Multi-Wavelength Observations of 1ES1959+650 in a Flaring State

The Astrophysical …, 2008

We report the detection of very high-energy γ-ray emission from the intermediate-frequencypeaked BL Lacertae object W Comae (z = 0.102) by VERITAS, an array of four imaging atmospheric-Cherenkov telescopes. The source was observed between January and April 2008. A strong outburst of γ-ray emission was measured in the middle of March, lasting for only four days. The energy spectrum measured during the two highest flare nights is fit by a power-law and is found to be very steep, with a differential photon spectral index of Γ = 3.81 ± 0.35 stat ± 0.34 syst . The integral photon flux above 200 GeV during those two nights corresponds to roughly 9% of the flux from the Crab Nebula. Quasi-simultaneous Swift observations at X-ray energies were triggered by the VERITAS observations. The spectral energy distribution of the flare data can be described by synchrotron-self-Compton (SSC) or external-Compton (EC) leptonic jet models, with the latter offering a more natural set of parameters to fit the data.

Astronomy & Astrophysics, 2012

Aims. We study the non-thermal jet emission of the BL Lac object B3 2247+381 during a high optical state. Methods. The MAGIC telescopes observed the source during 13 nights between September 30th and October 30th 2010, collecting a total of 14.2 hours of good quality very high energy (VHE) γ-ray data. Simultaneous multiwavelength data was obtained with X-ray observations by the Swift satellite and optical R-band observations at the KVA-telescope. We also use high energy γ-ray (HE, 0.1 GeV-100 GeV) data from the Fermi satellite.

Astronomy and Astrophysics, 2012

Aims. We study the non-thermal jet emission of the BL Lac object B3 2247+381 during a high optical state. Methods. The MAGIC telescopes observed the source during 13 nights between September 30th and October 30th 2010, collecting a total of 14.2 h of good quality very high energy (VHE) γ-ray data. Simultaneous multiwavelength data was obtained with X-ray observations by the Swift satellite and optical R-band observations at the KVA-telescope. We also use high energy γ-ray (HE, 0.1-100 GeV) data from the Fermi satellite. Results. The BL Lac object B3 2247+381 (z = 0.119) was detected, for the first time, at VHE γ-rays at a statistical significance of 5.6σ. A soft VHE spectrum with a photon index of -3.2 ± 0.6 was determined. No significant short term flux variations were found. We model the spectral energy distribution using a one-zone SSC-model, which can successfully describe our data.

Astronomy & Astrophysics, 2012

1RXS J101015.9−311909 is a galaxy located at a redshift of z = 0.14 hosting an active nucleus (called AGN) belonging to the class of bright BL Lac objects. Observations at high (HE, E > 100 MeV) and very high (VHE, E > 100 GeV) energies provide insights into the origin of very energetic particles present in such sources and the radiation processes at work. We report on results from VHE observations performed between 2006 and 2010 with the H.E.S.S. instrument, an array of four imaging atmospheric Cherenkov telescopes. H.E.S.S. data have been analysed with enhanced analysis methods, making the detection of faint sources more significant. VHE emission at a position coincident with 1RXS J101015.9−311909 is detected with H.E.S.S. for the first time. In a total good-quality livetime of about 49 hours, we measure 263 excess counts, corresponding to a significance of 7.1 standard deviations. The photon spectrum above 0.2 TeV can be described by a power-law with a photon index of Γ = 3.08 ± 0.42 stat ± 0.20 sys . The integral flux above 0.2 TeV is about 0.8% of the flux of the Crab nebula and shows no significant variability over the time reported. In addition, public Fermi/LAT data are analysed to search for high energy emission from the source. The Fermi/LAT HE emission in the 100 MeV to 200 GeV energy range is significant at 8.3 standard deviations in the chosen 25-month dataset. UV and X-ray contemporaneous observations with the Swift satellite in May 2007 are also reported, together with optical observations performed with the ATOM telescope located at the H.E.S.S. site. Swift observations reveal an absorbed X-ray flux of F (0.3−7)keV = 1.04 +0.04 −0.05 × 10 −11 erg cm −2 s −1 in the 0.3 − 7 keV range. Finally, all the available data are used to study the multi-wavelength properties of the source. The spectral energy distribution (SED) can be reproduced using a simple one-zone Synchrotron Self Compton (SSC) model with emission from a region with a Doppler factor of 30 and a magnetic field between 0.025 and 0.16 G. These parameters are similar to those obtained for other sources of this type.

The Astrophysical Journal, 2002

This paper reports X-ray spectral observations of a relatively nearby (z = 0.048) BL Lacertae (BL Lac) object 1ES1959+65, 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. 1ES1959+65 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 Γ ranges between ∼ 1.4 and 1.7, and the spectrum is harder when the source is brighter. This implies that 1ES1959+65 is an