abstract stringlengths 3 192k | title stringlengths 4 857 |
|---|---|
we propose a 100ks observation of the unique outbursting seyfert galaxyic 3599, to be triggered if it flares again. two giant-amplitude x-rayoutbursts (factor > 100) of ic 3599 in 1990 and 2010 were accompaniedby dramatic emission-line response never seen before in any agn, buthigh-resolution x-ray spectra where mis... | the nature of the x-ray outbursts in ic 3599 |
wz sge is the prototype of highly evolved, low-accretion rate dwarf novae (dne). during the decline from eruptions, its light curve displays a 'dip' followed by ≃10 'echo outbursts'. the standard disc instability model does not account for this behaviour, which is also seen in other low-accretion rate dne. one recent i... | plateaus, dips, and rebrightenings during the outbursts of wz sge: no magnetic propeller, but a veiling curtain |
planets form from gas and dust discs in orbit around young stars. the timescale for planet formation is constrained by the lifetime of these discs. the properties of the formed planetary systems depend thus on the evolution and final dispersal of the discs, which is the main topic of this thesis. observations reveal th... | proto-planetary disc evolution and dispersal |
plasma jets can be found in astrophysical systems (accretion disks, polars or young stellar objects), but they are also useful as a platform to study plasma properties and transport effects. on a experiment at the pals facility, we have studied the formation and propagation of rear-driven, collisional plasma jets from ... | modeling of young stellar objects through the study of magnetized rear-driven plasma jets from thin foil targets |
i present new narrow-band h-alpha imaging for 24 nearby edge-on galaxies in the chang-es survey. i use the images in conjunction with wise 22 micron imaging of the sample to estimate improved star formation rates (sfrs) using the updated recipe from vargas et al. (2018). i explore correlations between the updated star ... | h-alpha imaging of nearby edge-on galaxies, new sfrs, and an extreme star formation region (data release) |
cannizzo & nelemans (2015) applied the accretion disk limit cycle model to am cvn stars, using the width of the observed instability strip to derive three relations - (i) the mass transfer rate versus orbital period p_orbital, (ii) the recurrence time for outbursts versus p_orbital, and (iii) the outburst duration ... | the outburst duration versus orbital period relation for am cvn stars and the 2018 may/june outburst of sdss j141118.31+481257.6 |
binary black holes in which both spins are aligned with the orbital angular momentum do not precess. however, the up-down configuration, in which the spin of the heavier (lighter) black hole is aligned (anti-aligned) with the orbital angular momentum, is unstable to spin precession at small orbital separations. we firs... | unstable spin precession in binary black holes |
v630 cas is one of several long-period cataclysmic variables withrare, long-duration, dwarf nova outbursts. the characteristics of theseoutbursts are likely shaped by the large physical size of the accretiondisks. moreover, they often are luminous (> 10e33 ergs/s) x-ray sourcesin quiescence, severely challenging the... | probing accretion disks on intermediate size scales: the case of v630 cas |
the young star elias 2-27 has recently been observed with alma to posses a massive circumstellar disc with two prominent large-scale spiral arms out to 250au. these are the frst observations of extended spirals in the disc midplane. we perform three-dimensional smoothed particle hydrodynamics simulations, radiative tra... | the spiralling signatures of planet formation |
dwarf nova outbursts are nonlinear phenomena, and a time-dependent disk model is necessary to account for observations in detail. however, it is also necessary to elaborate a simpler steady-state fit to interpret observations. to know in what condition the outburst is initiated, understanding of the dwarf nova outburst... | critical temperature and accretion rate of outbursts in long-period dwarf novae |
young protostars that undergo episodic accretion can provide insight into the effects of stellar evolution and impact on their circumstellar environments. l1251 vla 6 is a four component protostar system with one of those being a fading outbursting protostar. here we examine structure in the disk around l1251 vla 6 at ... | observations of the fading outburst system l1251 vla 6 |
in order to improve the physical interpretation about innermost dusty regions in protoplanetary discs around brown dwarf (bd), and even very low mass star (vlms), we present a grid of models taking into account two different sets: (i) the set called standard model, that simulates an axisymmetric dusty disc with an inne... | about the modelling of the sed for the inner boundary of protoplanetary discs at the lower stellar mass regime |
