M. Krause

Deutsches Elektronen-Synchrotron DESY

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D. Kieda

University of Utah

J. Holder

University of Delaware

W. Benbow

Center for Astrophysics Harvard & Smithsonian

M. Pohl

University of Potsdam

R. A. Ong

University of California System

L. Fortson

University of Minnesota

P. Kaaret

Marshall Space Flight Center

T. B. Humensky

Goddard Space Flight Center

D. A. Williams

University of California, Santa Cruz

R. Bird

Istituto Nazionale di Fisica Nucleare, Sezione di Firenze

Cooperative Institutions

Centre National de la Recherche Scientifique

563

National Institute for Astrophysics

301

Max Planck Society

279

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

248

Max Planck Institute for Physics

247

University of Turku

244

Authorised Association Consortium

236

TU Dortmund University

227

Universitat de Barcelona

220

Université Paris Cité

210

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Wind velocity measurement

NASA Tech Briefs (1976)

W. C. Cliff R. M. Huffaker Werner Dahm T. R. Lawrence M. Krause

Homodyne laser-Doppler system determines three-component wind velocity at altitudes of several kilometers in clear-air conditions. There is no need for deployment of towers, radiosondes, or for seeding airflows.

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Dark matter constraints from a joint analysis of dwarf Spheroidal galaxy observations with VERITAS

Physical review. D/Physical review. D. (2017)

S. Archambault A. Archer W. Benbow R. Bird Etienne Bourbeau

We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of $\ensuremath{\sim}230$ hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is $1.35\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}23}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ at 1 TeV for the bottom quark ($b\overline{b}$) final state, $2.85\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ at 1 TeV for the tau lepton (${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$) final state and $1.32\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ at 1 TeV for the gauge boson ($\ensuremath{\gamma}\ensuremath{\gamma}$) final state.

Dwarf spheroidal galaxy

Dwarf galaxy problem

10.1103/physrevd.95.082001

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Citations (112)

CTA Contributions to the 34th International Cosmic Ray Conference (ICRC2015)

arXiv (Cornell University) (2015)

the CTA Consortium NULL AUTHOR_ID A. Abchiche A. U. Abeysekara Ó. Abril

List of contributions from the CTA Consortium presented at the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands.

10.48550/arxiv.1508.05894

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The role of massive stars in the turbulent infancy of Galactic globular clusters: Feedback on the intracluster medium, and detailed timeline

arXiv (Cornell University) (2013)

C. Charbonnel M. Krause T. Decressin Nikos Prantzos G. Meynet

A major paradigm shift has recently revolutionized our picture of globular clusters (GC) that were long thought to be simple systems of coeval stars born out of homogeneous material. Indeed, detailed abundance studies of GC long-lived low-mass stars performed with 8-10m class telescopes, together with high-precision photometry of Galactic GCs obtained with HST,have brought compelling clues on the presence of multiple stellar populations in individual GCs. These stellar subgroups can be recognized thanks to their different chemical properties (more precisely by abundance differences in light elements from carbon to aluminium; see Bragaglia, this volume) and by the appearance of multimodal sequences in the colour-magnitude diagrams (see Piotto, this volume). This has a severe impact on our understanding of the early evolution of GCs, and in particular of the possible role that massive stars played in shaping the intra-cluster medium (ICM) and in inducing secondary star formation. Here we summarize the detailed timeline we have recently proposed for the first 40 Myrs in the lifetime of a typical GC following the general ideas of our so-called "Fast Rotating Massive stars scenario" (FRMS, Decressin et al. 2007b) and taking into account the dynamics of interstellar bubbles produced by stellar winds and supernovae. More details can be found in Krause et al. (2012, 2013).

Time line

Intracluster medium

10.48550/arxiv.1301.5016

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A Very High Energy γ-Ray Survey toward the Cygnus Region of the Galaxy

The Astrophysical Journal (2018)

A. U. Abeysekara A. Archer T. Aune W. Benbow R. Bird

We present results from deep observations towards the Cygnus region using 300 hours of very-high-energy (VHE) $\gamma$-ray data taken with the VERITAS Cherenkov telescope array and over seven years of high-energy $\gamma$-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse $\gamma$-ray emission in the northern sky, the Cygnus region provides a promising area to probe the origins of cosmic rays. We report the identification of a potential Fermi-LAT counterpart to VER J2031+415 (TeV J2032+4130), and resolve the extended VHE source VER J2019+368 into two source candidates (VER J2018+367* and VER J2020+368*) and characterize their energy spectra. The Fermi-LAT morphology of 3FGL 2021.0+4031e (the Gamma-Cygni supernova remnant) was examined and a region of enhanced emission coincident with VER J2019+407 was identified and jointly fit with the VERITAS data. By modeling 3FGL J2015.6+3709 as two sources, one located at the location of the pulsar wind nebula CTB 87 and one at the quasar QSO J2015+371, a continuous spectrum from 1 GeV to 10 TeV was extracted for VER J2016+371 (CTB 87). An additional 71 locations coincident with Fermi-LAT sources and other potential objects of interest were tested for VHE $\gamma$-ray emission, with no emission detected and upper limits on the differential flux placed at an average of 2.3% of the Crab Nebula ux. We interpret these observations in a multiwavelength context and present the most detailed $\gamma$-ray view of the region to date.

