Serim, Muhammed Miraç

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S.,Muhammed Mirac
S., Muhammed Mirac
Serim, Muhammed Mirac
M., Serim
Muhammed Mirac, Serim
S.,Muhammed Miraç
M.,Serim
Serim,M.M.
Muhammed Miraç, Serim
Serim, Muhammed Miraç
M.M.Serim
Serim, M. M.
Job Title
Doktor Öğretim Üyesi
Email Address
mirac.serim@atilim.edu.tr
Main Affiliation
Department of Electrical & Electronics Engineering
Status
Former Staff
Website
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Scopus Author ID
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Scholarly Output

2

Articles

2

Citation Count

14

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0

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2022 - 20232
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    Article
    Citation - WoS: 8
    Citation - Scopus: 7
    Pulse Frequency Fluctuations of Persistent Accretion Powered Pulsars
    (Oxford University Press, 2023) Serim,D.; Serim,M.M.; Baykal,A.; Department of Electrical & Electronics Engineering
    In this study, we examine the long-term torque noise fluctuations of persistent X-ray binaries Her X-1, Vela X-1, GX 301-2, Cen X-3, 4U 1538-53, OAO 1657-415, and 4U 1626-67 using the historical pulse frequency measurements provided by CGRO/BATSE and Fermi/GBM. We find that known disc-fed sources exhibit a 1/ω2 red noise component in their power density spectra which is saturated over long time-scales. On the other hand, wind-fed sources form a clear white noise component, and the wind-fed sources with occasional transient disc formation imprint 1/ω type flicker noise. We discuss their long-term timing noise properties based on the models to describe the power density spectrum of pulse frequency derivative fluctuations in terms of monochromatic and coloured noise processes. Furthermore, we investigate the relation between measured timing noise strengths and other independently measured physical parameters. Despite the low number of sample sources, we suggest that the noise strengths of these sources are correlated with their luminosities and uncorrelated with their magnetic field strengths, implying that the dominant noise-generating mechanism is accretion. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
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    Article
    Citation - WoS: 14
    Citation - Scopus: 14
    Timing and Spectral Analysis of 2s 1417-624 During Its 2018 Outburst
    (Oxford University Press, 2022) Serim,M.M.; Özüdoǧru,Ö.C.; Dönmez,Ç.K.; Sahiner,S.; Serim,D.; Baykal,A.; Inam,S.Ç.; Department of Electrical & Electronics Engineering
    We investigate timing and spectral characteristics of the transient X-ray pulsar 2S 1417-624 during its 2018 outburst with NICER follow up observations. We describe the spectra with high-energy cut-off and partial covering fraction absorption (PCFA) model and present flux-dependent spectral changes of the source during the 2018 outburst. Utilizing the correlation-mode switching of the spectral model parameters, we confirm the previously reported sub-critical to critical regime transitions and we argue that secondary transition from the gas-dominated to the radiation pressure-dominated disc do not lead us to significant spectral changes below 12 keV. Using the existing accretion theories, we model the spin frequency evolution of 2S 1417-624 and investigate the noise processes of a transient X-ray pulsar for the first time using both polynomial and luminosity-dependent models for the spin frequency evolution. For the first model, the power density spectrum of the torque fluctuations indicate that the source exhibits red noise component (Γ ∼-2) within the time-scales of outburst duration which is typical for disc-fed systems. On the other hand, the noise spectrum tends to be white on longer time-scales with high timing noise level that indicates an ongoing accretion process in between outburst episodes. For the second model, most of the red noise component is eliminated and the noise spectrum is found to be consistent with a white noise structure observed in wind-fed systems. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.