A soft X-ray lag detected in Centaurus A

Yutaro Tachibana, Taiki Kawamuro, Yoshihiro Ueda, Megumi Shidatsu, Makoto Arimoto, Taketoshi Yoshii, Yoichi Yatsu, Yoshihiko Saito, Sean Pike, Nobuyuki Kawai

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

We performed time-lag analysis on the X-ray light curves of Centaurus A (Cen A) obtained by the Gas Slit Camera (GSC) aboard the Monitor of All-sky X-ray Image (MAXI) in three energy bands (2-4 keV, 4-10 keV, and 10-20 keV). We discovered a soft X-ray lag relative to higher energies (soft lag) on a timescale of days in a flaring episode by employing the discrete correlation function (DCF) and the z-transformed discrete correlation function (ZDCF) method. In the episode, a peak and a centroid in the DCF and the ZDCF was observed at a soft lag of ∼ 5 d in 2-4 keV versus 4-10 keV and in 4-10 keV versus 10-20 keV, and ∼ 10 d in 2-4 keV versus 10-20 keV. We found it difficult to explain the observed X-ray variation by a single energy injection with the one-zone synchrotron self-Compton (SSC) model, in which the soft lags in these three energy bands reflect the different cooling times of the relativistic electrons, by assuming the magnetic field and minimum Lorentz factor estimated from a broad-band spectral energy distribution. Alternatively, if the phenomenon is interpreted as cooling of Comptonizing electrons in a corona covering the accretion disk, the temperature of the corona producing the variable X-rays should be ∼ 10 keV for reconciliation with the soft lag in the energy range of 2-20 keV.

Original languageEnglish
Pages (from-to)S251-S2511
JournalPublications of the Astronomical Society of Japan
Volume68
DOIs
Publication statusPublished - 2016 Jun 1
Externally publishedYes

Fingerprint

time lag
energy
x rays
coronas
corona
energy bands
cooling
electron
spectral energy distribution
accretion disks
centroids
light curve
slits
sky
monitors
synchrotrons
coverings
electrons
cameras
accretion

Keywords

  • Galaxies: active
  • Galaxies: Seyfert
  • X-rays: individuals (Centaurus A)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Tachibana, Y., Kawamuro, T., Ueda, Y., Shidatsu, M., Arimoto, M., Yoshii, T., ... Kawai, N. (2016). A soft X-ray lag detected in Centaurus A. Publications of the Astronomical Society of Japan, 68, S251-S2511. https://doi.org/10.1093/pasj/psw001

A soft X-ray lag detected in Centaurus A. / Tachibana, Yutaro; Kawamuro, Taiki; Ueda, Yoshihiro; Shidatsu, Megumi; Arimoto, Makoto; Yoshii, Taketoshi; Yatsu, Yoichi; Saito, Yoshihiko; Pike, Sean; Kawai, Nobuyuki.

In: Publications of the Astronomical Society of Japan, Vol. 68, 01.06.2016, p. S251-S2511.

Research output: Contribution to journalArticle

Tachibana, Y, Kawamuro, T, Ueda, Y, Shidatsu, M, Arimoto, M, Yoshii, T, Yatsu, Y, Saito, Y, Pike, S & Kawai, N 2016, 'A soft X-ray lag detected in Centaurus A', Publications of the Astronomical Society of Japan, vol. 68, pp. S251-S2511. https://doi.org/10.1093/pasj/psw001
Tachibana Y, Kawamuro T, Ueda Y, Shidatsu M, Arimoto M, Yoshii T et al. A soft X-ray lag detected in Centaurus A. Publications of the Astronomical Society of Japan. 2016 Jun 1;68:S251-S2511. https://doi.org/10.1093/pasj/psw001
Tachibana, Yutaro ; Kawamuro, Taiki ; Ueda, Yoshihiro ; Shidatsu, Megumi ; Arimoto, Makoto ; Yoshii, Taketoshi ; Yatsu, Yoichi ; Saito, Yoshihiko ; Pike, Sean ; Kawai, Nobuyuki. / A soft X-ray lag detected in Centaurus A. In: Publications of the Astronomical Society of Japan. 2016 ; Vol. 68. pp. S251-S2511.
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AU - Ueda, Yoshihiro

AU - Shidatsu, Megumi

AU - Arimoto, Makoto

AU - Yoshii, Taketoshi

AU - Yatsu, Yoichi

AU - Saito, Yoshihiko

AU - Pike, Sean

AU - Kawai, Nobuyuki

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