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Professor Paula Chadwick's Outputs (210)

Diffuse Galactic gamma-ray emission with H.E.S.S (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Backes, M., …Collaboration, H. (2014). Diffuse Galactic gamma-ray emission with H.E.S.S. Physical Review D, 90(12), https://doi.org/10.1103/physrevd.90.122007

Diffuse γ-ray emission is the most prominent observable signature of celestial cosmic-ray interactions at high energies. While already being investigated at GeV energies over several decades, assessments of diffuse γ-ray emission at TeV energies rema... Read More about Diffuse Galactic gamma-ray emission with H.E.S.S.

Search for dark matter annihilation signatures in H.E.S.S. observations of dwarf spheroidal galaxies (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Backes, M., …Collaboration, H. (2014). Search for dark matter annihilation signatures in H.E.S.S. observations of dwarf spheroidal galaxies. Physical Review D, 90(11), https://doi.org/10.1103/physrevd.90.112012

Dwarf spheroidal galaxies of the Local Group are close satellites of the Milky Way characterized by a large mass-to-light ratio and are not expected to be the site of nonthermal high-energy gamma-ray emission or intense star formation. Therefore they... Read More about Search for dark matter annihilation signatures in H.E.S.S. observations of dwarf spheroidal galaxies.

Long-term monitoring of PKS 2155-304 with ATOM and H.E.S.S.: investigation of optical/γ-ray correlations in different spectral states (2014)
Journal Article
Collaboration, H., Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., …Zechlin, H. (2014). Long-term monitoring of PKS 2155-304 with ATOM and H.E.S.S.: investigation of optical/γ-ray correlations in different spectral states. Astronomy & Astrophysics, 571, Article A39. https://doi.org/10.1051/0004-6361/201424142

In this paper we report on the analysis of all the available optical and very high-energy γ-ray (>200 GeV) data for the BL Lac object PKS 2155−304, collected simultaneously with the ATOM and H.E.S.S. telescopes from 2007 until 2009. This study also i... Read More about Long-term monitoring of PKS 2155-304 with ATOM and H.E.S.S.: investigation of optical/γ-ray correlations in different spectral states.

Discovery of the Hard Spectrum VHE γ-Ray Source HESS J1641-463 (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Backes, M., …Collaboration, H. (2014). Discovery of the Hard Spectrum VHE γ-Ray Source HESS J1641-463. Astrophysical Journal Letters, 794(1), https://doi.org/10.1088/2041-8205/794/1/l1

This Letter reports the discovery of a remarkably hard spectrum source, HESS J1641−463, by the High Energy Stereoscopic System (H.E.S.S.) in the very high energy (VHE) domain. HESS J1641−463 remained unnoticed by the usual analysis techniques due to... Read More about Discovery of the Hard Spectrum VHE γ-Ray Source HESS J1641-463.

Photon-axion mixing within the jets of active galactic nuclei and prospects for detection (2014)
Journal Article
Harris, J., & Chadwick, P. (2014). Photon-axion mixing within the jets of active galactic nuclei and prospects for detection. Journal of Cosmology and Astroparticle Physics, 2014(10), Article 018. https://doi.org/10.1088/1475-7516/2014/10/018

Very high energy γ-ray observations of distant active galactic nuclei (AGN) generally result in higher fluxes and harder spectra than expected, resulting in some tension with the level of the extragalactic background light (EBL). If hypothetical axio... Read More about Photon-axion mixing within the jets of active galactic nuclei and prospects for detection.

The Cherenkov Telescope Array potential for the study of young supernova remnants (2014)
Journal Article
Acharya, B., Aramo, C., Babic, A., Barrio, J., Baushev, A., Becker Tjus, J., …Yoshikoshi, T. (2015). The Cherenkov Telescope Array potential for the study of young supernova remnants. Astroparticle Physics, 62, 152-164. https://doi.org/10.1016/j.astropartphys.2014.08.005

Supernova remnants (SNRs) are among the most important targets for γ-ray observatories. Being prominent non-thermal sources, they are very likely responsible for the acceleration of the bulk of Galactic cosmic rays (CRs). To firmly establish the SNR... Read More about The Cherenkov Telescope Array potential for the study of young supernova remnants.

