Identification of lines in the spectrum of the quasar 0237–233

The emission and absorption lines (3716–4290) in the spectrum of the quasar 0237–233 are identified within the framework of the PLS model. The available evidence indicates that it is a helium star. Similarities between the spectral properties of 0237–233 and the star Upsilon Sagittarii are pointed out. Predictions are made for the absorption-line spectrum which falls outside 3716–4290 and also for an expected discontinuity at 2600.     

Re-Evaluation of the Flare–Type II–CME Association

We have re-evaluated the association of type II solar radio bursts with flares and/or coronal mass ejections (CMEs) using the year 2000 solar maximum data. For this, we consider 52 type II events whose associations with flares or CMEs were absent or not clearly identified and reported. These events are classified as follows; group I: 11 type IIs for which there are no reports of GOES X-ray flares and CMEs; group II: 12 type IIs for which there are no reports of GOES X-ray flares; and group III: 29 type IIs for which the flare locations are not reported. By carefully re-examining their association from GOES X-ray and H, Yohkoh SXT and EIT-EUV data, we attempt to answer the following questions: (i) if there really were no X-ray flares associated with the above 23 type IIs of groups I and II; (ii) whether they can be regarded as backside events whose X-ray emission might have been occulted. From this analysis, we have found that two factors, flare background intensity and flare location, play important roles in the complete reports about flare–type II–CME associations. In the above 23 cases, for more than 50% of the cases in total, the X-ray flares were not noticed and reported, because the background intensity of X-ray flux was high. In the remaining cases, the X-ray intensity might be greatly reduced due to occultation. From the H flare data, Yohkoh SXT data and EIT-EUV data, we found that ten cases out of 23 might be frontside events, and the remaining are backside events. While the flare–type II association is found to be nearly 90%, the type II–CME association is roughly around 75%. This analysis might be useful to reduce some ambiguities regarding the association among type IIs, flares and CMEs.     

Sunspot Catalogue of the Observatory of the University of Coimbra (1929 – 1941)

A sunspot catalogue was published by the Coimbra Astronomical Observatory (Portugal), which is now called the Geophysical and Astronomical Observatory of the University of Coimbra, for the period 1929?–?1941. We digitalised data included in that catalogue and provide a machine-readable version. We show the reconstructions for the (total and hemispheric) sunspot number index and sunspot area according to this catalogue and compare it with the sunspot number index (version 2) and the Balmaceda sunspot area series (Balmaceda et al. in J. Geophys. Res.114, A07104, 2009). Moreover, we also compared the Coimbra catalogue with records made at the Royal Greenwich Observatory. The results demonstrate that the historical catalogue compiled by the Coimbra Astronomical Observatory contains reliable sunspot data and can therefore be considered for studies about solar activity.     

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.     

On the Dynamical Foundations of the Lidov–Kozai Theory

The Lidov–Kozai theory developed by each of the authors independently in 1961–1962 is based on qualitative methods of studying the evolution of orbits for the satellite version of the restricted three-body problem (Hill’s problem). At present, this theory is in demand in various fields of science: in the field of planetary research within the Solar system, the field of exoplanetary systems, and the field of high-energy physics in interstellar and intergalactic space. This has prompted me to popularize the ideas that underlie the Lidov–Kozai theory based on the experience of using this theory as an efficient tool for solving various problems related to the study of the secular evolution of the orbits of artificial planetary satellites under the influence of external gravitational perturbations with allowance made for the perturbations due to the polar planetary oblateness.     

Estimating the strength of the nucleus material of comet 67P Churyumov–Gerasimenko

Consideration is given to the estimates for the strength of the consolidated material forming the bulk of the nucleus of comet 67P Churyumov–Gerasimenko and those for the strength of the surface material overlying the consolidated material at the sites of the first and last contact of the Philae lander with the nucleus. The strength of the consolidated material was estimated by analyzing the terrain characteristics of the steep cliffs, where the material is exposed on the surface. Based on these estimates, the tensile strength of the material is in the range from 1.5 to 100 Pa; the shear strength, from ～13 to ?30 Pa; and the compressive strength, from 30 to 150 Pa, possibly up to 1.5 kPa. These are very low strength values. Given the dependence of the measurement results on the size of the measured object, they are similar to those of fresh dry snow at –10°C. The (compressive) strength of the surface material at the site of the first touchdown of Philae on the nucleus is estimated from the measurements of the dynamics of the surface impact by the spacecraft’s legs and the geometry of the impact pits as 1–3 kPa. For comparison with the measurement results for ice-containing materials in terrestrial laboratories, it needs to be taken into account that the rate of deformation by Philae’s legs is four orders of magnitude higher than that in typical terrestrial measurements, leading to a possible overestimation of the strength by roughly an order of magnitude. There was an attemp to put one of the MUPUS sensors into the surface material at the site of the last contact of Philae with the nucleus. Noticeable penetration of the tester probe was not achieved that led to estimation of the minimum compressive strength of the material to be ?4 MPa4 This fairly high strength appears to indicate the presence of highly porous ice with grains “frozen” at contacts.     

