RAS_WEB (Page 4,068)

Aperiodic phase masks for inscribing complex multi-notch OH-emission filters for astronomy. (arXiv:1812.08875v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Madhav_K/0/1/0/all/0/1">Kalaga Madhav</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_Z/0/1/0/all/0/1">Ziyang Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Roth_M/0/1/0/all/0/1">Martin M Roth</a> We demonstrate for the first time, a new type of aperiodic phase mask (APM) for fabricating multi-channel aperiodic fiber Bragg gratings. The mask is made of individual diffraction phase gratings with discrete unequal phase-steps incorporated at periodic locations. The diffraction at the discrete phase-steps in the phase mask produces corresponding half phase-steps at periodic locations along the fiber. The accumulated phase, along with index modulation, generates the desired multinotch reflection spectrum. Complex fiber Bragg grating filters fabricated using APM, in a standardRead More →

The impact of black hole seeding in cosmological simulations. (arXiv:1812.08892v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_E/0/1/0/all/0/1">Ella Xi Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Taylor_P/0/1/0/all/0/1">Philip Taylor</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Federrath_C/0/1/0/all/0/1">Christoph Federrath</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kobayashi_C/0/1/0/all/0/1">Chiaki Kobayashi</a> Most cosmological simulations of galaxy evolution include active galactic nucleus (AGN) feedback, typically seeding black holes with masses of $geq 10^5, h^{-1}, rm{M}_{odot}$ when the dark matter halo exceeds a given threshold mass. Taylor & Kobayashi (2014) introduced a new model, which seeds black holes at $10^3, h^{-1}, rm{M}_{odot}$ based on gas properties alone, and motivated by the channel of black hole formation due to the collapse of the most massive first stars in the Universe. We compare the black holeRead More →

Constraining nuclear matter parameters with GW170817. (arXiv:1812.08910v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Carson_Z/0/1/0/all/0/1">Zack Carson</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Steiner_A/0/1/0/all/0/1">Andrew W. Steiner</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Yagi_K/0/1/0/all/0/1">Kent Yagi</a> The tidal measurement of gravitational waves from the binary neutron star merger event GW170817 allows us to probe nuclear physics that suffers less from astrophysical systematics compared to neutron star radius measurements with electromagnetic wave observations. A recent work found strong correlation among neutron-star tidal deformabilities and certain combinations of nuclear parameters associated with the equation of state. These relations were then used to derive bounds on such parameters from GW170817 assuming that the relations and neutron star masses are known exactly. Here, we expand on thisRead More →

On the efficiency of primary cosmic ray composition evaluation using lateral distributions of air shower electromagnetic component. (arXiv:1812.08917v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Raikin_R/0/1/0/all/0/1">Roman Raikin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Serebryakova_T/0/1/0/all/0/1">Tatyana Serebryakova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Volkov_N/0/1/0/all/0/1">Nikolay Volkov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lagutin_A/0/1/0/all/0/1">Anatoly Lagutin</a> New analysis of simulations results for lateral distributions (LD) of electrons, muons and charged particles in extensive air showers generated by $10^{15}-10^{19}$~eV cosmic rays has been made with respect to the scaling formalism for LD and air shower universality paradigm. It is found that lateral distributions of electrons and muons, when considered separately, are well described by one-parametric scaling functions, while for the charged particles mixture distributions the scaling description is not accurate inRead More →

Polarimetric and photometric investigation of a dark globule LDN 1225: distance, extinction law, and magnetic fields. (arXiv:1812.08920v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Eswaraiah_C/0/1/0/all/0/1">Chakali Eswaraiah</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lai_S/0/1/0/all/0/1">Shih-Ping Lai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ma_Y/0/1/0/all/0/1">Yuehui Ma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pandey_A/0/1/0/all/0/1">Anil K. Pandey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jose_J/0/1/0/all/0/1">Jessy Jose</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Z/0/1/0/all/0/1">Zhiwei Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Samal_M/0/1/0/all/0/1">Manash R. Samal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_J/0/1/0/all/0/1">Jia-Wei Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sharma_S/0/1/0/all/0/1">Saurabh Sharma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ojha_D/0/1/0/all/0/1">D. K. Ojha</a> We present the results based on the optical $R$-band polarization observations of 280 stars distributed towards the dark globule LDN 1225. Gaia data release 2 parallaxes along with the polarization data of $sim$200 stars have been used to (a) constrain the distance of LDN 1225 to be 800$pm$80 pc, (b) determine the contribution ofRead More →

