We study the polarization produced by scattering from dust in a bow shock-shaped region of enhanced density surrounding a stellar source, using the Monte Carlo radiative transfer code SLIP. Bow shocks are structures formed by the interaction of the winds of fast-moving stars with the interstellar medium. Our previous study focused on the polarization produced in these structures by electron scattering; we showed that polarization is highly dependent on inclination angle and that multiple scattering changes the shape and degree of polarization. In contrast to electron scattering, dust scattering is wavelength-dependent, which changes the polarization behaviour. Here we explore different dust particle sizes and compositions and generate polarized spectral energy distributions for each case. We find that the polarization SED behaviour depends on the dust composition and grain size. Including dust emission leads to polarization changes with temperature at higher optical depth in ways that are sensitive to the orientation of the bow shock. In various scenarios and under certain assumptions, our simulations can constrain the optical depth and dust properties of resolved and unresolved bow shock-shaped scattering regions.Constraints on optical depth can provide estimates of local ISM density for observed bow shocks. We also study the impact of dust grains filling the region between the star and bow shock. We see that as the density of dust between the star and bow shock increases, the resulting polarization is suppressed for all the optical depth regimes.
A significant fraction of OB-type, main-sequence massive stars are classified as runaway and move supersonically through the interstellar medium (ISM). Their strong stellar winds interact with their surroundings where the typical strength of the local ISM magnetic field is about 3.5-7 micro-G, which can result in the formation of bow shock nebulae. We investigate the effects of such magnetic fields, aligned with the motion of the flow, on the formation and emission properties of these circumstellar structures. Our axisymmetric, magneto-hydrodynamical simulations with optically-thin radiative c…
Recent studies show that more than 70% of massive stars do not evolve as effectively single stars, but as members of interacting binary systems. The evolution of these stars is thus strongly altered compared to similar but isolated objects. We investigate the occurrence of parsec-scale mid-infrared nebulae around early-type stars. If they exist over a wide range of stellar properties, one possible overarching explanation is non-conservative mass transfer in binary interactions, or stellar mergers. For ~3850 stars (all OBA stars in the Bright Star Catalogue [BSC], Be stars, BeXRBs, and Be+sdO s…
Arcuate infrared nebulae are ubiquitous throughout the Galactic Plane and are candidates for partial shells, bubbles, or bowshocks produced by massive runaway stars. We tabulate infrared photometry for 709 such objects using images from the Spitzer Space Telescope (SST), Wide-Field Infrared Explorer (WISE), and Herschel Space Observatory (HSO). Of the 709 objects identified at 24 or 22 microns, 422 are detected at the HSO 70 micron bandpass. Of these, only 39 are detected at HSO 160 microns. The 70 micron peak surface brightnesses are 0.5 to 2.5 Jy/square arcminute. Color temperatures calculat…
最新的恒星弓激波观测（Peri et al. 2012）列出了28个在红外波段探测到的与大质量、早期型恒星相关的候选恒星，最大可达3kpc，并给出了这些恒星结构的几何参数。在对每个源的恒星风功率、红外通量、恒星辐射光度和射电通量极限进行估算后，我在这里提出了一些能量学方面的考虑。相对论粒子加速的最佳候选人被突出显示。
Many pulsars propagate through the interstellar medium (ISM) with supersonic velocities, and their pulsar winds interact with the interstellar medium (ISM), forming bow shocks and magnetotails (PWN). We model the propagation of pulsars through the inhomogeneous ISM using non-relativistic axisymmetric magneto-hydrodynamic (MHD) simulations. We take into account the wind from the star, and the azimuthal and poloidal components of the magnetic field, and investigate the PWN at different levels of magnetization (the ratio of magnetic to matter energy-densities) in the wind. We consider the interac…
Numerical simulations are performed using the WENO method of the SVS 13 micro-jet and bow shock bubble which reproduce the main features and dynamics of Keck Telescope/OSIRIS velocity-resolved integral field spectrograph data: an expanding cooler bow shock bubble, with the bubble center moving at approximately 50 km/s with a radial expansion velocity of 11 km/s, surrounding the fast hotter jet, which is propagating at 156 km/s. Contact and bow shock waves are visible in the simulations from both the initial short jet pulse which creates the nearly spherical bow shock bubble and from the fast m…