Erratum: HESS J1640−465 – an exceptionally luminous TeV γ-ray supernova remnant (2014)
Journal Article
Collaboration, H., Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., …Zechlin, H. (2014). Erratum: HESS J1640−465 – an exceptionally luminous TeV γ-ray supernova remnant. Monthly Notices of the Royal Astronomical Society, 441(4), 3640-3642. https://doi.org/10.1093/mnras/stu826

The paper ‘HESS J1640−465 – an exceptionally luminous TeV γ-ray supernova remnant’ was published in MNRAS, 439, 2828 (2014). Due to an error in the integration of the differential energy spectrum, the luminosities stated in Sections 2.2 and 4.3 are i... Read More about Erratum: HESS J1640−465 – an exceptionally luminous TeV γ-ray supernova remnant.

An investigation into the spectral properties of bright Fermi blazars (2014)
Journal Article
Harris, J., Chadwick, P., & Daniel, M. (2014). An investigation into the spectral properties of bright Fermi blazars. Monthly Notices of the Royal Astronomical Society, 441(4), 3591-3599. https://doi.org/10.1093/mnras/stu787

We investigate the spectral properties of blazars detected with the Fermi-Large Area Telescope (LAT) in the high-energy regime 100 MeV–100 GeV. We find that over long time-scales a log-parabola provides an adequate description of the spectrum in almo... Read More about An investigation into the spectral properties of bright Fermi blazars.

TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S. Monthly Notices of the Royal Astronomical Society, 441(1), 790-799. https://doi.org/10.1093/mnras/stu459

The non-thermal nature of the X-ray emission from the shell-type supernova remnants (SNRs) G1.9+0.3 and G330.2+1.0 is an indication of intense particle acceleration in the shock fronts of both objects. This suggests that the SNRs are prime candidates... Read More about TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S.

HESS J1640-465 - an exceptionally luminous TeV γ-ray supernova remnant (2014)
Journal Article
Abramowski, A., Aharonian, F., Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). HESS J1640-465 - an exceptionally luminous TeV γ-ray supernova remnant. Monthly Notices of the Royal Astronomical Society, 439(3), 2828-2836. https://doi.org/10.1093/mnras/stu139

The results of follow-up observations of the TeV γ-ray source HESS J1640−465 from 2004 to 2011 with the High Energy Stereoscopic System (HESS) are reported in this work. The spectrum is well described by an exponential cut-off power law with photon i... Read More about HESS J1640-465 - an exceptionally luminous TeV γ-ray supernova remnant.

Search for extended γ-ray emission around AGN with H.E.S.S. and Fermi-LAT (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Malyshev, D. (2014). Search for extended γ-ray emission around AGN with H.E.S.S. and Fermi-LAT. Astronomy & Astrophysics, 562, Article A145. https://doi.org/10.1051/0004-6361/201322510

Context. Very-high-energy (VHE; E > 100 GeV) γ-ray emission from blazars inevitably gives rise to electron-positron pair production through the interaction of these γ-rays with the extragalactic background light (EBL). Depending on the magnetic field... Read More about Search for extended γ-ray emission around AGN with H.E.S.S. and Fermi-LAT.

H.E.S.S. observations of the Crab during its March 2013 GeV gamma- ray flare (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). H.E.S.S. observations of the Crab during its March 2013 GeV gamma- ray flare. Astronomy & Astrophysics, 562, Article L4. https://doi.org/10.1051/0004-6361/201323013

Context. On March 4, 2013 the Fermi-LAT and AGILE reported a flare from the direction of the Crab nebula in which the high-energy (HE; E > 100 MeV) flux was six times above its quiescent level. Simultaneous observations in other energy bands give us... Read More about H.E.S.S. observations of the Crab during its March 2013 GeV gamma- ray flare.

HESS J1818–154, a new composite supernova remnant discovered in TeV gamma rays and X-rays (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). HESS J1818–154, a new composite supernova remnant discovered in TeV gamma rays and X-rays. Astronomy & Astrophysics, 562, Article A40. https://doi.org/10.1051/0004-6361/201322914

Composite supernova remnants (SNRs) constitute a small subclass of the remnants of massive stellar explosions where non-thermal radiation is observed from both the expanding shell-like shock front and from a pulsar wind nebula (PWN) located inside of... Read More about HESS J1818–154, a new composite supernova remnant discovered in TeV gamma rays and X-rays.

