The 16th International Conference on Accelerator Mass Spectrometry

Icebound Stardust: Tracing the Local Interstellar Cloud by Supernova-produced $^{60}$Fe in Antarctica

PSA-6

21 Oct 2024, 16:55

20m

Lobby and Hallway , 2nd Floor (( Poster session A should be set up in the morning.))

Poster Applications in Astrophysics and Nuclear Sciences Poster Session A

Speakers

Annabel Rolofs (Helmholtz-Zentrum Dresden-Rossendorf & University of Bonn) Dominik Koll (The Australian National University & TU Dresden & Helmholtz-Zentrum Dresden-Rossendorf)

Description

The solar neighborhood lies within the Local Bubble, a low-density region of space formed by stellar explosions [1]. The Local Interstellar Cloud (LIC) with the solar system inside is embedded in this cavity. Assuming the LIC contains remnants from supernovae events, the solar system may accumulate traces of long-lived supernova-produced radionuclides as it traverses the LIC. The radionuclide $^{60}$Fe with a half-life of 2.6 Myr [2] serves as an ideal indicator for supernova activity because it is predominantly produced inside of massive stars and ejected by supernovae.

Previous research yielded evidence for enhanced levels of interstellar $^{60}$Fe in million-year-old deep-sea samples [3] and a recent influx into Antarctic snow [4]. In this project, we investigate the deposition of live $^{60}$Fe in the still unexplored time interval of 50-80 kyr before present when the solar system was not yet within the LIC [5]. A 300 kg sample from an Antarctic ice core (EPICA EDML) is utilized to explore the origins of the recent influx and its relation to the trajectory of the solar environment through the LIC.

Investigating the ultra-low deposition rate of individual $^{60}$Fe atoms per cm$^{2}$ per year necessitates the use of the highly sensitive method of accelerator mass spectrometry. Moreover, the ice core sample is characterized by the analysis of the cosmogenic radionuclides $^{10}$Be and $^{26}$Al through the ratio $^{26}$Al/$^{10}$Be. The interplanetary radionuclides $^{41}$Ca and $^{53}$Mn serve to clearly distinguish the interstellar from the interplanetary $^{60}$Fe contributions [6]. The measurements of the cosmogenic radionuclides $^{10}$Be, $^{26}$Al, and $^{41}$Ca are carried out at HZDR's 6MV facility DREAMS, while HIAF at ANU is the only facility in the world equipped to detect $^{53}$Mn and $^{60}$Fe with its 14UD pelletron tandem accelerator. We report on the processing of 300 kg of Antarctic ice and the results of this project.

[1] Berghoefer et al., A\&A, 390 (1): 299–306 (2002)

[2] Rugel et al., PRL, 103, 072502 (2009)

[3] Wallner et al., Nature, 532(7597): 69–72 (2016)

[4] Koll et al., PRL, 103, 072701 (2019)

[5] Frisch et al., ASTRA, 2, 53-61 (2006)

[6] Koll et al., EPJ Web Conf., 260, 11022 (2022)