Publications (43)
A large high-energy gamma-ray flare from the blazar 3C 273
W. Collmar, O. Reimer, K. Bennett +8
The Compton Gamma-Ray Observatory (CGRO) experiments EGRET and COMPTEL observed the Virgo sky region continuously for 7 weeks between December 10, 1996 and January 28, 1997. The pr…
The Be(n,p)Li reaction and the Cosmological Lithium Problem: measurement of the cross section in a wide energy range at n_TOF (CERN)
L. Damone, M. Barbagallo, M. Mastromarco +155
We report on the measurement of the Be()Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2)…
Milagro Limits and HAWC Sensitivity for the Rate-Density of Evaporating Primordial Black Holes
A. A. Abdo, A. U. Abeysekara, R. Alfaro +118
Primordial Black Holes (PBHs) are gravitationally collapsed objects that may have been created by density fluctuations in the early universe and could have arbitrarily small masses…
VAMOS: a Pathfinder for the HAWC Gamma-Ray Observatory
A. U. Abeysekara, R. Alfaro, C. Alvarez +133
VAMOS was a prototype detector built in 2011 at an altitude of 4100m a.s.l. in the state of Puebla, Mexico. The aim of VAMOS was to finalize the design, construction techniques and…
Observation of Small-scale Anisotropy in the Arrival Direction Distribution of TeV Cosmic Rays with HAWC
A. U. Abeysekara, R. Alfaro, C. Alvarez +96
The High-Altitude Water Cherenkov (HAWC) Observatory is sensitive to gamma rays and charged cosmic rays at TeV energies. The detector is still under construction, but data acquisit…
From expanded digraphs to lifts of voltage digraphs and line digraphs
C. Dalfó, M. A. Fiol, M. Miller +1
In this note we present a general approach to construct large digraphs from small ones. These are called expanded digraphs, and, as particular cases, we show the close relationship…
Experimental setup and procedure for the measurement of the 7Be(n,α)α reaction at n_TOF
L. Cosentino, A. Musumarra, M. Barbagallo +129
The newly built second experimental area EAR2 of the n_TOF spallation neutron source at CERN allows to perform (n, charged particles) experiments on short-lived highly radioactive…
COMPTEL Observations of AGN at MeV-Energies
W. Collmar, K. Bennett, H. Bloemen +9
The COMPTEL experiment aboard CGRO, exploring the previously unknown sky at MeV-energies, has so far detected 10 Active Galactic Nuclei (AGN): 9 blazars and the radio galaxy Centau…
1.8 MeV Emission from the Carina Region
J. Knoedlseder, K. Bennett, H. Bloemen +5
Significant 1.8 MeV emission from the Carina region has been detected by COMPTEL. The emission is concentrated within 6 degrees or less near the Carina nebula NGC 3372, one of the…
HAWC Contributions to the 35th International Cosmic Ray Conference (ICRC2017)
A. U. Abeysekara, A. Albert, R. Alfaro +123
List of proceedings from the HAWC Collaboration presented at the 35th International Cosmic Ray Conference, 12 July - 20 July 2017, Bexco, Busan, Korea.