a young star inevitably accretes through a surrounding disk due to the conservation of angular momentum of the parent molecular cloud. such a protoplanetary disk typically forms a magnetically dead zone at the distance of a few au from the central protostar, where the turbulence resulting from magnetorotational instabi... | effects of metal poor environments on the episodic accretion in protoplanetary disks |
the properties of protostellar (class 0/i) disks play an important role in planet formation by setting the environment for dust grain growth and the initial conditions for subsequent protoplanetary (class ii) disk evolution. however, obtaining these properties, especially the disk mass, has been challenging because tra... | the majority of protostellar disks might be way more massive than we thought: new insights from theory and observation |
in accretion disks, magneto-rotational instability (mri; balbus & hawley, 1991) makes the disk gas in the magnetic turbulent state and drives efficient mass accretion into a central star. mri drives turbulence through the evolution of the parasitic instability (pi; goodman & xu, 1994), which is related to both ... | mhd simulation of transition process from the magneto-rotational instability to magnetic turbulence by using a high-order mhd simulation scheme |
we investigate dynamics of slender magnetic flux tubes (mft) in the accretion disks of young stars. simulations show that mft rise from the disk and can accelerate to 20-30 km/s causing periodic outflows. magnetic field of the disk counteracts the buoyancy, and the mft oscillate near the disk's surface with periods of ... | rising magnetic flux tubes as a source of ir-variability of the accretion disks of young stars |
the large-scale magnetic field in the accretion disks of young stars is investigated. main features of our magnetohydrodynamical (mhd) model of the accretion disks and typical simulation results are presented. we discuss the role of mhd effects, ionization structure, magnetic field geometry and strength of the accretio... | large-scale magnetic field of the accretion disks of t tauri stars |
calm, "secular" accretion and evolutionary processes, once thought to be relegated to the sidelines of galaxy evolution, are now understood to play a significant role in the buildup of stellar mass in galaxies. most galaxies are formed and evolve via a mix of secular-driven evolution and more violent processes like str... | the merger-free co-evolution of galaxies and supermassive black holes |
accretion disks are important at different {scales} in the physics of the universe. for instance, binaries systems called {redback} (close binaries systems composed of a normal giant star and a neutron star) have shown transitions from an x-ray emission state (the neutron stars is accreting material) to {a} radio pulsa... | estudio de la viscosidad en un disco de acreción delgado |
the evolution of the white dwarf remnant of the merger of two white dwarfs is still an open problem, and even more in the case when the mass of the remnant is larger than the chandrasekhar limiting mass, namely when a metastable super-chandrasekhar white dwarf is formed. angular momentum loss might bring the white dwar... | induced compression by angular momentum losses in fast-rotating, magnetized super-chandraskehar white dwarfs |
planetary mass companions to solar mass stars may form through core accretion, gravitational instabilities in the disk, or protostellar core fragmentation. recent searches have uncovered about 15 planetary mass companions to young sun-like stars in orbits of 50-300 au from the central star. these objects pose significa... | the very low mass object fw tau b: an edge-on brown dwarf disk or a planet caught in formation? |
the magnetorotational instability (mri) is a crucial mechanism of angular momentum transport in a variety of astrophysical scenarios, as e-e+ plasmas accretion disks nearness neutron stars and black holes. the mri has been widely studied using mhd models and simulations, in order to understand the behavior of astrophys... | pic simulations of the magnetorotational instability in electron-positron plasmas |
the post-merger evolution of black hole-neutron star and neutron star-neutron star systems is driven by magnetohydrodynamic turbulence. such multiscale problems are very costly to simulate. one approach is to use artificially large seed magnetic fields to resolve the magnetorotational instability. another is to add som... | black hole-neutron star post-merger evolution using viscous relativistic hydrodynamics |
the tidal disruption of a star by a massive black is expected to yield a luminous flare of thermal emission. optical transient surveys have collected about two dozen similar-looking nuclear transients that are consider examples of these stellar tidal disruption flares (tdfs). however, explaining the observed properties... | stellar tidal disruption flares provide evidence for a black hole event horizon |
in recent years, the first accretion bursts from massive ysos have been detected. this confirmed that episodic accretion, possibly driven by disk instabilities, is a feature of high-mass star formation as well. these bursts were accompanied by flares of class ii methanol masers. thus, maser monitoring will improve pros... | ir observations of a flaring maser source - revealing the unsteady growth of massive stars |