Expanding nebulae are produced by mass loss from stars, especially during late stages of evolution. Multi-dimensional simulation of these nebulae requires high resolution near the star and permits resolution that decreases with distance from the star, ideally with adaptive timesteps. We report the implementation and testing of static mesh-refinement in the radiation-magnetohydrodynamics code PION, and document its performance for 2D and 3D calculations. The bow shock produced by a hot, magnetized, slowly rotating star as it moves through the magnetized ISM is simulated in 3D, highlighting diff…
Second only to initial mass, the rate of wind-driven mass loss determines the final mass of a massive star and the nature of its remnant. Motivated by the need to reconcile observational values and theory, we use a recently vetted technique to analyze the mass-loss rates in a sample of OB stars that generate bowshock nebulae. We measure peculiar velocities from new Gaia parallax and proper motion data and their spectral types from new optical and infrared spectroscopy. For our sample of 67 central stars in morphologically selected bowshocks nebulae, 67 are OB stars. The median peculiar velocit…
We identify 709 arc-shaped mid-infrared nebula in 24 micron Spitzer Space Telescope or 22 micron Wide Field Infrared Explorer surveys of the Galactic Plane as probable dusty interstellar bowshocks powered by early-type stars. About 20% are visible at 8 microns or shorter mid-infrared wavelengths as well. The vast majority (660) have no previous identification in the literature. These extended infrared sources are strongly concentrated near Galactic mid-Plane with an angular scale height of ~0.6 degrees. All host a symmetrically placed star implicated as the source of a stellar wind sweeping up…
Bow-shaped mid-infrared emission regions have been discovered in satellite observations of numerous late-type O and early-type B stars with moderate velocities relative to the ambient interstellar medium. Previously, hydrodynamical bow shock models have been used to study this emission. It appears that such models are incomplete in that they neglect kinetic effects associated with long mean free paths of stellar wind particles, and the complexity of Weibel instability fronts. Wind ions are scattered in the Weibel instability and mix with the interstellar gas. However, they do not lose their mo…
We briefly introduce the VLBI maser astrometric analysis of IRAS 18043-2116 and IRAS 18113-2503, two remarkable and unusual water fountains with spectacular bipolar bow shocks in their high-speed collimated jet-driven outflows. The 22 GHz H2O maser structures and velocities clearly show that the jets are formed in very short-lived, episodic outbursts, which may indicate episodic accretion in an underlying binary system.
Aims. Various studies indicate that interacting binary stars of Algol type evolve non-conservatively. However, direct detections of systemic mass loss in Algols have been scarce so far. We study the systemic mass loss in Algols by looking for the presence of infrared excesses originating from the thermal emission of dust grains, which is linked to the presence of a stellar wind. Methods. In contrast to previous studies, we make use of the fact that stellar and interstellar material is piled up at the edge of the astrosphere where the stellar wind interacts with the interstellar medium. We anal…
Dust waves and bow waves result from the action of a star's radiation pressure on a stream of dusty plasma that flows past it. They are an alternative mechanism to hydrodynamic bow shocks for explaining the curved arcs of infrared emission seen around some stars. When gas and grains are perfectly coupled, for a broad class of stellar parameters, wind-supported bow shocks predominate when the ambient density is below 100 per cubic cm. At higher densities radiation-supported bows can form, tending to be optically thin bow waves around B stars, or optically thick bow shocks around early O stars. …
Bow shocks and related density enhancements produced by the winds of massive stars moving through the interstellar medium provide important information regarding the motions of the stars, the properties of their stellar winds, and the characteristics of the local medium. Since bow shocks are aspherical structures, light scattering within them produces a net polarization signal even if the region is spatially unresolved. Scattering opacity arising from free electrons and dust leads to a distribution of polarized intensity across the bow shock structure. That polarization encodes information abo…
