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Post Info TOPIC: HD34078 and IC405
Blobrana


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HD34078
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Title: AE Aurigae: first detection of non-thermal X-ray emission from a bow shock produced by a runaway star
Authors: J. Lopez-Santiago, M. Miceli, M. V. del Valle, G. E. Romero, R. Bonito, J. F. Albacete-Colombo, V. Pereira, E. de Castro, F. Damiani

Runaway stars produce shocks when passing through interstellar medium at supersonic velocities. Bow shocks have been detected in the mid-infrared for several high-mass runaway stars and in radio waves for one star. Theoretical models predict the production of high-energy photons by non-thermal radiative processes in a number sufficiently large to be detected in X-rays. To date, no stellar bow shock has been detected at such energies. We present the first detection of X-ray emission from a bow shock produced by a runaway star. The star is AE Aur, which was likely expelled from its birthplace by the encounter of two massive binary systems and now is passing through the dense nebula IC 405. The X-ray emission from the bow shock is detected at 30" to the northeast of the star, coinciding with an enhancement in the density of the nebula. From the analysis of the observed X-ray spectrum of the source and our theoretical emission model, we confirm that the X-ray emission is produced mainly by inverse Compton upscattering of infrared photons from dust in the shock front.

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Blobrana


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Posts: 131433
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AE Aurigae
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AE Aurigae is a blue O-type main sequence dwarf with a mean apparent magnitude of +5.99. It is classified as an Orion type variable star and its brightness varies irregularly between magnitudes +5.78 and +6.08. It is approximately 1460 light-years from Earth. It is a runaway star that might have been ejected during a collision of two binary star groups. This collision, which also is credited with ejecting Mu Columbae and 53 Arietis, has been traced to the Trapezium cluster in the Orion Nebula two million years ago.
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Blobrana


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"Is star AE Aurigae on fire? No. Even though AE Aurigae is named the flaming star, the surrounding nebula IC 405 is named the Flaming Star Nebula, and the region appears to harbour red smoke, there is no fire. Fire, typically defined as the rapid molecular acquisition of oxygen, happens only when sufficient oxygen is present and is not important in such high-energy, low-oxygen environments such as stars. The material that appears as smoke is mostly interstellar hydrogen, but does contain smoke-like dark filaments of carbon-rich dust grains. The bright star AE Aurigae, visible near the nebula center, is so hot it is blue, emitting light so energetic it knocks electrons away from surrounding gas. When a proton recaptures an electron, red light is frequently emitted, as seen in the surrounding emission nebula. Pictured above, the Flaming Star nebula lies about 1,500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of the Charioteer (Auriga)" - Astronomer Jorge Garcia.

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Position(2000): RA05 16 18.1497, Dec +34 18 44.341

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Blobrana


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Posts: 131433
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HD34078 and IC405
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Title: A Cometary Bow Shock and Mid-Infrared Emission Variations Revealed in Spitzer Observations of HD 34078 and IC 405
Authors: Kevin France (1,2), Stephan R. McCandliss (1), Roxana E. Lupu (1) (1-JHU, 2-CITA/U Toronto)

We present new infrared observations of the emission/reflection nebula IC 405 obtained with the Spitzer Space Telescope. Infrared images in the four IRAC bands (3.6, 4.5, 5.8, and 8.0 µm) and two MIPS bands (24 and 70 µm) are complemented by IRS spectroscopy (5-30 µm) of two nebular filaments. The IRAC (8.0 µm) and MIPS imaging shows evidence of a bow shock associated with the runaway O9.5V star, HD 34078, created by the interaction between the star and nebular material. The ratio of emission at 24 to 70 µm is higher in the immediate vicinity of HD 34078 than in the outer filaments, providing evidence for elevated dust temperatures (T_d > 90 K) in the shock region. The nebular imaging reveals that the morphology is band dependent, with varying contributions from aromatic emission features, H2, and dust emission. Nebular spectroscopy is used to quantify these contributions, showing several aromatic emission bands between 6-14 µm, the S(5), S(3), S(2), and S(1) pure rotational emission lines of H2, and atomic fine structure lines of Ne, S, and Ar. The low-dispersion spectra provide constraints on the ionisation state of the large molecules responsible for the aromatic infrared features. H2 rotational temperatures of the two bright nebular filaments are determined from the observed line strengths. An average T(H2) ~ 400 K is inferred, with evidence for additional non-uniform excitation by UV photons in the intense radiation field of HD 34078. The photoexcitation hypothesis is supported by direct measurement of the far-UV H2 fluorescence spectrum, obtained with FUSE.

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