Generic absence of strong singularities and geodesic completeness in modified loop quantum cosmologies. (arXiv:1812.08937v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Saini_S/0/1/0/all/0/1">Sahil Saini</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Singh_P/0/1/0/all/0/1">Parampreet Singh</a> Different regularizations of the Hamiltonian constraint in loop quantum cosmology yield modified loop quantum cosmologies, namely mLQC-I and mLQC-II, which lead to qualitatively different Planck scale physics. We perform a comprehensive analysis of resolution of various singularities in these modified loop cosmologies using effective spacetime description and compare with earlier results in standard loop quantum cosmology. We show that the volume remains non-zero and finite in finite time evolution for all considered loop cosmological models. Interestingly, even though expansion scalar and energy density areRead More →

Dusty Superwind from a Galaxy with a Compact Obscured Nucleus: Optical Spectroscopic Study of NGC 4418. (arXiv:1812.08953v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Ohyama_Y/0/1/0/all/0/1">Youichi Ohyama</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Sakamoto_K/0/1/0/all/0/1">Kazushi Sakamoto</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Aalto_S/0/1/0/all/0/1">Susanne Aalto</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Gallagher_J/0/1/0/all/0/1">John S. Gallagher III</a> (3) ((1) Academia Sinica, Institute of Astronomy and Astrophysics, (2) Department of Earth and Space Sciences, Chalmers University of Technology, (3) Department of Astronomy, University of Wisconsin-Madison) We report our optical spectroscopic study of the nucleus and its surrounding region of a nearby luminous infrared galaxy NGC 4418. This galaxy has been known to host a compact obscured nucleus, showing distinct characteristics such as a very compact ($sim 20$ pc)Read More →

Activity variation driven by flux emergence and transport on Sun-like stars. (arXiv:1812.08976v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Isik_E/0/1/0/all/0/1">Emre I&#x15f;&#x131;k</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Solanki_S/0/1/0/all/0/1">Sami K. Solanki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Krivova_N/0/1/0/all/0/1">Natalie A. Krivova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shapiro_A/0/1/0/all/0/1">Alexander I. Shapiro</a> In G dwarfs, the surface distribution, coverage and lifetimes of starspots deviate from solar-like patterns as the rotation rate increases. We set up a numerical platform which includes the large-scale rotational and surface flow effects, aiming to simulate evolving surface patterns over an activity cycle for up to 8 times the solar rotation and flux emergence rates. At the base of the convection zone, we assume a solar projected butterfly diagram. We then follow the rotationally distortedRead More →

Large-scale acoustic peak shift in the Planck CMB data. (arXiv:1812.08980v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Ho_M/0/1/0/all/0/1">Ming-Feng Ho</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chiang_L/0/1/0/all/0/1">Lung-Yih Chiang</a> Cosmic microwave background (CMB) temperature anisotropies encode the history of the universe, which manifest itself in the angular power spectrum. We test the angular power spectra of small patches from the ESA $textit{Planck}$ data. Known variations in the power spectra from small patches reveal informative details such as gravitational lensing and Doppler boosting effect. By computing the relative shifts of acoustic peak positions, we construct a full-sky peak-shift feature map. We found a significantly ($p=0.175 %$) strong global dipole signal compared with simulations. After ruling out the foregroundRead More →

The properties of broad absorption line outflows based on a large sample of quasars. (arXiv:1812.08982v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+He_Z/0/1/0/all/0/1">Zhicheng He</a> (USTC), <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_T/0/1/0/all/0/1">Tinggui Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_G/0/1/0/all/0/1">Guilin Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_H/0/1/0/all/0/1">Huiyuan Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bian_W/0/1/0/all/0/1">Weihao Bian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tchernyshyov_K/0/1/0/all/0/1">Kirill Tchernyshyov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mou_G/0/1/0/all/0/1">Guobin Mou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xu_Y/0/1/0/all/0/1">Youhua Xu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhou_H/0/1/0/all/0/1">Hongyan Zhou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Green_R/0/1/0/all/0/1">Richard Green</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xu_J/0/1/0/all/0/1">Jun Xu</a> Quasar outflows carry mass, momentum and energy into the surrounding environment, and have long been considered a potential key factor in regulating the growth of supermassive black holes and the evolution of their host galaxies. A crucial parameter for understanding the origin of these outflows and measuring their influence on their host galaxies is theRead More →

