Optical and near-infrared photometry, optical spectroscopy, and soft X-ray and UV monitoring of the changing-look active galactic nucleus NGC 2617 show that it continues to have the appearance of a ...type-1 Seyfert galaxy. An optical light curve for 2010–2016 indicates that the change of type probably occurred between 2010 October and 2012 February and was not related to the brightening in 2013. In 2016, NGC 2617 brightened again to a level of activity close to that in 2013 April. We find variations in all passbands and in both the intensities and profiles of the broad Balmer lines. A new displaced emission peak has appeared in Hβ. X-ray variations are well correlated with UV–optical variability and possibly lead by ∼2–3 d. The K band lags the J band by about 21.5 ± 2.5 d and lags the combined B + J filters by ∼25 d. J lags B by about 3 d. This could be because J-band variability arises from the outer part of the accretion disc, while K-band variability comes from thermal re-emission by dust. We propose that spectral-type changes are a result of increasing central luminosity causing sublimation of the innermost dust in the hollow bi-conical outflow. We briefly discuss various other possible reasons that might explain the dramatic changes in NGC 2617.
ABSTRACT
We present optical photometric observations of SN 2018aoq from 2 to 100 d after explosion, and 7 spectra at epochs from 11 to 71 d. The light curves and spectra are typical for SNe II-P. As ...previously reported, SN 2018aoq appears to be of intermediate brightness between subluminous and normal SNe II-P. SN 2018aoq was discovered in Seyfert galaxy NGC 4151, for which the distance is uncertain. We utilized the expanding photosphere method using three sets of filter combinations and velocities derived from the absorption minima of Fe ii lines and obtained a distance of 20.0 ± 1.6 Mpc. The standard candle method applied to SN 2018aoq yields a distance of 16.6 ± 1.1 Mpc. Both values are consistent with the distance measurements for NGC 4151 based on geometric method.
According to spectrophotometric measurements of Jupiter and Saturn obtained in 2014–2017 on an echelle spectrometer equipped with a CCD receiver at the Cassegrain focus of the 2-m telescope of the ...Nasreddin Tusi Shamakhy Astrophysical Observatory of the Azerbaijan National Academy of Sciences (ShAO), weak quadrupole lines of molecular hydrogen of the H
2
(4-0) band in the visible spectral region with a spectral resolution of
R
= 14 000 and
R
= 56 000 were studied. Using the lines of the H
2
(4-0) S(0) and S(1) bands, the pressure values at the levels of their formation, the rotational temperature, the content of molecular hydrogen in the above-cloud atmosphere, the amount of absorbing gas per the average free path of photons between two scattering acts in the cloud layer, and the specific gas content per unit free path in different parts of the disk of Jupiter and Saturn were calculated. It was necessary to monitor the change in the S
4
(2)/S
4
(0) ratio along the disk of Jupiter and Saturn in the spatial and temporal intervals. According to our measurements in 2016, the ratio
W
(0)/
W
(2) = 3.5 ± 0.6 for Jupiter, and
W
(0)/
W
(2) > 2.5 ± 0.4 for Saturn was obtained; in general, the Great Red Spot (GRS) has an average temperature of approximately 124 ± 6K.
The results of spectral observations of NGC 3516 with the 2-m telescope of the Shamakhy Astrophysical Observatory during 2016–2019 are presented. In the first half of 2016, the intensive broad ...component H
was found, which indicates a spectral type change compared to 2014, when the broad component was almost invisible. In the second half of 2016, the broad component H
again was weakened and was practically not observed, remaining weak until the end of 2019. At the end of 2019, the broad component H
strengthened again, and in May 2020 reached a typical level for the high state of the object. During 2016–2020 we observed several changing looks of NGC 3516.
Shamakhy Fiber Echelle Spectrograph Mikailov, Kh. M.; Musaev, F. A.; Alekberov, I. A. ...
Kinematics and physics of celestial bodies,
2020/1, Volume:
36, Issue:
1
Journal Article
Peer reviewed
The high-resolution fiber echelle Cassegrain spectrograph for the 2-m telescope at the Shamakhy Astrophysical Observatory (ShaFES) is described. The optical circuit and the schematic of the suspended ...part of the spectrograph are presented. The spectrograph operates in two modes with a spectral resolution of 27 500 and 55 000 in the 370–850 nm wavelength range. The results of its testing are analyzed. The results and the procedure of test observations are detailed, and the spectrograph itself and ShaFES observational data are compared with similar instruments and the corresponding experimental data. The spectrograph provides an opportunity to measure spectra of 8
m
and 10
m
stars with a signal-to-noise ratio of
S
/
N
= 150–200 at λ = 580 nm with a 1-h exposure and resolution of
R
= 55 000 and 27 500, respectively.