Crab Nebula

Pulsar wind nebula

10.3847/1538-4357/aac4a2

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HESS J1943+213: An Extreme Blazar Shining through the Galactic Plane

The Astrophysical Journal (2018)

A. Archer W. Benbow R. Bird Robert Brose M. Buchovecky

Abstract HESS J1943+213 is a very high energy (VHE; >100 GeV) γ -ray source in the direction of the Galactic plane. Studies exploring the classification of the source are converging toward its identification as an extreme synchrotron BL Lac object. Here we present 38 hr of VERITAS observations of HESS J1943+213 taken over 2 yr. The source is detected with a significance of ∼20 standard deviations, showing a remarkably stable flux and spectrum in VHE γ -rays. Multifrequency Very Long Baseline Array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with the European VLBI Network and detect this component in the 4.6 and 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, Fermi -LAT, Swift -XRT, the FLWO 48″ telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron self-Compton model. The well-measured γ -ray peak of the SED with VERITAS and Fermi -LAT provides constraining upper limits on the source redshift. Possible contribution of secondary γ -rays from ultra-high-energy cosmic-ray-initiated electromagnetic cascades to the γ -ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and γ -ray bands. No statistically significant flux or spectral variability is detected.

BL Lac object

Spectral energy distribution

Galactic plane

10.3847/1538-4357/aacbd0

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Citations (17)

PLM-driven manufacturing of medium-sized telescope structures of CTAO

M. Garczarczyk M. Krause L. Hagge

10.1117/12.3020134

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High energy astroparticle physics for high school students

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019) (2016)

M. Krause Hans-Peter Bretz Lew Classen Markus Holler Moritz Hütten

The questions about the origin and type of cosmic particles are not only fascinating for scientists in astrophysics, but also for young enthusiastic high school students.To familiarize them with research in astroparticle physics, the Pierre Auger Collaboration agreed to make 1% of its data publicly available.The Pierre Auger Observatory investigates cosmic rays at the highest energies and consists of more than 1600 water Cherenkov detectors, located near Malargüe, Argentina.With publicly available data from the experiment, students can perform their own hands-on analysis.In the framework of a so-called Astroparticle Masterclass organized alongside the context of the German outreach network Netzwerk Teilchenwelt, students get a valuable insight into cosmic ray physics and scientific research concepts.We present the project and experiences with students.

Astroparticle physics

Pierre Auger Observatory

Outreach

High-energy astronomy

10.22323/1.236.0304

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VERITAS Observations of the BL Lac Object TXS 0506+056

The Astrophysical Journal Letters (2018)

A. U. Abeysekara A. Archer W. Benbow R. Bird A. Brill

Abstract On 2017 September 22, the IceCube Neutrino Observatory reported the detection of the high-energy neutrino event IC 170922A, of potential astrophysical origin. It was soon determined that the neutrino direction was consistent with the location of the gamma-ray blazar TXS 0506+056 (3FGL J0509.4+0541), which was in an elevated gamma-ray emission state as measured by the Fermi satellite. Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations of the neutrino/blazar region started on 2017 September 23 in response to the neutrino alert and continued through 2018 February 6. While no significant very-high-energy (VHE; E > 100 GeV) emission was observed from the blazar by VERITAS in the two-week period immediately following the IceCube alert, TXS 0506+056 was detected by VERITAS with a significance of 5.8 standard deviations ( σ ) in the full 35 hr data set. The average photon flux of the source during this period was (8.9 ± 1.6) × 10 −12 cm −2 s −1 , or 1.6% of the Crab Nebula flux, above an energy threshold of 110 GeV, with a soft spectral index of 4.8 ± 1.3.

BL Lac object

Crab Nebula

10.3847/2041-8213/aad053

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Citations (40)

VizieR Online Data Catalog: NGC 4565 LOFAR images (Heesen+, 2019)

VizieR Online Data Catalog (2019)

V. Heesen Lily Whitler P. Schmidt A. Miskolczi S. S. Sridhar

LOFAR

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