Publications (42)
AGN: The High-Energy Status before INTEGRAL
W. Collmar
Much progress in the knowledge of the high-energy emission (>50 keV) from Active Galactic Nuclei has been made during the last decade, predominately by the experiments aboard the C…
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…
BlazEr1: The eROSITA Blazar Catalog. Blazars and Blazar Candidates in the First eROSITA Survey
S. Haemmerich, A. Gokus, F. McBride +28
Aims. eROSITA, on board the Spectrum Roentgen Gamma (SRG) spacecraft, performed its first X-ray all-sky survey (eRASS1) between December 2019 and June 2020. It detected about 93000…
The Spectral Variability of Cygnus X-1 at MeV Energies
M. L. McConnell, K. Bennett, H. Bloemen +8
In previous work, we have used data from the first three years of the CGRO mission to assemble a broad-band -ray spectrum of the galactic black hole candidate Cygnus X-1. Conte…
Evidence for Gamma-Ray Flares in 3C 279 and PKS 1622-297 at ~10 MeV
W. Collmar, V. Schoenfelder, H. Bloemen +6
The EGRET experiment aboard the Compton Gamma-Ray Observatory (CGRO) has observed at energies above 100 MeV strong gamma-ray flares with short-term time variability from the gamma-…
Spectral Variability in PKS 0528+134 at Gamma-Ray Energies
M. Boettcher, W. Collmar
We present model calculations to the observed spectral variability in the gamma-ray spectrum of the ultraluminous blazar-type quasar PKS 0528+134. We argue that the observed appear…
COMPTEL Observations of the Blazars 3C 454.3 and CTA 102
S. Zhang, W. Collmar, V. Schoenfelder +5
We have analyzed the two blazars of 3C 454.3 and CTA 102 using all available COMPTEL data from 1991 to 1999. In the 10-30 MeV band, emission from the general direction of the sourc…
Constraints on the 3-30 MeV emission of Seyfert galaxies
M. Maisack, K. Mannheim, W. Collmar
Seyfert galaxies have not been detected by COMPTEL on the Compton Gamma Ray Observatory (CGRO) in the energy range 0.75-3 MeV, placing upper limits on their emission which are more…
The structure and emission model of the relativistic jet in the quasar 3C 279 inferred from radio to high-energy gamma-ray observations in 2008-2010
M. Hayashida, G. M. Madejski, K. Nalewajko +90
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Tel…
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…
LS 5039 - the counterpart of the unidentified MeV source GRO J1823-12
W. Collmar, S. Zhang
The COMPTEL experiment on CGRO observed the gamma-ray sky at energies from 0.75 MeV to 30 MeV between April 1991 and June 2000. COMPTEL detected many gamma-ray sources, among them…
Gamma-Ray Spectral Variability of Cygnus X-1
M. L. McConnell, K. Bennett, H. Bloemen +11
We have used observations from CGRO to study the variation in the MeV emission of Cygnus X-1 between its low and high X-ray states. These data provide a measurement of the spectral…
An Unidentified Variable Gamma-Ray Source near the Galactic Plane Detected by COMPTEL
S. Zhang, W. Collmar, V. Schonfelder
We report the detection of an unidentified gamma-ray source near the Galactic plane by the COMPTEL experiment aboard the Compton Gamma-Ray Observatory. The source is detected at a…
Multifrequency Observations of the Blazar 3C 279 in January 2006
WEBT Collaboration, W. Collmar, M. Böttcher +13
We report first results of a multifrequency campaign from radio to hard X-ray energies of the prominent gamma-ray blazar 3C 279, which was organised around an INTEGRAL ToO observat…
COMPTEL detection of the high-energy gamma-ray source 2CG 135+01
R. van Dijk, K. Bennett, H. Bloemen +11
We present an analysis of COMPTEL observations made between November 1991 and May 1994 of 2CG 135+01, a bright gamma-ray source located near the Galactic plane. At energies above 1…
Science with e-ASTROGAM (A space mission for MeV-GeV gamma-ray astrophysics)
A. De Angelis, V. Tatischeff, I. A. Grenier +248
