Spectroscopic study of the envelopes of the novae V2467 Cyg and V2491 Cyg

Spectrophotometric observations are used to study the envelopes of the FeII nova V2467 Cyg and the HeN nova V2491 Cyg. The abundances of several elements in the nova envelopes and the envelope masses are estimated. The nitrogen mass abundance in the V2467 Cyg envelope is higher than the solar value by a factor of 186 and the oxygen abundance by the factor of 10. The nitrogen abundance in the envelope of V2491 Cyg exceeds the solar value by a factor of 56, the oxygen abundance by a factor of 12, and the neon abundance by a factor of 8. The masses of the envelopes were estimated to be 8.5×10^?5 M _⊙ for V2467 Cyg and 1.5×10^?5 M _⊙ for V2491 Cyg. These envelope elemental abundances and masses are in good agreement with those of low-mass CO white dwarfs (0.8 M _⊙) and ONe white dwarfs (1.15 M _⊙).     

Search for spatial and spectral fluctuations of the cosmic microwave background radiation using the RATAN-600 radio telescope

We report the results of a search for spatial and spectral fluctuations of the cosmic microwave background in the region of the North celestial pole carried out at 6.2 cm using the RATAN-600 radio telescope in 1999–2000. The spatial spectrum is flat and has no features exceeding ΔT/T =10^?3 in a ～1 MHz frequency band for spatial periods from 0.5′ to 16′. If this estimate is adopted as an upper limit for emission associated with the first rotational transition of primordial LiH at z=90.7, we obtain an upper limit for the LiH abundance of about 3×10^?14 for protocluster masses of about 10¹³ M _⊙.     

Multifrequency studies of massive cores with complex spatial and kinematic structures

Five regions of massive-star formation have been observed in various molecular lines in the frequency range～85?89 GHz. The studied regions comprise dense cores, which host young stellar objects. The physical parameters of the cores are estimated, including the kinetic temperatures (～20?40 K), the sizes of the emitting regions (～0.1?0.6 pc), and the virial masses (～40?500 M_⊙). The column densities and abundances of various molecules are calculated assuming Local Thermodynamical Equilibrium(LTE). The core in 99.982+4.17, which is associated with the weakest IRAS source, is characterized by reduced molecular abundances. The molecular line widths decrease with increasing distance from the core centers (b). For b ? 0.1 pc, the dependences ΔV (b) are close to power laws (∝b^?p), where p varies from ~0.2 to ~0.5, depending on the object. In four cores, the asymmetries of the optically thick HCN(1–0) and HCO⁺(1–0) lines indicates systematicmotions along the line of sight: collapse in two cores and expansion in two others. Approximate estimates of the accretion rates in the collapsing cores indicate that the forming stars have masses exceeding the solar mass.     

The evolutionary status of ultraluminous X-ray sources

We analyze models for quasi-stationary, ultraluminous X-ray sources (ULXs) with luminosities 10³⁸–10⁴⁰ erg/s exceeding the Eddington limit for a ～1.4M_⊙ neutron star. With the exception of relatively rare stationary ULXs that are associated with supernova remnants or background quasars, most ULXs are close binary systems containing a massive stellar black hole (BH) that accretes matter donated by a stellar companion. To explain the observed luminosities of ～10⁴⁰ erg/s, the mass of the BH must be ～40M_⊙ if the accreted matter is helium and ～60M_⊙ if the accreted matter has the solar chemical composition. We consider donors in the form of main-sequence stars, red giants, red supergiants, degenerate helium dwarfs, heavy disks that are the remnants of disrupted degenerate dwarfs, helium nondegenerate stars, and Wolf-Rayet stars. The most common ULXs in galaxies with active star formation are BHs with Roche-lobe-filling main-sequence companions with masses ～7M_⊙ or close Wolf-Rayet companions, which support the required mass-exchange rate via their strong stellar winds. The most probable candidate ULXs in old galaxies are BHs surrounded by massive disks and close binaries containing a BH and degenerate helium-dwarf, red-giant, or red-supergiant donor.     

Low-energy 3He and 4He ions in interplanetary space during quiet periods of the 23rd solar cycle

Data from the ULEIS instrument aboard the ACE spacecraft are used to study the energy spectra of ³He and ⁴He ions produced during periods of the quiet Sun in the 23rd solar cycle in the energy range ～0.08–2 MeV/nucleon. Differences in the spectra and ³He/⁴He relative abundances for three groups of quiet periods dominated by different sources of ions are demonstrated: weak impulsive solar flares, particles of the solar corona, and solar wind particles accelerated to energies of several MeV/nucleon.     