Stellar bow shocks, bow waves, and dust waves all result from the action of a star's wind and radiation pressure on a stream of dusty plasma that flows past it. The dust in these bows emits prominently at mid-infrared wavelengths in the range 8 to 60 micron. We propose a novel diagnostic method, the tau-eta diagram, for analyzing these bows, which is based on comparing the fractions of stellar radiative energy and stellar radiative momentum that is trapped by the bow shell. This diagram allows the discrimination of wind-supported bow shocks, radiation-supported bow waves, and dust waves in whi…
Stellar bow shocks result from relative motions between stars and their environment. The interaction of the stellar wind and radiation with gas and dust in the interstellar medium produces curved arcs of emission at optical, infrared, and radio wavelengths. We recently proposed a new two-dimensional classification scheme for the shape of such bow shocks, which we here apply to three very different observational datasets: mid-infrared arcs around hot OB stars; far-infrared arcs around luminous cool stars; and H alpha emission-line arcs around proplyds and other young stars in the Orion Nebula. …
We investigate the occurrence of stellar bow shocks around high-mass X-ray binaries (HMXBs) in the Galaxy. We seek to conduct a survey of HMXBs in the mid-infrared to search for the presence of bow shocks around these objects. Telescopes operating in the mid-infrared, such as the Spitzer Space Telescope or Wide-field Infrared Survey Explorer (WISE), are potent tools for searching for the stellar bow shocks. We used the available archival data from these telescopes to search for bow shock candidates around the confirmed and candidate HMXBs in the Galaxy. We detected extended mid-infrared struct…
Context. While the shapes of many observed bow shocks can be reproduced by simple astrosphere models, more elaborate approaches have recently been used to explain differing observable structures. Aims. By placing perturbations of an otherwise homogeneous interstellar medium in front of the astrospheric bow shock of the runaway blue supergiant $λ$ Cephei, the observable structure of the model astrosphere is significantly altered, providing insight into the origin of perturbed bow shock images. Methods. Three-dimensional single-fluid magnetohydrodynamic (MHD) models of stationary astrospheres we…
Astrophysical bow shocks are a common result of the interaction between two supersonic plasma flows, such as winds or jets from stars or active galaxies, or streams due to the relative motion between a star and the interstellar medium. For cylindrically symmetric bow shocks, we develop a general theory for the effects of inclination angle on the apparent shape. We propose a new two-dimensional classification scheme for bow shapes, which is based on dimensionless geometric ratios that can be estimated from observational images. The two ratios are related to the flatness of the bow's apex, which…
A persistent bow shock in a diskless magnetised accreting white dwarf
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（尼古拉·哥白尼天文学中心，波兰科学院）；Centre for Extragalactic Astronomy, Department of Physics, Durham University（杜伦大学物理系河外天文中心）；INAF-Osservatorio Astronomico di Capodimonte（意大利国家天体物理研究所卡波迪蒙特天文台）；School of Physics and Astronomy, University of Southampton（南安普顿大学物理与天文学院）；INAF-Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；University of Oxford, Department of Physics, Astrophysics（牛津大学物理系天体物理学）；Institute of Space Sciences (ICE, CSIC)（空间科学研究所（欧洲空间科学中心，西班牙高等科学研究委员会））；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚太空研究研究所）；South African Astronomical Observatory（南非天文台）；Department of Astronomy, University of Cape Town（开普敦大学天文系）；Department of Physics, University of the Free State（自由州大学物理系）；Department of Physics, University of Warwick（华威大学物理系）；Department of Astrophysics/IMAPP, Radboud University（拉德堡德大学天体物理学/IMAPP系）
Massive stars that have been ejected from their parent cluster and supersonically sailing away through the interstellar medium (ISM) are classified as exiled. They generate circumstellar bow shock nebulae that can be observed. We present two-dimensional, axisymmetric hydrodynamical simulations of a representative sample of stellar wind bow shocks from Galactic OB stars in an ambient medium of densities ranging from n_ISM=0.01 up to 10.0/cm3. Independently of their location in the Galaxy, we confirm that the infrared is the most appropriated waveband to search for bow shocks from massive stars.…
We constrain the proper motions of five OB stars associated with candidate stellar wind bow shocks in the Carina Nebula using HST ACS imaging over 9--10 year baselines. These proper motions allow us to directly compare each star's motion to the orientation of its candidate bow shock. Although these stars are saturated in our imaging, we assess their motion by the shifts required to minimize residuals in their Airy rings. The results limit the direction of each star's motion to sectors less than 90 degrees wide. None of the five stars are moving away from the Carina Nebula's central clusters as…
