scholarly journals On the ring nebulae around runaway Wolf–Rayet stars

2020 ◽  
Vol 496 (3) ◽  
pp. 3906-3911
Author(s):  
D M-A Meyer ◽  
L M Oskinova ◽  
M Pohl ◽  
M Petrov
Keyword(s):  
High Latitude ◽  
Stellar Wind ◽  
Near Infrared ◽  
Moving Objects ◽  
Galactic Plane ◽  
Massive Stars ◽  
Ambient Medium ◽  
Bow Shock ◽  
Fast Wind ◽  
Bow Shocks

ABSTRACT Wolf–Rayet stars are advanced evolutionary stages of massive stars. Despite their large mass-loss rates and high wind velocities, none of them displays a bow shock, although a fraction of them are classified as runaway. Our 2.5-D numerical simulations of circumstellar matter around a $60\mbox{-}\rm M_{\odot }$ 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 preceding evolutionary phases. The resulting fast-wind–slow-wind interaction leads to the formation of spherical shells of swept-up dusty material similar to those observed in the near-infrared at $24\, \rm \mu \rm m$ with Spitzer, which appear to be comoving with the runaway massive stars, regardless of their proper motion and/or the properties of the local ambient medium. We interpret bright infrared rings around runaway Wolf–Rayet stars in the Galactic plane as an indication of their very high initial masses and complex evolutionary history. Stellar-wind bow shocks become faint as stars run in diluted media, therefore our results explain the absence of bow shocks detected around Galactic Wolf–Rayet stars, such as the high-latitude, very fast-moving objects WR71, WR124 and WR148. Our results show that the absence of a bow shock is consistent with the runaway nature of some Wolf–Rayet stars. This questions the in situ star formation scenario of high-latitude Wolf–Rayet stars in favour of dynamical ejection from birth sites in the Galactic plane.

scholarly journals Wind nebulae and supernova remnants of very massive stars

2020 ◽  
Vol 493 (3) ◽  
pp. 3548-3564 ◽  
Author(s):  
D M-A Meyer ◽  
M Petrov ◽  
M Pohl
Keyword(s):  
Supernova Remnants ◽  
Galactic Plane ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Supernova Explosion ◽  
Bow Shock ◽  
High Mass ◽  
Fast Wind ◽  
High Mass Loss ◽  
Hydrodynamical Simulations

ABSTRACT A very small fraction of (runaway) massive stars have masses exceeding $60\!-\!70\, \rm M_{\odot }$ and are predicted to evolve as luminous blue variable and Wolf–Rayet stars before ending their lives as core-collapse supernovae. Our 2D axisymmetric hydrodynamical simulations explore how a fast wind ($2000\, \rm km\, \rm s^{-1}$) and high mass-loss rate ($10^{-5}\, \rm M_{\odot }\, \rm yr^{-1}$) can impact the morphology of the circumstellar medium. It is shaped as 100 pc-scale wind nebula that can be pierced by the driving star when it supersonically moves with velocity $20\!-\!40\, \rm km\, \rm s^{-1}$ through the interstellar medium (ISM) in the Galactic plane. The motion of such runaway stars displaces the position of the supernova explosion out of their bow shock nebula, imposing asymmetries to the eventual shock wave expansion and engendering Cygnus-loop-like supernova remnants. We conclude that the size (up to more than $200\, \rm pc$) of the filamentary wind cavity in which the chemically enriched supernova ejecta expand, mixing efficiently the wind and ISM materials by at least $10{{\ \rm per\ cent}}$ in number density, can be used as a tracer of the runaway nature of the very massive progenitors of such $0.1\, \rm Myr$ old remnants. Our results motivate further observational campaigns devoted to the bow shock of the very massive stars BD+43°3654 and to the close surroundings of the synchrotron-emitting Wolf–Rayet shell G2.4+1.4.

scholarly journals How to inflate a wind-blown bubble

2021 ◽  
Vol 508 (2) ◽  
pp. 1768-1776
Author(s):  
J M Pittard ◽  
C J Wareing ◽  
M M Kupilas
Keyword(s):  
Stellar Wind ◽  
External Medium ◽  
Reference Model ◽  
Massive Stars ◽  
Ambient Medium ◽  
Stellar Winds ◽  
Relative Importance ◽  
Numerical Resolution ◽  
Maximum Value ◽  
Injection Region

