Search

New results of measurements of the dependences of the flux of reactor antineutrinos and their spectrum on the distance from the center of the core of the SM-3 reactor (Dimitrovgrad, Russia) in the range from 6 to 12 m are presented. Additional measurements were conducted. The volume of accumulated experimental data was increased nearly by a factor of two. A model-independent analysis was performed on the basis of all data in order to determine the oscillation parameters $$\Delta m_{14}^{2}$$ and $$\sin^{2}2\theta_{14}$$ . The method of a coherent summation of measurement results makes it possible to demonstrate directly the oscillation effect. We observed the oscillation effect at a level of three standard deviations ( $$3.0\sigma$$ ) in the vicinities of parameters values of $$\Delta m_{14}^{2}\approx 7.25$$ eV $${}^{2}$$ and $$\sin^{2}2\theta_{14}\approx 0.26\pm 008\left({3.0}\right)\sigma$$ . Combining the results of the Neutrino-4 experiment with results for the gallium anomaly and for the reactor anomaly, we obtained the following value: $$\sin^{2}2\theta_{14}\approx 0.19\pm 0.04(4.6\sigma)$$ .

Full list of authors: Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A. ; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres de Almeida, U.; Barrio, J. A.; Batković, I.; Becerra González, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.; D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; Pierro, F. Di; Venere, L. Di; Do Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.; Ferrara, G.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jiménez, I.; Jormanainen, J.; Jouvin, L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menchiari, S.; Mender, S.; Mićanović, S.; Miceli, D.; Miener, T.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Neustroev, V.; Nigro, C.; Nilsson, K.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes, C.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.; Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.; Wunderlich, C.; Zarić, D.; Bissaldi, E.; Bonnoli, G.; Cutini, S.; D'Ammando, F.; Nabizadeh, A.; Marchini, A.; Orienti, M.; MAGIC Collaboration., We report here on the first multiwavelength (MWL) campaign on the blazar TXS 1515-273, undertaken in 2019 and extending from radio to very-high-energy gamma-rays (VHE). Up until now, this blazar had not been the subject of any detailed MWL observations. It has a rather hard photon index at GeV energies and was considered a candidate extreme high-synchrotron-peaked source. MAGIC observations resulted in the first-time detection of the source in VHE with a statistical significance of 7.6σ. The average integral VHE flux of the source is 6 ± 1 per cent of the Crab nebula flux above 400 GeV. X-ray coverage was provided by Swift-XRT, XMM-Newton, and NuSTAR. The long continuous X-ray observations were separated by ∼9 h, both showing clear hour scale flares. In the XMM-Newton data, both the rise and decay time-scales are longer in the soft X-ray than in the hard X-ray band, indicating the presence of a particle cooling regime. The X-ray variability time-scales were used to constrain the size of the emission region and the strength of the magnetic field. The data allowed us to determine the synchrotron peak frequency and classify the source as a flaring high, but not extreme synchrotron-peaked object. Considering the constraints and variability patterns from the X-ray data, we model the broad-band spectral energy distribution. We applied a simple one-zone model, which could not reproduce the radio emission and the shape of the optical emission, and a two-component leptonic model with two interacting components, enabling us to reproduce the emission from radio to VHE band. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., The financial support of the German BMBF, MPG, and HGF; the Italian INFN and INAF; the Swiss National Fund SNF; the ERDF under the Spanish Ministerio de Ciencia e Innovacion (MICINN) (FPA201787859-P, FPA2017-85668-P, FPA2017-82729-C6-5-R, FPA201790566-REDC, PID2019-104114RB-C31, PID2019-104114RB-C32, PID2019-105510GB-C31, PID2019-107847RB-C41, PID2019107847RB-C42, PID2019-107847RB-C44, PID2019-107988GBC22); the Indian Department of Atomic Energy; the Japanese ICRR, the University of Tokyo, JSPS, and MEXT; the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1268/16.12.2019 and the Academy of Finland grant nr. 317637 and 320045 are gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia `Severo Ochoa' SEV-20160588, SEV-2017-0709 and CEX2019-000920-S, and `Maria de Maeztu' CEX2019-000918-M, the Unidad de Excelencia `Maria de Maeztu' MDM-2015-0509-18-2 and the `la Caixa' Foundation (fellowshipLCF/BQ/PI18/11630012), by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq, and FAPERJ. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, theCommissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase from the following agencies is also gratefully acknowledged: the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Etudes Spatiales in France.