Impact of aerosols and adverse atmospheric conditions on the data quality for spectral analysis of the H.E.S.S. telescopes (2014)
Journal Article
Hahn, J., de los Reyes, R., Bernlöhr, K., Krüger, P., Lo, Y., Chadwick, P., …Marandon, V. (2014). Impact of aerosols and adverse atmospheric conditions on the data quality for spectral analysis of the H.E.S.S. telescopes. Astroparticle Physics, 54, 25-32. https://doi.org/10.1016/j.astropartphys.2013.10.003

The Earth’s atmosphere is an integral part of the detector in ground-based imaging atmospheric Cherenkov telescope (IACT) experiments and has to be taken into account in the calibration. Atmospheric and hardware-related deviations from simulated cond... Read More about Impact of aerosols and adverse atmospheric conditions on the data quality for spectral analysis of the H.E.S.S. telescopes.

Discovery of very high energy γ-ray emission from the BL Lacertae object PKS 0301−243 with H.E.S.S (2013)
Journal Article
Abramowski, A., Acero, F., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., …Zechlin, H. (2013). Discovery of very high energy γ-ray emission from the BL Lacertae object PKS 0301−243 with H.E.S.S. Astronomy & Astrophysics, 559, Article A136. https://doi.org/10.1051/0004-6361/201321639

The active galactic nucleus PKS 0301−243 (z = 0.266) is a high-synchrotron-peaked BL Lac object that is detected at high energies (HE, 100 MeV <E < 100 GeV) by Fermi/LAT. This paper reports on the discovery of PKS 0301−243 at very high energies (E >... Read More about Discovery of very high energy γ-ray emission from the BL Lacertae object PKS 0301−243 with H.E.S.S.

HESS and Fermi-LAT discovery of γ-rays from the blazar 1ES 1312−423 (2013)
Journal Article
Abramowski, A., Acero, F., Aharonian, F., Akhperjanian, A., Angüner, E., Anton, G., …Kadler, M. (2013). HESS and Fermi-LAT discovery of γ-rays from the blazar 1ES 1312−423. Monthly Notices of the Royal Astronomical Society, 434(3), 1889-1901. https://doi.org/10.1093/mnras/stt1081

A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of γ-rays from the blazar 1ES 1312−423, 2° away from the radio galaxy. With a differential flux at 1 TeV of ϕ(1 TeV) = (1.9 ± 0... Read More about HESS and Fermi-LAT discovery of γ-rays from the blazar 1ES 1312−423.

H.E.S.S. discovery of VHE γ-rays from the quasar PKS 1510−089 (2013)
Journal Article
H.E.S.S. Collaboration Abramowski, A. A., F. Aharonian, F. A., A.G. Anton, G. B., S. Balzer, A. B., A. Becherini, Y. B. T., J. Behera, B. B., …S., H. (2013). H.E.S.S. discovery of VHE γ-rays from the quasar PKS 1510−089. Astronomy & Astrophysics, 554, Article A107. https://doi.org/10.1051/0004-6361/201321135

The quasar PKS 1510−089 (z = 0.361) was observed with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes during high states in the optical and GeV bands, to search for very high energy (VHE, defined as E ≥ 0.1 TeV) emission. VHE γ-rays we... Read More about H.E.S.S. discovery of VHE γ-rays from the quasar PKS 1510−089.

Discovery of TeV γ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift (2013)
Journal Article
Collaboration, H., Abramowski, A., Acero, F., Akhperjanian, A., Anton, G., Balenderan, S., …Pelat, D. (2013). Discovery of TeV γ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift. Astronomy & Astrophysics, 552, Article A118. https://doi.org/10.1051/0004-6361/201321108

Very high-energy γ-ray emission from PKS 0447−439 was detected with the H.E.S.S. Cherenkov telescope array in December 2009. This blazar is one of the brightest extragalactic objects in the Fermi bright source list and has a hard spectrum in the MeV... Read More about Discovery of TeV γ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift.

H.E.S.S. observations of the binary system PSR B1259-63/LS 2883 around the 2010/2011 periastron passage (2013)
Journal Article
Abramowski, A., Acero, F., Aharonian, F., Akhperjanian, A., Anton, G., Balenderan, S., …Zechlin, H. (2013). H.E.S.S. observations of the binary system PSR B1259-63/LS 2883 around the 2010/2011 periastron passage. Astronomy & Astrophysics, 551, Article A94. https://doi.org/10.1051/0004-6361/201220612

Aims. We present very high energy (VHE; E > 100 GeV) data from the γ-ray binary system PSR B1259-63/LS 2883 taken around its periastron passage on 15th of December 2010 with the High Energy Stereoscopic System (H.E.S.S.) of Cherenkov Telescopes. We a... Read More about H.E.S.S. observations of the binary system PSR B1259-63/LS 2883 around the 2010/2011 periastron passage.