Topology of superbanana orbits in tokamaks with tf ripples

The topology of banana guiding center orbits of fast ions in tokamaks with toroidal field (TF) ripples is considered. Analytical expressions determining the stagnation orbits and boundaries of regions with the closed orbits in the phase space are derived. Thoroughly studied is the modification of the topology of superbanana orbits due to the variation of the TF ripple magnitude . Contour plots of the adiabatic invariant of banana guiding center motion are presented for different values of . A comparison of the results of semi-analytical consideration and graphical interpretation of the adiabatic invariant is provided. Рассматривается топология орбит ведущих центров бананов в токамаках при наличии гофрировки тороидального поля (ТП). Получены аналитические выражения, определяющие координаты особых точек орбит и границы областей с замкнутыми орбитами в координатах фазового пространства. Проанализировано изменение топологии супербанановых орбит, вследствие варьирования амплитуды гофров ТП. Построены линии равного уровня адиабатического инварианта движения ведущего центра банана для различных значений амплитуды гофрировки ТП. Проведено сравнение результатов квазианалитического рассмотрения и графического представления адиабатического инварианта. Досліджується топологія орбіт ведучих центрів бананів у токамаках з гофруванням тороїдального поля (ТП). Отримано аналітичні вирази для координат особливих точок орбіт та границі областей із замкненими орбітами у координатах фазового простору. Проаналізовано зміну топології супербанннових орбіт внаслідок варіювання амплітуди гофрування ТП. Побудовано лінії рівного значення адіабатичного інваріанту руху ведучого центру банана для різних значень амплітуди гофрування ТП. Проведено порівняння результатів квазіаналітичного розгляду та графічного представлення адіабатичного інваріанта

Energy and particle fluxes in presence of RMP in axissymetric 2D tokamak plasmas

The magnetic field model of the original IFOSIT code was improved by the analytical model of the magnetic field, which takes into account Shafranov shift, elongation, triangularity and up-down asymmetry. The spatial and velocity dependence of the CFP source can be taken into account in the renewed code. New options are employed in renewed IFOSIT: calculation of energy and particle fluxes, calculation of the spatial and velocity distributions of lost and confined particles and time evolution of these distributions.Модель магнитного поля в коде IFOSIT была расширена при помощи аналитической модели магнитного поля, которая учитывает шафрановский сдвиг, эллиптичность, треугольность и асимметрию «верх-низ». В обновленном коде теперь учитывается форма профиля источника заряженных продуктов синтеза как в реальном пространстве, так и в пространстве скоростей. В новой версии кода IFOSIT реализованы новые возможности: вычисление потоков энергии и частиц, расчет распределений теряемых и удерживаемых частиц в реальном и скоростном пространствах и эволюция этих распределений.Модель магнітного поля в коді IFOSIT була розширена за допомогою аналітичної моделі магнітного поля, яка враховує шафранівський зсув, еліптичність, трикутність та асиметрію «верх-низ». У оновленому коді тепер враховується форма профілю джерела заряджених продуктів синтезу як в реальному просторі, так і в просторі швидкостей. У новій версії коду IFOSIT реалізовані нові можливості: розрахунок потоків енергії та частинок; розрахунок розподілів у реальному та швидкісному просторах для частинок, які втрачаються, та тих, які утримуються, та еволюція цих розподілів

Study of Envelope Velocity Evolution of Type Ib-c Core-Collapse Supernovae from Observations of XRF 080109 / SN 2008D and GRB 060218 / SN 2006aj with BTA

Results of modeling the spectra of two supernovae SN 2008D and SN 2006aj related to the X-ray flash XRF 080109 and gamma-ray burst GRB / XRF 060218, respectively, are studied. The spectra were obtained with the 6-meter BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences in 6.48 and 27.61 days after the explosion of SN 2008D, and in 2.55 and 3.55 days after the explosion of SN 2006aj. The spectra were interpreted in the Sobolev approximation with the SYNOW code. An assumption about the presence of envelopes around the progenitor stars is confirmed by an agreement between the velocities of lines interpreted as hydrogen and helium, and the empiric power-law velocity drop with time for the envelopes of classic core-collapse supernovae. Detection of a P Cyg profile of the H-beta line in the spectra of optical afterglows of GRBs can be a determinative argument in favor of this hypothesis.Comment: 12 pages, 6 figures, accepted for publication in Astrophysical Bulletin

Evolution of the Type IIb SN 2011fu

The UBVRI photometric follow-up of SN 2011fu has been initiated a few days after the explosion, shows a rise followed by steep decay in all bands and shares properties very similar to that seen in case of SN 1993J, with a possible detection of the adiabatic cooling phase at very early epochs. The spectral modeling performed with SYNOW suggests that the early-phase line velocities for H and Fe ii features were ~ 16000 km s−1 and ~ 14000 km s−1, respectively. Studies of rare class of type IIb SNe are important to understand the evolution of the possible progenitors of core-collapse SNe in more details

Transition from Fireball to Poynting-flux-dominated Outflow in Three-Episode GRB 160625B