Nonlinear vibration transfer in torsion pendulums. (arXiv:1812.09000v1 [physics.ins-det]) <a href="http://arxiv.org/find/physics/1/au:+Shimoda_T/0/1/0/all/0/1">Tomofumi Shimoda</a>, <a href="http://arxiv.org/find/physics/1/au:+Ando_M/0/1/0/all/0/1">Masaki Ando</a> Torsion pendulums have been widely used in physical experiments, because their small restoring forces are suitable for tiny force measurement. Recently, some applications such as low-frequency gravity gradiometers have been proposed by focusing on their low resonant frequencies. Torsion pendulums with low resonant frequencies enable the suspended masses to be isolated from the ground, allowing for good response to the fluctuation of local gravity field at low frequencies. However, translational ground vibration can be transferred to the horizontal rotation of the torsion pendulum nonlinearly. This effect can have a non-negligible contributionRead More →

New light curve solution of V568 Peg and first determination of its fundamental parameters. (arXiv:1812.09020v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Kjurkchieva_D/0/1/0/all/0/1">Diana Kjurkchieva</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ibryamov_S/0/1/0/all/0/1">Sunay Ibryamov</a> We present V, Rc photometric observations of the short-period W UMa star V568 Peg. They allowed us to improve its period. The light curve solution revealed that V568 Peg is an overcontact binary of A subtype with moderate fill-out factor. Its components are K stars which undergo partial eclipses. The mass ratio was estimated by q-search analysis. We established existing of big cool spot on the primary component with almost the same parameters during the last 4 years. Based on our light curveRead More →

Height dependence of the penumbral fine-scale structure in the inner solar atmosphere. (arXiv:1812.09029v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Murabito_M/0/1/0/all/0/1">Mariarita Murabito</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ermolli_I/0/1/0/all/0/1">I. Ermolli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Giorgi_F/0/1/0/all/0/1">F. Giorgi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stangalini_M/0/1/0/all/0/1">M. Stangalini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guglielmino_S/0/1/0/all/0/1">S.L. Guglielmino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jafarzadeh_S/0/1/0/all/0/1">S. Jafarzadeh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Socas_Navarro_H/0/1/0/all/0/1">H. Socas-Navarro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Romano_P/0/1/0/all/0/1">P. Romano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zuccarello_F/0/1/0/all/0/1">F. Zuccarello</a> We studied the physical parameters of the penumbra in a large and fully-developed sunspot, one of the largest over the last two solar cycles, by using full-Stokes measurements taken at the photospheric Fe I 617.3 nm and chromospheric Ca II 854.2 nm lines with the Interferometric Bidimensional Spectrometer. Inverting measurements with the NICOLE code, we obtained the three-dimensional structure of the magnetic field inRead More →

Thermal emission and magnetic beaming in the radio and X-ray mode-switching PSR B0943+10. (arXiv:1812.09030v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Rigoselli_M/0/1/0/all/0/1">Michela Rigoselli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mereghetti_S/0/1/0/all/0/1">Sandro Mereghetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Turolla_R/0/1/0/all/0/1">Roberto Turolla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Taverna_R/0/1/0/all/0/1">Roberto Taverna</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Suleimanov_V/0/1/0/all/0/1">Valery Suleimanov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Potekhin_A/0/1/0/all/0/1">Alexander Y. Potekhin</a> PSR B0943+10 is a mode-switching radio pulsar characterized by two emission modes with different radio and X-ray properties. Previous studies, based on simple combinations of blackbody and power law models, showed that its X-ray flux can be decomposed in a pulsed thermal plus an unpulsed non-thermal components. However, if PSR B0943+10 is a nearly aligned rotator seen pole-on, as suggested by the radio data, it is difficult to reproduce the highRead More →

Sheets, filaments and clumps – high resolution simulations of how the thermal instability can form molecular clouds. (arXiv:1812.09051v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Wareing_C/0/1/0/all/0/1">C.J. Wareing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Falle_S/0/1/0/all/0/1">S.A.E.G. Falle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pittard_J/0/1/0/all/0/1">J.M. Pittard</a> (University of Leeds) The hydrodynamic version of the adaptive mesh refinement (AMR) code, MG, has been employed to perform 3D simulations of the formation of collapsing cold clumps on the scale of a few parsecs, inside a larger cloud complex. The diffuse atomic initial condition consists of a stationary, thermally unstable, 200pc diameter spherical cloud in pressure equilibrium with low density surroundings. The diffuse atomic cloud was seeded with 10% density perturbations at the finest initial gridRead More →