The Comptel 1.809 Mev Survey
S. Plueschke, R. Diehl, V. Schoenfelder +8
We present the latest update of the 1.809 MeV sky survey obtained with COMPTEL. Based on all observations taken since the launch of CGRO in spring 1991 to early summer this year we…
Modelling the 1.8 MeV Sky: Tests for Spiral Structure
J. Knoedlseder, N. Prantzos, K. Bennett +6
COMPTEL imaging analysis revealed a patchy, asymmetric distribution of diffuse 1.8 MeV emission along the Galactic plane, which is attributed to the decay of radioactive 26Al in th…
Data Acquisition Architecture and Online Processing System for the HAWC gamma-ray observatory
HAWC collaboration, A. U. Abeysekara, R. Alfaro +105
The High Altitude Water Cherenkov observatory (HAWC) is an air shower array devised for TeV gamma-ray astronomy. HAWC is located at an altitude of 4100 m a.s.l. in Sierra Negra, Me…
Assessment of Tracers of 1.8 MeV Emission
J. Knodlseder, R. Diehl, U. Oberlack +6
We examined the question of a possible correlation between 1.8 MeV emission and intensity distributions observed at other wavelengths by comparing the 1.8 MeV data to an extended s…
DUAL Gamma-Ray Mission
S. Boggs, C. Wunderer, P. von Ballmoos +30
Gamma-ray astronomy presents an extraordinary scientific potential for the study of the most powerful sources and the most violent events in the Universe. In order to take full adv…
POET: POlarimeters for Energetic Transients
J. E. Hill, M. L. McConnell, P. Bloser +15
POET (Polarimeters for Energetic Transients) is a Small Explorer mission concept proposed to NASA in January 2008. The principal scientific goal of POET is to measure GRB polarizat…
COMPTEL Time-Averaged All-Sky Point Source Analysis
W. Collmar, V. Schoenfelder, A. W. Strong +5
We use all COMPTEL data from the beginning of the CGRO mission (April '91) up to the end of CGRO Cycle 6 (November '97) to carry out all-sky point source analyses in the four stand…
COMPTEL gamma-ray study of the Crab nebula
R. D. van der Meulen, H. Bloemen, K. Bennett +6
We report on a study of the gamma-ray continuum emission from the Crab supernova nebula and on a search for nuclear de-excitation gamma-ray lines. Crab is the brightest continuum s…
COMPTEL upper limits for the 56Co gamma-ray emission from SN1998bu
R. Georgii, S. Plüschke, R. Diehl +6
Supernova 1998bu in the galaxy M96 was observed by COMPTEL for a total of 88 days starting 17 days after the explosion. We searched for a signal in the 847 keV and 1238 keV lines o…
Interplanetary magnetic flux rope observed at ground level by HAWC
S. Akiyama, R. Alfaro, C. Alvarez +59
We report the ground-level detection of a Galactic Cosmic-Ray (GCR) flux enhancement lasting 17 hr and associated with the passage of a magnetic flux rope (MFR) over the Ear…
Cosmic-ray Antinuclei as Messengers of New Physics: Status and Outlook for the New Decade
P. von Doetinchem, K. Perez, T. Aramaki +59
The precise measurement of cosmic-ray antinuclei serves as an important means for identifying the nature of dark matter and other new astrophysical phenomena, and could be used wit…
An improved Moore bound and some new optimal families of mixed Abelian Cayley graphs
C. Dalfó, M. A. Fiol, N. López +1
We consider the case in which mixed graphs (with both directed and undirected edges) are Cayley graphs of Abelian groups. In this case, some Moore bounds were derived for the maxim…
A Contribution of the HAWC Observatory to the TeV era in the High Energy Gamma-Ray Astrophysics: The case of the TeV-Halos
Ramiro Torres-Escobedo, Hao Zhou, Eduardo de la Fuente +130
We present a short overview of the TeV-Halos objects as a discovery and a relevant contribution of the High Altitude Water Äerenkov (HAWC) observatory to TeV astrophysics. We disc…
Image Reconstruction of COMPTEL 1.8 MeV 26Al Line Data
J. Knodlseder, D. Dixon, K. Bennett +7
We present a new algorithm, called Multiresolution Regularized Expectation Maximization (MREM), for the reconstruction of gamma-ray intensity maps from COMPTEL data. The algorithm…
The COMPTEL instrumental line background
G. Weidenspointner, M. Varendorff, U. Oberlack +8
The instrumental line background of the Compton telescope COMPTEL onboard the Compton Gamma-Ray Observatory is due to the activation and/or decay of many isotopes. The major compon…
COMPTEL Observations of the Blazar PKS 1622-297 during a Gamma-Ray High State in 1995
S. Zhang, W. Collmar, V. Schonfelder +6
PKS 1622-297 was detected as a source of gamma-rays by the EGRET experiment at energies above 100 MeV during a gamma-ray outburst June and July 1995. We analyzed the COMPTEL data (…
