Infrared variability of the nucleus of the Seyfert galaxy NGC 1068 in 1998–2004

Our 8-year-long JHKLM photometry of the Seyfert galaxy NGC 1068 has confirmed its IR variability. The amplitudes of the brightness variations in the J (1.25 μm) and K (2.2 μm) bands are within 0 _. ^m 15 and 0 _. ^m 3, respectively, and exceed the observational errors by more than a factor of 5. The nucleus of NGC 1068 is a variable source and can be at different phases of activity. The brightness of the galaxy in all bands except J decreased from 1998 until 2004. In this period, there was a tendency for the J brightness to increase. The variable source in NGC 1068 is a complex structured object. At least two sources radiate in the wavelength range 1.25–5 μm: a hot source whose radiation shows up in the range 1.25–1.65 μm and a cold source radiating at long wavelengths (2.2–5 μm). The color temperature of the hot source increased from 2300 K (the beginning of our observations) to ∼2700 K (the end of our observations). In contrast, the temperature of the cold source decreased by several tens of degrees (in the temperature range 800–900 K). The IR brightness and color variations observed in 1998–2004 are attributable to the dispersal of the dust envelope that formed around the galactic nucleus some 30 years ago and reached its maximum density in 1994–1995. Our analysis of the spectral energy distributions for the galaxy has shown that the observed radiation in the range 1.25–5 μm can be represented as the sum of radiations from two blackbody sources. For the first period of our observations (JD 2451400), the temperatures of the hot and cold sources are ∼3100 and 760 K, respectively. For the second period (JD 2453230), they are ∼3200 and 720 K, respectively. The hot source is relatively compact; it is smaller in size than the cold source by several tens of times. The mean sizes of the hot and cold sources are ∼2.35 × 10¹⁶ and ∼7.8 × 10¹⁷ cm, respectively. The total mean luminosity of the two sources did not change between the beginning and the end of our observations. The optical depth of the dust envelope averaged over the spectrum of the hot source is τ ∼ 1.5. In 2004, the state of the dust envelope almost returned to its 1974 level, i.e., the dust envelope formation and dispersal cycle was ∼11 000 days (∼30 yr). Original Russian Text ? O.G. Taranova, V.I. Shenavrin, 2006, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 7, pp. 489–496.     

The γ-ray emission from the Seyfert galaxy NGC 4151

Light curves at X-ray, ultraviolet, optical and infrared wavelengths of NGC 4151 over the period 1977–1980 are presented together with a summary of the large amount of observational data relating to this Seyfert galaxy. Intensity variations in different wavebands are discussed and compared with recent low energy -ray observations of this object. The positive measurement of gamma-radiation in May 1977 is shown to have been characterised by a high optical state and a possible infrared maximum. The data presented are compared with the predictions of some emission mechanisms, which have been proposed to account for the gamma-radiation. In particular, a synchrotron self-Compton model, which relates the infrared/optical emission to the X-ray/low energy -ray emission is discussed.     

Analysis of the activity of the blazar BL Lacertae over the period 1998–2011

In 1998–2011 the blazar (active galactic nucleus) BL Lacertae was observed at Crimean Astrophysical Observatory (CrAO) with the second-generation GT-48 Cherenkov telescope at energies >1 TeV with a total significance of 11.8σ. More than 20 flares and a fourfold change in yearly mean fluxes (>1 TeV) were recorded. The optical (B band) data obtained at CrAO and the TeV data are shown to correlate in some time intervals. The optical data are also compared with the X-ray RXTE/ASM (2–10 keV) data. In addition, the data from GT-48 are compared with the gamma-ray fluxes recorded by the Fermi LAT space telescope (0.1–300 GeV). The 2009 flare at TeV and Fermi energies has been studied. As a result, it has been found that as the activity rises the increase in flux at high energies exceeds its increase at low energies. This conclusion may be related to the conversion mechanism of particle acceleration. This is consistent with the results of studies for a similar object, 1ES 1426+428.     

