Journal article
Astrophysical Journal Letters, 2025
APA
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Audard, M., Awaki, H., Ballhausen, R., Bamba, A., Behar, E., Boissay-Malaquin, R., … Suzuki, N. (2025). Kinematic Evidence for Bipolar Ejecta Flows in the Galactic Supernova Remnant W49B. Astrophysical Journal Letters.
Chicago/Turabian
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Audard, M., H. Awaki, R. Ballhausen, A. Bamba, E. Behar, R. Boissay-Malaquin, L. Brenneman, et al. “Kinematic Evidence for Bipolar Ejecta Flows in the Galactic Supernova Remnant W49B.” Astrophysical Journal Letters (2025).
MLA
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Audard, M., et al. “Kinematic Evidence for Bipolar Ejecta Flows in the Galactic Supernova Remnant W49B.” Astrophysical Journal Letters, 2025.
BibTeX Click to copy
@article{m2025a,
title = {Kinematic Evidence for Bipolar Ejecta Flows in the Galactic Supernova Remnant W49B},
year = {2025},
journal = {Astrophysical Journal Letters},
author = {Audard, M. and Awaki, H. and Ballhausen, R. and Bamba, A. and Behar, E. and Boissay-Malaquin, R. and Brenneman, L. and Brown, G. V. and Corrales, Lia and Costantini, E. and Cumbee, R. and Trigo, M. Díaz and Done, C. and Dotani, T. and Ebisawa, K. and Eckart, M. and Eckert, Dominique and Eguchi, Satoshi and Enoto, T. and Ezoe, Y. and Foster, A. and Fujimoto, R. and Fujita, Y. and Fukazawa, Y. and Fukushima, Kotaro and Furuzawa, A. and Gallo, L. and García, Javier A. and Gu, L. and Guainazzi, M. and Hagino, Kouichi and Hamaguchi, Kenji and Hatsukade, I. and Hayashi, K. and Hayashi, T. and Hell, N. and Hodges-Kluck, E. and Hornschemeier, A. and Ichinohe, Y. and Ishi, D. and Ishida, Manabu and Ishikawa, K. and Ishisaki, Y. and Kaastra, J. and Kallman, T. and Kara, E. and Katsuda, S. and Kanemaru, Y. and Kelley, Rich and Kilbourne, C. and Kitamoto, S. and Kobayashi, S. and Kohmura, T. and Kubota, A. and Leutenegger, M. and Loewenstein, M. and Maeda, Y. and Markevitch, M. and Matsumoto, Hironori and Matsushita, K. and McCammon, D. and McNamara, Brian and Mernier, F. and Miller, Eric D. and Miller, Jon M. and Mitsuishi, I. and Mizumoto, M. and Mizuno, T. and Mori, K. and Mukai, K. and Murakami, Hiroshi and Mushotzky, R. and Nakajima, H. and Nakazawa, K. and Ness, J. and Nobukawa, K. and Nobukawa, M. and Noda, Hirofumi and Odaka, H. and Ogawa, S. and Ogorzałek, A. and Okajima, T. and Ota, Naomi and Paltani, S. and Petre, R. and Plucinsky, P. and Porter, F. and Pottschmidt, K. and Sano, H. and Sato, Kosuke and Sato, Toshiki and Sawada, M. and Seta, H. and Shidatsu, M. and Simionescu, A. and Smith, Randall K. and Suzuki, Hiromasa and Szymkowiak, A. and Takahashi, H. and Takeo, M. and Tamagawa, T. and Tamura, Keisuke and Tanaka, Takaaki and Tanimoto, A. and Tashiro, M. and Terada, Y. and Terashima, Y. and Tsuboi, Y. and Tsujimoto, M. and Tsunemi, H. and Tsuru, T. and Tümer, Ayşegül and Uchida, Hiroyuki and Uchida, N. and Uchida, Y. and Uchiyama, H. and Ueda, Y. and Uno, S. and Vink, J. and Watanabe, S. and Williams, Brian J. and Yamada, Satoshi and Yamada, S. and Yamaguchi, Hiroya and Yamaoka, K. and Yamasaki, N. and Yamauchi, M. and Yamauchi, S. and Yaqoob, T. and Yoneyama, T. and Yoshida, Tessei and Yukita, M. and Zhuravleva, I. and Amano, Yuki and Gall, Amy and Mitrani, S. and Murakami, Kaito and Rahin, R. and Suzuki, Nari}
}
W49B is a unique Galactic supernova remnant 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. Closely connected to the morphology of the ejecta is its velocity distribution, which provides critical details for understanding the explosion mechanism. We report the first ever observational constraint on the kinematics of the ejecta in W49B using the Resolve microcalorimeter spectrometer on the X-ray Imaging and Spectroscopy Mission (XRISM). Using XRISM/Resolve, we measured the line-of-sight velocity traced by the Fe Heα emission, which is the brightest feature in the Resolve spectrum, to vary by ±300 km s−1 with a smooth east-to-west gradient of a few tens of kilometers per second per parsec along the major axis. Similar trends in the line-of-sight velocity structure were found for other Fe-group elements Cr and Mn, traced by the Heα emission, and also for intermediate-mass elements Si, S, Ar, and Ca, traced by the Lyα emission. 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. In contrast, the observed velocity structure suggests bipolar flows reminiscent of a bipolar explosion scenario. An alternative scenario would be a collimation of the ejecta by an elongated cavity sculpted by bipolar stellar winds.