The FAST Detection of an H <scp>i</scp> Cloud around Supernova Remnant G116.6–26.1

Abstract G116.6−26.1 has been newly discovered as a supernova remnant (SNR) through the SRG/eROSITA X-ray survey, located in a high-latitude, low-density region. Its distance and progenitor nature remain uncertain. Our objective is to explore the surroundings of SNR G116.6−26.1 to determine its distance and surrounding environmental conditions. High-resolution and sensitive H i observations around G116.6−26.1 from the Five-hundred-meter Aperture Spherical radio Telescope, with an rms level of 1.0 mJy beam −1 , were utilized to study the distribution of cold gas in this SNR region. Furthermore, an extinction map for this area helps estimate the distance to G116.6−26.1. We identified four H i structures associated with G116.6−26.1 in the local standard of rest velocity range −133.9 to −63.9 km s −1 : clouds A1, B1, B2, and C1. Together with other components in the A-series and the C-series, they form a large cloud that exhibits a cavity in this SNR region. The A- and C-series share similar velocities, while B1 and B2, both in the SNR area, differ by 10−30 km s −1 . The X-ray morphology displays deformation features that align spatially with the H i structure C1 boundary interface. Using three-dimensional extinction data, we estimate the cloud’s distance to be 2.7 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.50</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>3.18</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> kpc, suggesting that G116.6−26.1 exploded within an H i cloud beyond the Galactic plane, about 2.7 kpc away.