Observation of X‐Ray Variability in the BL Lacertae Object 1ES 1959+65

Giebels, B.; Bloom, E. D.; Focke, W. B.; Godfrey, G.; Madejski, G. M.; Reilly, K. T.; Parkinson, P. M. Saz; Shabad, G.; Bandyopadhyay, Reba M.; Fritz, G.; Hertz, P.; Kowalski, Michael P.; Lovellette, M. N.; Ray, Paul S.; Wolff, M. T.; Wood, K. S.; Yentis, D.; Scargle, Jeffrey D.

doi:10.1086/340065

Cited by 35 publications

(33 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…and hence the Lorentz factor is constrained to γ e ≥ 1.3 × 10 6 which is higher than that calculated as above for Mkn 421 by Takahashi et al (1996) who derived γ e > 5 × 10 5 (and B ≈ 0.2 G) but lower than γ e ≈ 10 7 found in a similar way in 1ES1959+650 (Giebels et al 2002).…”

Section: Doppler Boosting and Synchrotron/compton Derived Parameterscontrasting

confidence: 60%

Multi-wavelength observations of PKS 2155-304 with HESS

Aharonian¹,

Akhperjanian²,

Bazer‐Bachi³

et al. 2005

A&A

145

138

View full text Add to dashboard Cite

The High Energy Stereoscopic System (HESS) has observed the high-frequency peaked BL Lac object PKS 2155−304 in 2003 between October 19 and November 26 in Very High Energy (VHE) γ-rays (E ≥ 160 GeV for these observations). Observations were carried out simultaneously with the Proportional Counter Array (PCA) on board the Rossi X-ray Timing Explorer satellite (RXTE), the Robotic Optical Transient Search Experiment (ROTSE) and the Nançay decimetric radiotelescope (NRT). Intra-night variability is seen in the VHE band, the source being detected with a high significance on each night it was observed. Variability is also found in the X-ray and optical bands on kilosecond timescales, along with flux-dependent spectral changes in the X-rays. A transient X-ray event with a 1500 s timescale is detected, making this the fastest X-ray flare seen in this object. No correlation can be established between the X-ray and the γ-ray fluxes, or any of the other wavebands, over the small range of observed variability. The average HESS spectrum shows a very soft power law shape with a photon index of 3.37 ± 0.07 stat ± 0.10 sys . The energy outputs in the 2-10 keV and in the VHE γ-ray range are found to be similar, with the X-rays and the optical fluxes at a level comparable to some of the lowest historical measurements, indicating that PKS 2155−304 was in a low or quiescent state during the observations. Both a leptonic and a hadronic model are used to derive source parameters from these observations. These parameters are found to be sensitive to the model of Extragalactic Background Light (EBL) that attenuates the VHE signal at this source's redshift (z = 0.117).

show abstract

Section: Doppler Boosting and Synchrotron/compton Derived Parameterscontrasting

confidence: 60%

Multi-wavelength observations of PKS 2155-304 with HESS

Aharonian¹,

Akhperjanian²,

Bazer‐Bachi³

et al. 2005

A&A

145

138

View full text Add to dashboard Cite

show abstract

“…2, the X-ray spectral slope varies between the different observations, e.g., s = 0.64 ± 0.08 (Pietsch & Read 2002), 0.78 ± 0.29 (Makishima et al 1994), 0.87 ± 0.15 (Reynolds et al 2000), and 1.11 ± 0.14 (Fiore et al 2001). In addition to instrumental reasons, it is very possible that such variations are intrinsic, as we know happens in some sources (e.g., Giebels et al 2002). We will therefore fit both the steepest (s = 1.11, from BeppoSAX) and the flattest (s = 0.64, from XMM-Newton) X-ray data in the framework of our model.…”

Section: Infrared To X-ray Spectral Fitting Resultsmentioning

confidence: 99%

NGC 4258: A jet-dominated low-luminosity AGN?