The experiment Neutrino-4 started in 2014 with a detector model and continued with a full-scale detector in 2016–2021. In this article, we describe all the steps of the preparatory work on this experiment. We present all results of the Neutrino-4 experiment with increased statistical accuracy provided to date. The experimental setup is constructed to measure the flux and spectrum of the reactor antineutrinos as a function of distance to the center of the active zone of the SM-3 reactor (Dimitrovgrad, Russia) in the range of 6–12 meters. Using all the collected data, we performed a model-independent analysis to determine the oscillation parameters Δm142 and sin22θ14. The method of coherent summation of measurement results allows us to directly demonstrate the oscillation effect. We present the analysis of possible systematic errors and the MC model of the experiment, which considers the possibility of the effect manifestation at the present precision level. As a result of the analysis, we can conclude that at currently available statistical accuracy, we observe the oscillations at the 2.9σ level with the parameters Δm142=(7.3±0.13st±1.16syst) eV2=(7.3±1.17) eV2 and sin22θ=0.36±0.12stat(2.9σ). Monte Carlo based statistical analysis gave an estimation of the confidence level at 2.7σ. We plan to improve the currently working experimental setup and create a completely new setup in order to increase the accuracy of the experiment by 3 times. We also provide a brief analysis of the general experimental situation in the search for sterile neutrinos.

We report Neutrino-4 experiment results of measurements of reactor antineutrinos flux and spectrum dependence on the distance in range 6–12 m from the center of the reactor core. The fit of experimental dependence with the law 1/L2, where L is the distance from the reactor center, gave satisfactory result with goodness of fit 81%. However, we discovered that the experimental neutrino spectrum is different from the calculated one. Using experimental spectrum, we performed the model independent analysis of restrictions on oscillation parameters Δm 14 2 and sin2 2θ14. The results of this analysis exclude area of reactor and gallium anomaly at CL more than 99.7% (>3σ) for values Δm 14 2 0.1. However, we observed an oscillation effect at CL 2.8σ in vicinity of Δm 14 2 Δm 14 2 ≈ 7.3 eV2 and sin2 2θ14 ≈ 0.39. The method of coherent addition of results of measurements, which allows us to directly observe the effect of oscillations, is proposed. The analysis of that effect is presented. In general, it seems that the effect predicted in gallium and reactor experiments is being confirmed but at sufficiently large value of Δm 14 2 . Future prospects of the experiment are discussed.

First results on the energy spectrum and flux of reactor antineutrinos as a function of the distance L from the reactor core, measured in the Neutrino-4 experiment for 6 < L < 12 m, are presented. The flux L‑dependence fits to the 1/L2 form with a statistical significance of ~10% corresponding to 1.64σ, so that the measured spectrum deviates from the 1/L2 law at a confidence level ~90%. The measured energy spectrum deviates from the predicted one at a similar confidence level ~90%. That both deviations are best described with oscillation parameters in the same regions of $$\Delta m_{{14}}^{2} \approx 0.7{\text{-}}0.8$$ eV2and $${{\sin }^{2}}2{{\Theta }_{{14}}} \approx 0.10{\text{-}}0.15$$ boosts the overall confidence level to ~95% (2σ). These results suggest that antineutrinos oscillate to a sterile state, but still fall short of reliably establishing the oscillation phenomenon. At present, the possibility of mimicking the oscillation effect by systematic errors cannot be completely excluded.

An experimental search for sterile neutrinos has been carried out at a neutrino facility based on the SM-3 nuclear reactor in Dimitrovgrad, Russia. The movable detector with passive shielding against the external radiation may be positioned at a distance varying between 6 and 12 m from the center of the reactor. The antineutrino flux has for the first time been measured using a movable detector placed close to the antineutrino source. The accuracy of the measurements is largely restricted by the cosmic background. The results of the measurements performed at small and large distances are analyzed in terms of the sterile-neutrino model parameters Δm 14 2 and sin22θ14.

A laboratory for searching for oscillations of reactor antineutrinos has been created based on the SM-3 reactor in order to approach the problem of the possible existence of a sterile neutrino. The multisection detector prototype with a liquid scintillator volume of 350 L was installed in mid-2015. This detector can move inside the passive shield in a range of 6–11 m from the active core of the reactor. The antineutrino flux was measured for the first time at these short distances from the active core of the reactor by the movable detector. The measurements with the multisection detector prototype demonstrated that it is possible to measure the antineutrino flux from the reactor in the complicated conditions of cosmic background on the Earth’s surface.