Evolution of stars with high metallicities

We have calculated evolutionary tracks for stars with high abundances of heavy elements. An abundance increase from the solar level (～0.02) to 0.1 (for ΔY/ΔZ=0–2.4), which corresponds to the central regions of the disk components of giant galaxies, shifts the main sequence towards lower effective temperatures; however, it does not appreciably affect either the luminosity of the stars or their lifetime on the main sequence. Increasing the heavy-element abundance to 0.2 for ΔY/ΔZ=2.4 shifts the main sequence towards higher effective temperatures, appreciably increases the luminosity of the stars, and substantially accelerates their evolution.     

Wolf-Rayet stars,black holes,and gamma-ray bursters in close binaries

We consider the evolutionary status of observed close binary systems containing black holes and Wolf-Rayet (WR) stars. When the component masses and the orbital period of a system are known, the reason for the formation of a WR star in an initial massive system of two main-sequence stars can be established. Such WR stars can form due to the action of the stellar wind from a massive OB star (M_OB≥50M_⊙), conservative mass transfer between components with close initial masses, or the loss of the common envelope in a system with a large (up to ～25) initial component mass ratio. The strong impact of observational selection effects on the creation of samples of close binaries with black holes and WR stars is demonstrated. We estimate theoretical mass-loss rates for WR stars, which are essential for our understanding the observed ratio of the numbers of carbon and nitrogen WR stars in the Galaxy \(\dot M_{WR} (M_ \odot yr^{ - 1} ) = 5 \times 10^{ - 7} (M_{WR} /M_ \odot )^{1.3} \). We also estimate the minimum initial masses of the components in close binaries producing black holes and WR stars to be ～25M_⊙. The spatial velocities of systems with black holes indicate that, during the formation of a black hole from a WR star, the mass loss reaches at least several solar masses. The rate of formation of rapidly rotating Kerr black holes in close binaries in the Galaxy is ～3×10^?6 yr^?1. Their formation may be accompanied by a burst of gamma radiation, possibly providing clues to the nature of gamma-ray bursts. The initial distribution of the component mass ratios for close binaries is dN～dq=dM₂/M₁ in the interval 0.04?q₀≤1, suggesting a single mechanism for their formation.     

The formation and evolution of the most massive stars

We consider the formation of massive stars under the assumption that a young star accretes material from the protostellar cloud through its accretion disk while losing gas in the polar directions via its stellar wind. The mass of the star reaches its maximum when the intensity of the gradually strengthening stellar wind of the young star becomes equal to the accretion rate. We show that the maximum mass of the forming stars increases with the temperature of gas in the protostellar cloud T ₀, since the rate at which the protostellar matter is accreted increases with T ₀. Numerical modeling indicates that the maximum mass of the forming stars increases to ～900 M _⊙ for T ₀ ～ 300 K. Such high temperatures of the protostellar gas can be reached either in dense star-formation regions or in the vicinity of bright active galactic nuclei. It is also shown that, the lower the abundance of heavy elements in the initial stellar material Z, the larger the maximum mass of the star, since the mass-loss rate due to the stellar wind decreases with decreasing Z. This suggests that supermassive stars with masses up to 10⁶ M _⊙ could be formed at early stages in the evolution of the Universe, in young galaxies that are almost devoid of heavy elements. Under the current conditions, for T ₀ = (30–100) K, the maximum mass of a star can reach ～100M _⊙, as is confirmed by observations. Another opportunity for the most massive stars to increase their masses emerges in connection with the formation and early stages of evolution of the most massive close binary systems: the most massive stars can be produced either by coalescence of the binary components or via mass transfer in such systems.     