The Inner and Outer Shock Layers of Bow Shocks in Cataclysmic Variables
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；School of Physics and Astronomy, University of Southampton（南安普顿大学物理与天文学院）；Centre for Extragalactic Astronomy, Department of Physics, Durham University（达勒姆大学物理系河外天文研究中心）；INAF-Osservatorio Astronomico di Capodimonte（意大利国家天体物理研究所卡波迪蒙特天文台）；Astronomy and Astrophysics Group, Department of Physics, University of Warwick（华威大学物理系天文与天体物理学组）；Department of Space, Earth and Environment, Chalmers University of Technology（查尔姆斯理工大学空间、地球与环境系）；Institute of Space Sciences (ICE, CSIC)（空间科学研究所（西班牙高等科学研究理事会））；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究研究所）
Massive stars moving at supersonic peculiar velocities through the interstellar medium (ISM) can create bow shocks, arc-like structures at the interface between the stellar wind and the ISM. Many such bow shocks have been detected and catalogued at IR wavelengths, but detections in other wavebands remain rare. Strikingly, while electrons are expected to be accelerated in the bow shock and their non-thermal emission may include synchrotron emission at low frequencies, only two massive runaway stellar bow shocks have to date been detected in the radio band. Here, we examine a sample of fifty IR-…
We present a deep radio-polarimetric observation of the stellar bow shock EB27 associated to the massive star BD+43 3654. This is the only stellar bow shock confirmed to have non-thermal radio emission. We used the Jansky Very Large Array in S band (2 - 4GHz) to test whether this synchrotron emission is polarised. The unprecedented sensitivity achieved allowed us to map even the fainter regions of the bow shock, revealing that the more diffuse emission is steeper and the bow shock brighter than previously reported. No linear polarisation is detected in the bow shock above 0.5%, although we det…
Stellar bow shocks are observed in a variety of interstellar environments and are shaped by the conditions of gas in the interstellar medium (ISM). In situ measurements of turbulent density fluctuations near stellar bow shocks are only achievable with a few observational probes, including H$α$ emitting bow shocks and the Voyager Interstellar Mission (VIM). In this paper, we examine density variations around the Guitar Nebula, an H$α$ bow shock associated with PSR B2224$+$65, in tandem with density variations probed by VIM near the boundary of the solar wind and ISM. High-resolution Hubble Spac…
Wolf-Rayet stars are advanced evolutionary stages of massive stars. Despite their large mass-loss rates and high wind velocities, none of them display a bow shock, although a fraction of them are classified as runaway. Our 2.5-D numerical simulations of circumstellar matter around a 60Mo runaway star show that the fast Wolf-Rayet stellar wind is released into a wind-blown cavity filled with various shocks and discontinuities generated throughout the precedent evolutionary phases. The resulting fast-wind slow-wind interaction leads to the formation of spherical shells of swept-up dusty material…
A targeted radio survey of infrared-selected bow shock candidates
Leibniz-Institut für Astrophysik Potsdam (AIP)（波茨坦阿斯特罗物理学会莱布尼茨研究所）；Universidad Nacional Autónoma de México. Instituto de Astronomía（墨西哥国立自治大学天文学研究所）；Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México（墨西哥国立自治大学射电天文与天体物理研究所）；Institute of Physics and Astronomy, University of Potsdam（波茨坦大学物理与天文学研究所）；Astronomy & Astrophysics Section, School of Cosmic Physics, Dublin Institute for Advanced Studies, DIAS Dunsink Observatory（都柏林高等研究院宇宙物理学院天文与天体物理系邓辛克天文台）；School of Physics, University College Dublin（都柏林大学学院物理学院）；Purple Mountain Observatory, and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences（中国科学院紫金山天文台射电天文重点实验室）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；National Radio Astronomy Observatory（美国国家射电天文台）
Citizen science has helped astronomers comb through large data sets to identify patterns and objects that are not easily found through automated processes. The Milky Way Project (MWP), a citizen science initiative on the Zooniverse platform, presents internet users with infrared (IR) images from Spitzer Space Telescope Galactic plane surveys. MWP volunteers make classification drawings on the images to identify targeted classes of astronomical objects. We present the MWP second data release (DR2) and an updated data reduction pipeline written in Python. We aggregate ${\sim}3$ million classific…