ABSTRACT Stellar winds are one of several ways that massive stars can affect the star formation process on local and galactic scales. In this paper, we investigate the numerical resolution needed to inflate an energy-driven stellar wind bubble in an external medium. We find that the radius of the wind injection region, rinj, must be below a maximum value, rinj,max, in order for a bubble to be produced, but must be significantly below this value if the bubble properties are to closely agree with analytical predictions. The final bubble momentum is within 25 per cent of the value from a higher resolution reference model if χ = rinj/rinj,max = 0.1. Our work has significance for the amount of radial momentum that a wind-blown bubble can impart to the ambient medium in simulations, and thus on the relative importance of stellar wind feedback.

scholarly journals On the Energetics and Momentum Distribution of Bow Shocks and Colliding Winds

1997 ◽  
Vol 182 ◽  
pp. 343-352
Author(s):  
Francis P. Wilkin ◽  
Jorge Cantó ◽  
Alex C. Raga
Keyword(s):  
Column Density ◽  
Recent Progress ◽  
Ambient Medium ◽  
Bow Shock ◽  
Upper Limit ◽  
Internal Flux ◽  
Bow Shocks ◽  
Conservation Of Momentum ◽  
Analytic Models ◽  
Colliding Winds

We discuss recent progress in analytic modeling of stellar wind bow shocks and colliding winds. For thin, radiative shocked layers in steady-state, the shape of the layer as well as its internal flux of mass and momentum are found from the conservation laws of mass, momentum and angular momentum. For the case that the shocked gas is well-mixed, the velocity distribution and mass column density of shocked material are also obtained. These solutions are extended to the problem of a jet bow shock, treated as a non-isotropic “wind” interacting with the ambient medium. We also examine the shell energetics for these simple analytic models. The constraint of conservation of momentum leads to an upper limit to the efficiency of thermalization and radiation of the pre-shock wind kinetic energy. Calculations are presented of this thermalization rate as a function of the input momentum rates of the pre-shock winds.

scholarly journals The Milky Way Project second data release: bubbles and bow shocks

2019 ◽  
Vol 488 (1) ◽  
pp. 1141-1165 ◽  
Author(s):  
Tharindu Jayasinghe ◽  
Don Dixon ◽  
Matthew S Povich ◽  
Breanna Binder ◽  
Jose Velasco ◽  
...  
Keyword(s):  
Citizen Science ◽  
Milky Way ◽  
Galactic Plane ◽  
Learning Algorithm ◽  
Large Data ◽  
Bow Shock ◽  
H Ii Regions ◽  
Data Sets ◽  
Data Release ◽  
Bow Shocks

ABSTRACT 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 ∼3 million classifications made by MWP volunteers during the years 2012–2017 to produce the DR2 catalogue, which contains 2600 IR bubbles and 599 candidate bow shock driving stars. The reliability of bubble identifications, as assessed by comparison to visual identifications by trained experts and scoring by a machine-learning algorithm, is found to be a significant improvement over DR1. We assess the reliability of IR bow shocks via comparison to expert identifications and the colours of candidate bow shock driving stars in the 2MASS point-source catalogue. We hence identify highly reliable subsets of 1394 DR2 bubbles and 453 bow shock driving stars. Uncertainties on object coordinates and bubble size/shape parameters are included in the DR2 catalogue. Compared with DR1, the DR2 bubbles catalogue provides more accurate shapes and sizes. The DR2 catalogue identifies 311 new bow shock driving star candidates, including three associated with the giant H ii regions NGC 3603 and RCW 49.

scholarly journals 2D kinematics of massive stars near the Galactic Centre

2020 ◽  
Vol 500 (3) ◽  
pp. 3213-3239
Author(s):  
Mattia Libralato ◽  
Daniel J Lennon ◽  
Andrea Bellini ◽  
Roeland van der Marel ◽  
Simon J Clark ◽  
...  
Keyword(s):  
Moving Objects ◽  
Hubble Space Telescope ◽  
Massive Stars ◽  
Line Of Sight ◽  
Galactic Centre ◽  
Harsh Environment ◽  
Proper Motions ◽  
Sgr A ◽  
Better Than ◽  
Rule Out