In connection with the question of possible existence of sterile neutrino the laboratory on the basis of SM-3 reactor was created to search for oscillations of reactor antineutrino. A prototype of a neutrino detector with scintillator volume of 400 l can be moved at the distance of 6–11 m from the reactor core. The measurements of background conditions have been made. It is shown that the main experimental problem is associated with cosmic radiation background. Test measurements of dependence of a reactor antineutrino flux on the distance from a reactor core have been made. The prospects of search for oscillations of reactor antineutrino at short distances are discussed.

A research program aimed at studying fundamental interactions by means of ultracold and polarized cold neutrons at the GEK-4-4′ channel of the PIK reactor is presented. The apparatus to be used includes a source of cold neutrons in the heavy-water reflector of the reactor, a source of ultracold neutrons based on superfluid helium and installed in a cold-neutron beam extracted from the GEK-4 channel, and a number of experimental facilities in neutron beams. An experiment devoted to searches for the neutron electric dipole moment and an experiment aimed at a measurement the neutron lifetime with the aid of a large gravitational trap are planned to be performed in a beam of ultracold neutrons. An experiment devoted to measuring neutron-decay asymmetries with the aid of a superconducting solenoid is planned in a beam of cold polarized neutrons from the GEK-4′ channel. The second ultracold-neutron source and an experiment aimed at measuring the neutron lifetime with the aid of a magnetic trap are planned in the neutron-guide system of the GEK-3 channel. In the realms of neutrino physics, an experiment intended for sterile-neutrino searches is designed. The state of affairs around the preparation of the experimental equipment for this program is discussed.

To check the existence of a sterile neutrino, a neutrino laboratory aimed at searching reactor antineutrino oscillations is created at the SM-3 reactor. A prototype of a neutrino detector with a scintillator volume of 400 L is moved at distances 6–11 m from the core of the reactor. Background conditions are measured. It is shown that the cosmic rays background is the main problem in the experiment. The prospects of the search for reactor antineutrino oscillations at short distances are discussed.

In view of the possibility of the existence of a sterile neutrino, test measurements of the dependence of the reactor antineutrino flux on the distance from the reactor core has been performed on SM-2 reactor with the Neutrino-2 detector model in the range of 6–11 m. Prospects of the search for reactor antineutrinos at short distances have been discussed.

The paper deals with the results of Monte Carlo simulation of light propagation in a media with complex structure and dynamics by an original speckle-correlometry approach based on ring-like apertures and localized source of probe light. The «dynamic» lengthy objects with different geometry and depth location in the «static» inhomogeneous layer imitating biotissues with different characteristics of blood microcirculation were chosen as simulated media. The backscattering coefficient of laser light for the simulated media evaluated as a ratio of the «dynamic» partial components of the backscattered field to the full backscattered field is obtained. At the same time the «dynamic» partial components of the backscattered field and the full backscattered field are detected by the ring detector with the set value of ring aperture radius. The depth location of «dynamic» lengthy objects was determined analyzing the results of the dependence of the backscattering coefficient on the ring detector radii. It was also shown that the dependences of the backscattering coefficient on the ring detector radius in the case of probed media with different optical properties and containing the «dynamic» lengthy object with different geometric sizes can be described by the δ-like function. But the displacement of the peak value of δ-like function can be caused by the change of the scattering anisotropy factor.

In order to carry out research in the field of possible existence of a sterile neutrino the laboratory based on SM-3 reactor (Dimitrovgrad, Russia) was created to search for oscillations of reactor antineutrino. The prototype of a multi-section neutrino detector with liquid scintillator volume of 350 l was installed in the middle of 2015. It is a moveable inside the passive shielding detector, which can be set at distance range from 6 to 11 meters from the reactor core. Measurements of antineutrino flux at such short distances from the reactor core are carried out with moveable detector for the first time. The measurements with full-scale detector with liquid scintillator volume of 3 m^3 (5x10 sections) was started only in June, 2016. The today available data is presented in the article., 4 pages, 4 figures

Original data on the diameter of bear trees and trees in the stand were collected during the years 2002–2009 at the Upper Pechora and in the Western Sayan. The data were processed using the two-sample Student’s test and correlation analysis. Comparison was based on the published data on the thickness of bear trees. Brown bears use the trees 2 to 89 cm in diameter for marking. As a rule bear trees exceed the trees of the stand in the average diameter that proves that bears select trees with larger diameter for marking.