The ejecta composition is an open question in gamma-ray bursts (GRB) physics. Some GRBs possess a quasi-thermal spectral component in the time-resolved spectral analysis, suggesting a hot fireball origin. Others show a featureless non-thermal spectrum known as the "Band" function, consistent with a synchrotron radiation origin and suggesting that the jet is Poynting-flux-dominated at the central engine and likely in the emission region as well. There are also bursts showing a sub-dominant thermal component and a dominant synchrotron component suggesting a likely hybrid jet composition. Here we report an extraordinarily bright GRB 160625B, simultaneously observed in gamma-rays and optical wavelengths, whose prompt emission consists of three isolated episodes separated by long quiescent intervals, with the durations of each "sub-burst" being $\sim$ 0.8 s, 35 s, and 212 s, respectively. Its high brightness (with isotropic peak luminosity L$_{\rm p, iso}\sim 4\times 10^{53}$ erg/s) allows us to conduct detailed time-resolved spectral analysis in each episode, from precursor to main burst and to extended emission. The spectral properties of the first two sub-bursts are distinctly different, allowing us to observe the transition from thermal to non-thermal radiation between well-separated emission episodes within a single GRB. Such a transition is a clear indication of the change of jet composition from a fireball to a Poynting-flux-dominated jet.Comment: Revised version reflecting the referees' comments. 27 pages, 11 figures, 5 tables. The final edited version will appear in Nature Astronom

The optical identifcation of events with poorly defined locations: The case of the Fermi GBM GRB140801A

We report the early discovery of the optical afterglow of gamma-ray burst (GRB) 140801A in the 137 deg$^2$ 3-$\sigma$ error-box of the Fermi Gamma-ray Burst Monitor (GBM). MASTER is the only observatory that automatically react to all Fermi alerts. GRB 140801A is one of the few GRBs whose optical counterpart was discovered solely from its GBM localization. The optical afterglow of GRB 140801A was found by MASTER Global Robotic Net 53 sec after receiving the alert, making it the fastest optical detection of a GRB from a GBM error-box. Spectroscopy obtained with the 10.4-m Gran Telescopio Canarias and the 6-m BTA of SAO RAS reveals a redshift of $z=1.32$. We performed optical and near-infrared photometry of GRB 140801A using different telescopes with apertures ranging from 0.4-m to 10.4-m. GRB 140801A is a typical burst in many ways. The rest-frame bolometric isotropic energy release and peak energy of the burst is $E_\mathrm{iso} = 5.54_{-0.24}^{+0.26} \times 10^{52}$ erg and $E_\mathrm{p, rest}\simeq280$ keV, respectively, which is consistent with the Amati relation. The absence of a jet break in the optical light curve provides a lower limit on the half-opening angle of the jet $\theta=6.1$ deg. The observed $E_\mathrm{peak}$ is consistent with the limit derived from the Ghirlanda relation. The joint Fermi GBM and Konus-Wind analysis shows that GRB 140801A could belong to the class of intermediate duration. The rapid detection of the optical counterpart of GRB 140801A is especially important regarding the upcoming experiments with large coordinate error-box areas.Comment: in press MNRAS, 201

Search for and study of photometric variability in magnetic white dwarfs

© 2017, Pleiades Publishing, Ltd.We report the results of photometric observations of a number of magnetic white dwarfs in order to search for photometric variability in these stars. These V-band observations revealed significant variability in the classical highly magnetized white dwarf GRW+70◦8247 with a likely period from several days to several dozen days and a half-amplitude of about 0.m 04. Our observations also revealed the variability of the well-known white dwarf GD229. The half amplitude of its photometric variability is equal to about 0.m 005, and the likely period of this degenerate star lies in the 10–20 day interval. This variability is most likely due to the rotation of the stars considered.We also discuss the peculiarities of the photometric variability in a number of other white dwarfs. We present the updated “magnetic field–rotation period” diagram for the white dwarfs

Detection of regular low-amplitude photometric variability of the magnetic dwarf WD0009+501. On the possibility of photometric investigation of exoplanets on the basis of 1-meter class telescopes of the special and crimean astrophysical observatories

© 2015, Pleiades Publishing, Ltd. We present the results of photometric observations of the weak magnetic white dwarf WD0009+501. The observations were carried out for two years with the 1-m telescopes of the Special and Crimean Astrophysical Observatories. As a result of these observations, we detected regular V -band luminosity variations with a period of P ≈ 8 hours. The amplitude of the variability is stable on timescales greater than two years and amounts to 11 ± 1 mmag. The difference in the variability amplitude from observations with different telescopes is 1–3 mmag. The result is interpreted within the concept of a rotation-modulated variability of magnetic properties of the star’s atmosphere. We also discuss a possible variability due to the presence of planetary companions around stars of this type. The results of monitoring were used to explore the capabilities of the telescopes for exoplanet investigation. We studied the dependences between the characteristic times of exposures, magnitudes of the objects, and a threshold level of the expected variability amplitudes for all the telescopes involved in our program. A program of exoplanet monitoring with the mentioned telescopes was drawn up for the next few years based on the results of the study