Boron concentrations in carbonaceous chondrites

We have analyzed B in carbonaceous chondrites in order to clarify a factor of 100 difference between the solar system B abundance derived from the solar photosphere and that inferred from previous meteorite data. Consistent results were obtained from two instrumental methods for B analysis: (a) counting of the high energy betas from ¹²B produced by the ¹¹B(d,p) reaction, and (b) measurement of particle track densities from ¹⁰B(n,α)⁷Li in a plastic track detector affixed to a homogenized meteorite sample. Contamination is a major problem in B analyses, but extensive testing showed that our results were not seriously affected. Our B concentrations are typically 1–2 ppm and are a factor of 2–6 lower than previous carbonaceous chondrite measurements. Our data for the Cl chondrites Ivuna and Orgueil would indicate a solar system B/Si atomic abundance ratio of 58 × 10^?6, but this is still a factor of 2–10 higher than the photospheric estimates. It may be that B is depleted in the sun by thermonuclear processes; however, the similarity of photospheric and meteoritic Be abundances is a problem for this point of view. Alternatively, B may be enhanced in carbonaceous chondrites, but this would make B a cosmochemically unique element. A mm-sized (Fe,Mn,Mg)CO₃ crystal from Orgueil shows no B enrichment. We find ¹⁰B ≤ 10¹⁶ atoms/g in two Allende fine-grained inclusions suggesting that B is not a refractory element under solar nebula conditions. This ¹⁰B limit, when taken as a limit on ¹⁰Be when the inclusion formed, puts constraints on the possibility of a solar system synthesis of ²⁶Al. For a proton spectrum of E^?a, a must be ≥ 3 if a solar gas is irradiated or a ≥1.5 if dust of solar composition is irradiated.     

The role of external factors in the evolution of galaxies

We consider the evolution of galaxies in dense galactic clusters. Observations and theoretical estimates indicate that this evolution may be specified to a large extent by collisions between galaxies, as well as interactions between the gaseous components of disk galaxies and intergalactic gas. We analyze collisions between disk galaxies with gaseous components using a simple model based on a comparison of the duration of a collision and the characteristic cooling time for the gas heated by the collision, and also of the relative masses of stars and gas in the colliding disk galaxies. This model is used to analyze scenarios for collisions between disk galaxies with various masses as a function of their relative velocities. Our analysis indicates that galaxies can merge, lose one or both of their gaseous components, or totally disintegrate as a result of a collision; ultimately, a new galaxy may form from the gas lost by the colliding galaxies. Disk galaxies with mass M _G and velocities exceeding ～300 (M _G/10¹⁰ M _⊙)^1/2 km/s in intergalactic gas in clusters with densities ～10^?27 g/cm³ can lose their gas due to the pressure of inflowing intergalactic gas, thereby developing into E(SO) galaxies.     

Formation of supermassive black holes due to the tidal deceleration of stellar black holes, globular clusters, and galaxies

The formation and evolution of supermassive (10²?10¹⁰ M _⊙) black holes (SMBHs) in the dense cores of globular clusters and galaxies is investigated. The raw material for the construction of the SMBHs is stellar black holes produced during the evolution of massive (25?150M _⊙) stars. The first SMBHs, with masses of ～1000M _⊙, arise in the centers of the densest and most massive globular clusters. Current scenarios for the formation of SMBHs in the cores of globular clusters are analyzed. The dynamical deceleration of the most massive and slowly moving stellar-mass (< 100M _⊙) black holes, accompanied by the radiation of gravitational waves in late stages, is a probable scenario for the formation of SMBHs in the most massive and densest globular clusters. The dynamical friction of the most massive globular clusters close to the dense cores of their galaxies, with the formation of close binary black holes due to the radiation of gravitational waves, leads to the formation of SMBHs with masses ? 10³ M _⊙ in these regions. The stars of these galaxies form galactic bulges, providing a possible explanation for the correlation between the masses of the bulge and of the central SMBHs. The deceleration of the most massive galaxies in the central regions of the most massive and dense clusters of galaxies could lead to the appearance of the most massive (to 10¹⁰ M _⊙) SMBHs in the cores of cD galaxies. A side product of this cascade scenario for the formation of massive galaxies with SMBHs in their cores is the appearance of stars with high spatial velocities (> 300 km/s). The velocities of neutron stars and stellar-mass black holes can reach ～10⁵ km/s.     

A study of eruptive solar events with negative radio bursts

Solar events of June 15/16, 2000, June 1/2, 2002, February 6, 2002, and February 7, 2002, have been studied. These events probably belong to a poorly studied class of explosive eruptions. In such events disintegration of the magnetic structure of an eruptive filament and dispersing of its fragments as a cloud over a considerable part of the solar surface are possible. The analysis of SOHO/EIT extreme ultraviolet images obtained in the 195 Å and 304 Å channels has revealed the appearance of dimmings of various shapes and propagation of a coronal wave for June 1/2, 2002. In all the events the Nobeyama, Learmonth, and Ussuriysk observatories recorded negative radio bursts at several frequencies in the 1–10 GHz range. Most likely, these bursts were due to absorption of solar radio emission in clouds produced by fragments of filaments. Absorption of the solar background radiation can be observed as a depression of the emission in the 304 Å channel. A model has been developed, which permits one to estimate parameters of absorbing plasma such as temperature, optical thickness, area of the absorbing cloud, and its height above the chromosphere from the radio absorption observed at several frequencies. The obtained values of the temperature, 8000–9000 K, demonstrate that the absorber was the material of an erupted cool filament. The model estimate of the masses of the ejecta in the considered events were ～10¹⁵ g, which is comparable to masses of typical filaments and coronal mass ejections.     

