A HaloSat Analysis of the Cygnus Superbubble

Abstract

The Cygnus Superbubble (CSB) is a region of soft X-ray emission approximately 13 degrees wide in the direction of the local spiral arm. Such a large region might be the result of strong stellar winds and supernovae from nearby stellar nurseries, or it could be the result of a single event—a hypernova. HaloSat observed four nonoverlapping 10 degree diameter fields in the CSB region over the 0.4-7 keV band. The CSB absorption and temperature was found to be consistent over all four fields, with a weighted average of 6.1 × 1021 cm−2 and 0.190 keV, respectively. These observations suggest that the CSB is a cohesive object with a singular origin. The total thermal energy for the CSB is estimated at 4 × 1052 erg, based upon a shell-like physical model of the CSB. Absorption and distance estimates to Cyg OB associations are examined. The CSB absorption is found to be most consistent with the absorption seen in Cyg OB1, implying that the CSB lies at a similar distance of 1.1–1.4 kpc.

Observations of Magnetospheric Solar Wind Charge Exchange

“…In addition, it is curious that there is a signature at 3 keV in the stacked CGM spectrum compared to the lack of such a signature in both the Crab and CasA spectra (compare Figures 11,13,and 14b in that work) and the ECL stacked spectrum (Figure 8 of Ringuette et al 2021), even though those spectra have good statistics and were created with similar count rate cuts on the same high energy band (0.25, 0.25, and 0.50 counts s −1 on the 3-7 keV energy band; see also the related note in Bluem et al 2023). Once the spectral modeling is refined as suggested here, one could further investigate the signature at 3 keV, namely to investigate a possible faint signature of higher-energy emission in the stacked CGM spectrum at higher Galactic latitudes.…”

The HaloSat and PolarLight CubeSat Missions for X-ray Astrophysics

“…The HaloSat results on pressure and electron density favor a Galactic-scale event with an energy of ∼ 6 × 10 54 erg and an age of ∼10 Myr [14]. HaloSat data on the Cygnus superbubble, a region of bright soft X-ray emission in the direction of local spiral arm, show that the temperature and absorption are consistent across different parts, suggesting a singular origin, potentially as a hypernova remnant [19]. HaloSat observations have also been used to make the first measurement of the total X-ray luminosity of the Vela supernova remnant using CCD-level energy resolution [20].…”

Multiple emission components in the Cygnus cocoon detected from Fermi-LAT observations

“…The brightest emission in the central region of the cocoon lies in the cavities bounded by the photo-dissociation regions traced by 8 µm emission (right panel), as found by Ackermann et al (2011), and the majority of it is traced by our ionised gas template and associated to source CoCent. The extended cocoon component, CoExt, overlaps with the northern rim of the X-ray structure known as Cygnus SB (Cash et al 1980), which may be associated with star-forming regions in Cygnus X (Uyanıker et al 2001), although recent data may suggest that the entire X-ray structure is rather a hypernova remnant at a distance of 1.1-1.4 kpc (Bluem et al 2020). Last, source CoWest is situated along a bright arc of 8 µm emission, but does not coincide with any over-densities in neutral or ionised gas densities (see Figs.…”

“…The characterisation of the cocoon requires a careful modelling of the interstellar gas distribution in the region that is presented in Section 2, while we describe the analysis of gamma-ray data, including morphological, spectral, and spectro-morphological characterisation of the cocoon emission in Section 3. The observables we derived 1 Throughout the paper we refer to a source extension as its 68% containment radius r 68 . For a 2D Gaussian intensity distribution, r 68 = 1.51σ.…”