Variations of the harmonic components of the X-ray pulse profile of PSR B1509–58

We used the Fourier decomposition technique to investigate the stability of the X-ray pulse profile of a young pulsar PSR B1509–58 by studying the relative amplitudes and phase differences of its harmonic components with respect to the fundamental using data from the Rossi X-Ray Timing Explorer. Like most young rotation powered pulsars, PSR B1509–58 has a high spin down rate. It also has less timing noise, allowing accurate measurement of higher order frequency derivatives which in turn helps in the study of the physics of pulsar spin down. Detailed investigation of pulse profiles over the years will help us establish any possible connection between the timing characteristics and the high energy emission characteristics for this pulsar.Furthermore, the study of pulse profiles of short period X-ray pulsars can also be useful when used as a means of interplanetary navigation. The X-ray pulse profile of this source has been analyzed for 15 yr(1996–2011). The long term average amplitudes of the first, second and third harmonics(and their standard deviation for individual measurements) compared to the fundamental are 36.9%(1.7%), 13.4%(1.9%) and 9.4%(1.8%) respectively. Similarly, the phases of the three harmonics(and standard deviations) with respect to the fundamental are 0.36(0.06), 1.5(0.2) and 2.5(0.3) radian respectively. We do not find any significant variation of the harmonic components of the pulse profile in comparison to the fundamental.     

Variation of the inner disk radius during the onset of the 2010 outburst of MAXI J1659–152

Low mass black hole binaries are generally transient sources and spend most of their time in the quiescent state. It is believed that the inner accretion flow in the quiescent state is in the form of advection dominated accretion flow and the cold outer accretion disk is truncated far away from the central black hole. During the onset of an outburst, the disk gradually extends towards the central black hole.However, the observational evidence for this general picture is indirect at best. Here we present the results of a study performed to understand the variation of the inner disk radius during the early phase of an outburst. We investigated the variation of the inner disk radius during the 2010 outburst of the black hole candidate MAXI J1659-152 using the method of simultaneous spectral fitting. We found that the inner edge of the disk is truncated at a large radius in the beginning of the outburst when the source was in the hard state. We found a systematic decrease in the inner disk radius as the outburst progressed. We also estimated an upper limit on the mass of the black hole to be 8.1 ± 2.9 M within the uncertainty of the distance and inclination angle.     

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.     

Study of the nuclear activity of the Seyfert galaxy NGC 7469 over the period of observations 2008–2014

We present the results of our multicolor UBV RI observations of NGC 7469, a type 1 Seyfert galaxy (SyG 1), in 2008–2014 at the Maidanak Observatory. Analysis of the long-term variability of NGC 7469 for two observing periods, 1990–2007 and 2008–2014, has shown the existence of yet another activity cycle of the slow component in 2009–2014 with an activity maximum in 2011–2012. We have studied the slow variability component in 2009–2014 and constructed the color–color (U ? B), (B ? V) diagrams for the variability maxima and minima of NGC 7469 in various apertures and for the blackbody gas radiation modeling the accretion disk radiation. It can be seen from the color–color diagram that the color of the nuclear part of NGC 7469 becomes bluer at maximum brightness, suggesting a higher temperature of the accretion disk. We have analyzed the X-ray variability of NGC 7469 in 2008 and 2009 in comparison with the activity minimum in 2003. The optical–X ray correlation coefficient in 2008 is close to 0.5. The weak correlation is explained by the influence of an SN 1a explosion in the circumnuclear part of NGC 7469, which manifests itself in the optical band but does not change the pattern of X-ray variability. Comparison of the variability data for 2009 shows an optical–X ray (U band–7–10 keV) correlation with a correlation coefficient of about 0.93. The correlation coefficient and the lag depend on the wavelength in the optical and X-ray bands. The lag between the X-ray and optical fluxes in 2009 is observed to a lesser extent in 2003.     