We have observed a new cataclysmic variable (CV) SDSS J080434.20+510349.2 and study the origin of a long-term variability found in its light curve. Multi-longitude time-resolved photometric observations were carried out to analyze the uncommon behavior also found recently in two newly discovered CVs. This study of SDSS J080434.20+510349.2 mainly concerns the understanding of the nature of the observed double-humped light curve and its relation to a cyclic brightening occurring during quiescence. The observations were obtained early in 2007, when the object was at about V~17.1, 0.4 mag brighter than the pre-outburst magnitude. The light curve shows a sinusoidal variability with an amplitude of about 0.07 mag and a periodicity of 42.48 min, which is half of the orbital period of the system. In addition, we have observed two "mini-outbursts" of the system up to 0.6 mag, with a duration of about 4 days each. The "mini-outburst" had a symmetric profile and repeated in about 32 days. Subsequent monitoring of the system shows a cyclical behaviour of such "mini-outbursts" with a similar recurrence period. The origin of the double-humped light curve and the periodic brightening is discussed in the light of the evolutionary state of SDSS J080434.20+510349.2., 7 pages, 6 figures, Accepted by A&A, typos added, figure corrected

In order to carry out research in the field of possible existence of sterile neutrino the laboratory based on SM-3 reactor (Dimitrovgrad, Russia) was created to search for oscillations of reactor antineutrino. The prototype of a multi-section neutrino detector with liquid scintillator volume of 350 l was installed in the middle of 2015. It is a moveable inside the passive shielding detector, which can be set at distance range from 6 to 11 meters from the reactor core. Measurements of antineutrino flux at such small distances from the reactor core carried out with movable detector for the first time. The measurements carried out with detector prototype demonstrated a possibility of measuring a reactor antineutrino flux in difficult conditions of cosmic background at Earth surface., Comment: 15 pages, 6 figures

Aims: To investigate the extension of the very-high-energy spectral tail of the Crab pulsar at energies above 400 GeV. Methods: We analyzed $\sim$320 hours of good quality data of Crab with the MAGIC telescope, obtained from February 2007 until April 2014. Results: We report the most energetic pulsed emission ever detected from the Crab pulsar reaching up to 1.5 TeV. The pulse profile shows two narrow peaks synchronized with the ones measured in the GeV energy range. The spectra of the two peaks follow two different power-law functions from 70 GeV up to 1.5 TeV and connect smoothly with the spectra measured above 10 GeV by the Large Area Telescope (LAT) on board of the Fermi satellite. When making a joint fit of the LAT and MAGIC data, above 10 GeV, the photon indices of the spectra differ by 0.5$\pm$0.1. Conclusions: We measured with the MAGIC telescopes the most energetic pulsed photons from a pulsar to date. Such TeV pulsed photons require a parent population of electrons with a Lorentz factor of at least $5\times 10^6$. These results strongly suggest IC scattering off low energy photons as the emission mechanism and a gamma-ray production region in the vicinity of the light cylinder.

We report simultaneous photometric and echelle-spectroscopic observations of the dwarf nova BZ UMa during which we were lucky to catch the system at the onset of an outburst, the development of which we traced in detail from quiescence to early decline. The outburst had a precursor, and was of a short duration (~5 days) with a highly asymmetrical light curve. On the rise we observed a `jump' during which the brightness almost doubled over the course of half an hour. Power spectra analysis revealed well-defined oscillations with period of ~42 minutes. Using Doppler tomography we found that the unusual emission distribution detected in quiescence held during the outburst. After the maximum a new emission source arose, from the inner hemisphere of the secondary star, which became the brightest at that time. We analyse this outburst in terms of `inside-out' and `outside-in' types, in order to determine which of these types occured in BZ UMa., Comment: 8 pages, 8 figures (12 eps files). Accepted for publication in MNRAS. The paper with high resolution colour images can be downloaded from http://urania.it.nuigalway.ie/papers/bz_outburst.pdf