26Al in the local interstellar medium
J. Knoedlseder, K. Bennett, H. Bloemen +6
We estimate the 1.8 MeV luminosity of the Sco-Cen association due to radioactive decay of 26Al to (4-15) 10e-5 ph cm**-2 s**-1. We propose a low surface brightness, limb brightened…
COMPTEL observations of the quasar PKS 0528+134 during the first 3.5 years of the CGRO mission
W. Collmar, K. Bennett, H. Bloemen +9
The COMPTEL observations of the blazar-type quasar PKS 0528+134 in the energy range 0.75 MeV to 30 MeV carried out between April 1991 and September 1994 have been analyzed. During…
COMPTEL MeV Observations of the TeV Sources Markarian 421 and Markarian 501
W. Collmar, K. Bennett, H. Bloemen +5
The COMPTEL experiment aboard the COMPTON Gamma-Ray Observatory (CGRO) has observed the prominent TeV-blazars Mkn 421 and Mkn 501 many times between the start of its mission in Apr…
A New Look at Image Reconstruction of COMPTEL 1.8 MeV Data
J. Knodlseder, D. Dixon, R. Diehl +7
Deconvolving COMPTEL gamma-ray data into images presents a major methodological challenge. We developed a new algorithm called Multiresolution Regularized Expectation Maximization…
The Sensitivity of HAWC to High-Mass Dark Matter Annihilations
A. U. Abeysekara, R. Alfaro, C. Alvarez +101
The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in central Mexico at 19 degre…
The Be()Li reaction and the Cosmological Lithium Problem: measurement of the cross section in a wide energy range at n_TOF (CERN)
L. Damone, M. Barbagallo, M. Mastromarco +155
We report on the measurement of the Be()Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2)…
56Co gamma-rays from SN1998bu: COMPTEL upper limits
S. Plueschke, R. Georgii, R. Diehl +7
The type Ia supernova SN1998bu in M96 was observed by COMPTEL for a total of 88 days starting 17 days after the first detection of the supernova. The accumulated effective observat…
The gamma-ray burst GB 920622
J. Greiner, M. Sommer, N. Bade +12
We have analyzed the Ulysses, BATSE, and COMPTEL spectral data from the -ray burst of June 22, 1992 (GB 920622). COMPTEL data reveal a hard to soft evolution within the first p…
GAPS: A New Cosmic Ray Anti-matter Experiment
S. Quinn, T. Aramaki, R. Bird +37
The General AntiParticle Spectrometer (GAPS) is a balloon-borne instrument designed to detect cosmic-ray antimatter using the novel exotic atom technique, obviating the strong magn…
HAWC Contributions to the 36th International Cosmic Ray Conference (ICRC2019)
A. U. Abeysekara, A. Albert, R. Alfaro +127
List of proceedings from the HAWC Collaboration presented at the 36th International Cosmic Ray Conference, 24 July - 1 August 2019, Madison, Wisconsin, USA.
GAPS, low-energy antimatter for indirect dark-matter search
E. Vannuccini, T. Aramaki, R. Bird +37
The General Antiparticle Spectrometer (GAPS) is designed to carry out indirect dark matter search by measuring low-energy cosmic-ray antiparticles. Below a few GeVs the flux of ant…
COMPTEL Observations of 3C 279 during the first 4 Years of the CGRO-Mission
W. Collmar, J. J. Blom, K. Bennett +6
The COMPTEL experiment aboard the Compton Gamma-Ray Observatory (CGRO) has observed the gamma-ray blazar 3C 279 several times between April 1991 and September 1995. This paper repo…
Section on Extragalactic Science Topics of the White Paper on the Status and Future of Ground-Based TeV Gamma-Ray Astronomy
H. Krawczynski, A. M. Atoyan, M. Beilicke +32
This is a report on the findings of the extragalactic science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissione…
An algebraic approach to lifts of digraphs
C. Dalfó, M. A. Fiol, M. Miller +2
We study the relationship between two key concepts in the theory of (di)graphs: the quotient digraph, and the lift of a base (voltage) digraph. These techniques contract or…
Astrophysics with Radioactive Atomic Nuclei
R. Diehl, P. von Ballmoos, S. Boggs +11
We propose to advance investigations of electromagnetic radiation originating in atomic nuclei beyond its current infancy to a true astronomy. This nuclear emission is independent…
Multifrequency Observations of the Virgo Blazars 3C 273 and 3C 279 in CGRO Cycle 8
W. Collmar, S. Benlloch, J. E. Grove +15
We report first observational results of multifrequency campaigns on the prominent Virgo blazars 3C 273 and 3C 279 which were carried out in January and February 1999. Both blazars…
HAWC Contributions to the 34th International Cosmic Ray Conference (ICRC2015)
HAWC Collaboration, A. U. Abeysekara, R. Alfaro +112
List of proceedings from the HAWC Collaboration presented at the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands.