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Astrop | Simultaneous Swift and REM monitoring of the blazar PKS0537-441 in 2005 | The blazar PKS0537-441 has been observed by Swift between the end of 2004 and November 2005. The BAT monitored it recurrently for a total of 2.7 Ms, and the XRT and UVOT pointed it on seven occasions for a total of 67 ks, making it one of the AGNs best monitored by Swift. The automatic optical and infrared telescope RE... |
Astrop | On the orbital period of the magnetic Cataclysmic Variable HS 0922+1333 | Context: The object HS 0922+1333 was visited briefly in 2002 in a mini survey of low accretion rate polars (LARPs) in order to test if they undergo high luminosity states similar to ordinary polars. On the basis of that short observation the suspicion arose that the object might be an asynchronous polar (Tovmassian et ... |
Astrop | Nova Geminorum 1912 and the Origin of the Idea of Gravitational Lensing | Einstein's early calculations of gravitational lensing, contained in a scratch notebook and dated to the spring of 1912, are reexamined. A hitherto unknown letter by Einstein suggests that he entertained the idea of explaining the phenomenon of new stars by gravitational lensing in the fall of 1915 much more seriously ... |
Astrop | Criteria in the Selection of Target Events for Planetary Microlensing Follow-Up Observation | To provide criteria in the selection of target events preferable for planetary lensing follow-up observations, we investigate the variation of the probability of detecting planetary signals depending on the observables of the lensing magnification and source brightness. In estimating the probability, we consider variat... |
Astrop | Magnetic fields in protoplanetary disks | Magnetic fields likely play a key role in the dynamics and evolution of protoplanetary discs. They have the potential to efficiently transport angular momentum by MHD turbulence or via the magnetocentrifugal acceleration of outflows from the disk surface, and magnetically-driven mixing has implications for disk chemist... |
Astrop | X-ray Timing Observations of PSR J1930+1852 in the Crab-like SNR G54.1+0.3 | We present new X-ray timing and spectral observations of PSR J1930+1852, the young energetic pulsar at the center of the non-thermal supernova remnant G54.1+0.3. Using data obtained with the Rossi X-ray Timing Explorer and Chandra X-ray observatories we have derived an updated timing ephemeris of the 136 ms pulsar span... |
Astrop | Distribution of the molecular absorption in front of the quasar B0218+357 | The line of sight to the quasar B0218+357, one of the most studied lensed systems, intercepts a z=0.68 spiral galaxy, which splits its image into two main components A and B, separated by ca. 0.3'', and gives rise to molecular absorption. Although the main absorption component has been shown to arise in front of image ... |
Astrop | Cosmogenic neutrinos as a probe of the transition from Galactic to extragalactic cosmic rays | There are two promising scenarios that explain the ankle, which is a dip in the spectrum of cosmic rays at $\sim 10^{19}$ eV. A scenario interprets the ankle as the transition from Galactic to extragalactic cosmic rays ({\it ankle-transition scenario}), while the other is that the dip caused by pair production on the c... |
Astrop | Evidence for a Massive Protocluster in S255N | S255N is a luminous far-infrared source that contains many indications of active star formation but lacks a prominent near-infrared stellar cluster. We present mid-infrared through radio observations aimed at exploring the evolutionary state of this region. Our observations include 1.3mm continuum and spectral line dat... |
Astrop | SBF: multi-wavelength data and models | Recent applications have proved that the Surface Brightness Fluctuations (SBF) technique is a reliable distance indicator in a wide range of distances, and a promising tool to analyze the physical and chemical properties of unresolved stellar systems, in terms of their metallicity and age. We present the preliminary re... |
Astrop | Simulating CCD images of elliptical galaxies | We introduce a procedure developed by the ``Teramo Stellar Populations Tools'' group (Teramo-SPoT), specifically optimized to obtain realistic simulations of CCD images of elliptical galaxies. Particular attention is devoted to include the Surface Brightness Fluctuation (SBF) signal observed in ellipticals and to simul... |
Astrop | Unstable and Stable Galaxy Models | To determine the stability and instability of a given steady galaxy configuration is one of the fundamental problems in the Vlasov theory for galaxy dynamics. In this article, we study the stability of isotropic spherical symmetric galaxy models $f_{0}(E)$, for which the distribution function $f_{0}$ depends on the par... |
Astrop | Simulation of Ultra High Energy Neutrino Interactions in Ice and Water | The CORSIKA program, usually used to simulate extensive cosmic ray air showers, has been adapted to work in a water or ice medium. The adapted CORSIKA code was used to simulate hadronic showers produced by neutrino interactions. The simulated showers have been used to study the spatial distribution of the deposited ene... |