close binary systems are formed by a varied family of objects, in particular, the named redback systems, i.e. the donor star transfers material to the neutron star, putting it in an accretion disc surrounding this star. later, this material falls on the neutron star. in the last years it was observed that some members ... | inestabilidad radiativa en un disco de acreción en sistemas binarios interactuantes |
the magnetorotational instability (mri) is a crucial mechanism of angular momentum transport in a variety of astrophysical scenarios, as accretion disks nearness neutron stars and black holes. the mri has been widely studied using mhd models and simulations, in order to understand the behaviour of astrophysical fluids ... | 2d mri-induced turbulence in high β pic simulation |
using 0d, 1d, and 3d models of galaxies, i explore different problems in galaxy evolution most suited to each technique. in the simplest case, a galaxy is described by a few numbers integrated via coupled ordinary differential equations. by allowing the galaxies to respond to a stochastic accretion rate, i show a natur... | numerical experiments in galactic disks: gravitational instability, stochastic accretion, and galactic winds |
the magnetorotational instability (mri) is the most promising mechanism in driving angular momentum transport in the radial direction in accretion discs associated to t tauri stars. however, the fact that this instability requires a minimum ionization fraction, makes it ineffective in the inner regions (i.e. at the mid... | heating of protostellar accretion discs associated with plasma inhomogeneities |
redback millisecond pulsars (hereafter redbacks) are a sub-population of eclipsing millisecond pulsars in close binaries. the formation processes of these systems are not clear. the three pulsars showing transitions between rotation- and accretion-powered states belong to both redbacks and transient low-mass x-ray bina... | evolution of transient low-mass x-ray binaries to redback millisecond pulsars |
in march 2018, the transient asassn-18el occurred in the nucleus of seyfert 2 galaxy 1es1927+654. monitoring the source over several months our team discovered the emergence of broad balmer emission lines, suggesting a transition from type 2 to a type 1 agn on timescales consistent with the light travel time between th... | the ongoing transformation of seyfert galaxy 1es 1927+654 |
investigation of instability in fluid galactic and accretion discs, in contrast to stellar discs, has not yet been formalised in standard methods. recently, it has been proposed to use the finite element method for this purpose, which makes it possible to reduce the problem of finding unstable modes to a linear algebra... | investigation of instability by the finite element method on the example of one exactly solvable model of the fluid disc |
to study the effects of a gas component on the formation and evolution of a stellar bar, we run fully self-consistent three-dimensional simulations of isolated barred galaxies similar to the milky way. our models consider feedbacks from star formation and accretion to a black hole, but neglect the effects of magnetic f... | effects of gas on the formation and evolution of a bar in milky-way sized galaxies |
the majority of detected exoplanets are close-in super earths (planets of a few earth masses) orbiting their host star roughly inside 0.5 au. additionally nearly all systems of super earths feature multiple planets within the same system, where the period ratios between adjacent planets are mostly outside of resonance.... | origin of super-earths planets: influence of pebble accretion, migration and instabilities |
protoplanetary discs (ppds) have been widely observed around young stars and are the birth cradle of planets. they are cold, dense and magnetised objects among which stand the transition discs (tds) characterised by a dust cavity in the inner regions that extends from a few au to a few hundreds au and whose formation r... | transition discs and magnetohydrodynamic winds: global numerical simulations |
clone from phase 1: this 8-orbit mid-cycle proposal requests hst/stis coronagraphic imaging to confirm a candidate wide-separation protoplanet seen around ab aur. near infrared data sets obtained over multiple epochs but only fully analyzed in may 2020 suggest a protoplanet whose colors/spectrum are distinguishable fro... | confirming a wide-separation directly-imaged infant planet around a young, dusty star |
complex a is a high-velocity cloud (hvc) that is traversing through the galactic halo toward the milky way's disk. we used green bank telescope observations to construct a spectroscopically resolved hi 21 cm map of this entire complex at roughly log(nhi/cm-2) = 17.9 (1-sigma) sensitivity and 25 pc spatial resolution. w... | exploring hydrodynamic instabilities along the infalling high-velocity cloud complex a |
neutron star high mass x-ray binaries that exhibit superorbital variability offer an opportunity to study the geometry and stability of warped accretion disks. the high mass x-ray binary smc x-1 is an ideal system in which to investigate these questions because the supeorbital period has epochs of instability known as ... | constraining the evolution of the unstable accretion disk in smc x-1 with nicer |
in recent years, the first accretion bursts from massive ysos (mysos) have been detected. this confirmed that episodic accretion, possibly driven by disk instabilities, is a feature of high-mass star formation as well. since mysos are usually deeply embedded, such events are hard to find at near-ir wavelengths. moreove... | watching massive stars grow with sofia |
v630 cas and v1017 sgr are long-period cataclysmic variables withrare, long-duration, dwarf nova outbursts. the characteristics of theseoutbursts are likely shaped by the large physical size of the accretiondisks. they also appear to be luminous (> 10e33 ergs/s) x-ray sourcesin quiescence, severely challenging the d... | v630 cas and v1017 sgr: probing accretion disks on intermediate scales |
stratified vortices can be found from small to large scales in geophysical and astrophysical flows. on the one hand, tornadoes and hurricanes can lead to devastation and even a large number of casualties. on the other hand, vortices can distribute heat and momentum in the atmosphere which is important for a habitable e... | high-performance computing and laboratory experiments on strato-rotational instabilities |
twenty-five years ago, pringle suggested a boundary-layer origin for jets from ysos. the jets were driven by a toroidal magnetic field generated by strong shear in the accretion boundary layer. such a mechanism is clearly non-magnetocentrifugal in nature.nearly fifteen years ago, we suggested a cartoon of the jet-launc... | boundary-layer origin for jets, and non-existence of the boundary layer in young jet-producing protostars |
we report the analysis of infrared jhk_s high speed photometry of the dwarf nova v2051 oph in quiescence. we model the ellipsoidal variations in the light curve to measure the fluxes of the mass donor star. its colors are consistent with an m8 ± 1 spectral type with an equivalent blackbody temperature of t_{bb}= (2700±... | the mass donor star and the accretion disc of the dwarf nova v2051 ophiuchi in the infrared |
galaxies need to accrete gas to form stars. stars form near the center of the galactic halo within the galactic disc. the most proficient star forming galaxies, starburst galaxies, are those that involve filaments that withstand the shock that forms at the edge of the galactic halo and transport matter deep into the ga... | experiments to study kh evolution of filaments feeding starburst galaxies on omega-ep |
exoplanet surveys have discovered that a large fraction of planetary systems (perhaps, a third around sun-like stars) possess super-earth planets on orbits tighter than earth's. these super-earths with masses between that of earth and neptune are not found in the solar system, however it has been proposed that they for... | formation of planetary systems from pebble accretion and migration i: the growth dichotomy between close-in rocky super-earth systems and terrestrial planets |
laboratory astrophysics reproduces on laboratory scales processes that in reality are tremendously larger. scaling can be formalised rigorously [1] but the best tool to bridge the scale gap is numerical simulation. it can consider the real astrophysical processes and the actual laboratory using very different scales. s... | high performance computing (hpc) simulations of laboratory experiments probing astrophysical processes |
high-contrast imaging surveys are discovering a growing number of brown dwarf companions and giant planets orbiting stars at wide separations between 10-100 au, but the formation of these objects is poorly understood because multiple routes (disk instability, core accretion plus dynamical scattering, and cloud fragment... | near-infrared spectroscopy of a quadruple system spanning the stellar to planetary mass regimes |
we analyze two sectors of transiting exoplanet sky survey (tess) photometry of the nova-like cataclysmic variable star v533 her. we detect a periodicity consistent with the binary orbital period and estimate a revised value of 3.53709(2) hr. we also detect a strong signal near a period of 3.8 hr that we associate with ... | characteristics of the permanent superhumps in v533 herculis |
compact binaries consist of a "normal" star accreting material onto the surface of a white dwarf, neutron star, or black hole. the white dwarf case constitutes cataclysmic variables (cvs), which are often distinguishable from the others by their characteristic optical light curve variability. cvs make up the vast major... | outbursting compact binary candidates from the zwicky transient facility |
space telescopes have provided unprecedented depictions of the manifold variability behaviors typical of young stellar objects (ysos). however, the lack of coordinated, multiband data often limited our understanding of the observed flux patterns. we conducted a comprehensive variability survey of 278 b-to-k ysos in the... | multicolor variability of young stars with disks: insights from coordinated space and ground observations |
bright hard states are observed during the outbursts of stellar mass black hole candidates. this state appears when the luminosity exceeds 0.1% of the eddington luminosity in the hard x-ray dominant state. when the luminosity increase further, the black hole candidate transit to the soft x-ray dominant state. such a tr... | radiation magnetohydrodynamic simulations of black hole accretion flows in bright hard state |
dense cores are the places where stars are formed within the supersonic molecular clouds. these dense regions (n ∼ 105 cc) are cold (t ∼10 k) and display subsonic levels of turbulence (mach ∼ 0.5), and represent the initial conditions for both star and disk formation. however, the influence of the parental core propert... | feeding a protostar with 10 000 au scale streamers |
black hole x-ray binaries (bhxbs) provide the easiest means to study stellar-mass black holes. outbursts of bhxbs typically last months-years and are quite often characterized by a fast-rise, exponential decay light curve profile. however there are many exceptions, with some sources rising slowly, some having multiple ... | seven re-flares and a mini-outburst: high amplitude optical variations in swift j1910.2-0546 |
the vast majority of the known galactic population of stellar-mass black holes and a significant fraction of the neutron stars are found in low mass x-ray binaries (lmxbs). these stellar systems have sub-solar companion stars that transfer material to the compact object via roche lobe overflow. among lmxbs, the populat... | the hunt for ultracompact x-ray binaries |
in this contribution we present an initial analysis of the properties of a set of about 30 planets and brown dwarfs associated with forming stars of the t tauri type, with ages 10 10 years, belonging to different star-forming regions. the 18 of the sample (6 out of 33) are hot-jupiter-like planets. the remaining 82, de... | propiedades de planetas y enanas marrones en estrellas jóvenes |
planets form in the gaseous and dusty disks orbiting young stars. these protoplanetary disks are dispersed in a few million years, being accreted onto the central star or evaporated into the interstellar medium. to explain the observed accretion rates, it is commonly assumed that matter is transported through the disk ... | large scale dynamics of protoplanetary discs |
we will present a set of three-dimensional, global, general relativistic radiation magnetohydrodynamic (grrmhd) simulations of geometrically thin radiation-pressure-dominated accretion disks around stellar-mass black hole. we test the hypothesis that strong magnetic fields can both drive accretion through the magneto-r... | 3d global radiative grmhd models of strongly magnetized accretion flows |
due to the conservation of angular momentum contained in the parent molecular cloud, a protostar is inevitably surrounded by a flattened, centrifugally-supported circumstellar disk. for mass accretion to proceed, angular momentum transport must take place in such disks. canonically, the magnetorotational instability (m... | global model of magnetic wind-driven accretion in protoplanetary disks |
the observed gaps in the protoplanetary disk are often considered an imprint of planets orbiting around the central star. the width and the depth of the gaps depend on the mass of the planet along with the disk properties, for example, aspect ratio, viscosity, and particle size. an estimate of the masses and the locati... | using machine learning to infer planet mass from observed gap in protoplanetary disks |
accretion disks are observed around young stellar objects such as t tauri stars. in order to complete the star formation, particles in the disk need to loose angular momentum in order to be accreted into the central object. the magneto-rotational instability (mri) is probably the mechanism responsible for a magneto-hyd... | heating mechanisms in accretion disks around young stellar objects |
shear flows and magnetic fields are ubiquitous in astrophysical bodies such as stars and accretion discs. furthermore,the interaction between flows and magnetic field plays a key role in the dynamics of plasma fusion devices. typically,the flows and magnetic field are both sheared, and it is therefore a problem of fund... | joint instabilities of sheared flows and magnetic fields |
x-ray binaries radiate brightly from radio to x-ray due to the accretion and ejection of matter in the system. there are complex, correlated flux variations that probe links between emitting components. studying the nature of accretion onto these compact objects sheds light on several broad fields in astrophysics. this... | long-term correlations between optical, infrared and x-ray observations of x-ray binaries |
