines are usually interpreted in terms of magnetically driven accretion or winds (e.g., Muzerolle et al. 2001;Kurosawa & Romanova 2013;Tambovtseva et al. 2014Tambovtseva et al. , 2016Tambovtseva et al. , 2020. However, our sample includes two stars whose strong nUV excess cannot be modelled from MA, and there is a lack of alternative BL models of line emission (Mendigutía 2020, and references therein). ...
- Citing Article
April 2020
Astronomy Reports
... A central compact radio-bright source has been found to be consistent with an outflow from AB Aur (Rodríguez et al. 2014;Rivière-Marichalar et al. 2023;Rota et al. 2024). Grady et al. (1999) identified regular sporadic infall of material onto AB Aur which may be related to evaporating exocomets, and infrared variability of the disk itself has been observed over a broad range of timescales and wavelengths (Shenavrin et al. 2019;Prusti & Mitskevich 1994;Chen & Jura 2003). On larger scales, outer spiral arms extend to at least ∼450 AU (Grady et al. 1999;Fukagawa et al. 2004;Corder et al. 2005;Perrin et al. 2009). ...
- Citing Article
December 2019
Astronomy Reports
... During such events an interesting phenomenon was observed: the change in the position angle of polarization was out of sync with the change in the star brightness [14,21]. Simulation of such events showed [22] that the reason of these anomalies was an obscuration of a noticeable part of the disk with the dust screen. This led to the appearance of vast shadows on the disk whose movement on the disk behind the screen generated changes in the parameters of the disk intrinsic polarization. ...
- Citing Article
October 2019
Astronomy Letters