Variability timescales of TeV blazars observed in the ASCA continuous long-look X-ray monitoring

Chiharu Tanihata, C. Megan Urry, Tadayuki Takahashi, Jun Kataoka, Stefan J. Wagner, Greg M. Madejski, Makoto Tashiro, Manabu Kouda

研究成果: Article

55 引用 (Scopus)

抄録

Three uninterrupted, long (lasting respectively 7, 10, and 10 days) ASCA observations of the well-studied TeV-bright blazars Mrk 421, Mrk 501, and PKS 2155-304 all show continuous strong X-ray flaring. Despite the relatively faint intensity states in two of the three sources, there was no identifiable quiescent period in any of the observations. Structure function analysis shows that all blazars have a characteristic timescale of ∼1 day, comparable to the recurrence time and to the timescale of the stronger flares. On the other hand, examination of these flares in more detail reveals that each of the strong flares is not a smooth increase and decrease but exhibits substructures of shorter flares having timescales of ∼10 ks. We verify via simulations that in order to explain the observed structure function, these shorter flares ("shots") are unlikely to be fully random, but in some way are correlated with each other. The energy dependent cross-correlation analysis shows that interband lags are not universal in TeV blazars. This is important since in the past only positive detections of lags were reported. In this work, we determine that the sign of a lag may differ from flare to flare; significant lags of both signs were detected from several flares, while no significant lag was detected from others. However, we also argue that the nature of the underlying component can affect these values. The facts that all flares are nearly symmetric and that fast variability shorter than the characteristic timescale is strongly suppressed, support the scenario where the light crossing time dominates the variability timescales of the day-scale flares.

元の言語English
ページ(範囲)569-581
ページ数13
ジャーナルAstrophysical Journal
563
発行部数2 PART 1
DOI
出版物ステータスPublished - 2001 12 20
外部発表Yes

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blazars
flares
timescale
monitoring
x rays
time lag
substructures
cross correlation
shot
simulation
energy
examination

ASJC Scopus subject areas

  • Space and Planetary Science

これを引用

Tanihata, C., Urry, C. M., Takahashi, T., Kataoka, J., Wagner, S. J., Madejski, G. M., ... Kouda, M. (2001). Variability timescales of TeV blazars observed in the ASCA continuous long-look X-ray monitoring. Astrophysical Journal, 563(2 PART 1), 569-581. https://doi.org/10.1086/323960

Variability timescales of TeV blazars observed in the ASCA continuous long-look X-ray monitoring. / Tanihata, Chiharu; Urry, C. Megan; Takahashi, Tadayuki; Kataoka, Jun; Wagner, Stefan J.; Madejski, Greg M.; Tashiro, Makoto; Kouda, Manabu.

:: Astrophysical Journal, 巻 563, 番号 2 PART 1, 20.12.2001, p. 569-581.

研究成果: Article

Tanihata, C, Urry, CM, Takahashi, T, Kataoka, J, Wagner, SJ, Madejski, GM, Tashiro, M & Kouda, M 2001, 'Variability timescales of TeV blazars observed in the ASCA continuous long-look X-ray monitoring', Astrophysical Journal, 巻. 563, 番号 2 PART 1, pp. 569-581. https://doi.org/10.1086/323960
Tanihata C, Urry CM, Takahashi T, Kataoka J, Wagner SJ, Madejski GM その他. Variability timescales of TeV blazars observed in the ASCA continuous long-look X-ray monitoring. Astrophysical Journal. 2001 12 20;563(2 PART 1):569-581. https://doi.org/10.1086/323960
Tanihata, Chiharu ; Urry, C. Megan ; Takahashi, Tadayuki ; Kataoka, Jun ; Wagner, Stefan J. ; Madejski, Greg M. ; Tashiro, Makoto ; Kouda, Manabu. / Variability timescales of TeV blazars observed in the ASCA continuous long-look X-ray monitoring. :: Astrophysical Journal. 2001 ; 巻 563, 番号 2 PART 1. pp. 569-581.
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AU - Tanihata, Chiharu

AU - Urry, C. Megan

AU - Takahashi, Tadayuki

AU - Kataoka, Jun

AU - Wagner, Stefan J.

AU - Madejski, Greg M.

AU - Tashiro, Makoto

AU - Kouda, Manabu

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N2 - Three uninterrupted, long (lasting respectively 7, 10, and 10 days) ASCA observations of the well-studied TeV-bright blazars Mrk 421, Mrk 501, and PKS 2155-304 all show continuous strong X-ray flaring. Despite the relatively faint intensity states in two of the three sources, there was no identifiable quiescent period in any of the observations. Structure function analysis shows that all blazars have a characteristic timescale of ∼1 day, comparable to the recurrence time and to the timescale of the stronger flares. On the other hand, examination of these flares in more detail reveals that each of the strong flares is not a smooth increase and decrease but exhibits substructures of shorter flares having timescales of ∼10 ks. We verify via simulations that in order to explain the observed structure function, these shorter flares ("shots") are unlikely to be fully random, but in some way are correlated with each other. The energy dependent cross-correlation analysis shows that interband lags are not universal in TeV blazars. This is important since in the past only positive detections of lags were reported. In this work, we determine that the sign of a lag may differ from flare to flare; significant lags of both signs were detected from several flares, while no significant lag was detected from others. However, we also argue that the nature of the underlying component can affect these values. The facts that all flares are nearly symmetric and that fast variability shorter than the characteristic timescale is strongly suppressed, support the scenario where the light crossing time dominates the variability timescales of the day-scale flares.

AB - Three uninterrupted, long (lasting respectively 7, 10, and 10 days) ASCA observations of the well-studied TeV-bright blazars Mrk 421, Mrk 501, and PKS 2155-304 all show continuous strong X-ray flaring. Despite the relatively faint intensity states in two of the three sources, there was no identifiable quiescent period in any of the observations. Structure function analysis shows that all blazars have a characteristic timescale of ∼1 day, comparable to the recurrence time and to the timescale of the stronger flares. On the other hand, examination of these flares in more detail reveals that each of the strong flares is not a smooth increase and decrease but exhibits substructures of shorter flares having timescales of ∼10 ks. We verify via simulations that in order to explain the observed structure function, these shorter flares ("shots") are unlikely to be fully random, but in some way are correlated with each other. The energy dependent cross-correlation analysis shows that interband lags are not universal in TeV blazars. This is important since in the past only positive detections of lags were reported. In this work, we determine that the sign of a lag may differ from flare to flare; significant lags of both signs were detected from several flares, while no significant lag was detected from others. However, we also argue that the nature of the underlying component can affect these values. The facts that all flares are nearly symmetric and that fast variability shorter than the characteristic timescale is strongly suppressed, support the scenario where the light crossing time dominates the variability timescales of the day-scale flares.

KW - BL Lacertae objects: individual (Markarian 421, Markarian 501, PKS 2155-304)

KW - Galaxies : active

KW - Radiation mechanisms: nonthermal

KW - X-rays: galaxies

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