Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Natal kicks and spins are characteristic properties of neutron stars (NSs) and black holes (BHs). Both offer valuable clues to dynamical processes during stellar core collapse and explosion. Moreover, they influence the evolution of stellar multiple systems and the gravitational-wave signals from their inspiral and merger. Observational evidence of a possibly generic spin-kick alignment has been interpreted as an indication that NS spins are either induced with the NS kicks or inherited from the progenitor rotation, which thus might play a dynamically important role during stellar collapse. Current three-dimensional supernova simulations suggest that NS kicks are transferred in the first seconds of the explosion, mainly by anisotropic mass ejection and, on a secondary level, anisotropic neutrino emission. By contrast, the NS spins are only determined minutes to hours later by the angular momentum associated with the fallback of matter that does not become gravitationally unbound in the supernova. Here, we propose a novel scenario to explain spin-kick alignment as a consequence of tangential vortex flows in the fallback matter that is accreted mostly from the direction of the NS’s motion. For this effect the initial NS kick is crucial, because it produces a growing offset of the NS away from the explosion center, thus promoting one-sided accretion. In this new scenario conclusions based on traditional concepts are reversed. For example, pre-kick NS spins are not required, and rapid progenitor core rotation can hamper spin-kick alignment. We also discuss implications for natal BH kicks and the possibility of tossing the BH’s spin axis during its formation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>ASASSN-21au is an ultracompact accreting white dwarf binary (AM CVn type) with a period of ∼58 minutes. Using multiwavelength observations of the system, we discovered a dichotomy in the behavior of outbursts in AM CVns. The binary showed an initial increase in brightness that lasted for at least 82 days, followed by an additional increase that lasted two weeks. Afterward, ASASSN-21au went into superoutburst with a total duration of 19 days, showing an amplitude with respect to quiescence of ∼7.5 mag in <jats:italic>g</jats:italic>, with a precursor and an echo outburst. A correlation between X-rays, UV, and optical was identified for the first time in an AM CVn during this stage. The color evolution of ASASSN-21au indicates that during the superoutburst the dominant component was the accretion disk. The short duration, large amplitude, and color evolution of the superoutburst agree with expectations from the disk instability model. These characteristics are opposite to those observed in SDSS J080710+485259 and SDSS J113732+405458, which have periods of ∼53 minutes and ∼60 minutes, respectively. The initially slow increase in brightness in the light curve of ASASSN-21au and the behavior after the superoutburst favor a scenario in which changes in the mass-transfer rate led to disk instabilities, while the outburst mechanism of SDSS J080710+485259 and SDSS J113732+405458 has been attributed to enhanced mass transfer alone. Further observations are needed to understand the origin of this dichotomy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A large-scale magnetic field is crucial in launching and collimating jets/outflows. It is found that the magnetic flux can be efficiently transported inward by a fast-moving corona above a thin disk. In this work, we investigate the dynamical structure of the outflows driven by the large-scale magnetic field advected by a hot corona. With the derived large-scale magnetic field, the outflow solution along every field line is obtained by solving a set of magneto-hydrodynamic equations self-consistently with boundary conditions at the upper surface of the corona. We find that the terminal speeds of the outflows driven from the inner region of the disk are ∼0.01–0.1<jats:italic>c</jats:italic>. The temperatures of the outflows at a large distance from the black hole are still as high as several ten keV. The properties of the magnetic outflows derived in this work are roughly consistent with the fast outflows detected in some luminous quasars and X-ray binaries (XRBs). The total mass-loss rate in the outflows from the corona is about 7%–12% of the mass-accretion rate of the disk. The three-dimensional field geometry, the velocity, temperature, and density of the outflows derived in this work can be used for calculating the emergent spectra and their polarization of the accretion disk/corona/outflow systems. Our results may help understand the features of the observed spectra of XRBs and active galactic nuclei.