VERITAS and Multiwavelength Observations of the BL Lacertae Object 1ES 1741+196
Multiwavelength spectral energy distribution for 1ES1741+196. For details, see Figure 5 below.
Reference: A.U. Abeysekara et al. (The VERITAS Collaboration), MNRAS 459: 2250, 2016
The BL Lacertae object 1ES 1741+196 is located at redshift z=0.084+/-0.001 within a triplet of interacting galaxies. VERITAS detected the source at a significance of 5.9 sigma, based on ~30 hours of observation over six years. The photon spectrum was found to be well-described by a power law, and the integral flux was measured to be ~1.6% of the Crab Nebula flux above 180 GeV. Notably, no evidence for strong flaring behavior in any energy band was found in the six years of VERITAS observations of 1ES 1741+196, making this study a rare characterization of a blazar in a non-flaring state.
Multiwavelength observations using Fermi-LAT (high energy), Swift-XRT (X-ray), Swift-UVOT (optical and ultraviolet), and Super-LOTIS (optical) were carried out during time periods contemporaneous with VERITAS observations. A multiwavelength spectral energy distribution was constructed, and was found to be consistent with the predictions of a single-zone synchrotron-self-Compton model. The position of the high-frequency peak in the spectral energy distribution suggests that 1ES 1741+196 may be an extreme-high-frequency-peaked BL Lac object. This source is potentially interesting for studies of the intergalactic magnetic field and extragalactic background light, but such studies would require long exposure times, given the source's low gamma-ray flux.
Figures from paper (click to get full size image):
Figure 1: The distribution of the angular distance between the reconstructed arrival direction of the shower and the nominal source position for events reconstructed by VERITAS. The area to the left of the dashed line is the signal region.
Figure 2: VERITAS photon spectrum. The fitted spectrum is consistent with a power law.
Figure 3: Multiwavelength light curve for 1ES 1741+196. From top to bottom, the optical and ultraviolet, X-ray, high-energy, and very-high-energy light curves are shown. The Swift–UVOT light curves are derived from data taken with different filters, and exhibit variability for all filters.
Figure 4: Fitted photon index (Γ) versus normalisation (K) measured in Swift–XRT data. The photon indices are consistent with a single value of 1.78, as indicated by the red dashed line, in dicating no spectral variability.
Figure 5: Multiwavelength spectral energy distribution for 1ES1741+196. Grey symbols are archival data, blue symbols are observations analysed here: VERITAS (open cross), Swift–XRT (open square), Super-LOTIS and Swift–UVOT (open stars). The maximum and minimum Swift–XRT bow-ties are also shown (red) as well as the average Fermi–LAT bow-tie (grey). Note that the lowest frequency peak, the thermal component due to the host galaxy, is not included in the non-thermal SED model. A single SSC model is overlaid on the SED, showing consistency between the data and a one-zone SSC scenario. The same model, including EBL absorption (using the model of Franceschini 2008), is also shown by the dashed line.
Last Updated on Friday, 27 May 2016 13:15