We present new results of our photometric and spectroscopic monitoring of the WTTS star V715 Per that is located in the young cluster IC 348 and exhibits a complex pattern of variability. We show that the variability of the H α line equivalent width is modulated with the rotation period of the star and is in antiphase with its brightness variations. This serves as a confirmation of the previously proposed model for the photometric variability of V715 Per based on variable circumstellar extinction in the inner disk at the corotation radius. According to our estimates, the radical change in the pattern of variability occurred after 2010 is attributable with a high probability to changes in the rate of accretion in the system. Our new photometric data have shown the end of the long fading of the star observed in the period 2017–2023 and caused by the occultation of an extended dusty structure in the outer disk. The refined period of the low-amplitude variability component is 5.22^d and showed stability over the entire series of observations

In this paper, we have analyzed the properties of the photometric and spectral variability of 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 V718 Per A system—with an effective temperature of 5200 K—is periodically shielded by two extended dust 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 equal to 1 : 8, and the ratio of the large semi-axes is 1 : 4. The masses of the planets have not exceeded 6 M_Jup . At the moments of total eclipses V718 Per A, the radiation of the system has been dominated by a colder component with an effective temperature of 4150 ± 100 K, which has explained the reddening of the star observed in the brightness minima, as well as its spectral changes during brightness weakening. Speckle interferometric observations performed using the 2.5-m telescope of the Sternberg Astronomical Institute have 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 AU. The unique feature of this system has been that the planes of the planetary orbits practically coincide with the line of sight. Such an orientation of the system has been 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.

A near infrared and optical photometric study of Herbig star V517 Cyg has been carried out. Infrared data were obtained in 2003–2017 at the Campo Imperatory Observatory (Italy) with the Pulkovo telescope AZT-24 in Johnson’s \(JHK\) bands. Optical light curves in Johnson \(UBVR\) bands were obtained at the Maidanak observatory. Additional optical photometry from different sources (ASSAS, WISE, and AAVSO) was also used. It was shown that the behavior of V517 Cyg in the near infrared is typical for UX Ori stars. A considerable contribution to the near infrared variability is due to variable extinction along the line of sight, but the disk radiation becomes strong in the \(H\) and \(K\) bands: there is a significant correlation of \(V\) and \(J\) magnitudes (\(r \sim 0.84\)), while \(H\) and \(K\) bands correlates poorly with \(V\) band. The amplitude of variability in \(J\) is quite large (\( \sim {\kern 1pt} {{1.8}^{m}}\)). The deepest minimum (\(\Delta V \sim {{3.6}^{m}}\)) in the \(V\) band demonstrates quasi-periodic variations with an amplitude of \( \sim {\kern 1pt} {{0.8}^{m}}\) and a period of \( \sim {\kern 1pt} 19\) days, the origin of which is still unclear. It is possible that these quasi-periodic variations are related to rotation period of a second companion, a cold T Tauri star. The spectrum V517 Cyg reveals typical for UX Ori stars the double-peaked emission line Hα. The NaI D doublet has inverse P Cyg profiles, indicating intense accretion of gas onto the star. The accretion rate from an equivalent width of the Hα line is \({{\dot {M}}_{{acc}}} = 3.6 \times {{10}^{{ - 8}}}\,{{M}_{ \odot }}\) per year.

Results of a long-term (17 years) photometric monitoring of five T Tau stars in the VRI bands are presented. All the studied objects are members of the young cluster IC 348 and show the UX Ori type variability caused by changes in the circumstellar extinction. Three of them (V712 Per, V716 Per, and V909 Per) are classical T Tau type stars (CTTS) and the other two (V695 Per, V715 Per) are weak-line T Tauri stars (WTTS). Their light curves demonstrate the large diversity. Three of the objects have a combination of two different types of activity: stochastic UX Ori type variability and periodic brightness variations similar to those observed in AA Tau stars. Two of the stars demonstrate only the stochastic brightness variations owing to fluctuations in circumstellar extinction at different characteristic times. The features of the photometric activity of the stars investigated are discussed in detail in this article.

This paper presents the results of the study of long-term photometric activity in the near infrared spectral region of the young Herbig Ae star VX Cas belonging to the family of irregular UX Ori variables. The infrared data were obtained in 2003–2017 at the Campo Imperatore Observatory (Italy) using the Pulkovo telescope AZT-24 in Johnson’s photometric bands $$JHK$$ . Additional optical photometry from various sources was used as well. It was shown that the observed photometric activity of the star in the $$J$$ band and partly in the $$H$$ band was caused mainly by variations in circumstellar extinction in the protoplanetary disk. In a number of episodes, anticorrelation was observed between brightness variations in the optical $$V$$ band and $$H$$ and $$K$$ bands: the brightness in the $$H$$ and $$K$$ bands increased with weakening of the brightness in the $$V$$ band. This indicates that the gas and dust clouds that screened the star from the observer consisted of hot dust and were located near the sublimation zone.

В статье представлены результаты длительного (17 лет) фотометрического мониторинга пяти звезд типа Т Тельца в полосах VRI. Все исследуемые объекты являются членами молодого скопления IC 348 и демонстрируют переменность типа UX Ori, обусловленную изменениями околозвездной экстинкции. Три из них (V712 Per, V716 Per, V909 Per) являются классическими звездами типа Т Тельца, другие две (V695 Per, V715 Per) - звезды типа Т Тельца со слабыми эмиссионными линиями (WTTS). Их кривые блеска демонстрируют большое разнообразие. У трех объектов наблюдается комбинация двух разных типов активности: стохастическая переменность типа UX Ori и периодические колебания блеска, похожие на те, которые наблюдаются у звезд типа AA Tau. У двух звезд наблюдалась лишь переменность блеска, вызванная флуктуациями околозвездной экстинкции на разных характерных временах. В статье детально обсуждаются особенности фотометрической активности исследуемых звезд.

We report the results of spectroscopic and photometric observations of the emission-line object IRAS 07080+0605 carried out in 2004–2021. We found that the object is significantly underluminous for its spectroscopic properties ( T eff = 8500 ± 500 K, log g = 2.0 ± 0.5), if a strong visual attenuation by a factor of ∼43 found through the spectral energy distribution modeling is not taken into account. Visual brightness variations with a stable period of 190 days but a variable amplitude of ∼0.2 mag were found in the ASAS SN data and attributed to variable circumstellar extinction in the dusty disk. We also found that the observed behavior of IRAS 07080+0605 is similar to that of the protoplanetary nebula Red Rectangle. The dusty disk of IRAS 07080+0605 shows the presence of carbonaceous particles (∼10%–20% of the total dust content) and polycyclic aromatic hydrocarbon emission bands. However, IRAS 07080+0605 shows no obvious signs of the refractory element depletion, which is common in post–asymptotic giant branch (AGB) dusty binaries, or of a visual nebula. Absorption-line positions vary with an amplitude of ∼25 km s −1 , suggesting the presence of a secondary component. Spectroscopic monitoring on a timescale from days to months is needed to search for regular variations. We conclude that IRAS 07080+0605 is most likely a binary system with an A-type component on its way toward the post-AGB evolutionary stage, as binarity is capable of explaining most of the observed features.

We present the results of optical and near-IR spectroscopy and multicolor photometry of the emission-line star MWC 645, which exhibits the B[e] phenomenon. The presence of positionally variable absorption lines of a cool star detected for the first time indicates that the object is a binary system. Using a combination of the photometric and spectroscopic data as well as the Gaia EDR3 distance (D = 6.5 ± 0.9 kpc), we disentangled the components’ contributions and estimated their surface temperatures and luminosities (18, 000 ± 2000 K and 4250 ± 250 K, log L/L ⊙ = 4.0 ± 0.5 and 3.1 ± 0.3 for the hot and cool components, respectively). Quasi-cyclic short-period (months) and long-period (∼4 yr) photometric variations were detected in both optical and near-IR regions, and are most likely due to variable circumstellar extinction. Our analysis suggests that MWC 645 is a member of the FS CMa group. The object’s properties can be described by an evolutionary model of a close binary system that currently undergoes a nonconservative mass transfer between intermediate-mass stars (e.g., 7 M ⊙ + 2.8 M ⊙).

In this contribution, we achieve the primary goal of the active galactic nucleus (AGN) STORM campaign by recovering velocity–delay maps for the prominent broad emission lines (Ly α , C iv , He ii , and H β ) in the spectrum of NGC 5548. These are the most detailed velocity–delay maps ever obtained for an AGN, providing unprecedented information on the geometry, ionization structure, and kinematics of the broad-line region. Virial envelopes enclosing the emission-line responses show that the reverberating gas is bound to the black hole. A stratified ionization structure is evident. The He ii response inside 5–10 lt-day has a broad single-peaked velocity profile. The Ly α , C iv , and H β responses extend from inside 2 to outside 20 lt-day, with double peaks at ±2500 km s −1 in the 10–20 lt-day delay range. An incomplete ellipse in the velocity–delay plane is evident in H β . We interpret the maps in terms of a Keplerian disk with a well-defined outer rim at R = 20 lt-day. The far-side response is weaker than that from the near side. The line-center delay τ = ( R / c ) ( 1 − sin i ) ≈ 5 days gives the inclination i ≈ 45°. The inferred black hole mass is M BH ≈ 7 × 10 7 M ⊙ . In addition to reverberations, the fit residuals confirm that emission-line fluxes are depressed during the “BLR Holiday” identified in previous work. Moreover, a helical “Barber-Pole” pattern, with stripes moving from red to blue across the C iv and Ly α line profiles, suggests azimuthal structure rotating with a 2 yr period that may represent precession or orbital motion of inner-disk structures casting shadows on the emission-line region farther out.

