Photospheric emission from stratified jets

Hirotaka Ito, Shigehiro Nagataki, Masaomi Ono, Shiu Hang Lee, Jirong Mao, Shoichi Yamada, Asaf Pe'Er, Akira Mizuta, Seiji Harikae

    Research output: Contribution to journalArticle

    30 Citations (Scopus)

    Abstract

    We explore photospheric emissions from stratified two-component jets, wherein a highly relativistic spine outflow is surrounded by a wider and less relativistic sheath outflow. Thermal photons are injected in regions of high optical depth and propagated until the photons escape at the photosphere. Because of the presence of shear in velocity (Lorentz factor) at the boundary of the spine and sheath region, a fraction of the injected photons are accelerated using a Fermi-like acceleration mechanism such that a high-energy power-law tail is formed in the resultant spectrum. We show, in particular, that if a velocity shear with a considerable variance in the bulk Lorentz factor is present, the high-energy part of observed gamma-ray bursts (GRBs) photon spectrum can be explained by this photon acceleration mechanism. We also show that the accelerated photons might also account for the origin of the extra-hard power-law component above the bump of the thermal-like peak seen in some peculiar bursts (e.g., GRB 090510, 090902B, 090926A). We demonstrate that time-integrated spectra can also reproduce the low-energy spectrum of GRBs consistently using a multi-temperature effect when time evolution of the outflow is considered. Last, we show that the empirical E p-L p relation can be explained by differences in the outflow properties of individual sources.

    Original languageEnglish
    Article number62
    JournalAstrophysical Journal
    Volume777
    Issue number1
    DOIs
    Publication statusPublished - 2013 Nov 1

    Fingerprint

    outflow
    photons
    gamma ray bursts
    power law
    spine
    energy
    sheaths
    temperature effect
    optical depth
    shear
    photosphere
    optical thickness
    escape
    temperature effects
    bursts
    energy spectra

    Keywords

    • gamma-ray burst: general
    • radiation mechanisms: thermal
    • radiative transfer
    • scattering

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Ito, H., Nagataki, S., Ono, M., Lee, S. H., Mao, J., Yamada, S., ... Harikae, S. (2013). Photospheric emission from stratified jets. Astrophysical Journal, 777(1), [62]. https://doi.org/10.1088/0004-637X/777/1/62

    Photospheric emission from stratified jets. / Ito, Hirotaka; Nagataki, Shigehiro; Ono, Masaomi; Lee, Shiu Hang; Mao, Jirong; Yamada, Shoichi; Pe'Er, Asaf; Mizuta, Akira; Harikae, Seiji.

    In: Astrophysical Journal, Vol. 777, No. 1, 62, 01.11.2013.

    Research output: Contribution to journalArticle

    Ito, H, Nagataki, S, Ono, M, Lee, SH, Mao, J, Yamada, S, Pe'Er, A, Mizuta, A & Harikae, S 2013, 'Photospheric emission from stratified jets', Astrophysical Journal, vol. 777, no. 1, 62. https://doi.org/10.1088/0004-637X/777/1/62
    Ito, Hirotaka ; Nagataki, Shigehiro ; Ono, Masaomi ; Lee, Shiu Hang ; Mao, Jirong ; Yamada, Shoichi ; Pe'Er, Asaf ; Mizuta, Akira ; Harikae, Seiji. / Photospheric emission from stratified jets. In: Astrophysical Journal. 2013 ; Vol. 777, No. 1.
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