Physical properties of molecular clouds as functions of their Galactocentric distance from CS and C<Superscript>34</Superscript>S observations

Twenty-eight CS molecular clouds toward HII regions with Galactocentric distances from ～ 4 to 20 kpc have been studied based on observations obtained in the J=2→1 lines of CS and C³⁴S on the 20-meter radio telescope of the Onsala Space Observatory (Sweden) in March 2001. All 28 clouds have been mapped with an angular resolution of ～40″. The peak intensity in the C³⁴S line has been measured for 20 objects. An LTE analysis has been performed and the parameters of the molecular cloud cores derived. The core sizes are d_A=0.3–4.8 pc, with a median value of ～1.6 pc. The mean hydrogen densities in the cloud cores are n_H2=3.5×10²–3.7 × 10⁴ cm^?3, with a median value of ～7.2×10³ cm^?3. The value of n_H2 ends to decrease with increasing Galactocentric distance of the cloud. The masses of most clouds are 10²?6×10³M_⊙, with the most probable value being M_CS～10³M_⊙. The data follow the dependence M_CS ∝d _A ^(2.4–3.2) . As a rule, the cloud masses are lower than the virial masses for M_CS<10³M_⊙.     

Suprathermal ions in quiescent periods at 1 AU in the 23rd and 24th solar-activity cycles

The relative abundances of suprathermal (with energies ～0.04–2 MeV/nucleon) ³He, ⁴He, C, O, and Fe ions and the energy spectra of 3He and Fe ions in near-Earth space during quiescent periods of solar activity are studied. Measurements obtained with the ULEIS instrument onboard the ACE spacecraft during the 23rd and 24th solar cycles are used. Substantial differences in the energy spectra of suprathermal ions in the 23rd and 24th solar cycles are observed for the selected quiescent periods. Appreciable differences in the energy dependences of the relative ion abundances are also found. One possible explanation for the results obtained is that the background ions were accelerated to suprathrmal energies under different conditions in the solar corona in these two cycles.     

Ionospheric response to X-class solar flares in the ascending half of the subdued solar cycle 24

The signature of 11 X-class solar flares that occurred during the ascending half of the present subdued solar cycle 24 from 2009 to 2013 on the ionosphere over the low- and mid-latitude station, Dibrugarh (27.5^°N, 95^°E; magnetic latitude 17.6^°N), are examined. Total electron content (TEC) data derived from Global Positioning System satellite transmissions are used to study the effect of the flares on the ionosphere. A nonlinear significant correlation (R² = 0.86) has been observed between EUV enhancement (ΔEUV) and corresponding enhancement in TEC (ΔTEC). This nonlinearity is triggered by a rapid increase in ΔTEC beyond the threshold value ～1.5 (×10¹⁰ ph cm^?2 s^?1) in ΔEUV. It is also found that this nonlinear relationship between TEC and EUV flux is driven by a similar nonlinear relationship between flare induced enhancement in X-ray and EUV fluxes. The local time of occurrence of the flares determines the magnitude of enhancement in TEC for flares originating from nearly similar longitudes on the solar disc, and hence proximity to the central meridian alone may not play the dominating role. Further, the X-ray peak flux, when corrected for the earth zenith angle effect, did not improve the correlation between ΔX-ray and ΔTEC.     

Early formation of galaxies induced by clusters of black holes

A model for the formation of supermassive black holes at the center of a cluster of primordial black holes is developed. It is assumed that ～10^?3 of the mass of the Universe consists of compact clusters of primordial black holes that arose as a result of phase transitions in the early Universe. These clusters also serve as centers for the condensation of dark matter. The formation of protogalaxies with masses of the order of 2 × 10⁸ M _⊙ at redshift z = 15 containing clusters of black holes is investigated. The nuclei of these protogalaxies contain central black holes with masses ～10⁵ M _⊙, and the protogalaxies themselves resemble dwarf spherical galaxies with their maximum density at their centers. Subsequent merging of these induced protogalaxies with ordinary halos of dark matter leads to the standard picture for the formation of the large-scale structure of the Universe. The merging of the primordial black holes leads to the formation of supermassive black holes in galactic nuclei and produces the observed correlation between the mass of the central black hole and the bulge velocity dispersion.     