The quasar 3C 454.3 is a blazar known for its rapid and violent outbursts seen across the electromagnetic spectrum. Using γ -ray, X-ray, multiband optical, and very-long-baseline interferometric data we investigate the nature of two such events that occurred in 2013 and 2014 accompanied by strong variations in optical polarization, including a ∼230° electric vector position angle (EVPA) rotation. Our results suggest that a single disturbance was responsible for both flaring events. We interpret the disturbance as a shock propagating down the jet. Under this interpretation the 2013 flare originated most likely due to changes in the viewing angle caused by perhaps a bent or helical trajectory of the shock upstream of the radio core. The 2014 flare and optical polarization behavior are the result of the shock exiting the 43 GHz radio core, suggesting that shock crossings are one of the possible mechanisms for EVPA rotations.

We present geometric and dynamical modeling of the broad line region (BLR) for the multi-wavelength reverberation mapping campaign focused on NGC 5548 in 2014. The data set includes photometric and spectroscopic monitoring in the optical and ultraviolet, covering the H beta, Civ, and Ly alpha broad emission lines. We find an extended disk-like H beta BLR with a mixture of near-circular and outflowing gas trajectories, while the Civand Ly alpha BLRs are much less extended and resemble shell-like structures. There is clear radial structure in the BLR, with Civand Ly alpha emission arising at smaller radii than the H beta emission. Using the three lines, we make three independent black hole mass measurements, all of which are consistent. Combining these results gives a joint inference of log(10) (M-BH/M-circle dot) = 7.64(-0.18)(+0.21). We examine the effect of using the V band instead of the UV continuum light curve on the results and find a size difference that is consistent with the measured UV-optical time lag, but the other structural and kinematic parameters remain unchanged, suggesting that theVband is a suitable proxy for the ionizing continuum when exploring the BLR structure and kinematics. Finally, we compare the H beta results to similar models of data obtained in 2008 when the active galactic nucleus was at a lower luminosity state. We find that the size of the emitting region increased during this time period, but the geometry and black hole mass remained unchanged, which confirms that the BLR kinematics suitably gauge the gravitational field of the central black hole.

ABSTRACT The object 4C 71.07 is a high-redshift blazar whose spectral energy distribution shows a prominent big blue bump and a strong Compton dominance. We present the results of a 2-yr multiwavelength campaign led by the Whole Earth Blazar Telescope (WEBT) to study both the quasar core and the beamed jet of this source. The WEBT data are complemented by ultraviolet and X-ray data from Swift, and by γ-ray data by Fermi. The big blue bump is modelled by using optical and near-infrared mean spectra obtained during the campaign, together with optical and ultraviolet quasar templates. We give prescriptions to correct the source photometry in the various bands for the thermal contribution, in order to derive the non-thermal jet flux. The role of the intergalactic medium absorption is analysed in both the ultraviolet and X-ray bands. We provide opacity values to deabsorb ultraviolet data, and derive a best-guess value for the hydrogen column density of $N_{\rm H}^{\rm best}=6.3 \times 10^{20} \rm \, cm^{-2}$ through the analysis of X-ray spectra. We estimate the disc and jet bolometric luminosities, accretion rate, and black hole mass. Light curves do not show persistent correlations among flux changes at different frequencies. We study the polarimetric behaviour and find no correlation between polarization degree and flux, even when correcting for the dilution effect of the big blue bump. Similarly, wide rotations of the electric vector polarization angle do not seem to be connected with the source activity.

Context. The flat-spectrum radio quasar 4C +71.07 is a high-redshift (z = 2.172), γ-loud blazar whose optical emission is dominated by thermal radiation from the accretion disc. Aims. 4C +71.07 has been detected in outburst twice by the AGILE γ-ray satellite during the period from the end of October to mid-November 2015, when it reached a γ-ray flux of the order of F(E > 100 MeV)=(1.2 ± 0.3)×10−6 photons cm−2 s−1 and F(E > 100 MeV)=(3.1 ± 0.6)×10−6 photons cm−2 s−1, respectively, allowing us to investigate the properties of the jet and the emission region. Methods. We investigated its spectral energy distribution by means of almost-simultaneous observations covering the cm, mm, near-infrared, optical, ultraviolet, X-ray, and γ-ray energy bands obtained by the GASP-WEBT Consortium and the Swift, AGILE, and Fermi satellites. Results. The spectral energy distribution of the second γ-ray flare (whose energy coverage is more dense) can be modelled by means of a one-zone leptonic model, yielding a total jet power of about 4 × 1047 erg s−1. Conclusions. During the most prominent γ-ray flaring period our model is consistent with a dissipation region within the broad-line region. Moreover, this class of high-redshift, flat-spectrum radio quasars with high-mass black holes might be good targets for future γ-ray satellites such as e-ASTROGAM.

ABSTRACT We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013–2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz data from the Atacama Large Millimeter Array, near-infrared data from the Rapid Eye Monitor telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi (γ-rays) satellites to study flux and spectral variability and the correlation between flux changes at different wavelengths. Unprecedented γ-ray flaring activity was observed during 2016 November–2017 February, with four major outbursts. A peak flux of (2158 ± 63) × 10−8 ph cm−2 s−1, corresponding to a luminosity of (2.2 ± 0.1) × 1050 erg s−1, was reached on 2016 December 28. These four γ-ray outbursts have corresponding events in the near-infrared, optical, and UV bands, with the peaks observed at the same time. A general agreement between X-ray and γ-ray activity is found. The γ-ray flux variations show a general, strong correlation with the optical ones with no time lag between the two bands and a comparable variability amplitude. This γ-ray/optical relationship is in agreement with the geometrical model that has successfully explained the low-energy flux and spectral behaviour, suggesting that the long-term flux variations are mainly due to changes in the Doppler factor produced by variations of the viewing angle of the emitting regions. The difference in behaviour between radio and higher energy emission would be ascribed to different viewing angles of the jet regions producing their emission.

The results of multicolor photometric and polarization observations of the blazar 4C 38.41 (Q 1633+382) performed at St. Petersburg State University, the Pulkovo Astronomical Observatory of the Russian Academy of Sciences, Boston University, and Steward Observatory in 2006–2017 are analyzed. Separate variable sources responsible for the observed activity are distinguished, whose power-lawspectra and high degree of polarization confirm their synchrotron nature. The observed color variability of the object (redder when brighter) can be explained by an increase in the contribution to the total emission of a red component with variable flux and a constant relative spectral energy distribution. A close correlation between the optical and gamma-ray light curves is identified, suggesting the same location of the variable sources responsible for the radiation in these bands.

We report the results of spectroscopic and photometric observations of the emission-line object AS 386. For the first time we found that it exhibits the B[e] phenomenon and fits the definition of an FS CMa type object. The optical spectrum shows the presence of a B-type star with the following properties: T eff = 11,000 ± 500 K, log L / L ⊙ = 3.7 ± 0.3, a mass of 7 ± 1 M ⊙ , and a distance D = 2.4 ± 0.3 kpc from the Sun. We detected regular radial velocity variations of both absorption and emission lines with the following orbital parameters: P orb =131.27 ± 0.09 days, semiamplitude K 1 = 51.7 ± 3.0 km s −1 , systemic radial velocity γ = −31.8 ± 2.6 km s −1 , and a mass function of f ( m ) = 1.9 ± 0.3 M ⊙ . AS 386 exhibits irregular variations of the optical brightness ( V = 10.92 ± 0.05 mag), while the near-IR brightness varies up to ∼0.3 mag following the spectroscopic period. We explain this behavior by a variable illumination of the dusty disk inner rim by the B-type component. Doppler tomography based on the orbital variations of emission-line profiles shows that the material is distributed near the B-type component and in a circumbinary disk. We conclude that the system has undergone a strong mass transfer that created the circumstellar material and increased the B-type component mass. The absence of any traces of a secondary component, whose mass should be ≥7 M ⊙ , suggests that it is most likely a black hole.

The results of many-year photometric observations of the weak-line T Tauri star V715 Per in the optical ( V RI ) and infrared ( JHK ) photometric bands are presented. The period of the star’s lowamplitude brightness variations in the V RI bands detected earlier, 5.23d, is confirmed. This period persists during the entire 14-year time interval of the observations, but its amplitude varies with time. The same period was found in the variations of JHK infrared fluxes, with the brightness variations in the two ranges being almost synchronous. The most probable origin of these variations is periodic eclipses of the star by its own disk, perturbed by its interaction with the magnetosphere (AA Tau-type variations). In addition to the periodic brightness variations, the star also displayed sporadic Algol-like minima characteristic of UX Ori stars during several years (2005–2011). The amplitude of these variations increasedmonotonically, reaching approximately 1 m in the V band by the end of 2010, after which the deep fadings ended. During this entire time interval, the amplitude of the periodic variations was observed to decrease. After 2011, the periodic component began to become stronger again. These changes of the photometric activity of V715 Per can be explained by an increasing rate of gas accretion onto the star, decreasing the radius of warped regions of the disk and leading to accompanying Algol-like fadings. This model assumes a low inclination of the circumstellar disk in V715 Per to the line of sight.