Flatness without CMB – the Entanglement of Spatial Curvature and Dark Energy Equation of State. (arXiv:1812.09100v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Xu_H/0/1/0/all/0/1">Haoting Xu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huang_Z/0/1/0/all/0/1">Zhiqi Huang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_Z/0/1/0/all/0/1">Zhenjie Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Miao_H/0/1/0/all/0/1">Haitao Miao</a> The cosmic spatial curvature parameter $Omega_k$ is constrained, primarily by cosmic microwave background (CMB) data, to be very small. Observations of the cosmic distance ladder and the large scale structure can provide independent checks of the cosmic flatness. Such late-universe constraints on $Omega_k$, however, are sensitive to the assumptions of the nature of dark energy. For minimally coupled scalar-field models of dark energy, the equation of state $w$ has nontrivial dependence on the cosmic spatial curvatureRead More →

Probing the $pi^0$ spectrum at high-$x$ in proton-Air interactions at ultra-high energies. (arXiv:1812.09121v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Cazon_L/0/1/0/all/0/1">Lorenzo Cazon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Conceicao_R/0/1/0/all/0/1">Ruben Concei&#xe7;&#xe3;o</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martins_M/0/1/0/all/0/1">Miguel Alexandre Martins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Riehn_F/0/1/0/all/0/1">Felix Riehn</a> The average number of muons in air showers and its connection with shower development has been studied extensively in the past. With the upcoming detector upgrades, UHECR observatories will be able to probe higher moments of the distribution of the number of muons. Here a study of the physics of the fluctuations of the muon content is presented. In addition to proving that the fluctuations must be dominated by the first interactions, we show that low-$N_{mu}$ tail ofRead More →

Analytical solution for magnetized thin accretion disk in comparison with numerical simulations. (arXiv:1812.09132v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Cemeljic_M/0/1/0/all/0/1">Miljenko &#x10c;emelji&#x107;</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Parthasarathy_V/0/1/0/all/0/1">Varadarajan Parthasarathy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kluzniak_W/0/1/0/all/0/1">W&#x142;odek Klu&#x17a;niak</a> We obtained equations for a thin magnetic accretion disk, using the method of asymptotic approximation. They cannot be solved analytically-without solutions for a magnetic field in the magnetosphere between the star and the disk, only a set of general conditions on the solutions can be derived. To compare the analytical results with numerical solutions, we find expressions for physical quantities in the disk, using our results from resistive and viscous star-disk magnetospheric interaction simulations. We obtained equations for a thin magnetic accretionRead More →

Prospects of detecting Fast Radio Bursts using Indian Radio Telescopes. (arXiv:1812.09143v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Bhattacharyya_S/0/1/0/all/0/1">Siddhartha Bhattacharyya</a> Fast Radio Bursts (FRBs) are short duration highly energetic dispersed radio pulses. We developed a generic formalism (Bera {em et al.}, 2016) to estimate the FRB detection rate for any radio telescope with given parameters. By using this model, we estimated the FRB detection rate for two Indian radio telescope; the Ooty Wide Field Array (OWFA) (Bhattacharyya {em et al.}, 2017) and the upgraded Giant Metrewave Radio Telescope (uGMRT) (Bhattacharyya {em et al.}, 2018) with three beam forming modes. In this review article, I summarize these two works. We consideredRead More →

The true nature of Swift J0746.3-1608: a possible Intermediate Polar showing accretion state changes. (arXiv:1812.09153v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Bernardini_F/0/1/0/all/0/1">F. Bernardini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martino_D/0/1/0/all/0/1">D. de Martino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mukai_K/0/1/0/all/0/1">K. Mukai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Falanga_M/0/1/0/all/0/1">M. Falanga</a> Optical and X-ray observations suggested that the 9.38 h binary, SWIFT J0746.3- 1608 could be a Cataclysmic Variable of the magnetic or nova-like type, or a low mass X-ray binary. Its optical, UV, and X-ray light curves are strongly variable over years. We report on a recent XMM-Newton observation (28 April 2018), when the source had recovered from a deep low state that likely begun mid-late 2011. We detect for the first time a signal atRead More →