Physical properties of the particles composing the Martian dust storm of 1971–1972

Infrared spectra obtained from the Mariner 9 spacecraft during the 1971–1972 dust storm are used to derive information on the composition and particle size distribution of the dust and to study the time evolution of the storm. The dust is not composed of pure granite, basalt, basaltic glass, obsidian, quartz, andesite, or montmorillonite. The infrared spectra suggest that the dust is a mixture of materials, dominated by igneous silicates with >62;60% SiO₂, or weathering products such as clay minerals, but the dust could possibly have a significant component of lower SiO₂ materials such as basalt. Substantial quantities of carbonates, nitrates, or carbon suboxide are excluded from the mixture. All infrared, visible, and ultraviolet data on the Martian surface composition seem consistent with a mixture of basalt and clay minerals or high SiO₂ igneous rocks, with a surface patina of oxides of iron. For all candidate compositions, the data are best matched with a size distribution that approximates a differential power law function of slope ?4. This size distribution is quite similar to terrestial size distributions in regions remote from sources of dust. The relative abundance of particles between 1- and 10-μm radius did not change during the Mariner 9 mission; thus suspended particles did not experience Stokes-Cunningham fallout but instead were supported by turbulence with an eddy diffusion coefficient, $\text{K}{}_{\mathrm{<mtext>e</mtext>}}\text{? 7 × 10}{}^6\text{cm}{}^2\text{sec}{}^{\mathrm{?1}}$. The aerosol optical depth, standardized to 0.3-μm wavelength, varied from about 1.5 early in the mission to about 0.2 at Orbit 200.     

Meteorological conditions at the Caucasus Observatory of the SAI MSU from the results of the 2007–2015 campaign

Based on the measurements performed from 2007 to 2015 at the summit of Mount Shatdzhatmaz adjacent to the 2.5-m telescope at the Caucasus Observatory of the SAI MSU, we have determined the statistical characteristics of basic meteorological parameters: the ambient air temperature, the ground wind speed, and the relative humidity. The stability of these parameters over the entire period of our measurements and their variations within an annual cycle have been studied. The median temperature on clear nights is +3.2°C, although there are nights with a temperature below ?15°C. The typical ground wind speed is 3 m s^?1; the probability of a wind stronger than 10 m s^?1 does not exceed 2%. The losses of observing time due to high humidity are maximal in the summer period but, on the whole, are small over a year, less than 10%. We have estimated the absolute water vapor content in the atmosphere, which is especially important for infrared observations. Minimum precipitablewater vapor is observed in December–February; the median value over these months is 5 mm. We additionally provide the wind speeds at various altitudes above the ground (from 1 to 16 km) that we obtained when measuring the optical turbulence. We present the results and technique of our measurements of the annual amount of clear night astronomical time, which is, on average, 1320 h, i.e., 45% of the possible one at the latitude of the observatory. The period from mid-September to mid-March accounts for about 70% of the clear time. A maximum of clear skies is observed in November, when its fraction reaches 60% of the possible astronomical night time.     

Transport Characteristics of the Near-Surface Layer of the Nucleus of Comet 67P/Churyumov–Gerasimenko

Solar System Research - The paper considers the free molecular flow of gas through the dusty porous surface layer of a comet nucleus. The study is based on computer models of generation of a porous...     

Periodic orbits of the generalized Friedmann–Robertson–Walker Hamiltonian systems

The averaging theory of first order is applied to study a generalization of the Friedmann–Robertson–Walker Hamiltonian systems with three parameters. We provide sufficient conditions on the three parameters of the generalized system to guarantee the existence of continuous families of periodic orbits parameterized by the energy, and these families are given up to first order in a small parameter.     

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.     

FUV spectroscopy of the central star of the planetary nebula Sh 2–216

The far-ultraviolet (FUV) spectrum of LS?V +46°21, the central star (CS) of the planetary nebula (PN) Sh?2?216, is strongly contaminated by interstellar absorption and thus, we have to simultaneously model both, the stellar as well as the interstellar spectrum in order to identify strategic metal lines which are only accessible in the FUV wavelength range. These lines are necessary to determine the photospheric parameters reliably. We present results of a NLTE spectral analysis of the FUV spectrum of LS?V+46°21.     

Study of the quality of the Zeiss-1000 telescope optical system using the Shack–Hartmann wavefront sensor

The results of studies of the optics of the 1-m Zeiss-1000 telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) by the Shack–Hartmann (SH) method are presented. Using a Shack–Hartmann wavefront sensor (SH WFS) we have adjusted the telescope optical system by means of shifts and tilts of the secondary mirror. The procedure has significantly reduced the aberrations that appeared during the long-term instrument operation. A new method to investigate the surface quality of the mirrors of the Zeiss-1000 being applied, characteristics close to the diffraction limit are achieved. In general, the entire opto-mechanical telescope system provides an image quality of about 0.5″ at 80%energy level.     

Activity of the Leonid meteor shower in the years 1944–1953

The activity of the Leonid shower in the years 1944–1953 was derived from visual records obtained at the Skalnaté Pleso Observatory, using the zenithal exponent = 1.47 in the reduction factor cos z _R.