Astrop | The Measure for the Multiverse and the Probability for Inflation | We investigate the measure problem in the framework of inflationary cosmology. The measure of the history space is constructed and applied to inflation models. Using this measure, it is shown that the probability for the generalized single field slow roll inflation to last for $N$ e-folds is suppressed by a factor $\ex... |
Astrop | Cool Stars in Hot Places | During the last three decades, evidence has mounted that star and planet formation is not an isolated process, but is influenced by current and previous generations of stars. Although cool stars form in a range of environments, from isolated globules to rich embedded clusters, the influences of other stars on cool star... |
Astrop | Bar-Halo Friction in Galaxies III: Particle Number Requirements for Simulations | The question whether the dark matter halo density in the centers of galaxies could be changed through interactions with a rotating bar in the baryonic disk is of considerable current interest. While N-body simulations have been used to address this question, it has also been claimed that results from such simulations c... |
Astrop | The Angular Separation of the Components of the Cepheid AW Per | The 6.4 day classical Cepheid AW Per is a spectroscopic binary with a period of 40 years. Analyzing the centroids of HST/STIS spectra obtained in November 2001, we have determined the angular separation of the binary system. Although we currently have spatially resolved data for a single epoch in the orbit, the success... |
Astrop | Probing the Structure of Gamma-Ray Burst Jets with Steep Decay Phase of their Early X-ray Afterglows | We show that the jet structure of gamma-ray bursts (GRBs) can be investigated with the tail emission of the prompt GRB. The tail emission which we consider is identified as a steep-decay component of the early X-ray afterglow observed by the X-ray Telescope onboard Swift. Using a Monte Carlo method, we derive, for the ... |
Astrop | Dark energy, gravitation and supernovae | The discovery of the acceleration of the rate of expansion of the Universe fosters new explorations of the behavior of gravitation theories in the cosmological context. Either the GR framework is valid but a cosmic component with a negative equation of state is dominating the energy--matter contents or the Universe is ... |
Astrop | SiO maser observations of a wide dust-temperature range sample | We present the results of SiO line observations of a sample of known SiO maser sources covering a wide dust-temperature range. The aim of the present research is to investigate the causes of the correlation between infrared colors and SiO maser intensity ratios among different transition lines. We observed in total 75 ... |
Astrop | Expected Planets in Globular Clusters | We argue that all transient searches for planets in globular clusters have a very low detection probability. Planets of low metallicity stars typically do not reside at small orbital separations. The dependance of planetary system properties on metallicity is clearly seen when the quantity Ie=Mp[a(1-e)]^2 is considered... |
Astrop | Bulk viscosity of superfluid neutron stars | The hydrodynamics, describing dynamical effects in superfluid neutron stars, essentially differs from the standard one-fluid hydrodynamics. In particular, we have four bulk viscosity coefficients in the theory instead of one. In this paper we calculate these coefficients, for the first time, assuming they are due to no... |
Astrop | Higher harmonics increase LISA's mass reach for supermassive black holes | Current expectations on the signal to noise ratios and masses of supermassive black holes which the Laser Interferometer Space Antenna (LISA) can observe are based on using in matched filtering only the dominant harmonic of the inspiral waveform at twice the orbital frequency. Other harmonics will affect the signal-to-... |
Astrop | Bouncing Universe with Quintom Matter | The bouncing universe provides a possible solution to the Big Bang singularity problem. In this paper we study the bouncing solution in the universe dominated by the Quintom matter with an equation of state (EoS) crossing the cosmological constant boundary. We will show explicitly the analytical and numerical bouncing ... |
Astrop | SUBARU HDS Observations of a Balmer-Dominated Shock in Tycho's Supernova Remnant | We present an Ha spectral observation of a Balmer-dominated shock on the eastern side of Tycho's supernova remnant using the Subaru Telescope. Utilizing the High Dispersion Spectrograph (HDS), we measure the spatial variation of the line profile between preshock and postshock gas. Our observation clearly shows a broade... |
Astrop | Protostellar clusters in intermediate-mass (IM) star forming regions | The transition between the low density groups of T Tauri stars and the high density clusters around massive stars occurs in the intermediate-mass (IM) range (M$_*$$\sim$2--8 M$_\odot$). High spatial resolution studies of IM young stellar objects (YSO) can provide important clues to understand the clustering in massive ... |
Astrop | Neutrino Astronomy with High Spatial Resolution is Already Existing | By basing on observations of skeletal structures of the Sun and assuming that some of them are located inside of star, and also that a filamentary (linear) matter (whose a model earlier was put forward by B.U. Rodionov) is in basis of these internal structures the author consider possible processes of images formation ... |
Astrop | The dependence of the estimated luminosities of ULX on spectral models | Data from {\it Chandra} observations of thirty nearby galaxies were analyzed and 365 X-ray point sources were chosen whose spectra were not contaminated by excessive diffuse emission and not affected by photon pile up. The spectra of these sources were fitted using two spectral models (an absorbed power-law and a disk ... |
Astrop | On spherically symmetrical accretion in fractal media | We use fractional integrals to generalize the description of hydrodynamic accretion in fractal media. The fractional continuous medium model allows the generalization of the equations of balance of mass density and momentum density. These make it possible to consider the general case of spherical hydrodynamic accretion... |
Astrop | Can GLAST detect gamma-rays from the extended radio features of radio galaxies? | A few FRI radio galaxies were detected at GeV gamma-rays with CGRO EGRET, with peroperties suggesting that the gamma-ray flux originates from the core. Here we discuss the possibility that the extended radio features of radio galaxies could be detected with the LAT, focusing on the particularly promising case of the ne... |
Astrop | The VLT-FLAMES survey of massive stars: Wind properties and evolution of hot massive stars in the LMC | [Abridged] We have studied the optical spectra of 28 O- and early B-type stars in the Large Magellanic Cloud, 22 of which are associated with the young star-forming region N11. Stellar parameters are determined using an automated fitting method, combining the stellar atmosphere code FASTWIND with the genetic-algorithm ... |
Astrop | Identification of Absorption Features in an Extrasolar Planet Atmosphere | Water absorption is identified in the atmosphere of HD209458b by comparing models for the planet's transmitted spectrum to recent, multi-wavelength, eclipse-depth measurements (from 0.3 to 1 microns) published by Knutson et al. (2007). A cloud-free model which includes solar abundances, rainout of condensates, and phot... |
Astrop | VIMOS-VLT spectroscopy of the giant Ly-alpha nebulae associated with three z~2.5 radio galaxies | The morphological and spectroscopic properties of the giant (>60 kpc) Ly-alpha nebulae associated with three radio galaxies at z~2.5 (MRC 1558-003, MRC 2025-218 and MRC 0140-257) have been investigated using integral field spectroscopic data obtained with VIMOS on VLT. The morphologies are varied. The nebula of one sou... |
Astrop | Observation of Anti-correlation between Scintillation and Ionization for MeV Gamma-Rays in Liquid Xenon | A strong anti-correlation between ionization and scintillation signals produced by MeV gamma-rays in liquid xenon has been measured and used to improve the energy resolution by combining the two signals. The improvement is explained by reduced electron-ion recombination fluctuations of the combined signal compared to f... |
Astrop | Massive Stars: From the VLT to the ELT | New facilities and technologies have advanced our understanding of massive stars significantly over the past 30 years. Here I introduce a new large survey of massive stars using VLT-FLAMES, noting the target fields and observed binary fractions. These data have been used for the first empirical test of the metallicity ... |
Astrop | Investigation of Energy Spectrum of EGRET Gamma-ray Sources by an Extensive Air Shower Experiment | Ultra-High-Energy (UHE) ($E>100 $TeV) Extensive Air Showers (EASs) have been monitored for a period of five years (1997-2003), using a small array of scintillation detectors in Tehran, Iran. The data have been analyzed to take in to account of the dependence of source counts on zenith angle. Because of varying thicknes... |
Astrop | High Galactic Latitude Interstellar Neutral Hydrogen Structure and Associated (WMAP) High Frequency Continuum Emission | Spatial associations have been found between interstellar neutral hydrogen (HI) emission morphology and small-scale structure observed by the Wilkinson Microwave Anisotropy Probe (WMAP) in an area bounded by l = 60 & 180 deg, b = 30 & 70 deg, which was the primary target for this study. This area is marked by the prese... |
Astrop | Sensitivity of solar off-limb line profiles to electron density stratification and the velocity distribution anisotropy | The effect of the electron density stratification on the intensity profiles of the H I Ly-$\alpha$ line and the O VI and Mg X doublets formed in solar coronal holes is investigated. We employ an analytical 2-D model of the large scale coronal magnetic field that provides a good representation of the corona at the minim... |
Astrop | SW Sextantis stars: the dominant population of CVs with orbital periods between 3-4 hours | [Abridged] We present time-series optical photometry of five new CVs identified by the Hamburg Quasar Survey. The eclipses observed in HS 0129+2933, HS 0220+0603, and HS 0455+8315 provided very accurate orbital periods of 3.35129827(65), 3.58098501(34), and 3.56937674(26) h, respectively. HS 0805+3822 shows grazing ecl... |
Astrop | Finding (or not) New Gamma-ray Pulsars with GLAST | Young energetic pulsars will likely be the largest class of Galactic sources observed by GLAST, with many hundreds detected. Many will be unknown as radio pulsars, making pulsation detection dependent on radio and/or x-ray observations or on blind periodicity searches of the gamma-rays. Estimates for the number of puls... |
Astrop | Did time begin? Will time end? | Did time begin at a Big Bang? Will the present expansion of the universe last for a finite or infinite time? These questions sound philosophical but are becoming, now in the twenty-first century, central to the scientific study of cosmology. The answers, which should become clarified in the next decade or two, could ha... |
Astrop | FUSE Observations of the Dwarf Novae UU Aql, BV Cen, and CH UMa in Quiescence | We report on FUSE spectra of three U Gem-type, long period, dwarf novae, UU Aql, BV Cen and CH UMa taken during their quiescence intervals. We discuss the line identifications in their spectra and attempt to characterize the source(s) of their FUV flux distribution. Archival IUE spectrum of CH UMa and BV Cen in quiesce... |
Astrop | Inflation, bifurcations of nonlinear curvature Lagrangians and dark energy | A possible equivalence of scalar dark matter, the inflaton, and modified gravity is analyzed. After a conformal mapping, the dependence of the effective Lagrangian on the curvature is not only singular but also bifurcates into several almost Einsteinian spaces, distinguished only by a different effective gravitational ... |
Astrop | Testing Disk Instability Models for Giant Planet Formation | Disk instability is an attractive yet controversial means for the rapid formation of giant planets in our solar system and elsewhere. Recent concerns regarding the first adiabatic exponent of molecular hydrogen gas are addressed and shown not to lead to spurious clump formation in the author's disk instability models. ... |
Astrop | Observations of chemical differentiation in clumpy molecular clouds | We have extensively mapped a sample of dense molecular clouds (L1512, TMC-1C, L1262, Per 7, L1389, L1251E) in lines of HC3N, CH3OH, SO and C^{18}O. We demonstrate that a high degree of chemical differentiation is present in all of the observed clouds. We analyse the molecular maps for each cloud, demonstrating a system... |
Astrop | Distortion of Gravitational-Wave Packets Due to their Self-Gravity | When a source emits a gravity-wave (GW) pulse over a short period of time, the leading edge of the GW signal is redshifted more than the inner boundary of the pulse. The GW pulse is distorted by the gravitational effect of the self-energy residing in between these shells. We illustrate this distortion for GW pulses fro... |
Astrop | Old Main-Sequence Turnoff Photometry in the Small Magellanic Cloud. I. Constraints on the Star Formation History in Different Fields | We present ground-based B and R-band color-magnitude diagrams (CMDs), reaching the oldest main-sequence turnoffs with good photometric accuracy for twelve fields in the Small Magellanic Cloud (SMC). Our fields, located between ~1 and ~4 degrees from the center of the galaxy, are situated in different parts of the SMC s... |
Astrop | Curvature perturbations from ekpyrotic collapse with multiple fields | A scale-invariant spectrum of isocurvature perturbations is generated during collapse in the ekpyrotic scaling solution in models where multiple fields have steep negative exponential potentials. The scale invariance of the spectrum is realized by a tachyonic instability in the isocurvature field. This instability driv... |
Astrop | The Mid-Infrared Emission of M87 | We discuss Subaru and Spitzer Space Telescope imaging and spectroscopy of M87 in the mid-infrared from 5-35 um. These observations allow us to investigate mid-IR emission mechanisms in the core of M87 and to establish that the flaring, variable jet component HST-1 is not a major contributor to the mid-IR flux. The Spit... |
Astrop | Characterization of open cluster remnants | Despite progress in the theoretical knowledge of open cluster remnants and the growing search for observational identifications in recent years, open questions still remain. The methods used to analyze open cluster remnants and criteria to define them as physical systems are not homogeneous. In this work we present a s... |
Astrop | Binary Capture Rates for Massive Protostars | The high multiplicity of massive stars in dense, young clusters is established early in their evolution. The mechanism behind this remains unresolved. Recent results suggest that massive protostars may capture companions through disk interactions with much higher efficiency than their solar mass counterparts. However, ... |
Astrop | Externally-polluted white dwarfs with dust disks | We report Spitzer Space Telescope photometry of eleven externally-polluted white dwarfs. Of the nine stars for which we have IRAC photometry, we find that GD 40, GD 133 and PG 1015+161 each has an infrared excess that can be understood as arising from a flat, opaque, dusty disk. GD 56 also has an infrared excess charac... |
Astrop | Hydrodynamical model atmospheres and 3D spectral synthesis | We discuss three issues in the context of three-dimensional (3D) hydrodynamical model atmospheres for late-type stars, related to spectral line shifts, radiative transfer in metal-poor 3D models, and the solar oxygen abundance. We include a brief overview about the model construction, taking the radiation-hydrodynamics... |
Astrop | An Optical Source Catalog of the North Ecliptic Pole Region | We present a five (u*,g',r',i',z') band optical photometry catalog of the sources in the North Ecliptic Pole (NEP) region based on deep observations made with MegaCam at CFHT. The source catalog covers about 2 square degree area centered at the NEP and reaches depths of about 26 mag for u*, g', r' bands, about 25 mag f... |
Astrop | The Kinematics and Dynamics of the Globular Clusters and the Planetary Nebulae of NGC 5128 | A new kinematic and dynamic study of the halo of the giant elliptical galaxy, NGC 5128, is presented. From a spectroscopically confirmed sample of 340 globular clusters and 780 planetary nebulae, the rotation amplitude, rotation axis, velocity dispersion, and the total dynamical mass are determined for the halo of NGC ... |
Astrop | Five Intermediate-Period Planets from the N2K Sample | We report the detection of five Jovian mass planets orbiting high metallicity stars. Four of these stars were first observed as part of the N2K program and exhibited low RMS velocity scatter after three consecutive observations. However, follow-up observations over the last three years now reveal the presence of longer... |
Astrop | Statistical properties of giant pulses from the Crab pulsar | We have studied the statistics of giant pulses from the Crab pulsar for the first time with particular reference to their widths. We have analyzed data collected during 3.5 hours of observations conducted with the Westerbork Synthesis Radio Telescope operated in a tied-array mode at a frequency of 1200 MHz. The PuMa pu... |
Astrop | Colour pairs for constraining the age and metallicity of stellar populations | Using a widely used stellar population synthesis model, we study the ability of using pairs of AB system colours to break the well-known stellar age--metallicity degeneracy and give constraints on the two stellar-population parameters (age and metallicity). The relative age and metallicity sensitivities of AB system co... |
Astrop | The effect of supernova asymmetry on coalescence rates of binary neutron stars | We study the effect of the kick velocity -- neutron star spin alignment observed in young radio pulsars on the coalescence rate of binary neutron stars. The effect is shown to be especially strong for large kick amplitudes and tight alignments, reducing the galactic rate of binary neutron star coalescences up to an ord... |
Astrop | The dynamics of Jupiter and Saturn in the gaseous proto-planetary disk | We study the possibility that the mutual interactions between Jupiter and Saturn prevented Type II migration from driving these planets much closer to the Sun. Our work extends previous results by Masset and Snellgrove (2001), by exploring a wider set of initial conditions and disk parameters, and by using a new hydrod... |
Astrop | Possible origin of Larson's lows | It was found that approximately constant column densities of giant molecular clouds (Larson's low) can be explained as cloud existence condition in external (galactic) gravitational field. This condition can be also applied to objects (clumps and cores) embedded into the cloud and its gravitational field. Derived exist... |
Astrop | Double Neutron Stars: Evidence For Two Different Neutron-Star Formation Mechanisms | Six of the eight double neutron stars known in the Galactic disk have low orbital eccentricities (< 0.27) indicating that their second-born neutron stars received only very small velocity kicks at birth. This is similar to the case of the B-emission X-ray binaries, where a sizable fraction of the neutron stars received... |
Astrop | Large Scale Self-Similar Skeletal Structure of the Universe | An analysis of the redshift maps of galaxies and quasars has revealed large-scale self-similar skeletal structures of the Universe of the same topology which had been found earlier in a wide range of phenomena, spatial scales and environments. The "cartwheel" type of structure with diameter ~ 1.5 10^27 cm is discovered... |
Astrop | The impact of radio feedback from active galactic nuclei in cosmological simulations: Formation of disk galaxies | In this paper, we present a new implementation of feedback due to active galactic nuclei (AGN) in cosmological simulations of galaxy formation. We assume that a fraction of jet energy, which is generated by an AGN, is transferred to the surrounding gas as thermal energy. Combining a theoretical model of mass accretion ... |
Astrop | A multi-transition molecular line study of candidate massive young stellar objects associated with methanol masers | We characterize the molecular environment of candidate massive young stellar objects (MYSOs) signposted by methanol masers. Single pixel observations of 10 transitions of HCO^+, CO and CS isotopomers were carried out, using the IRAM 30m telescope. We studied a sample of 28 targets for which the 6.7GHz maser emission po... |
Astrop | Plasmaneutrino spectrum | Spectrum of the neutrinos produced in the massive photon and longitudal plasmon decay process has been computed with four levels of approximation for the dispersion relations. Some analytical formulae in limiting cases are derived. Interesting conclusions related to previous calculations of the energy loss in stars are... |
Astrop | Non-minimal Wu-Yang wormhole | We discuss exact solutions of three-parameter non-minimal Einstein-Yang-Mills model, which describe the wormholes of a new type. These wormholes are considered to be supported by SU(2)-symmetric Yang-Mills field, non-minimally coupled to gravity, the Wu-Yang ansatz for the gauge field being used. We distinguish between... |
Astrop | Hydrogen 2p--2s transition: signals from the epochs of recombination and reionization | We propose a method to study the epoch of reionization based on the possible observation of 2p--2s fine structure lines from the neutral hydrogen outside the cosmological H {\sc ii} regions enveloping QSOs and other ionizing sources in the reionization era. We show that for parameters typical of luminous sources observ... |
Astrop | Near- and Far-Infrared Counterparts of Millimeter Dust Cores in the Vela Molecular Ridge Cloud D | The aim of this paper is to identify the young protostellar counterparts associated to dust millimeter cores of the Vela Molecular Ridge Cloud D through new IR observations (H_2 narrow-band at 2.12 micron and N broad band at 10.4 micron) along with an investigation performed on the existing IR catalogues. The associati... |
Astrop | Infrared High-Resolution Spectroscopy of Post-AGB Circumstellar Disks. I. HR 4049 - The Winnowing Flow Observed? | High-resolution infrared spectroscopy in the 2.3-4.6 micron region is reported for the peculiar A supergiant, single-lined spectroscopic binary HR 4049. Lines from the CO fundamental and first overtone, OH fundamental, and several H2O vibration-rotation transitions have been observed in the near-infrared spectrum. The ... |
Astrop | SN 2003du: 480 days in the Life of a Normal Type Ia Supernova | An extensive set of optical and NIR photometry and low-resolution spectra the Type Ia supernova (SN Ia) 2003du was obtained using a number of facilities. The observations started 13 days before B-band maximum light and continued for 480 days with exceptionally good time sampling. The optical photometry was calibrated t... |
Astrop | Outflow and Infall in a Sample of Massive Star Forming Regions | We present single pointing observations of SiO, HCO$^+$ and H$^{13}$CO$^+$ from the James Clerk Maxwell Telescope towards 23 massive star forming regions previously known to contain molecular outflows and ultracompact HII regions. We detected SiO towards 14 sources and suggest that the non-detections in the other nine ... |
Astrop | Gemini Mid-IR Polarimetry of NGC1068: Polarized Structures Around the Nucleus | We present diffraction limited, 10um imaging polarimetry data for the central regions of the archetypal Seyfert AGN, NGC1068. The position angle of polarization is consistent with three dominant polarizing mechanisms. We identify three distinct regions of polarization: (a) north of the nucleus, arising from aligned dus... |
Astrop | LNRF-velocity hump-induced oscillations of a Keplerian disc orbiting near-extreme Kerr black hole: A possible explanation of high-frequency QPOs in GRS 1915+105 | At least four high-frequency quasiperiodic oscillations (QPOs) at frequencies 41Hz, 67Hz, 113Hz, and 167Hz were reported in a binary system GRS 1915+105 hosting near-extreme Kerr black hole with a dimensionless spin a>0.98. We use the idea of oscillations induced by the hump of the orbital velocity profile (related to ... |
Astrop | Compton thick AGN in the Suzaku era | Suzaku observations of two hard X-ray (> 10 keV) selected nearby Seyfert 2 galaxies are presented. Both sources were clearly detected with the PIN Hard X-ray Detector up to several tens of keV, allowing for a fairly good characterization of the broad band X-ray continuum. Both sources are heavily obscured, one of which... |
Astrop | Evidence for a merger of binary white dwarfs: the case of GD 362 | GD 362 is a massive white dwarf with a spectrum suggesting a H-rich atmosphere which also shows very high abundances of Ca, Mg, Fe and other metals. However, for pure H-atmospheres the diffusion timescales are so short that very extreme assumptions have to be made to account for the observed abundances of metals. The m... |
Astrop | Radio and X-ray nebulae associated with PSR J1509-5850 | We have discovered a long radio trail at 843 MHz which is apparently associated with middle age pulsar PSR J1509-5850. The radio trail has a length of ~7 arcmin. In X-rays, Chandra observations of PSR J1509-5850 reveal an associated X-ray trail which extends in the same orientation as the radio trail. Moreover, two clu... |
Astrop | Core-Corona Separation in Ultra-Relativistic Heavy Ion Collisions | Simple geometrical considerations show that the collision zone in high energy nuclear collisions may be divided into a central part (``core''), with high energy densities, and a peripheral part (``corona''), with smaller energy densities, more like in pp or pA collisions. We present calculations which allow to separate... |
Astrop | On the Structure and Properties of Differentially Rotating Main-Sequence Stars in the 1-2 M_sun Range | We conduct a systematic examination of the properties of models for chemically homogeneous, differentially rotating, main-sequence stars of mass 1-2 M_sun. The models were constructed using a code based on a reformulation of the self-consistent field method of computing the equilibrium stellar structure for a specified... |
Astrop | SDSS J102146.44+234926.3: New WZ Sge-type dwarf nova | We report CCD photometry and spectroscopy during 2006 outburst of the dwarf nova SDSS J102146.44+234926.3 (SDSS J1021). The photographic plates from the MAO, SAI and CrAO plate archives, which cover the position of the SDSS J1021, were inspected for the presence of previous outbursts. We also present the BVRcIc photome... |
Astrop | Turbulent Mixing in the Surface Layers of Accreting Neutron Stars | During accretion a neutron star (NS) is spun up as angular momentum is transported through its surface layers. We study the resulting differentially rotating profile, focusing on the impact this has for type I X-ray bursts. The predominant viscosity is likely provided by the Tayler-Spruit dynamo. The radial and azimuth... |
Astrop | The Galactic Center | In the past decade high resolution measurements in the infrared employing adaptive optics imaging on 10m telescopes have allowed determining the three dimensional orbits stars within ten light hours of the compact radio source at the center of the Milky Way. These observations show the presence of a three million solar... |
Astrop | Prospects of using simulations to study the photospheres of brown dwarfs | We discuss prospects of using multi-dimensional time-dependent simulations to study the atmospheres of brown dwarfs and extrasolar giant planets, including the processes of convection, radiation, dust formation, and rotation. We argue that reasonably realistic simulations are feasible, however, separated into two class... |
Astrop | The exceptionally extended flaring activity in the X-ray afterglow of GRB 050730 observed with Swift and XMM-Newton | We present the results of a detailed spectral and temporal analysis of Swift and XMM-Newton observations of the high redshift (z=3.969) GRB 050730. The X-ray afterglow of GRB 050730 was found to decline with time with superimposed intense flaring activity that extended over more than two orders of magnitude in time. Se... |
Astrop | The obscured quasar population from optical, mid-infrared, and X-ray surveys | Over the last few years, optical, mid-infrared and X-ray surveys have brought to light a significant number of candidate obscured AGN and, among them, many Type 2 quasars, the long-sought after "big cousins'' of local Seyfert 2 galaxies. However, despite the large amount of multi-wavelength data currently available, a ... |
Astrop | The Realm of the First Quasars in the Universe: the X-ray View | We review the X-ray studies of the highest redshift quasars, focusing on the results obtained with Chandra and XMM-Newton. Overall, the X-ray and broad-band properties of z>4 quasars and local quasars are similar, suggesting that the small-scale X-ray emission regions of AGN are insensitive to the significant changes o... |
Astrop | The obscured X-ray source population in the HELLAS2XMM survey: the Spitzer view | Recent X-ray surveys have provided a large number of high-luminosity, obscured Active Galactic Nuclei (AGN), the so-called Type 2 quasars. Despite the large amount of multi-wavelength supporting data, the main parameters related to the black holes harbored in such AGN are still poorly known. Here we present the results... |
Astrop | IRAS 18317-0757: A Cluster of Embedded Massive Stars and Protostars | We present high-resolution, multiwavelength continuum and molecular-line images of the massive star forming region IRAS 18317-0757. The IR through mm spectral energy distribution can be approximated by a two-temperature model (25 and 63 K) with a total luminosity of approximately log(L/Lsun)=5.2. Previous submm imaging... |
