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I take notes on ArXiv articles that pique my personal interest, just in case I forget.
This file was originally written in markdown.
SNR/W49BKinematic Evidence for Bipolar Ejecta Flows in the Galactic SNR W 49B (2506.05455)
XRISM Collaboration
Tags:
SNR
X-Ray
W49B, a unique Galactic SNR with centrally peaked, “bar”-like ejecta distribution, which was once considered evidence for a hypernova origin that resulted in a bipolar ejection of the stellar core. However, chemical abundance measurements contradict this interpretation. The morphology and velocity distribution of the ejecta provide critical details for understanding the explosion mechanism.
Using XRISM/Resolve, they measured the line-of-sight velocity
traced by the Fe Heα emission to vary by ±300 km/s with a smooth east-to-west gradient of a few tens of km/s/pc along the major axis.
The discovery of the east-west gradient in the line-of-sight velocity, together with the absence of a twin-peaked line profile or enhanced broadening in the central region, clearly rejects the equatorially expanding disk model. They propose an alternative scenario that would be a collimation of the ejecta by an elongated cavity sculpted by bipolar stellar winds.
Sgr B2/water maserProperties of H2O masers and their associated sources in Sagittarius B2 (2506.09115)
Nazar Budaiev, Adam Ginsburg, Ciriaco Goddi, Álvaro Sánchez-Monge, Anika Schmiedeke, Desmond Jeff, Peter Schilke, Christopher De Pree
Tags:
H2O maser
Sgr B2
Sgr B2, known for its high star-formation rate (∼0.04 M⊙ yr−1, 10% of the star formation in the CMZ; Ginsburg et al. 2018), whose extreme environmental conditions and clustered star formation makes it a compelling analog for star formation at during the peak epoch of cosmic star formation (z ∼ 2; Madau & Dickinson 2014).
High-resolution multi-wavelength observations resolve the immediate environments of individual massive protostars, and feedback, infall, and dynamical interactions within the forming star clusters, thereby providing crucial context for the physical interpretation of maser emission.
They detected 499 H2O masers in observed velocities (-39 to 172 km/s) and identified 144 unique sites of H2O maser emission.
The outflow-associated H2O maser emission is confined to within < 2000 au of the central continuum source, while shocked SiO emission extending over tens of thousands of au.