Yuan

Markoff

Falcke

et al. 2002

A&A

View full text Add to dashboard Cite

Abstract. Low-luminosity AGNs (LLAGNs) are a very important class of sources since they occupy a significant fraction of local galaxies. Their spectra differ significantly from the canonical luminous AGNs, most notably by the absence of the "big blue bump". In the present paper, taking a typical LLAGN-NGC 4258-as an example, we investigate the origin of their spectral emission. The observational data of NGC 4258 is extremely abundant, including water maser emission, putting very strict constraints to its theoretical models. The infrared (IR) spectrum is well described by a steep power-law form f ν ∝ ν −1.4 , and may extend to the optical/UV band. Up until now there is no model which can explain such a steep spectrum, and we here propose a coupled jet plus accretion disk model for NGC 4258. The accretion disk is composed of an inner ADAF (or radiatively inefficient accretion flow) and an outer standard thin disk. A shock occurs when the accretion flow is ejected out of the ADAF to form the jet near the black hole, accelerating the electrons into a power-law energy distribution. The synchrotron and self-Comptonized emission from these electrons greatly dominates over the underlying accretion disk and can well explain the spectrum ranging from IR to X-ray bands. The further propagation of the shocked gas in the jet can explain the flat radio spectrum of NGC 4258. Several predictions of our model are presented for testing against future observations, and we briefly discuss the application of the model to other LLAGNs.

show abstract

“…We summarize and discuss the results in x 6, focusing on a very interesting result from the X-ray observations: a secular evolution of the possible X-ray flux versus an X-ray photon index correlation. Throughout the paper we compare results from 2003 with those obtained in 2002 ( Paper I ) and in earlier observations in 2000 (Giebels et al 2002). In the following, fit results are given in the text and in the tables with 90% confidence interval errors; in figures, we show 1 error bars and 90% confidence level upper limits computed with the method described in Helene (1983).…”

Section: Introductionmentioning

confidence: 83%

“…In the following, fit results are given in the text and in the tables with 90% confidence interval errors; in figures, we show 1 error bars and 90% confidence level upper limits computed with the method described in Helene (1983). Giebels et al (2002) and the 2002 data from Paper I, which we reanalyze here. The TeV -ray data comprise 13.1 hr.…”

Section: Introductionmentioning

confidence: 99%

Multiwavelength Observations of 1ES 1959+650, 1 Year after the Strong Outburst of 2002

Gutierrez¹,

Badran²,

Bradbury³

et al. 2006

ApJ

View full text Add to dashboard Cite

In 2003 April-May, the blazar 1ES 1959+650 showed an increased level of X-ray activity. This prompted a multiwavelength observation campaign with the Whipple 10 m -ray telescope, the Rossi X-Ray Timing Explorer, the Bordeaux Optical Observatory, and the University of Michigan Radio Astronomy Observatory. We present the multiwavelength data taken from 2003 May 2 to June 7 and compare the source characteristics with those measured during observations taken during the years 2000 and 2002. The X-ray observations gave a data set with high signal-tonoise ratio light curves and energy spectra; however, the -ray observations did not reveal a major TeV -ray flare. Furthermore, we find that the radio and optical fluxes do not show statistically significant deviations from those measured during the 2002 flaring periods. While the X-ray flux and X-ray photon index appear correlated during subsequent observations, the apparent correlation evolved significantly among the years 2000, 2002, and 2003. We discuss the implications of this finding for the mechanism that causes the flaring activity.

show abstract

Observation of X‐Ray Variability in the BL Lacertae Object 1ES 1959+65

Cited by 35 publications

References 37 publications

Multi-wavelength observations of PKS 2155-304 with HESS

Multi-wavelength observations of PKS 2155-304 with HESS

NGC 4258: A jet-dominated low-luminosity AGN?

Multiwavelength Observations of 1ES 1959+650, 1 Year after the Strong Outburst of 2002

Contact Info

Product

Resources

About