THE EFFECT OF BRAKING INDEX ON X-RAY PLATEAU FIT QUALITY: A NUMERICAL INVESTIGATION OF THE MAGNETAR MODEL

Türkoğlu M. M.

20. Uluslararası MAS Uygulamalı Bilimler Kongresi,, İstanbul, Türkiye, 12 Mayıs 2025, ss.1-8, (Tam Metin Bildiri)

  • Yayın Türü: Bildiri / Tam Metin Bildiri
  • Basıldığı Şehir: İstanbul
  • Basıldığı Ülke: Türkiye
  • Sayfa Sayıları: ss.1-8
  • İstanbul Gelişim Üniversitesi Adresli: Evet

Özet

In this study, the sensitivity of the parametric structure of the magnetar model—used to explain the plateau phases observed in the X-ray afterglows of short and long gamma-ray bursts (GRBs)—to variations in the braking index (n) is investigated. Based on the hypothesis that the plateau phase arises from energy injection driven by the spin-down process of a newly formed, rapidly rotating neutron star (magnetar), the effect of the braking index on the quality of model fits is analyzed. Utilizing the method developed by Stratta et al. (2018), three braking index values— 𝑛 = 3, 2 𝑎 1.2 —corresponding to 𝛼 = 0, 0.5 𝑎 0.9, respectively, are tested using the same GRB dataset to compare fit performance. Numerical analyses show that decreasing the braking index results in significantly improved fits while yielding magnetar parameters that remain physically plausible. In particular, for 𝑛 < 3, both the magnetic field strength (B) and the spin period (P) are found to align more closely with the ranges reported in the literature. Moreover, the model’s fit quality—as indicated by reduced chi-square and p-values—improves markedly, and the plateau morphology is represented more accurately. These findings suggest that the plateau phases observed in GRB afterglows can be more effectively described by non-ideal dipole spin-down processes rather than by idealized magnetic dipole braking alone.