the evolution of the kelvin-helmholtz instability (khi) and magnetohydrodynamic (mhd) wave emission is investigated at shear-flow boundaries of magnetized plasmas. while mhd wave emission has been suggested to be only possible during the nonlinear stages, we find that there is also significant wave emission during the ... | linear and nonlinear kelvin-helmholtz instability and magnetohydrodynamic wave emission in sheared astrophysical plasma flows |
massive stars (> 8 solar masses) form in turbulent, magnetized regions. because of their strong radiative pressure stopping accretion in 1d models, numerical efforts have been focused on radiative transfer. spherical symmetry has been broken in multidimensional simulations, and disk accretion (2d, yorke+02) then acc... | high-mass turbulent core collapse with ambipolar diffusion and hybrid radiative transfer |
the embedded phase of star formation witnesses the birth of stars, the formation of circumstellar disks, and the launch of jets and outflows. it sets the stage for the disk and star evolution in the subsequent optically visible t tauri phase, largely determining disk and stellar masses and paving the way for planet ass... | the embedded phase of star formation : outflows, envelopes, first conditions of disk formation |
accretion disks around bhs are an under-studied potential gw source. the hydrodynamic papaloizou-pringle instability (ppi) can cause persistent orbiting matter clumps to grow and produce copious gws. via full numerical relativity simulations of self-gravitating disks, we have extended the understanding of these bh-disk... | nr simulations of ppi-unstable bh-disk systems: bh spin, magnetic fields, and gravitational wave detectability |
the liberation of gravitational binding energy to produce the photons that we observe from accreting systems remains a problem of fundamental importance in theoretical astrophysics. this problem is now becoming tractable thanks to modern computer codes which can simulate both the complex dynamics of magnetohydrodynamic... | variability and spectra of global radiation mhd simulations of am cvn accretion disks |
it has been shown that disk fragmentation within several tens of au from the star is very difficult when the gravitational instability and cooling time criterion are considered. however, in the stochastic fragmentation scenario, things may be different. we investigate stochastic fragmentation in protoplanetary disks. i... | stochastic fragmentation in protoplanetary disks under external irradiation |
at all redshifts rest-frame ultraviolet morphologies tend to be patchy and clumpy or extremely compact in nature. these morphological signatures could result from either merger interactions between two or multiple systems that trigger star formation, cloud collapse via gravitational instabilities in a gaseous disk that... | rest-frame ultraviolet morphologies: connecting local galaxies with the epoch of disk formation |
the intermediate palomar transient factory (iptf) has discovered a quasar the brightly-shining, active nucleus of a galaxy abruptly turning on in what appears to be the fastest such transition ever seen in such an object.a rapid transitionquasars are expected to show variations in brightness on timescales of hours to m... | a quasar turns on |
we perform a large timescale core collapse simulation to explore the secular evolution of embedded protoplanetary discs. the secular evolution properties point towards evolved discs. the disc experiments three accretion phases where the magnetic braking is the main accretion driver in the pseudo-disc while self-gravity... | probing the secular evolution of embedded protoplanetary discs |
fu ori stars are a rare class of young stellar object, with less than two dozen examples known. yet the long-lasting fu ori outburst events play a prominent role in our understanding of stellar mass assembly at the individual star level. the currently favored model is that of an inner disk instability causing a factor ... | the innermost regions of fu ori disks: a spectral legacy for hst/stis+cos |
in this paper, we analyze the so-called master equation of the linear backreaction of a plasma disk in the central object magnetic field, when small scale ripples are considered. this study allows to single out two relevant physical properties of the linear disk backreaction: (i) the appearance of a vertical growth of ... | general features of the linear crystalline morphology of accretion disks |
we study the structure and temporal variabilty properties of the grb jets considering a magnetically arrested disk as their central engine. we numerically evolve the accretion disk around a kerr black hole using 3d general relativistic magnetohydrodynamic simulations. we consider two analytical equilibrium disk configu... | modeling the grb jet properties with 3d general relativistic simulations of magnetically arrested accretion flows |
