初の高速電波バースト、古い楕円銀河に由来することを特定(First fast radio burst traced to old, dead, elliptical galaxy)

2025-01-21 ノースウェスタン大学

＜関連情報＞

• https://news.northwestern.edu/stories/2025/01/first-fast-radio-burst-traced-to-old-dead-elliptical-galaxy/
• https://iopscience.iop.org/article/10.3847/2041-8213/ad9ddc
• https://iopscience.iop.org/article/10.3847/2041-8213/ad9de2

静止銀河外縁部における繰り返し高速電波バースト源 A Repeating Fast Radio Burst Source in the Outskirts of a Quiescent Galaxy

Vishwangi Shah, Kaitlyn Shin, Calvin Leung, Wen-fai Fong, Tarraneh Eftekhari, Mandana Amiri, Bridget C. Andersen, Shion Andrew, Mohit Bhardwaj, Charanjot Brar,…
The Astrophysical Journal Letters  Published: 2025 January 21
DOI:10.3847/2041-8213/ad9ddc

Abstract

We report the discovery of the repeating fast radio burst (FRB) source FRB 20240209A using the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB telescope. We detected 22 bursts from this repeater between 2024 February and July, 6 of which were also recorded at the Outrigger station k’niʔatn k’lstk’masqt (KKO). The multiple very long baseline interferometry localizations using the 66 km long CHIME–KKO baseline, each with a different baseline vector orientation due to the repeater’s high decl. of ∼86°, enabled the combined localization region to be constrained to 1” × 2”. We present deep Gemini optical observations that, combined with the FRB localization, enabled a robust association of FRB 20240209A to the outskirts of a luminous galaxy (P(O∣x) = 0.99; L ≈ 5.3 × 10¹⁰ L_⊙). FRB 20240209A has a projected physical offset of 40 ± 5 kpc from the center of its host galaxy, making it the FRB with the largest host galaxy offset to date. When normalized by the host galaxy size, the offset of FRB 20240209A (5.1 R_eff) is comparable to that of FRB 20200120E (5.7 R_eff), the only FRB source known to originate in a globular cluster. We consider several explanations for the large offset, including a progenitor that was kicked from the host galaxy or in situ formation in a low-luminosity satellite galaxy of the putative host, but find the most plausible scenario to be a globular cluster origin. This, coupled with the quiescent, elliptical nature of the host as demonstrated in our companion Letter, provides strong evidence for a delayed formation channel for the progenitor of the FRB source.

繰り返し高速電波バーストFRB 20240209Aの大質量で静止した楕円銀河ホスト銀河 The Massive and Quiescent Elliptical Host Galaxy of the Repeating Fast Radio Burst FRB 20240209A

T. Eftekhari, Y. Dong (董雨欣), W. Fong, V. Shah, S. Simha, B. C. Andersen, S. Andrew, M. Bhardwaj, T. Cassanelli, S. Chatterjee,…
The Astrophysical Journal Letters  Published: 2025 January 21
DOI:10.3847/2041-8213/ad9de2

Abstract

The discovery and localization of FRB 20240209A by the Canadian Hydrogen Intensity Mapping Fast Radio Burst (CHIME/FRB) experiment marks the first repeating FRB localized with the CHIME/FRB Outriggers and adds to the small sample of repeating FRBs with associated host galaxies. Here we present Keck and Gemini observations of the host that reveal a redshift z = 0.1384 ± 0.0004. We perform stellar population modeling to jointly fit the optical through mid-IR data of the host and infer a median stellar mass log(M_*/M_⊙) = 11.35 ± 0.01 and a mass-weighted stellar population age  ~11 Gyr, corresponding to the most massive and oldest FRB host discovered to date. Coupled with a star formation rate  <0.31 M_⊙ yr⁻¹, the specific star formation rate  <10^−11.9 yr⁻¹ classifies the host as quiescent. Through surface brightness profile modeling, we determine an elliptical galaxy morphology, marking the host as the first confirmed elliptical FRB host. The discovery of a quiescent early-type host galaxy within a transient class predominantly characterized by late-type star-forming hosts is reminiscent of short-duration gamma-ray bursts, Type Ia supernovae, and ultraluminous X-ray sources. Based on these shared host demographics, coupled with a large offset as demonstrated in our companion Letter, we conclude that preferred sources for FRB 20240209A include magnetars formed through merging binary neutron stars/white dwarfs or the accretion-induced collapse of a white dwarf, or a luminous X-ray binary. Together with FRB 20200120E localized to a globular cluster in M81, our findings provide strong evidence that some fraction of FRBs may arise from a process distinct from the core collapse of massive stars.