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The zero offset of the fluxgate magnetometer (FGM) on board the spacecraft varies slowly with time, therefore the FGM needs regular in-flight calibration. There are abundant physical phenomena in the solar wind, such as waves, mirror mode structures, and current sheets. Several in-flight calibration methods have been developed based on the properties of Alfvén waves or mirror mode structures instead of current sheets. Here, we develop a method to determine the zero offset <jats:bold> <jats:italic>O</jats:italic> </jats:bold> using current sheets in the solar wind, which is based on an assumption that the magnetic field in the normal direction of the current sheet is zero. The nonzero magnetic field in the normal direction is the projection of <jats:bold> <jats:italic>O</jats:italic> </jats:bold>, therefore we can obtain the component of <jats:bold> <jats:italic>O</jats:italic> </jats:bold> in the normal direction. In the offset cube, the zero offset is expected to be in a plane, which is referred to as the optimal offset plane (OOP). Each current sheet can obtain an OOP in the offset cube. At least three nonparallel OOPs must be used to determine the zero offset. We test our method by using data from the Magnetospheric Multiscale mission and find that our method is able to determine the zero offset. Our method can simultaneously use Alfvén waves, mirror mode structures, and current sheets to determine the zero offset, thus it might be a useful tool to perform the in-flight calibration of the FGM for solar wind monitors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present new reflection models specifically tailored to model the X-ray radiation reprocessed in accretion disks around neutron stars, in which the primary continuum is characterized by a single-temperature blackbody spectrum, emitted either at the surface of the star or at the boundary layer. These models differ significantly from those with a standard power-law continuum, typically observed in most accreting black holes. We show comparisons with earlier reflection models and test their performance in the NuSTAR observation of the neutron star 4U 1705−44. Simulations of upcoming missions such as XRISM-Resolve and Athena X-IFU are shown to highlight the diagnostic potential of these models for high-resolution X-ray reflection spectroscopy. These new reflection models <jats:monospace>xillverNS</jats:monospace>, and their relativistic counterpart <jats:monospace>relxillNS</jats:monospace>, are made publicly available to the community as an additional flavor in the <jats:sc>relxill</jats:sc> suite of reflection models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The streaming instability (SI) is one of the most promising pathways to the formation of planetesimals from pebbles. Understanding how this instability operates under realistic conditions expected in protoplanetary disks (PPDs) is therefore crucial to assess the efficiency of planet formation. Contemporary models of PPDs show that magnetic fields are key to driving gas accretion through large-scale, laminar magnetic stresses. However, the effect of such magnetic fields on the SI has not been examined in detail. To this end, we study the stability of dusty, magneftized gas in a protoplanetary disk. We find the SI can be enhanced by passive magnetic torques and even persist in the absence of a global radial pressure gradient. In this case, instability is attributed to the azimuthal drift between dust and gas, unlike the classical SI, which is driven by radial drift. This suggests that the SI can remain effective inside dust-trapping pressure bumps in accreting disks. When a live vertical field is considered, we find the magneto-rotational instability can be damped by dust feedback, while the classic SI can be stabilized by magnetic perturbations. We also find that Alfvén waves can be destabilized by dust–gas drift, but this instability requires nearly ideal conditions. We discuss the possible implications of these results for dust dynamics and planetesimal formation in PPDs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Applying halo models to analyze the small-scale clustering of galaxies is a proven method for characterizing the connection between galaxies and their host halos. Such works are often plagued by systematic errors or limited to clustering statistics that can be predicted analytically. In this work, we employ a numerical mock-based modeling procedure to examine the clustering of Sloan Digital Sky Survey DR7 galaxies. We apply a standard halo occupation distribution (HOD) model to dark matter only simulations with a ΛCDM cosmology. To constrain the theoreStical models, we utilize a combination of galaxy number density and selected scales of the projected correlation function, redshift-space correlation function, group multiplicity function, average group velocity dispersion, mark correlation function, and counts-in-cells statistics. We design an algorithm to choose an optimal combination of measurements that yields tight and accurate constraints on our model parameters. Compared to previous work using fewer clustering statistics, we find a significant improvement in the constraints on all parameters of our halo model for two different luminosity-threshold galaxy samples. Most interestingly, we obtain unprecedented high-precision constraints on the scatter in the relationship between galaxy luminosity and halo mass. However, our best-fit model results in significant tension (&gt;4<jats:italic>σ</jats:italic>) for both samples, indicating the need to add second-order features to the standard HOD