Please use this identifier to cite or link to this item:
Scopus Web of Science® Altmetric
Type: Journal article
Title: Multi-wavelength observations of H 2356-309
Author: Nicholas, B.
Rowell, G.
Citation: Astronomy and Astrophysics: a European journal, 2010; 516(6):A56-A66
Publisher: E D P Sciences
Issue Date: 2010
ISSN: 0004-6361
Organisation: H.E.S.S. Collaboration
Statement of
A. Abramowski...B. Nicholas...G. Rowell...and H.-S. al., and the HESS Collaboration
Abstract: AIMS: The properties of the broad-band emission from the high-frequency peaked BL Lac H 2356-309 (z=0.165) are investigated. METHODS: Very High Energy (VHE; E > 100 GeV) observations of H 2356-309 were performed with the High Energy Stereoscopic System (HESS) from 2004 through 2007. Simultaneous optical/UV and X-ray observations were made with the XMM-Newton satellite on June 12/13 and June 14/15, 2005. NRT radio observations were also contemporaneously performed in 2005. ATOM optical monitoring observations were also made in 2007. RESULTS: A strong VHE signal, ~13 sigma total, was detected by HESS after the four years HESS observations (116.8 hrs live time). The integral flux above 240 GeV is I(>240 GeV) = (3.06 +- 0.26 {stat} +- 0.61 {syst}) x 10^{-12} cm^{-2} s^{-1}, corresponding to ~1.6% of the flux observed from the Crab Nebula. A time-averaged energy spectrum is measured from 200 GeV to 2 TeV and is characterized by a power law (photon index of Gamma = 3.06 +- 0.15 {stat} +- 0.10 {syst}). Significant small-amplitude variations in the VHE flux from H 2356-309 are seen on time scales of months and years, but not on shorter time scales. No evidence for any variations in the VHE spectral slope are found within these data. The XMM-Newton X-ray measurements show a historically low X-ray state, characterized by a hard, broken-power-law spectrum on both nights. CONCLUSIONS: The broad-band spectral energy distribution (SED) of the blazar can be adequately fit using a simple one-zone synchrotron self-Compton (SSC) model. In the SSC scenario, higher VHE fluxes could be expected in the future since the observed X-ray flux is at a historically low level.
Keywords: galaxies: active / BL Lacertae objects: individual: H 2356–309 / gamma rays: galaxies
Rights: Copyright © ESO, 2010. All rights reserved. Submitted to Cornell University’s online archive in 2010 by Wystan Benbow.
DOI: 10.1051/0004-6361/201014321
Published version:
Appears in Collections:Aurora harvest
IPAS publications
Physics publications

Files in This Item:
File Description SizeFormat 
hdl_61686.pdfPublished version489.44 kBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.