Optical variability of NGC 7469 in 1967–1987

Within the framework of a five-year campaign of coordinated multifrequency observations of the 3 Tauri star RU Lupi, we present results obtained in X-ray, UV, optical, and IR spectral regions. In five cases, simultaneous data from UV to IR were collected. Data analysis shows a large variability at different wavelengths both in the continuum and lines, stronger in the UV and weaker in the IR. Correlations among variations in the UV and optical continua have been found. Moreover flare-like events (FLEs), probably due to strong activity in the surface layers of the star and burst phenomena on large scale, were detected. No forbidden coronal lines were detected in UV and optical regions with IUE and ESO 1.4m CAT telescope, respectively. This means either the used instruments have not enough sensitivity to detect the predicted forbidden lines, or the low X-ray detected intensity — with ASTRON satellite (2–25 keV) — is due to the absorption of the X-rays in the circumstellar envelope. In this paper we will discuss these results within the framework of the current models.Based on observations with IUE satellite (VILSPA) and ESO telescopes.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain     

On the Hβ, [OIII] lines and continuum variability character in the nucleus of Seyfert galaxy NGC 1275

The radiation fluxes of the NGC 1275 galaxy central region are being observed on the 1.25-m telescope, using a scanning spectrophotometer with the entrance aperture 10″ in three Δλ=80 Å spectral regions: Hβ, 4959+5007 Å [OIII] and continuum. There were 35 nights of observations during 1982–1987. With the time resolution of half an hour 379 measurements were obtained in each spectral region. The analysis of these results shows:

1. The standard deviations of measurements in each spectral region 2–3 times exceed the errors of observations.
2. The radiation flux distribution resembles to normal one only for Hβ line.
3. Two-humps forms of continuum flux distribution curve is like that of radio emission in 8 mm and 2.6 cm wavelengths.
4. Various forms of fluxes distribution curves of Hβ and [OIII] lines permit us to suppose that the location of these lines emission regions near the sources of excitation are different.

     

Diurnal anisotropy of cosmic rays during intensive solar activity for the period 2001–2014

The diurnal variation of cosmic ray intensity, based on the records of two neutron monitor stations at Athens (Greece) and Oulu (Finland) for the time period 2001 to 2014, is studied. This period covers the maximum and the descending phase of the solar cycle 23, the minimum of the solar cycles 23/24 and the ascending phase of the solar cycle 24.These two stations differ in their geographic latitude and magnetic threshold rigidity. The amplitude and phase of the diurnal anisotropy vectors have been calculated on annual and monthly basis.From our analysis it is resulted that there is a different behaviour in the characteristics of the diurnal anisotropy during the different phases of the solar cycle, depended on the solar magnetic field polarity, but also during extreme events of solar activity, such as Ground Level Enhancements and cosmic ray events, such as Forbush decreases and magnetospheric events. These results may be useful to Space Weather forecasting and especially to Biomagnetic studies.     

Photoelectric and spectroscopic observations of the binary star VV8=V471 Per over the period 1971–2007

We present our photoelectric observations of the binary star VV8=V471 Per over the period 1971–2007. A long-term photometric variability with a period of about 17 yr in the V and B bands has been confirmed. A systematic rise in brightness was recorded in the U band, suggesting that the gas ionization increases in the binary system. Our spectroscopic observations from 1995 to 2007 have shown that the emission line fluxes, on average, did not change compared to the data of other authors obtained in the previous decades. We have shown that the cool giant is a G5III star and is probably enriched with nucleosynthesis products from the evolved former primary component of the binary. We provide arguments for the hypothesis that the hot component in V471 Per is the massive nucleus of a young planetary nebula that rapidly evolved to a temperature of 65 000–75 000 K, while the surrounding nebula is very dense and optically thick and has not yet been entirely ionized.     

The saturation of the cosmic diffuse γ-ray background by the Seyfert galaxy component

The nature of the diffuse cosmic background in the low -ray energy range has been widely discussed but not definitively solved. Unresolved active galaxies have become good candidates for its origin ever since they have been identified as -ray emitting objects. In particular, the summed contribution of Seyfert galaxies is expected to be dominant to such an extent that a straight forward calculation, based on their volume emissivity, predicts a considerable excess above the observed level of the isotropic background flux. In this letter we explore different ways to reconcile the observational data on these active galactic nuclei with the measured intensity of the cosmic diffuse -radiation.     