In this work, for planetary nebulae İC 1295, İC 4191, Zanstra temperatures were calculated using the Hβ line of the central stars. Respectively, the temperatures 64252 K and 47663 K were determined. ...The flux in the Hβ radiative line used in the calculations, has been determined from the spectra retrieved from the archive of the European Southern Observatory. Our results have been compared with results of the other authors.
We present the results of our studies of the H
α
line in the spectrum of a UX Ori star (WW Vul) based on our spectroscopic observations performed with the 2-m telescope at the Shamakhi Astrophysical ...Observatory, the National Academy of Sciences of Azerbaijan, in 2006–2010. We have detected variability in all the measured parameters of the H
α
profile both during each observing season and from season to season. A comparative analysis of our data and published studies has led to the conclusion that the regime of outflow with a variable power in the star WW Vul, on the whole, is preserved for almost 40 years (1972–2010) and the accretion of gas from the circumstellar disk onto the stellar surface is occasionally observed. Changes in the regime of variability in the behavior of the H
α
emission line have been revealed in the 2006–2010 observing seasons. In four cases (for July 8, 2006, August 17, 2008, June 13, 2010, and August 2, 2010), we have detected a second emission component in the blue wing of the H
α
emission line.
We present the results of spectral observations of the symbiotic star CH Cyg, carried out at the Cassegrain focus of the 2-m telescope of the ShAO named after N. Tusi, by using the Shamakhy Fiber ...Echelle Spectrograph (ShAFES). The spectra of star CH Cyg were obtained with the spectral resolution of R = 28000, between June and November 2016. We also present the results of the comparative analysis of the brightness curve of the star with the main parameters of Hα and Hβ emission lines. During the observation period, both lines exhibited changing profiles characterized by complex structures, predominantly with double peaks. The ratio of the intensities of the blue and red components was typically IB/IR < 1 for the Hα line and IB/IR ≥ 1 for the Hβ line. A quasi-period of 241 days was found in the variation of the equivalent widths of Hα and Hβ emission lines as well as in the intensities of their components.
The results of spectral observations of the Algol-type binary star δ Lib are presented. The behavior of Hα and Hβ lines in the star’s spectrum during the orbital period phase is described. Based on ...our measurements of the radial velocities of the Hα and Hβ lines and using published data, the radial velocity curves of both components of the δ Lib system were constructed. In some phases of the orbital period, an absorption component was detected in the blue, or red, part of the Hα and Hβ line profiles. The observed Hα and Hβ absorption lines are attributed to the main component of the binary system δ Lib. It is assumed that the appearance of absorption components at these lines is associated either with suspicion of a third component in the system, or at these phases of the Hα and Hβ lines, the primary and secondary components of the δ Lib system are observed simultaneously.
Optical and near-infrared photometry, optical spectroscopy, and soft X-ray and UV monitoring of the changing-look active galactic nucleus NGC 2617 show that it continues to have the ...appearance of a type-1 Seyfert galaxy. An optical light curve for 2010–2017 indicates that the change of type probably occurred between 2010 October and 2012 February and was not related to the brightening in 2013. In 2016 and 2017 NGC 2617 brightened again to a level of activity close to that in 2013 April. However, in 2017 from the end of the March to end of July 2017 it was in very low level and starting to change back to a Seyfert 1.8. We find variations in all passbands and in both the intensities and profiles of the broad Balmer lines. A new displaced emission peak has appeared in Hβ. X-ray variations are well correlated with UV–optical variability and possibly lead by ~2–3 d. The K band lags the J band by about 21.5 ± 2.5 d and lags the combined B + J bands by ~25 d. J lags B by about 3 d. This could be because J-band variability arises predominantly from the outer part of the accretion disc, while K-band variability is dominated by thermal re-emission by dust. We propose that spectral-type changes are a result of increasing central luminosity causing sublimation of the innermost dust in the hollow bi-conical outflow. We briefly discuss various other possible reasons that might explain the dramatic changes in NGC 2617.
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