Possible Association of Two Stellar Bowshocks with Unidentified Fermi Sources

Sánchez-Ayaso, E.; Valle, Maŕıa Victoria del; Martı́, Josep; Romero, Gustavo E.; Luque-Escamilla, Pedro L.

doi:10.3847/1538-4357/aac7c7

Cited by 12 publications

(9 citation statements)

References 33 publications

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“…While cyclotron radiation is emitted at very low and ultra-low frequencies, far below the spectral range of observational instruments, the bremsstrahlung spectrum reaches frequencies in the extreme ultraviolet and soft X-ray regime. Higher thermal speeds of electrons would result in even higher frequencies, as were observed by Sánchez-Ayaso et al (2018), for example.…”

Section: Discussionmentioning

confidence: 72%

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Skymaps of observables of three-dimensional magnetohydrodynamic astrosphere models

Baalmann

Scherer

Fichtner

et al. 2020

A&A

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Context. Three-dimensional models of astrospheres have recently become of interest. However, comparisons between these models and observations are non-trivial because of the two-dimensional nature of observations. Aims. By projecting selected physical values of three-dimensional models of astrospheres onto the surface of a sphere that is centred on a virtual all-sky observer, these models can be compared to observational data in different observables: the column density, bremsstrahlung flux, rotation measure, Hα flux, and synchrotron or cyclotron flux. Methods. Projections were calculated by rotating and moving the astrosphere model to the desired position and orientation and by then computing the value of a given patch on the sphere by a modified line-of-sight integration. Contributions to the selected observable made by all model cells that are connected to the patch by the line of sight in question were taken into account.Results. When the model produces a bow shock, a distinct parabolic structure produced by the outer astrosheath can be seen in every observable of the projection, the exact shape depending on the orientations of the line of sight and the stellar motion. Of all four examined astrosphere models, only that of λ Cephei shows fluxes that are higher than current observational thresholds. This is due to the strong stellar wind and interstellar inflow of the λ Cephei model.

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Section: Discussionmentioning

confidence: 72%

“…The resulting models have been successfully compared to observational images and data in various observables (e.g. Kobulnicky et al 2017;Sánchez-Ayaso et al 2018, and references therein). The shapes of these structures strongly depend on the physical parameters of the star and on the surrounding interstellar medium (ISM) (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Skymaps of observables of three-dimensional magnetohydrodynamic astrosphere models

Baalmann

Scherer

Fichtner

et al. 2020

A&A

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“…No associated emission was found, but from the resulting upper limits a constraint on the very high energy emission was obtained: it should be less than 0.1 to 1% of the kinetic wind energy. Recently, Sánchez-Ayaso et al (2018) presented two runaway stars (Lambda Cephei and LS 2355) whose bow shocks are coincident with two unidentified Fermi gamma-ray sources from the third Fermi 3FGL catalog (Acero et al 2015). After cross-correlation between different catalogs at distinct wavelengths, the authors found that these bow shocks are the most peculiar objects in the Fermi position ellipses.…”

Section: Introductionmentioning

confidence: 99%

Nonthermal Emission from Stellar Bow Shocks

Valle

Pohl

2018

ApJ

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Since the detection of nonthermal radio emission from the bow shock of the massive runaway star BD +43°3654, simple models have predicted high-energy emission, at X-rays and gamma-rays, from these Galactic sources. Observational searches for this emission so far give no conclusive evidence but a few candidates at gamma-rays. In this work we aim at developing a more sophisticated model for the nonthermal emission from massive runaway star bow shocks. The main goal is to establish whether these systems are efficient nonthermal emitters, even if they are not strong enough yet to be detected. For modeling the collision between the stellar wind and the interstellar medium we use 2D hydrodynamic simulations. We then adopt the flow profile of the wind and the ambient medium obtained with the simulation as the plasma state for solving the transport of energetic particles injected in the system, as well as the nonthermal emission they produce. For this purpose we solve a 3D (two spatial + energy) advection-diffusion equation in the test-particle approximation. We find that a massive runaway star with a powerful wind converts 0.16%-0.4% of the power injected in electrons into nonthermal emission, mostly produced by inverse Compton scattering of dust-emitted photons by relativistic electrons, and second by synchrotron radiation. This represents a fraction of ∼10 −5 to 10 −4 of the wind kinetic power. Given the better sensibility of current instruments at radio wavelengths, these systems are more prone to be detected at radio through the synchrotron emission they produce rather than at gamma energies.

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“…E. S. S. Collaboration et al 2018) emission from stellar BSs. The only exception is the possible association of two stellar BSs with Fermi sources (Sánchez-Ayaso et al 2018). Moreover, nonthermal radio emission from other BSs also remains elusive (C.S.…”

Section: Introductionmentioning

confidence: 99%

High-sensitivity radio study of the non-thermal stellar bow shock EB27

Benaglia

Palacio

Hales

et al. 2021

Monthly Notices of the Royal Astronomical Society

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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 (2–4 GHz) 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 detected polarised emission from two southern sources, probably extragalactic in nature. We modeled the intensity and morphology of the radio emission to better constrain the magnetic field and injected power in relativistic electrons. Finally, we derived a set of more precise parameters for the system EB27–BD+43○3654 using Gaia Early Data Release 3, including the spatial velocity. The new trajectory, back in time, intersects the core of the Cyg OB2 association.

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Possible Association of Two Stellar Bowshocks with Unidentified Fermi Sources

Cited by 12 publications

References 33 publications

Skymaps of observables of three-dimensional magnetohydrodynamic astrosphere models

Skymaps of observables of three-dimensional magnetohydrodynamic astrosphere models

Nonthermal Emission from Stellar Bow Shocks

High-sensitivity radio study of the non-thermal stellar bow shock EB27

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