Study of the optical variability of T Tau in the period 1962–2003

We present the results of our long-term U BV R observations of the star T Tauri performed at Mt. Maidanak Observatory from 1986 until 2003. These data, together with previous photoelectric observations of other authors, suggest that the long-term variations of the light curve are not periodic, but have a cycle with a time scale of 6–9 yr. The light curve also exhibits slower variations with time scales of ～30–40 yr. We confirm the existence of periodic brightness variations with a period of \(P = 2\mathop .\limits^d 798\) over many years; this process is peculiar in that the phase and shape of the phase curve change from season to season. We analyze the color behavior of the star. We found evidence of a strong flare occurred on October 5, 1999, when the brightness of the star reached \(9\mathop .\limits^m 22\). This is the strongest flare recorded during its photoelectric observations.     

Optical spectra of supernova remnant candidates in the Sculptor Group galaxy NGC 300

We present moderate-resolution (<5 Å) long-slit optical spectra of 51 nebular objects in the nearby Sculptor Group galaxy NGC 300 obtained with the 2.3 meter Advanced Technology Telescope at Siding Spring Observatory, Australia. Adopting the criterion of [S?ii]_Total:Hα≥0.4 to confirm supernova remnants (SNRs) from optical spectra, we find that of 28 objects previously proposed as SNRs from optical observations, 22 meet this criterion with six showing [S?ii]_Total:Hα of less than 0.4. Of 27 objects suggested as SNRs from radio data, four are associated with the 28 previously proposed SNRs. Of these four, three (included in the 22 above) meet the criterion. In all, 22 of the 51 nebular objects meet the [S ii]_Total:Hα criterion as SNRs while the nature of the remaining 29 objects remains undetermined by these observations.     

A Kinematical Study of the NGC 7538 IRS 1 Region

We present high angular resolution images of both NH3(1,1)and (2,2) lines toward NGC 7538 IRS 1.The density and velocity-position plots have been used to study the interaction among the outflows,winds and their environment.For the first time we have found an expanding half-shell of molecular gas around the HⅡ region associated with IRS 1,which may be produced by the interaction of the bipolar outflows and the winds originating in IRS 1-3,and optical HⅡ region NGC 7538 with ambient molecular gas.     

The annual period of the Earth’s seismic activity for 1964–2007

The catalog of the United States National Earthquake Information Center (NEIC, 2007) was used for a Fourier analysis of planetary seismic activity from 1964 to 2007 (401219 earthquakes with M ≥ 3 and hypocenter depths H ≥ 1 km) for the Northern Hemisphere (248291 events) and for the Southern Hemisphere (152928 events). The annual periodicity of weak earthquakes (M < 5.0) was verified with a high degree of reliability. All regularities (depending on the geographic latitude, hypocenter depths, and north-south asymmetry) revealed earlier (in 1964–1990) for this period are shown to exist for the period of 1964–2007.     

A Study of the Star-forming Dwarf Galaxy NGC 855 with Spitzer

We present a study of the dwarf elliptical galaxy NGC 855 using the narrow-band Hα and Spitzer data. Both the Hα and Spitzer IRAC images confirm star-forming activity in the center of NGC 855. We obtained a star formation rate (SFR) of 0.022 and 0.025M◎yr-1,respectively,from the Spitzer IRAC 8.0μm and MIPS 24μm emission data. The HI observa-tion suggests that the star-forming activity might be triggered by a minor merger. We also find that there is a distinct IR emission region in 5.8 and 8.0μm bands,located at about 10 away from the nucleus of NGC 855. Given the strong 8.0μm but faint Hα emission,we expect that it is a heavily obscured star-forming region,which needs to be confirmed by further optical spectroscopic observations.     

A Study of the Star-forming Dwarf Galaxy NGC 855 with Spitzer

We present a study of the dwarf elliptical galaxy NGC 855 using the narrow-band Hα and Spitzer data. Both the Hα and Spitzer IRAC images confirm star-forming activity in the center of NGC 855. We obtained a star formation rate （SFR） of 0.022 and 0.025Mo yr^-1, respectively, from the Spitzer IRAC 8.0 μm and MIPS 24 #m emission data. The HI observation suggests that the star-forming activity might be triggered by a minor merger. We also find that there is a distinct IR emission region in 5.8 and 8.0 μm bands, located at about 10＂ away from the nucleus of NGC 855. Given the strong 8.0 μm but faint Hα emission, we expect that it is a heavily obscured star-forming region, which needs to be confirmed by further optical spectroscopic observations.     