We present the analysis of high-speed photometric observations of FS Aur taken with the 4.2-m William Herschel Telescope and the high-speed camera ULTRACAM in late 2003. These observations were intended to determine whether there was any evidence of photometric variability with a period in the range 50-100 seconds. The discovery of such variations would help to explain existence, in FS Aur, of the very coherent photometric period of 205.5 min that exceeds the spectroscopic period by 2.4 times. Such a discrepancy in the photometric and spectroscopic periods is an unusual for a low mass binary system that is unambiguously identified as a Cataclysmic Variable. Using various methods, including wavelet-analysis, we found that with exception of the 205.5-minute periodicity, the main characteristic of variability of FS Aur is usual flickering and Quasi-Periodic Oscillations. However, we detected variability with a period of ~101 and/or ~105 sec, seen for a short time every half of the orbital period. These oscillations may be associated with the spin period of the white dwarf, not ruling out the possibility that we are observing a precessing rapidly rotating white dwarf in FS Aur.

We analyze the possibility of observational identification of white dwarfs in the state of an ejector. Among the distinctive features of this class of objects are a high rate of rotational energy loss comparable to or higher than the observed luminosity of the object and nonthermal gamma-ray and/or radio spectra. The manifestations of the white dwarf in the close binary system AE Aquarii closely match these criteria. We show that most of the peculiar manifestations of this object in the hard spectral range and the observed pattern of mass transfer in the system can be explained in terms of a model in which the state of the white dwarf is classified as an ejector.

The main goal of experiment "Neutrino-4" is to search for the oscillation of reactor antineutrino to a sterile state. Experiment is conducted on SM-3 research reactor (Dimitrovgrad, Russia). Data collection with full-scale detector with liquid scintillator volume of 3m3 was started in June 2016. We present the results of measurements of reactor antineutrino flux dependence on the distance in range 6– 12 meters from the center of the reactor. At that distance range, the fit of experimental dependence has good agreement with the law 1/L2. Which means, at achieved during the data collecting accuracy level oscillations to sterile state are not observed. In addition, the spectrum of prompt signals of neutrino-like events at different distances have been presented.

We present results of non-simultaneous time-resolved photometric and spectroscopic observations of the little-studied dwarf nova FS Aur in quiescence. The spectrum of FS Aur shows strong and broad emission lines of hydrogen and HeI, and of weaker HeII 4686 and CIII/NIII blend, similar to other quiescent dwarf novae. All emission lines are single-peaked, however their form varies with orbital phase. Absorption lines from a late-type secondary are not detected. From the radial velocity measurements of the hydrogen lines H$_\beta$ and H$_\gamma$ we determined a most probable orbital period P=0.059+-0.002. This period agrees well with the 0.0595+-0.0001 estimate by Thorstensen et al. (1996). On the other hand, the period of photometric modulations is longer than the spectroscopic period and can be estimated as 3 hours. Longer time coverage during a single night is needed to resolve this problem. Using the semi-amplitude of the radial velocities, obtained from measurements of hydrogen and helium lines, and some empirical and theoretical relations we limited the basic parameters of the system: a mass ratio q>=0.22, a primary mass M_1=0.34 - 0.46 M_sun, a secondary mass M_2, Comment: 11 pages, LaTeX, 10 figures (= 21 EPS files), submitted to A&A, noticed typos corrected

We present new, high signal-to-noise spectroscopy of the Crab Pulsar in the range 5000 7000 A. The observations were carried out with the 6-meter telescope of the SAO with the spectrograph SP-124 with a resolution of 2 A. After reduction of the Crab Nebula emission, the dereddened pulsar spectrum can be tted by ap ower law with = 0:15 0:15. There are no lines (emission and absorption) with a relative intensity (depth) of more than 2% (with a condential probability of 99%). At this level we did not nd absorption at 6000 A, possibly of ion-cyclotron origin, as detected by Nasuti et al. (1996). This detail can be variable as a consequence of the variability of the ion ejection from the neutron star (NS) surface. We suggest a possible relationship between ejection intensity and inhomogeneity of the NS surface connected with pulsar glitches.

We present an analysis of time‐resolved, medium resolution optical spectroscopic observations of UX UMa in the blue (3920–5250 A) and red (6100–7200 A) wavelength ranges in April 1999 and March 2008, respectively. UX UMa has been in different states during those observations. Doppler tomography method was used to accretion disc structure investigation in both states. During the observations in 1999, UX UMa showed many of the defining properties of the SW Sex stars. However, all these features almost completely disappeared in 2008. We have also estimated the radial velocity semi‐amplitude K1.