Astrop | Photometry of the SW Sex-type nova-like BH Lyncis in high state | Aims: We present a photometric study of the deeply eclipsing SW Sex-type nova-like cataclysmic variable star BH Lyn Methods: Time-resolved V-band CCD photometry was obtained for seven nights between 1999 and 2004. Results: We determined 11 new eclipse timings of BH Lyn and derived a refined orbital ephemeris with an or... |
Astrop | The Reverse Shock of SNR 1987A | The reverse shock of supernova remnant (SNR) 1987A emits in H-alpha and Ly-alpha, and comes in two flavors: surface and interior. The former is due to direct, impact excitation of hydrogen atoms crossing the shock, while the latter is the result of charge transfer reactions between these atoms and slower, post-shock io... |
Astrop | 3.8-Micron Photometry During the Secondary Eclipse of the Extrasolar Planet HD 209458b | We report infrared photometry of the extrasolar planet HD 209458b during the time of secondary eclipse (planet passing behind the star). Observations were acquired during two secondary eclipses at the NASA Infrared Telescope Facility (IRTF) in September 2003. We used a circular variable filter (1.5-percent bandpass) ce... |
Astrop | Colliding Branes and Formation of Spacetime Singularities | We construct a class of analytic solutions with two free parameters to the five-dimensional Einstein field equations, which represents the collision of two timelike 3-branes. We study the local and global properties of the spacetime, and find that spacelike singularities generically develop after the collision, due to ... |
Astrop | Observations towards early-type stars in the ESO-POP survey: II -- searches for intermediate and high velocity clouds | We present CaII K and TiII optical spectra of early-type stars taken mainly from the UVES Paranal Observatory Project, plus HI 21-cm spectra from the Vila-Elisa and Leiden-Dwingeloo surveys, which are employed to obtain distances to intermediate and high velocity clouds. HI emission at a velocity of -117 km/s towards t... |
Astrop | The Haunted Halos of Andromeda and Triangulum: A panorama of galaxy formation in action | We present a deep photometric survey of M31, conducted with the CFHT and INT, covering the inner 50 kpc of the galaxy, the Southern quadrant out to 150 kpc, and extending to M33. This is the first systematic panoramic study of this very outermost region of galaxies. We detect several streams and other large-scale struc... |
Astrop | Identifying Dark Matter Burners in the Galactic center | If the supermassive black hole (SMBH) at the center of our Galaxy grew adiabatically, then a dense "spike" of dark matter is expected to have formed around it. Assuming that dark matter is composed primarily of weakly interacting massive particles (WIMPs), a star orbiting close enough to the SMBH can capture WIMPs at a... |
Astrop | Instabilities in the time-dependent neutrino disc in Gamma-Ray Bursts | We investigate the properties and evolution of accretion tori formed after the coalescence of two compact objects. At these extreme densities and temperatures, the accreting torus is cooled mainly by neutrino emission produced primarily by electron and positron capture on nucleons (beta reactions). We solve for the dis... |
Astrop | Developing the Galactic diffuse emission model for the GLAST Large Area Telescope | Diffuse emission is produced in energetic cosmic ray (CR) interactions, mainly protons and electrons, with the interstellar gas and radiation field and contains the information about particle spectra in distant regions of the Galaxy. It may also contain information about exotic processes such as dark matter annihilatio... |
Astrop | Prompt Emission of High Energy Photons from Gamma Ray Bursts | Within the internal shock scenario we consider different mechanisms of high energy ($>1$ MeV) photon production inside a Gamma Ray Burst (GRB) fireball and derive the expected high energy photon spectra from individual GRBs during the prompt phase. The photon spectra of leptonic and hadronic origins are compared within... |
Astrop | SkyMapper and the Southern Sky Survey - a resource for the southern sky | SkyMapper is amongst the first of a new generation of dedicated, wide-field survey telescopes. The 1.3m SkyMapper telescope features a 5.7 square degree field-of-view Cassegrain imager and will see first light in late 2007. The primary goal of the facility is to conduct the Southern Sky Survey a six colour, six epoch s... |
Astrop | Prediction of future fifteen solar cycles | In the previous study (Hiremath 2006a), the solar cycle is modeled as a forced and damped harmonic oscillator and from all the 22 cycles (1755-1996), long-term amplitudes, frequencies, phases and decay factor are obtained. Using these physical parameters of the previous 22 solar cycles and by an {\em autoregressive mod... |
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