On the latitude migration of polar faculae in the solar activity cycle period: 1970–1978

Coordinates of polar faculae have been measured and processed using daily photoheliograms of the Kislovodsk Station of the Pulkovo observatory with the final goal of studying their latitude distribution during the solar cycles 20–21. The results obtained are as follows:

1. The first polar faculae emerge immediately after the polarity inversion of the solar magnetic field at the latitudes from 40° to 70° with the average ?-55°.
2. The zone of the emergence of polar faculae migrates poleward during the period between the neighbouring polarity inversions of the solar magnetic field. This migration is about 20° for 8 years, which corresponds to a velocity of 0.5 m s^-1.
3. The maximum number of polar faculae was reached at the activity minimum (1975–1976).
4. The last polar faculae were observed in the second half of 1978 at the latitudes from 70° to 80°.

     

The phenomenon of the galaxy NGC 6286: A forming polar ring or a superwind?

We present our observations of the pair of interacting galaxies NGC 6285/86 carried out with the 6-m Special Astrophysical Observatory (SAO) telescope using 1D and 2D spectroscopy. The observations of NGC 6286 with a long-slit spectrograph (UAGS) near the Hα line revealed the rotation of the gaseous disk around an axis offset by 5″–7″ from the photometric center and a luminous gas at a distance up to 9 kpc in a direction perpendicular to the galactic plane. Using a multipupil fiber spectrograph (MPFS), we constructed the velocity fields of the stellar and gaseous components in the central region of this galaxy, which proved to be similar. The close radial velocities of the pair and the wide (5′×5′) field of view of the scanning Fabry-Perot interferometer (IFP) allowed us to simultaneously obtain images in the Hα and [N II]λ6583 lines and in the continuum, as well as to construct the radial velocity fields and to map the distribution of the [N II]λ6583/Hα ratio for both galaxies. Based on all these data, we studied the gas kinematics in the galaxies, constructed their rotation curves, and estimated their masses (2 × 10¹¹M_⊙ for NGC 6286 and 1.2 × 10¹⁰M_⊙ for NGC 6285). We found no evidence of gas rotation around the major axis of NGC 6286, which argues against the assumption that this galaxy has a forming polar ring. The IFP observations revealed an emission nebula around this galaxy with a structure characteristic of superwind galaxies. The large [N II]λ6583/Hα ratio, which suggests the collisional excitation of its emission, and the high infrared luminosity are additional arguments for the hypothesis of a superwind in the galaxy NGC 6286. A close encounter between the two galaxies was probably responsible for the starburst and the bipolar outflow of hot gas from the central region of the disk.     

A research of the Orionid meteor shower by television observations in 2006–2008

The results of observations of the Orionid meteor shower are given in the period from 2006 to 2008. Observations were carried out using a highly sensitive camera FAVOR (FAst Variability Optical Registrator) a limiting magnitude of above +11.0^m (for stars) and a field of view of 18° × 20°. Over the period of the shower from October 2 to November 7, 2006–2008, there were 3713 meteors. 449 of these meteors were associated with the Orionid meteor shower. The distributions of Orionid meteors by the stellar magnitude is presented. It turned out that most of meteors (65%) of this shower have a brightness of +5.0^m-+7.0^m. On each night of observation the index of meteor activity was calculated for Orionids.     

Correlation of near-infrared and optical variability of NGC 4151 in 2008–2013

We investigate the correlation between infrared (JHKL) and optical (B) fluxes of the variable nucleus of the Seyfert galaxy NGC4151 using partially published data for the last 6 years (2008–2013). We find that the lag of flux in all the infrared bands is the same, 40±6 days, to within the measurement accuracy. Variability in the J and K bands is not quite simultaneous, perhaps due to the differing contributions of the accretion disk in these bands. The lag found for the K band compared with the B band is not significantly different from earlier values obtained for the period 2000–2007. However, finding approximately the same lags in all IR bands for 2008–2013 differs from previous results at earlier epochs when the lag increased with increasing wavelength. Examples of almost the same lag in different IR bands are known for some other active nuclei. In the case of NGC 4151 it appears that the relative lags between the IR bands may be different in different years. The available data, unfortunately, do not allow us to investigate a possible change in the lags during the test interval. We discuss our results in the framework of the standard model where the variable infrared radiation is mainly due to thermal re-emission from the part of the dusty torus closest to the central source. There is also a contribution of some IR emission from the accretion disk, and this contribution increases with decreasing wavelength.