The Structure of the Local Hot Bubble

Liu, W.; Chiao, Meng P.; Collier, M. R.; Cravens, T. E.; Galeazzi, M.; Koutroumpa, Dimitra; Küntz, K. D.; Lallement, R.; Lepri, S. T.; McCammon, D.; Morgan, Kelsey M.; Porter, F. S.; Snowden, S. L.; Thomas, Nicholas E.; Uprety, Y.; Ursino, Eugenio; Walsh, Brian M.

doi:10.3847/1538-4357/834/1/33

Cited by 73 publications

(71 citation statements)

References 49 publications

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“…λ max is inversely proportional to the particle size of dust in the interstellar medium (Draine 1995). A value of 550 nm is typical for our Galaxy (Serkowski et al 1975) and in the rim of the Local Hot Bubble (Cotton et al 2019a) -a region of space largely devoid of gas and dust, carved out by ancient supernovae, that extends roughly 75 to 150 pc beyond the Sun (Liu et al 2016).…”

Section: Interstellar Parametersmentioning

confidence: 97%

The rotation of α Oph investigated using polarimetry

Bailey

Cotton

Howarth

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Recently we have demonstrated that high-precision polarization observations can detect the polarization resulting from the rotational distortion of a rapidly rotating Btype star. Here we investigate the extension of this approach to an A-type star. Linearpolarization observations of α Oph (A5IV) have been obtained over wavelengths from 400 to 750 nm. They show the wavelength dependence expected for a rapidly-rotating star combined with a contribution from interstellar polarization. We model the observations by fitting rotating-star polarization models and adding additional constraints including a measured v e sin i. However, we cannot fully separate the effects of rotation rate and inclination, leaving a range of possible solutions. We determine a rotation rate (ω = Ω/Ω c ) between 0.83 and 0.98 and an axial inclination i > 60 • . The rotationaxis position angle is found to be 142 • ± 4 • , differing by 16 • from a value obtained by interferometry. This might be due to precession of the rotation axis due to interaction with the binary companion. Other parameters resulting from the analysis include a polar temperature T p = 8725 ± 175 K, polar gravity log g p = 3.93 ± 0.08 (dex cgs), and polar radius R p = 2.52 ± 0.06 R . Comparison with rotating-star evolutionary models indicates that α Oph is in the later half of its main-sequence evolution and must have had an initial ω of 0.8 or greater. The interstellar polarization has a maximum value at a wavelength (λ max ) of 440 ± 110 nm, consistent with values found for other nearby stars.

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Section: Interstellar Parametersmentioning

confidence: 97%

The rotation of α Oph investigated using polarimetry

Bailey

Cotton

Howarth

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…10). Nevertheless, recent results from the December 2012 Diffuse X-rays from the Local galaxy (DXL) rocket flight have conclusively demonstrated that ∼ 40% of background emissions in a direction of very low cosmic background intensity originate from the He focusing cone and not the local hot bubble surrounding the heliosphere Uprety et al 2016;Liu et al 2017). Koutroumpa et al (2007) employed a dynamic model to simulate the effects of a propagating corotating interaction region on line of sight soft X-ray emissions.…”

Section: Modeling Soft X-ray Emissions From the Heliospherementioning

confidence: 99%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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Both heliophysics and planetary physics seek to understand the complex nature of the solar wind's interaction with solar system obstacles like Earth's magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in con- text by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the KelvinHelmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1-2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles. The introduction notes that theory, local, and global simulations predict the characteristics of plasma boundaries such the bow shock and magnetopause (including location, density gradient, and motion) and regions such as the magnetosheath (including density and width) as a function of location, solar wind conditions, and the particular mechanism operating. In situ measurements confirm the existence of time-and spatial-dependent plasma density structures like the bow shock, magnetosheath, and magnetopause/ionopause at Venus, Mars, comets, and the Earth. However, in situ measurements rarely suffice to determine the global extent of these density structures or their global variation as a function of solar wind conditions, except in the form of empirical studies based on observations from many different times and solar wind conditions. Remote sensing observations provide global information about auroral ovals (FUV and hard X-ray), the terrestrial plasmasphere (EUV), and the terrestrial ring current (ENA). ENA instruments with low energy thresholds (∼ 1 keV) have recently been used to obtain important information concerning the magnetosheaths of Venus, Mars, and the Earth. Recent technological developments make these magnetosheaths valuable potential targets for high-cadence wide-field-of-view soft X-ray imagers.Section 2 describes proposed dayside interaction mechanisms, including reconnection, the Kelvin-Helmholtz instability, and other processes in greater detail with an emphasis on the plasma density structures that they generate. It focuses upon the questions that remain as yet unanswered, such as the significanc...

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“…As mentioned in Section 5.2, at high latitudes we are unable to separate the local plasma from the low temperature component of the halo, which affects our derived values for emission measure, as well as possibly temperature. Liu et al (2017) combined SWCX maps from Uprety et al (2016) with data from Snowden et al (1998) to estimate the local and distant astrophysical contributions to the R12 band. In Table 9, we compare the results of our spectral model fits to that work.…”

Section: The Local Hot Bubblementioning

confidence: 99%

A High Spectral Resolution Study of the Soft X-Ray Background with the X-Ray Quantum Calorimeter

Wulf

Eckart

Galeazzi

et al. 2019

ApJ

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We present here a combined analysis of four high spectral resolution observations of the Diffuse X-ray Background (DXRB), made using the University of Wisconsin-Madison/Goddard Space Flight Center X-ray Quantum Calorimeter (XQC) sounding rocket payload. The observed spectra support the existence of a ∼0.1 keV Local Hot Bubble and a ∼0.2 keV Hot Halo, with discrepancies between repeated observations compatible with expected contributions of time-variable emission from Solar Wind Charge Exchange (SWCX). An additional component of ∼0.9 keV emission observed only at low galactic latitudes can be consistently explained by unresolved dM stars.

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The Structure of the Local Hot Bubble

Cited by 73 publications

References 49 publications

The rotation of α Oph investigated using polarimetry

The rotation of α Oph investigated using polarimetry

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

A High Spectral Resolution Study of the Soft X-Ray Background with the X-Ray Quantum Calorimeter

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