The heated dust can emit in the infrared, which has been one of the major tracers of stellar BSs ( van Buren & McCray 1988 Peri et al. The FS compresses and heats the ISM gas and dust. In this case, the interaction between the highly supersonic stellar wind and the ISM leads to the formation of a bow shock (BS), which includes a forward shock (FS) that propagates through the ISM and a reverse shock (RS) that propagates through the stellar wind ( Weaver et al. An interesting case of study is when a massive OB star moves with a supersonic velocity with respect to its surrounding medium (see e.g., Mackey 2022, for a recent review). Stellar winds play an important role in the evolution of massive stars and their feedback in the interstellar medium (ISM). Subscribe to A&A to support open access publication. This article is published in open access under the Subscribe to Open model. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Finally, BD+43☃654 may be detected in GeV in the near future, while bow shocks in general may turn out to be non-negligible sources of (at least leptonic) low-energy cosmic rays. The prospects of detections with next-generation observatories such as SKA and ngVLA are very promising. This work provides multi-wavelength predictions of their emission and demonstrates the key role of low-frequency radio observations in unveiling particle acceleration processes. Stellar bow shocks can potentially be very efficient particle accelerators. ![]() We also estimated the gamma-ray fluxes from the HII regions around the bow shocks of BD+43☃654 and BD+60☂522, and obtained luminosities at GeV energies of ∼10 33 erg s −1 and 10 32 erg s −1, respectively, under reasonable assumptions.Ĭonclusions. We also show how complementary observations at other frequencies can allow us to place stronger constraints in the model. In the other systems, the interpretation of the observed flux density is more ambiguous, although a non-thermal scenario is also favoured. We can only explain the radio data from the best sampled systems (BD+43☃654 and BD+60☂522) assuming a hard electron energy distribution below ∼1 GeV, a high efficiency of conversion of (shocked) wind kinetic power into relativistic electrons (∼1 − 5%), and a relatively high magnetic-to-thermal pressure ratio of η B ∼ 0.2. In addition, we used a simplified one-zone model to estimate the gamma-ray emission from particles escaping the bow shocks. We fitted this model to the available radio data (spectral and intensity maps), including largely unexplored data at low frequencies. We used an extended non-thermal emission model for stellar bow shocks for which we incorporated a consistent calculation of the thermal emission from the forward shock. We aim to interpret this radio emission and assess under which conditions it could be either thermal (free–free) or non-thermal (synchrotron), and how to use the observational data to infer physical properties of the bow shocks. Recent observations revealed radio emission from a few of these objects, but the origin of this radiation remains poorly understood.Īims. Massive runaway stars produce bow shocks in the interstellar medium. Bosch-Ramon 4įacultad de Ciencias Exactas, UNLP, Calle 47 y 115, CP(1900), La Plata, Buenos Aires, ArgentinaĮ-mail: Argentino de Radioastronomía (CCT La Plata, CONICET), C.C.5, (1894) Villa Elisa, Buenos Aires, Argentinaĭepartment of Space, Earth and Environment, Chalmers University of Technology, 412 96 Gothenburg, Swedenĭepartament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, SpainĬontext. Astronomical objects: linking to databases.Including author names using non-Roman alphabets. ![]() Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
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