An Investigation of Magnetar Giant Flares in the Virgo Cluster and Nearby Galaxies Using INTEGRAL Satellite Data

Core Concepts

This research paper investigates the rate of magnetar giant flares (MGFs) using INTEGRAL satellite data of the Virgo Cluster and nearby galaxies, finding an upper limit on the rate of high-energy MGFs and a lower limit for lower-energy events.

Abstract

• Bibliographic Information: Pacholski, D.P., Arrigoni, E., Mereghetti, S., & Salvaterra, R. (2024). INTEGRAL search for magnetar giant flares from the Virgo Cluster and in nearby galaxies with high star formation rate. Monthly Notices of the Royal Astronomical Society, 000, 1–6. Preprint: arXiv:2411.03235v1 [astro-ph.HE]

• Research Objective: The study aims to constrain the rate of magnetar giant flares (MGFs) by searching for these events in archival INTEGRAL satellite data of the Virgo Cluster and a sample of nearby galaxies with high star formation rates.

• Methodology: The researchers analyzed data from the IBIS instrument on INTEGRAL, focusing on the ISGRI detector's observations in the 15-300 keV energy range. They searched for short-duration bursts in the light curves of individual science windows (ScWs) covering the target galaxies. The analysis involved background level evaluation, count rate excess detection, and imaging analysis to eliminate spurious events.

• Key Findings: No MGFs were detected in the Virgo Cluster observations. Combining this non-detection with observations of nearby galaxies, including one MGF detection in M82, the study derived a 90% confidence level upper limit of approximately one MGF with energy greater than 3 × 10^45 erg every 500 years per magnetar. Additionally, they established a lower limit for the rate of MGFs with energies below 10^45 erg.

• Main Conclusions: The study concludes that targeted searches for MGFs in distant galaxies, particularly those with high star formation rates, are crucial for expanding the limited sample of observed events and refining the constraints on their rate of occurrence. The authors emphasize the importance of rapid and precise localization capabilities, along with good spectral and timing resolution instruments, for future MGF observations.

• Significance: This research contributes valuable data to the understanding of MGFs, which are among the most energetic events in the universe. By constraining their rate, the study helps to refine models of magnetar evolution and the overall population of these extreme objects.

• Limitations and Future Research: The study acknowledges limitations due to the sensitivity of current instruments and the challenges in detecting MGFs at large distances. Future research with more sensitive telescopes and improved detection techniques is necessary to further constrain the MGF rate and uncover the properties of these powerful events.

Stats

The researchers analyzed 34.8 Ms of INTEGRAL observation data of the Virgo Cluster, gathered between May 2003 and August 2023.
The study used a sample of seven nearby galaxies with high star formation rates, in addition to the Virgo Cluster data.
The analysis assumed an average of 30 magnetars in the Milky Way and Magellanic Clouds.
The study found a power law index of 𝛾= 1.97 for the energy distribution of MGFs.
The estimated rate of MGFs per magnetar was ˜𝑘= 3.5 x 10^-3 yr^-1.
The study assumed spectral parameters of 𝛼=0.04 and 𝐸𝑝=551 keV for a representative MGF initial spike.

Quotes

"Giant flares from magnetars can reach, for a fraction of a second, luminosities greater than 10^47 erg s−1 in the hard X-ray/soft 𝛾-ray range."
"Since magnetars are young neutron stars, nearby galaxies with a high rate of star formation are optimal targets to search for magnetar giant flares (MGFs)."
"From the lack of detections in this extensive data set (besides 231115A in M82) we derive a 90% c.l. upper limit on the rate of MGF with 𝐸> 3 × 10^45 erg of ∼2 × 10−3 yr−1 per magnetar and a lower limit of 𝑅(𝐸) >∼4 × 10−4 yr−1 magnetar−1 for 𝐸< 10^45 erg."

Key Insights Distilled From

INTEGRAL search for magnetar giant flares from the Virgo Cluster and in nearby galaxies with high star formation rate

by Dominik P. P... at arxiv.org 11-06-2024

https://arxiv.org/pdf/2411.03235.pdf