the atomic and molecular gas in galaxies comes from a combination of accretion and stellar reprocessing. accretion can occur either through mergers, by cooling of hot halo gas, or by cold flows, with the latter likely most important at early times. star formation occurs in cold molecular regions of this gas, so for man... | atomic and molecular phases of the interstellar medium |
many x-ray sources are now understood to be "black hole x-ray binaries'' in which a stellar remnant black hole either tidally "squeezes'' gas off a companion star, or pulls in some fraction the companion's wind. this gas can drain inward through a dense, thin disk characterized by thermalized radiation, or a sparse and... | testing theories for longterm accretion variability in black hole x-ray binaries |
magneto-gas-dynamic (mgd) outflows from the accretion disks of t tauri stars with fossil large-scale magnetic fileld are investigated. we consider two mechanisms of the outflows: rise of the magnetic flux tubes (mft) formed in the regions of efficient generation of the toroidal magnetic fileld in the disk due to parker i... | outflows and particle acceleration in the accretion disks of young stars |
in the past decade, the atacama large millimeter/sub-millimeter array (alma) became the first telescope capable of collecting a myriad of highly-resolved protoplanetary disc observations, confirming the long-thought belief that protoplanetary discs are not featureless and instead are rich in structure. among the struct... | generating planet-induced vortices with slowly-growing gap-opening planets |
kepler light curves of short period dwarf novae have resparked interest in the nature of superoutbursts and led to the question: is the thermal-tidal instability needed, or can the plain vanilla version of the accretion disk limit cycle do the job all by itself? a detailed time-resolved study of an eclipsing su uma sys... | recent developments on su uma stars - theory vs. observation |
the high metallicity of stars might favor planet formation either through nucleus accretion or disk instability. for this reason there is a great interest in the study of the atmospheres of stars that host planets. we present preliminary results of an analysis of the atmospheres of five of these stars. we determine che... | abundancias químicas y parámetros físicos de estrellas con planetas |
this contribution presented high-resolution numerical simulations of the colliding wind system η carinae, showing accretion of the primary wind onto the secondary star close to periastron passage. we found that the stellar winds collide and develop instabilities, mainly the non-linear thin shell instability, and form f... | accretion simulations of η carinae and implications for the evolution of massive binaries |
modern observational techniques are still not powerful enough to directly view planet formation, and so it is necessary to rely on theory. however, observations do give two important clues to the formation process. the first is that the most primitive form of material in interstellar space exists as a dilute gas. some ... | planet formation |
during the lifetime of a galaxy, secular radial mass redistribution is expected to gradually build up a bulge and transform the hubble type from late to early. the dominant dynamical process responsible for this transformation is a collective instability mediated by density-wave collisionless shocks (zhang 1996, 1998, ... | the role of collective effects and secular mass migration on galactic transformation |
we study the evolution of simulated galaxies in the presence of feedback from active galactic nuclei (agn). first, we present a study conducted with a semi-analytic model (sam) of galaxy formation and evolution that includes prescriptions for bulge growth and agn feedback due to galaxy mergers and disk instabilities. w... | exploring the effect of active galactic nuclei on quenching, morphological transformation and gas flows with simulations of galaxy evolution |
generally it has been assumed that the presence of a fast (close to the escape velocity) accretion is an indication of the magnetospheric accretion. however, observations indicate that fast accretion also occurs even in a weakly magnetized stars like herbig ae stars, which poses a question about the picture of accretio... | fast accretion into a weakly magnetized star |
we report the results of 1978-2019 time-series photometry of am cvn, the prototype of the "double-degenerate" or ultracompact class of cataclysmic variable. the star remained faithfully in the range v=14.10-14.25 throughout the ~1400 nights of observation, and flashed its familiar positive and negative superhumps, at p... | 40 years of periodic signals in the ultracompact binary am canum venaticorum |
giant planets have been discovered at large separations from the central star. a striking number of young circumstellar disks also have gas and/or dust gaps at large orbital separations, indicating the potential population of young planets there. but to form massive planets at large orbital separations quickly through ... | the direct formation of planetary embryos in self-gravitating disks |
