ASCA observation of an X-ray/TeV flare from the BL Lacertae object Markarian 421

T. Takahashi, M. Tashiro, G. Madejski, H. Kubo, T. Kamae, Jun Kataoka, T. Kii, F. Makino, K. Makishima, N. Yamasaki

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Abstract

We observed the BL Lac object Mrk 421 with the X-ray satellite ASCA in 1994 as part of a multifrequency observation. The 24 hr observation was conducted 1 day after the onset of a TeV flare detected by the Whipple Observatory and detected an X-ray flare, with no apparent variability in the optical, UV, and EGRET GeV flux. The ASCA 2-10 keV flux peaked at 3.7 × 10-10 ergs cm-2 s-1 and then decreased to 1.8 × 10-10 ergs cm-2 s-1 with a doubling timescale of ∼12 hr. The shape of the X-ray spectrum varied during the observation, such that the hard X-rays always led the soft X-rays, both in brightening and dimming of the source, with a lag of the 0.5-1 keV photons versus those in the 2-7.5 keV band of ∼1 hr. The rapid TeV variability indicates a compact TeV-producing region, suggesting relativistic beaming with a Doppler factor δ ≥ 5. The correlation of the flux in the X-ray and the TeV bands indicates that a high-energy tail of a single electron population is responsible for both X-rays and TeV γ-rays, with radio, IR, UV and X-rays produced via the synchrotron process and GeV and TeV γ-rays produced via Comptonization. Under the assumption that the "soft lag" observed in the X-ray band is due to the synchrotron-lifetime effects, with δ = 5, we calculate the magnetic field for the X-ray-producing region to be ∼0.2 G. The Lorentz factors γcl of the electrons responsible for the emission in the keV and TeV bands are ∼106, consistent with the values implied by the Klein-Nishina limit.

Original languageEnglish
JournalAstrophysical Journal
Volume470
Issue number2 PART II
Publication statusPublished - 1996
Externally publishedYes

Fingerprint

BL Lacertae objects
flares
x rays
erg
rays
synchrotrons
time lag
dimming
electron
observatories
electrons
observatory
radio
magnetic field

Keywords

  • BL Lacertae objects: general
  • BL Lacertae objects: individual (Markarian 421)
  • X-rays: general

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Takahashi, T., Tashiro, M., Madejski, G., Kubo, H., Kamae, T., Kataoka, J., ... Yamasaki, N. (1996). ASCA observation of an X-ray/TeV flare from the BL Lacertae object Markarian 421. Astrophysical Journal, 470(2 PART II).

ASCA observation of an X-ray/TeV flare from the BL Lacertae object Markarian 421. / Takahashi, T.; Tashiro, M.; Madejski, G.; Kubo, H.; Kamae, T.; Kataoka, Jun; Kii, T.; Makino, F.; Makishima, K.; Yamasaki, N.

In: Astrophysical Journal, Vol. 470, No. 2 PART II, 1996.

Research output: Contribution to journalArticle

Takahashi, T, Tashiro, M, Madejski, G, Kubo, H, Kamae, T, Kataoka, J, Kii, T, Makino, F, Makishima, K & Yamasaki, N 1996, 'ASCA observation of an X-ray/TeV flare from the BL Lacertae object Markarian 421', Astrophysical Journal, vol. 470, no. 2 PART II.
Takahashi T, Tashiro M, Madejski G, Kubo H, Kamae T, Kataoka J et al. ASCA observation of an X-ray/TeV flare from the BL Lacertae object Markarian 421. Astrophysical Journal. 1996;470(2 PART II).
Takahashi, T. ; Tashiro, M. ; Madejski, G. ; Kubo, H. ; Kamae, T. ; Kataoka, Jun ; Kii, T. ; Makino, F. ; Makishima, K. ; Yamasaki, N. / ASCA observation of an X-ray/TeV flare from the BL Lacertae object Markarian 421. In: Astrophysical Journal. 1996 ; Vol. 470, No. 2 PART II.
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abstract = "We observed the BL Lac object Mrk 421 with the X-ray satellite ASCA in 1994 as part of a multifrequency observation. The 24 hr observation was conducted 1 day after the onset of a TeV flare detected by the Whipple Observatory and detected an X-ray flare, with no apparent variability in the optical, UV, and EGRET GeV flux. The ASCA 2-10 keV flux peaked at 3.7 × 10-10 ergs cm-2 s-1 and then decreased to 1.8 × 10-10 ergs cm-2 s-1 with a doubling timescale of ∼12 hr. The shape of the X-ray spectrum varied during the observation, such that the hard X-rays always led the soft X-rays, both in brightening and dimming of the source, with a lag of the 0.5-1 keV photons versus those in the 2-7.5 keV band of ∼1 hr. The rapid TeV variability indicates a compact TeV-producing region, suggesting relativistic beaming with a Doppler factor δ ≥ 5. The correlation of the flux in the X-ray and the TeV bands indicates that a high-energy tail of a single electron population is responsible for both X-rays and TeV γ-rays, with radio, IR, UV and X-rays produced via the synchrotron process and GeV and TeV γ-rays produced via Comptonization. Under the assumption that the {"}soft lag{"} observed in the X-ray band is due to the synchrotron-lifetime effects, with δ = 5, we calculate the magnetic field for the X-ray-producing region to be ∼0.2 G. The Lorentz factors γcl of the electrons responsible for the emission in the keV and TeV bands are ∼106, consistent with the values implied by the Klein-Nishina limit.",
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AU - Takahashi, T.

