Observation of X-ray variability in the BL Lac object 1ES1959+65

Abstract

This paper reports X-ray spectral observations of a relatively nearby z = 0.048 BL Lacertae (BL Lac) object 1ES1959+650, which is a potential TeV emitter. The observations include 31 short pointings made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS), and 17 pointings by the PCA on board the Rossi X-ray Timing Explorer (RXTE). Most of these observations were spaced by less than 1 day. \es was detected by the ARGOS USA detector in the range 1-16 keV, and by the PCA in the 2-16 keV range but at different times. During the closely spaced RXTE observations beginning on 2000 July 28, an ending of one flare and a start of another are visible, associated with spectral changes, where the photon index Gamma ranges between ~ 1.4 and 1.7, and the spectrum is harder when the source is brighter. This implies that 1ES1959 is an XBL-type blazar, with the X-ray emission likely to originate via the synchrotron process. The USA observations reveal another flare that peaked on 2000 November 14 and doubled the flux within a few days, again associated with spectral changes of the same form. The spectral variability correlated with the flux and timing characteristics of this object that are similar to those of other nearby BL Lacs, and suggest relativistic beaming with a Doppler factor delta > 1.6 and magnetic fields of the order of a few mG. We also suggest that the steady component of the X-ray emission -- present in this object as well as in other XBLs -- may be due to the large-scale relativistic jet (such as measured by Chandra in many radio-loud AGN), but pointing very closely to our line of sight.

To appear in ApJ June 1, 2002 issue

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Cited by in corpus (25)

• The Parsec-Scale Structure and Jet Motions of the TeV Blazars 1ES 1959+650, PKS 2155-304, and 1ES 2344+514
• VHE gamma-ray emission of PKS 2155-304: spectral and temporal variability
• Detection of TeV Gamma Rays from the BL Lac Object 1ES1959+650 with the Whipple 10m Telescope
• Multi-wavelength observations of PKS 2155-304 with H.E.S.S
• Simultaneous multiwavelength observations of the blazar 1ES1959+650 at a low TeV flux
• X-ray Flaring Activity of Mrk 421
• NGC4258: a jet-dominated low-luminosity AGN?
• Month-Timescale Optical Variability in the M87 Jet
• X-ray Intraday Variability of Five TeV Blazars with NuSTAR
• Unveiling the X-ray/TeV engine in Mkn 421
• Hard X-ray properties of NuSTAR blazars
• PoGOLite - A High Sensitivity Balloon-Borne Soft Gamma-ray Polarimeter
• X-ray Flares from Markarian 501
• Spectral Survey of X-Ray Bright Active Galactic Nuclei from the Rossi X-ray Timing Explorer
• Long-term optical polarization variability of the tev blazar 1es~1959+650
• Do the mildly superluminal VLBI knots exclude ultrarelativistic blazar jets?
• Peak of spectral energy distribution play an important role in intra-day variability of Blazars?
• Wide band X-ray and optical observations of the BL Lac object 1ES 1959+650 in high state
• Multiwavelength Observations of 1ES 1959+650, One Year After the Strong Outburst of 2002
• Factors Determining Variability Time in Active Galactic Nucleus Jets
• Systematic investigation of X-ray spectral variability of TeV blazars during flares in the $RXTE$ era
• Particle Acceleration and Magnetic Field Structure in PKS 2155-304: Optical Polarimetric Observations
• AstroSat observation of the HBL 1ES 1959+650 during its October 2017 flaring
• X-ray Studies of Blazar 1ES 1959+650 Using SWIFT & XMM-NEWTON Satellite
• Correlated Short-Timescale Hard-Soft X-ray Variability of the Blazars Mrk 421 and 1ES 1959+650 using $\text{AstroSat}$