A Caltech Library Service

First Results from NuSTAR Observations of Mkn 421

Baloković, M. and Forster, K. and Fürst, F. and Grefenstette, B. W. and Harrison, F. A. and Madsen, K. K. and Ogle, P. (2013) First Results from NuSTAR Observations of Mkn 421. EPJ Web of Conferences, 61 . Art. No. 04013. ISSN 2100-014X. doi:10.1051/epjconf/20136104013.

PDF - Published Version
Creative Commons Attribution.


Use this Persistent URL to link to this item:


Mkn 421 is a nearby active galactic nucleus dominated at all wavelengths by a very broad nonthermal continuum thought to arise from a relativistic jet seen at a small angle to the line of sight. Its spectral energy distribution peaks in the X-ray and TeV γ-ray bands, where the energy output is dominated by cooling of high-energy electrons in the jet. In order to study the electron distribution and its evolution, we carried out a dedicated multi-wavelength campaign, including extensive observations by the recently launched highly sensitive hard X-ray telescope NuSTAR, between December 2012 and May 2013. Here we present some initial results based on NuSTAR data from January through March 2013, as well as calibration observations conducted in 2012. Although the observations cover some of the faintest hard X-ray flux states ever observed for Mkn 421, the sensitivity is high enough to resolve intra-day spectral variability. We find that in this low state the dominant flux variations are smooth on timescales of hours, with typical intra-hour variations of ≲ 5%. We do not find evidence for either a cutoff in the hard X-ray spectrum, or a rise towards a high-energy component, but rather that at low flux the spectrum assumes a power law shape with a photon index of approximately 3. The spectrum is found to harden with increasing brightness.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Forster, K.0000-0001-5800-5531
Fürst, F.0000-0003-0388-0560
Grefenstette, B. W.0000-0002-1984-2932
Harrison, F. A.0000-0003-2992-8024
Madsen, K. K.0000-0003-1252-4891
Ogle, P.0000-0002-3471-981X
Additional Information:© 2013 Owned by the authors, published by EDP Sciences. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Published online: 9 December 2013.
Record Number:CaltechAUTHORS:20141202-100055952
Persistent URL:
Official Citation:First Results from NuSTAR Observations of Mkn 421 M. Baloković, M. Ajello, R. D. Blandford, S. E. Boggs, F. Borracci, J. Chiang, F. E. Christensen, W. W. Craig, K. Forster, A. Furniss, F. Fürst, G. Ghisellini, B. Giebels, P. Giommi, B. W. Grefenstette, C. J. Hailey, F. A. Harrison, M. Hayashida, B. Humensky, Y. Inoue, J. E. Koglin, H. Krawczynski, G. M. Madejski, K. K. Madsen, D. L. Meier, T. Nelson, P. Ogle, D. Paneque, M. Perri, S. Puccetti, C. S. Reynolds, T. Sbarrato, D. Stern, G. Tagliaferri, C. M. Urry, A. E. Wehrle, W. W. Zhang EPJ Web of Conferences 61 04013 (2013) DOI: 10.1051/epjconf/20136104013
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52261
Deposited By: Tony Diaz
Deposited On:02 Dec 2014 21:28
Last Modified:10 Nov 2021 19:23

Repository Staff Only: item control page