Evolution of galaxies and the Tully-Fisher relation

We study the evolution of the [O/Fe]-[Fe/H] relation and the dependence of the iron abundance on distance from the galactic plane z in a one-zone model for a disk galaxy, starting from the beginning of star formation. We obtain good agreement with the observational data, including, for the first time, agreement for the [Fe/H]-z relation out to heights of 16 kpc. We also study the influence of the presence of dark matter in the galaxies on the star-formation rate. Comparison of the observed luminosity of the Galaxy with the model prediction places constraints on the fractional mass of dark matter, which cannot be much larger than the fractional mass of visible matter, at least within the assumed radius of the Galaxy, ～20 kpc. We studied the evolution of disk galaxies with various masses, which should obey the Tully-Fisher relation, M ? R². The Tully-Fisher relation can be explained as a combination of a selection effect related to the observed surface brightnesses of galaxies with large radii and the conditions for the formation for elliptical galaxies.     

Two decadally resolved records from north‐west European peat bogs show rapid climate changes associated with solar variability during the mid–late Holocene

Two ¹⁴C accelerator mass spectrometry (AMS) wiggle‐match dated peat sequences from Denmark and northern England record changes in mire surface wetness reconstructed using plant macrofossil and testate amoebae analyses. A number of significant mid–late Holocene climatic deteriorations (wet shifts) associated with declines in solar activity were recorded (at ca. 2150 cal. yr BC, 740 cal. yr BC, cal. yr AD 930, cal. yr AD 1020, cal. yr AD 1280–1300, cal. yr AD 1640 and cal. yr AD 1790–1830). The wet shifts identified from ca. cal. yr AD 930 are concurrent with or lag decreases in solar activity by 10–50 years. These changes are replicated by previous records from these and other sites in the region and the new records provide improved precision for the ages of these changes. The rapidly accumulating (up to 2–3 yr cm^?1, ～1310 yr old, 34 ¹⁴C dates) Danish profile offers an unprecedented high‐resolution record of climate change from a peat bog, and has effectively recorded a number of significant but short‐lived climate change events since ca. cal. yr AD 690. The longer time intervals between samples and the greater length of time resolved by each sample in the British site due to slower peat accumulation rates (up to 11 yr cm^?1, ～5250 yr old, 42 ¹⁴C dates) acted as a natural smoothing filter preventing the clear registration of some of the rapid climate change events. Not all the significant rises in water table registered in the peat bog archives of the British and Danish sites have been caused by solar forcing, and may be the result of other processes such as changes in other external forcing factors, the internal variability of the climate system or raised bog ecosystem. Copyright © 2008 John Wiley & Sons, Ltd.     

Origins and properties of the quasi-stationary slow solar wind

Comparisons of the brightness distributions of the white corona observed at distances of several solar radii with solar wind velocities derived from interplanetary-scintillation observations, as well as analyses of solar wind data obtained on spacecraft from December 1994 to June 1995, indicate that the fast solar wind can contain plasma with velocities V ≈ 300–450 km/s, approaching those typical for the slow solar wind that flows in the streamer belt and chains of streamers. At the same time, certain other parameters, first and foremost the plasma density N and ratio T/N ^0.5 (where T is the temperature), indicate that these two flows differ considerably. The slow solar wind flowing in the streamer belt and chains displays high densities N > 10 ± 2 cm^?3 and low T/N ^0.5 < 1.7 × 10⁴ K cm^3/2 at the Earth’s orbit. The number of slow solar-wind sources observed in chains can be comparable with the number observed in the belt. The fast solar wind flowing from coronal holes always displays low densities N≤ 8 cm^?3 and high T/N ^0.5 > 1.7 × 10⁴ K cm^3/2. These properties probably indicate different origins of the fast and slow solar winds.     

Investigation of magnetic fields in solar active regions

The magnetic-field structure in solar active regions outside spots is studied. The line-of-sight fields were measured using the new Crimean digital magnetograph in three spectral lines—Fe I 5253 Å, Fe II 5234 Å, and Ti I 5193 Å. Observations in the Fe II 5234 Å line indicate systematically higher field strengths than those in the Fe I 5253 Å line. The magnetic fluxes in 2″ elements are ～4.3×10¹⁸ Mx, ～4.6×10¹⁸ Mx, and ～6.2×10¹⁸ Mx according to the Fe I 5253 Å, Ti I 5193 Å, and FeII 5234 Å observations, respectively. Elements 2″–8″ in size make the largest contribution to the magnetic fluxes of active regions outside spots.