model. To guarantee the robustness of these results, we perform an extensive analysis of the systematic and statistical errors in our modeling procedure, including a first of its kind study of the sensitivity of our constraints to changes in the halo mass function due to baryonic physics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a comprehensive multiwavelength investigation of a likely massive young cluster “IRAS 05100+3723” and its environment with the aim to understand its formation history and feedback effects. We find that IRAS 05100+3723 is a distant (∼3.2 kpc), moderate-mass (∼500 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), young (∼3 Myr) cluster with its most massive star being an O8.5V type. From spectral modeling, we estimate the effective temperature and log <jats:italic>g</jats:italic> of the star to be ∼33,000 K and ∼3.8, respectively. Our radio continuum observations reveal that the star has ionized its environment, forming a H <jats:sc>ii</jats:sc> region of size ∼2.7 pc, temperature ∼5700 K, and electron density ∼165 cm<jats:sup>−3</jats:sup>. However, our large-scale dust maps reveal that it has heated the dust up to several parsecs (∼10 pc) in the range 17−28 K and the morphology of warm dust emission resembles a bipolar H <jats:sc>ii</jats:sc> region. From dust and <jats:sup>13</jats:sup>CO gas analyses, we find evidence that the formation of the H <jats:sc>ii</jats:sc> region has occurred at the very end of a long filamentary cloud around 3 Myr ago, likely due to edge collapse of the filament. We show that the H <jats:sc>ii</jats:sc> region is currently compressing a clump of mass ∼2700 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> at its western outskirts, at the junction of the H <jats:sc>ii</jats:sc> region and filament. We observe several 70 <jats:italic>μ</jats:italic>m point sources of intermediate mass and class 0 nature within the clump. We attribute these sources as the second-generation stars of the complex. We propose that the star formation in the clump is either induced or being facilitated by the compression of the expanding H <jats:sc>ii</jats:sc> region onto the inflowing filamentary material.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>AQ Col (EC 05217-3914) is one of the first detected pulsating subdwarf B (sdB) stars and has been considered to be a single star. Photometric monitoring of AQ Col reveals a pulsation timing variation with a period of 486 days, interpreted as time delay due to reflex motion in a wide binary formed with an unseen companion with expected mass larger than 1.05 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. The optical spectra and color–magnitude diagram of the system suggested that the companion is not a main-sequence star but a white dwarf or neutron star. The pulsation timing variation also shows that the system has an eccentricity of 0.424, which is much larger than any known sdB long period binary system. That might be due to the existence of another short period companion to the sdB star. Two optical spectra obtained on 1996 December 5 show a radial velocity change of 49.1 km s<jats:sup>−1</jats:sup> in 46.1 minutes, which suggests the hot subdwarf in the wide binary is itself a close binary formed with another unseen white dwarf or neutron star companion; if further observations show this interpretation to be correct, AQ Col is an interesting triple system worthy of further study.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Solar filaments exist as stable structures for extended periods of time before many of them form the core of a coronal mass ejection (CME). We examine the properties of an erupting filament on 2017 May 29–30 with high-resolution He <jats:sc>i</jats:sc> 10830 Å and H<jats:italic>α</jats:italic> spectra from the Dunn Solar Telescope, full-disk Dopplergrams of He <jats:sc>i</jats:sc> 10830 Å from the Chromospheric Telescope, and EUV and coronograph data from SDO and STEREO. Pre-eruption line-of-sight velocities from an inversion of He <jats:sc>i</jats:sc> with the HAZEL code exhibit coherent patches of 5 Mm extent that indicate counter-streaming and/or buoyant behavior. During the eruption, individual, aligned threads appear in the He <jats:sc>i</jats:sc> velocity maps. The distribution of velocities evolves from Gaussian to strongly asymmetric. The maximal optical depth of He <jats:sc>i</jats:sc> 10830 Å decreased from <jats:italic>τ</jats:italic> = 1.75 to 0.25, the temperature increased by 13 kK, and the average speed and width of the filament increased from 0 to 25 km s<jats:sup>−1</jats:sup> and 10 to 20 Mm, respectively. All data sources agree that the filament rose with an exponential acceleration reaching 7.4 m s<jats:sup>−2</jats:sup> that increased to a final velocity of 430 km s<jats:sup>−1</jats:sup> at 22:24 UT; a CME was associated with this filament eruption. The properties during the eruption favor a kink/torus instability, which requires the existence of a flux rope. We conclude that full-disk chromospheric Dopplergrams can be used to trace the initial phase of on-disk filament eruptions in real time, which might potentially be useful for modeling the source of any subsequent CMEs.</jats:p>