Observational High Time Resolution Astrophysics differs from conventional astrophysics in regard to the detectors employed which have a time resolution less than that obtainable through CCD with a normal readout τ < a few minutes. This paper looks at the implications for HTRA from extremely large telescopes and specifically, as an exemplar its possible impact on pulsar astrophysics. We demonstrate, by using the derived point-spread-function from models of the Euro50 telescope, the possible effects active and adaptive mirrors have on observing rapidly varying astronomical objects.

We present high- and medium-resolution spectroscopic observations of the cataclysmic variable BF Eri during its low and bright states. The orbital period of this system was found to be 0.270881(3) days. The secondary star is clearly visible in the spectra through absorption lines of the neutral metals MgI, FeI and CaI. Its spectral type was found to be K3+-0.5. A radial velocity study of the secondary yielded a semi-amplitude of K_2=182.5+-0.9 km/s. The radial velocity semiamplitude of the white dwarf was found to be K_1=74+-3 km/s from the motion of the wings of the Halpha and Hbeta emission lines. From these parameters we have obtained that the secondary in BF Eri is an evolved star with a mass of 0.50-0.59 Msun, whose size is about 30 per cent larger than a zero-age main-sequence single-star of the same mass. We also show that BF Eri contains a massive white dwarf (M1>1.23 Msun), allowing us to consider the system as a SN Ia progenitor. BF Eri also shows a high gamma-velocity (gamma=-94 km/s) and substantial proper motion. With our estimation of the distance to the system (d~700+-200 pc), this corresponds to a space velocity of ~350 km/s with respect to the dynamical local standard of rest. The cumulative effect of repeated nova eruptions with asymmetric envelope ejection might explain the high space velocity of the system. We analyze the outburst behaviour of BF Eri and question the current classification of the system as a dwarf nova. We propose that BF Eri might be an old nova exhibiting "stunted" outbursts., 15 pages, 11 figures (36 eps files) and 5 tables. Accepted for publication in MNRAS. The paper with high resolution colour images can be downloaded from http://urania.it.nuigalway.ie/papers/bf_eri.pdf

Cataclysmic Variables (CV) are close binary systems, in which the primary, the more massive star, is a white dwarf. CVs usually exhibit a number of periodicities, most of which are now understood. However, recently, a new phenomenon was discovered that does not fit the standard picture. Two objects have been discovered to show periods that are much longer than orbital, and have no relation to it, either in light curves or in radial velocity (RV) variations measured from spectroscopy. Here, we show that the precession of the fast rotating magnetically accreting white dwarf can successfully explain these phenomena. The theory of compact objects predicts certain relations between the spin and precession periods, and our finding provides a good test for the theory and establishes a qualitative model to be explored both theoretically and observationally. Detection of precession can become a powerful tool in searching for the internal properties of compact stars, which would be otherwise inaccessible for us., Comment: 12 pages, 7 figures, accepted for publication in the ApJ

The observed properties of the close binary AE Aqr indicate that the mass transfer in this system operates via the Roche lobe overflow mechanism, but the material transferred from the normal companion is neither accreted onto the surface of the white dwarf nor stored in a disk around its magnetosphere. As previously shown, such a situation can be realized if the white dwarf operates as a propeller. At the same time, the efficiency of the propeller action by the white dwarf is insufficient to explain the rapid braking of the white dwarf, which implies that the spin-down power is in excess of the bolometric luminosity of the system. To avoid this problem we have simulated the mass-transfer process in AE Aqr assuming that the observed braking of the white dwarf is governed by a pulsar-like spin-down mechanism. We show that the expected H_alpha Doppler tomogram in this case resembles the tomogram observed from the system. We find that the agreement between the simulated and the observed tomograms is rather good provided the mean value of the mass-transfer rate ~5x10^16 g/s. Three spatially separated sources of H_alpha emission can be distinguished within this approach. The structure of the tomogram depends on the relative contributions of these sources to the H_alpha emission and is expected to vary from night to night., Comment: 12 pages, 3 figures (6 eps files). Published in A&A. The paper with high resolution images can be downloaded from http://urania.it.nuigalway.ie/papers/ae_aqr.ps.gz