AU - Tashiro, M.

AU - Madejski, G.

AU - Kubo, H.

AU - Kamae, T.

AU - Kataoka, Jun

AU - Kii, T.

AU - Makino, F.

AU - Makishima, K.

AU - Yamasaki, N.

PY - 1996

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N2 - We observed the BL Lac object Mrk 421 with the X-ray satellite ASCA in 1994 as part of a multifrequency observation. The 24 hr observation was conducted 1 day after the onset of a TeV flare detected by the Whipple Observatory and detected an X-ray flare, with no apparent variability in the optical, UV, and EGRET GeV flux. The ASCA 2-10 keV flux peaked at 3.7 × 10-10 ergs cm-2 s-1 and then decreased to 1.8 × 10-10 ergs cm-2 s-1 with a doubling timescale of ∼12 hr. The shape of the X-ray spectrum varied during the observation, such that the hard X-rays always led the soft X-rays, both in brightening and dimming of the source, with a lag of the 0.5-1 keV photons versus those in the 2-7.5 keV band of ∼1 hr. The rapid TeV variability indicates a compact TeV-producing region, suggesting relativistic beaming with a Doppler factor δ ≥ 5. The correlation of the flux in the X-ray and the TeV bands indicates that a high-energy tail of a single electron population is responsible for both X-rays and TeV γ-rays, with radio, IR, UV and X-rays produced via the synchrotron process and GeV and TeV γ-rays produced via Comptonization. Under the assumption that the "soft lag" observed in the X-ray band is due to the synchrotron-lifetime effects, with δ = 5, we calculate the magnetic field for the X-ray-producing region to be ∼0.2 G. The Lorentz factors γcl of the electrons responsible for the emission in the keV and TeV bands are ∼106, consistent with the values implied by the Klein-Nishina limit.

AB - We observed the BL Lac object Mrk 421 with the X-ray satellite ASCA in 1994 as part of a multifrequency observation. The 24 hr observation was conducted 1 day after the onset of a TeV flare detected by the Whipple Observatory and detected an X-ray flare, with no apparent variability in the optical, UV, and EGRET GeV flux. The ASCA 2-10 keV flux peaked at 3.7 × 10-10 ergs cm-2 s-1 and then decreased to 1.8 × 10-10 ergs cm-2 s-1 with a doubling timescale of ∼12 hr. The shape of the X-ray spectrum varied during the observation, such that the hard X-rays always led the soft X-rays, both in brightening and dimming of the source, with a lag of the 0.5-1 keV photons versus those in the 2-7.5 keV band of ∼1 hr. The rapid TeV variability indicates a compact TeV-producing region, suggesting relativistic beaming with a Doppler factor δ ≥ 5. The correlation of the flux in the X-ray and the TeV bands indicates that a high-energy tail of a single electron population is responsible for both X-rays and TeV γ-rays, with radio, IR, UV and X-rays produced via the synchrotron process and GeV and TeV γ-rays produced via Comptonization. Under the assumption that the "soft lag" observed in the X-ray band is due to the synchrotron-lifetime effects, with δ = 5, we calculate the magnetic field for the X-ray-producing region to be ∼0.2 G. The Lorentz factors γcl of the electrons responsible for the emission in the keV and TeV bands are ∼106, consistent with the values implied by the Klein-Nishina limit.

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