we model the intermediate-mass black hole hlx-1, using hst, xmm-newton, and swift. we quantify the relative contributions of a bluer optical component, function of x-ray irradiation, and a redder component, constant and likely coming from an old stellar population. we estimate a bh mass m ≈ 2 × 10^4 m_{⊙}, a spin param... | outbursts of the intermediate-mass black hole hlx-1: a wind instability scenario |
fingering convection is an important source of mixing in stars, which are low prandtl number fluids. quantifying transport by fingering convection is therefore crucial to a better understanding of stellar evolution. in the absence of magnetic fields, brown et al. have shown that fingering-induced fluxes measured in dns... | mhd effects on fingering convection in stars: the problem with parasites |
a widely accepted picture of an accretion flow in a soft spectral state x-ray binary system is a geometrically thin disk structure much alike the classic analytic solution of shakura and sunyaev. despite the fact that the analytic models are troubled by instabilities and miss important aspects of physics such as magnet... | grrmhd simulation of sub-eddington accretion onto stellar mass black hole |
accretion disc winds in x-ray binaries have been recently recognised to be a major ingredient of accretion. recent results indicate that they can carry away more matter than the one accreted onto the compact object, that their presence appears connected with the state of the accretion disc and with the absence of the j... | photoionisation instability of winds in x-ray binaries |
disks of gas and dust around forming stars - circumstellar disks - last only a few million years. this is a very small fraction of the entire lifetime of sun-like stars, several billion years. nevertheless, by the time circumstellar disks dissipate stars complete building up their masses, giant planets finish accreting... | studies of young, star-forming circumstellar disks |
x-ray transients, such as accreting neutron stars, can periodically undergo outbursts. the exact mechanism that causes the onset of outburst is unknown, but it is theorised that these kinds of outbursts are caused by a thermal-viscous instability in the accretion disk. usually outbursts of accreting neutron stars are c... | capturing a pulsar powering up |
over the past decade direct imaging searches for self-luminous giant planets have uncovered an unexpected population of young planetary-mass companions on extremely wide orbits (>100 au). the masses of these companions typically straddle the deuterium burning limit, throwing into question whether these are high mass... | the world is spinning: constraining the origin of gas giants using planetary spin |
we present results from two-dimensional, general relativistic, radiation, magnetohydrodynamic (grrmhd) numerical simulations of radiation-pressure-dominated, shakura-sunyaev thin disks accreting onto a stellar-mass, schwarzschild black hole. in previous work, we showed that such disks are thermally unstable. here we te... | testing the role of strong magnetic fields in stabilizing radiation-pressure-dominated thin accretion disks |
the driving mechanism of protostellar outflows and jets and their effects on the star formation process obtained from recent theoretical and numerical studies are described. low-velocity outflows are driven by an outer region of the circumstellar disk, while high-velocity jets are driven near an inner edge of the disk.... | protostellar jets and outflows in low-mass star formation |
accretion discs around neutron stars are bright in x-rays. this emission has long been known to vary with energy, revealing the material composition of the disc. but also to vary the with a multitude of periods, revealing geometric structures in the disc. understanding how, exactly, these spectral and temporal signatur... | spectral-timing of aquila x-1 |
we present a numerical analysis of the spin evolution of neutron stars in low-mass x-ray binaries, trying to explain the discrepancy in the spin period distribution between observations of millisecond pulsars and theoretical results. in our calculations, we take account of possible effects of radiation pressure and irr... | evolution of the spin periods of neutron stars in low mass x-ray binaries |
we present a detailed study of the circular geodesic motion of neutral test particles on the equatorial plane of a spherically symmetric scalarized neutron star (ns). we also examined the stability criteria for massive and massless particles for the said ns by computing the effective potential. we compute the radii of ... | paczy'{n}ski-witta potential form of scalarized neutron star |
the two favored mechanisms suggested for forming gas giants are disk instability and core accretion. the latter is the generally accepted mechanism on short orbits. according to this model, one would expect to observe a positive correlation between the transit depth of gas giants and the metallicity of the host star. h... | revising the transit depth-metallicity correlation of kepler's giant candidates |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.