ABSTRACT The presence of massive stars (MSs) in the region close to the Galactic Centre (GC) poses several questions about their origin. The harsh environment of the GC favours specific formation scenarios, each of which should imprint characteristic kinematic features on the MSs. We present a 2D kinematic analysis of MSs in a GC region surrounding Sgr A* based on high-precision proper motions obtained with the Hubble Space Telescope. Thanks to a careful data reduction, well-measured bright stars in our proper-motion catalogues have errors better than 0.5 mas yr−1. We discuss the absolute motion of the MSs in the field and their motion relative to Sgr A*, the Arches, and the Quintuplet. For the majority of the MSs, we rule out any distance further than 3–4 kpc from Sgr A* using only kinematic arguments. If their membership to the GC is confirmed, most of the isolated MSs are likely not associated with either the Arches or Quintuplet clusters or Sgr A*. Only a few MSs have proper motions, suggesting that they are likely members of the Arches cluster, in agreement with previous spectroscopic results. Line-of-sight radial velocities and distances are required to shed further light on the origin of most of these massive objects. We also present an analysis of other fast-moving objects in the GC region, finding no clear excess of high-velocity escaping stars. We make our astro-photometric catalogues publicly available.

Polarimetric and photometric observations of CB54, with analysis of four other dark clouds

2021 ◽  
Vol 503 (4) ◽  
pp. 5274-5290
Author(s):  
A K Sen ◽  
V B Il’in ◽  
M S Prokopjeva ◽  
R Gupta
Keyword(s):  
Magnetic Field ◽  
Near Infrared ◽  
Galactic Plane ◽  
Photometric Data ◽  
Dust Particles ◽  
Dark Cloud ◽  
Dark Clouds ◽  
High Polarization ◽  
Field Parallel ◽  
Photometric Observations

ABSTRACT We present the results of our BVR-band photometric and R-band polarimetric observations of ∼40 stars in the periphery of the dark cloud CB54. From different photometric data, we estimate E(B − V) and E(J − H). After involving data from other sources, we discuss the extinction variations towards CB54. We reveal two main dust layers: a foreground, E(B − V) ≈ 0.1 mag, at ∼200 pc and an extended layer, $E(B-V) \gtrsim 0.3$ mag, at ∼1.5 kpc. CB54 belongs to the latter. Based on these results, we consider the reason for the random polarization map that we have observed for CB54. We find that the foreground is characterized by low polarization ($P \lesssim 0.5$ per cent) and a magnetic field parallel to the Galactic plane. The extended layer shows high polarization (P up to 5–7 per cent). We suggest that the field in this layer is nearly perpendicular to the Galactic plane and both layers are essentially inhomogeneous. This allows us to explain the randomness of polarization vectors around CB54 generally. The data – primarily observed by us in this work for CB54, by A. K. Sen and colleagues in previous works for three dark clouds CB3, CB25 and CB39, and by other authors for a region including the B1 cloud – are analysed to explore any correlation between polarization, the near-infrared, E(J − H), and optical, E(B − V), excesses, and the distance to the background stars. If polarization and extinction are caused by the same set of dust particles, we should expect good correlations. However, we find that, for all the clouds, the correlations are not strong.

scholarly journals Infrared nebulae around bright massive stars as indicators for binary interactions

2018 ◽  
Vol 618 ◽  
pp. A110 ◽  
Author(s):  
J. Bodensteiner ◽  
D. Baade ◽  
J. Greiner ◽  
N. Langer
Keyword(s):  
Supernova Remnants ◽  
Binary Systems ◽  
Massive Stars ◽  
Space Velocity ◽  
Be Stars ◽  
Global Risk ◽  
Wide Range ◽  
Bow Shocks ◽  
Binary Evolution ◽  
Stellar Properties