FS Aur is a known dwarf nova with an orbital period of about 85.7 minutes. It has been assumed to be a member of the SU UMa subclass of cataclysmic variables (CVs), but previous searches for superhumps and superoutburst have been unsuccessful. We conducted a series of photometric and spectroscopic observations of FS Aur during quiescence. We confirmed its short orbital period from radial velocity measurements. However, the long-term photometry revealed an unexpected result: the system also shows a distinct 0.24 mag modulation in the BVR photometric bands with a period of 205.5 min, which is 2.4 times longer than the orbital period. We discuss various possible causes for such a peculiar behavior., 12 pages, 1 table, 12 figures, accepted for publication in PASP

We present the results of spectral investigations of the cataclysmic variable IP Peg in quiescence. Optical spectra obtained on the 6-m telescope at the Special Astrophysical Observatory (Russia), and on the 3.5-m telescope at the German-Spanish Astronomical Center (Calar Alto, Spain), have been analysed by means of Doppler tomography and Phase Modelling Technique. From this analysis we conclude that the quiescent accretion disk of IP Peg has a complex structure. There are also explicit indications of spiral shocks. The Doppler maps and the variations of the peak separation of the emission lines confirm this interpretation. We have detected that all the emission lines show a rather considerable asymmetry of their wings varying with time. The wing asymmetry shows quasi-periodic modulations with a period much shorter than the orbital one. This indicates the presence of an emission source in the binary rotating asynchronously with the binary system. We also have found that the brightness of the bright spot changes considerably during one orbital period. The spot becomes brightest at an inferior conjunction, whereas it is almost invisible when it is located on the distant half of the accretion disk. Probably, this phenomenon is due to an anisotropic radiation of the bright spot and an eclipse of the bright spot by the outer edge of the accretion disk., 13 pages, 11 figures (= 21 EPS files), accepted for publication in A&A

We report here on the identification and study of the optical counterpart of the ROSAT source RX J0704.2+6203. Extensive spectral and photometric observation showed that the object belongs to the class of magnetic Cataclysmic Variables. We determined the orbital period of the system to be 97.27m and estimated the strength of its magnetic field to be on the order of 20 MG. The system was observed in both high and low states, common for its class. Other parameters of the magnetic close binary system were estimated. The spectral and photometric behavior of the object is similar to that of the well studied polar BL Hyi., 9 pages, 9 figures, accepted in A&A

A simple and objective rapid method for assessing serum and plasma toxicity is proposed, based on registration of the frog cardiac contractions. The method permits assessment of disease severity and monitoring the time course of pathological process after surgery and plasmapheresis. The level of toxemia and disease severity did not correlate in 20% of cases. Causes of this disagreement are discussed.

Tests on surviving cultures of bone marrow cells from rats with experimental polycythemia showed that the chalone activity of, erythrocytic chalone is considerably reduced in the presence of phytohemagglutinin (PHA). The chalone depresses the agglutinating activity of PHA on bone marrow cells. Adsorption of the chalone preparation on immobilized PHA leads to disappearance of electrophoretically recorded PAS-positive bands from it and a sharp decrease in the intensity of the PAS-negative band. Experiments with preliminary incubation on rat erythrocytes before isolation of the chalone preparation suggest that in the course of its isolation two polypeptides are selectively liberated into the medium, one of them being PAS-positive. It is suggested that erythrocyte surface membrane proteins, are components of the chalone. The possible mechanism of liberation of chalones from the surface of the cells and the particular features of their action on cells are discussed.

Five fractions were isolated by cell electrophoresis in a Ficoll density gradient from the bone marrow of mice receiving physiological saline (control) and erythrocytic chalone (experiment). The absolute and relative distribution of the cells in the control and experimental fractions differed: the maximal number of cells in the control (up to 78%) was found in fractions 3–5 and the minimal (up to 22%) in fractions 1–2. A redistribution of the cellular material in all the fractions took place 25 min after treatment with erythrocytic chalone. The number of cells in fraction 1 was particularly increased (by 2.6 times). Analysis of the “myelograms” of films from fraction 1 in the experimental and control series showed that the number of cells in fraction 1 was increased on account of cells of the erythroid series. Among the proliferating cells of the erythron, the greatest decrease in electrophoretic mobility was observed in the proerythroblasts. It is suggested that as a result of interaction between erythrocytic chalone and membrane receptors of proliferating cells of the erythron their electric charge is reduced and changes take place in intracellular processes leading to delay in mitosis.