Context. 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. Aims. 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. Methods. For ∼3850 stars (all OBA stars in the Bright Star Catalogue (BSC), Be stars, BeXRBs, and Be+sdO systems), we visually inspect WISE 22 μm images. Based on nebular shape and relative position, we distinguish five categories: offset bow shocks structurally aligned with the stellar space velocity, unaligned offset bow shocks, and centered, unresolved, and not classified nebulae. Results. In the BSC, we find that 28%, 13%, and 0.4% of all O, B, and A stars, respectively, possess associated infrared (IR) nebulae. Additionally, 34/234 Be stars, 4/72 BeXRBs, and 3/17 Be+sdO systems are associated with IR nebulae. Conclusions. Aligned or unaligned bow shocks result from high relative velocities between star and interstellar medium (ISM) that are dominated by the star or the ISM, respectively. About 13% of the centered nebulae could be bow shocks seen head- or tail-on. For the rest, the data disfavor explanations as remains of parental disks, supernova remnants of a previous companion, and dust production in stellar winds. The existence of centered nebulae also at high Galactic latitudes strongly limits the global risk of coincidental alignments with condensations in the ISM. Mass loss during binary evolution seems a viable mechanism for the formation of at least some of these nebulae. In total, about 29% of the IR nebulae (2% of all OBA stars in the BSC) may find their explanation in the context of binary evolution.

scholarly journals Maser, infrared and optical emission for late-type stars in the Galactic plane

2017 ◽  
Vol 13 (S336) ◽  
pp. 184-186
Author(s):  
L. H. Quiroga-Nuñez ◽  
H. J. van Langevelde ◽  
L. O. Sjouwerman ◽  
Y. M. Pihlström ◽  
M. J. Reid ◽  
...  
Keyword(s):  
Galactic Plane ◽  
Population Distribution ◽  
Massive Stars ◽  
Optical Emission ◽  
Proper Motions ◽  
Late Type ◽  
Intrinsic Properties ◽  
Radio Observations ◽  
Evolved Stars

AbstractRadio astrometric campaigns using VLBI have provided distances and proper motions for masers associated with young massive stars (BeSSeL survey). The ongoing BAaDE project plans to obtain astrometric information of SiO maser stars located in the inner Galaxy. These stars are associated with evolved, mass-losing stars. By overlapping optical (Gaia), infrared (2MASS, MSX and WISE) and radio (BAaDE) sources, we expect to obtain important clues on the intrinsic properties and population distribution of late-type stars. Moreover, a comparison of the Galactic parameters obtained with Gaia and VLBI can be done using radio observations on different targets: young massive stars (BeSSeL) and evolved stars (BAaDE).

scholarly journals Near-infrared Characterization of Four Massive Stars in Transition Phases

2020 ◽  
Vol 160 (4) ◽  
pp. 166
Author(s):  
Yanina R. Cochetti ◽  
Michaela Kraus ◽  
María L. Arias ◽  
Lydia S. Cidale ◽  
Tõnis Eenmäe ◽  
...  
Keyword(s):  
Near Infrared ◽  
Massive Stars

scholarly journals An Interpretation of the Distribution of Metre Wavelength Radio Emission

1968 ◽  
Vol 21 (2) ◽  
pp. 167 ◽  
Author(s):  
KW Yates
Keyword(s):  
High Latitude ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Absolute Calibration ◽  
Fundamental Difficulty ◽  
The Galaxy ◽  
Calibration Accuracy ◽  
Limit Estimate ◽  
Spiral Arm

A recent 85 MHz survey of the southern sky had an absolute calibration accuracy and resolution comparable with a number of surveys made for the northern skies. By combining the results of these surveys in both hemispheres a complete sky map has been produced, and in this paper an analysis is made of the distribution of the medium and high latitude emission. A fundamental difficulty encountered is the identification and isolation of the spurs of emission projecting from the galactic plane. Two hypotheses are proposed. The first attributes the spurs to a large-scale feature associated with the galactic core and the remaining emission to a galactic halo. The second postulates the origin of the spurs within the local spiral arm, which is itself considered to contribute significantly to the high latitude background. An upper-limit estimate of the emissivity of the local arm is made from currently available independent data. Using this result a model local arm is proposed, which, together with an isotropic component from beyond the Galaxy and a small additional galactic component, explains the observed distribution.

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