e-ASTROGAM (enhanced ASTROGAM) is a breakthrough Observatory space mission, with a detector composed by a Silicon tracker, a calorimeter, and an anticoincidence system, dedicated t…
Multifrequency Observations of the Gamma-Ray Blazar 3C 279 in Low-State during Integral AO-1
W. Collmar, M. Böttcher, V. Burwitz +19
We report first results of a multifrequency campaign from radio to hard X-ray energies of the prominent gamma-ray blazar 3C 279 during the first year of the INTEGRAL mission. The v…
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 (…
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…
INTEGRAL observations of the blazar Mrk 421 in outburst (Results of a multi-wavelength campaign)
G. G. Lichti, E. Bottacini, M. Ajello +15
We report the results of a multi-wavelength campaign on the blazar Mrk 421 during outburst. We observed four strong flares at X-ray energies that were not seen at other wavelengths…
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 model for the high-energy emission of Cyg X-1
I. V. Moskalenko, W. Collmar, V. Schoenfelder
We construct a model of Cyg X-1 which describes self-consistently its emission from soft X-rays to MeV gamma rays. Instead of a compact pair-dominated gamma-ray emitting region, we…
A combined model for the X-ray to gamma-ray emission of Cyg X-1
I. V. Moskalenko, W. Collmar, V. Schoenfelder
We use recent data obtained by three (OSSE, BATSE, and COMPTEL) of four instruments on board the Compton Gamma Ray Observatory, to construct a model of Cyg X-1 which describes its…
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 Multifrequency Campaign on 3C 279 in January 2006
W. Collmar, M. Böttcher, T. P. Krichbaum +7
We present the results of a multifrequency campaign from radio to hard X-ray energies on the blazar 3C 279 during an optical high-state in January 2006. We give the observational r…
COMPTEL Observations of the Gamma-ray Blazars 3C~454.3 and CTA 102 During the CGRO Mission
S. Zhang, W. Collmar, V. Schonfelder
We have investigated the MeV behaviour of the \gray blazars 3C~454.3 and CTA 102 by analyzing all COMPTEL observations of this sky region during the complete CGRO mission. Both sou…
Day-Scale Variability of 3C 279 and Searches for Correlations in Gamma-Ray, X-Ray, and Optical Bands
R. C. Hartman, M. Villata, T. J. Balonek +36
Light curves of 3C 279 are presented in optical (R-band), X-rays (RXTE/PCA), and gamma rays (CGRO/EGRET) for 1999 Jan-Feb and 2000 Jan-Mar. During both of those epochs the gamma-ra…
A pair plasma model for PKS 0208-512
I. V. Moskalenko, W. Collmar
Assuming that the enhanced MeV emission from the MeV blazar PKS 0208-512 observed by COMPTEL on occasions is due to annihilation in a pair plasma, we estimate parameters of the ann…
Discovery of luminous pulsed hard X-ray emission from anomalous X-ray pulsars 1RXS J1708-4009, 4U 0142+61 and 1E 2259+586 by INTEGRAL and RXTE
L. Kuiper, W. Hermsen, P. R. den Hartog +1
We report on the discovery of hard spectral tails for energies above 10 keV in the total and pulsed spectra of anomalous X-ray pulsars 1RXS J1708-4009, 4U 0142+61 and 1E 2259+586 u…
A High Sensitivity Measurement of the MeV Gamma-Ray Spectrum of Cygnus X-1
M. L. McConnell, J. M. Ryan, W. Collmar +9
The Compton Gamma-Ray Observatory (CGRO) has observed the Cygnus region on several occasions since its launch in 1991. The data collected by the COMPTEL experiment on CGRO represen…
INTEGRAL and Multiwavelength Observations of the Blazar Mrk 421 during an Active Phase
G. G. Lichti, E. Bottacini, P. Charlot +9
A ToO observation of the TeV-emitting blazar Mrk 421 with INTEGRAL was triggered in June 2006 by an increase of the RXTE count rate to more than 30 mCrab. The source was then obser…
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…
COMPTEL Observations of the Gamma-Ray Blazar PKS 1622-297
S. Zhang, W. Collmar, K. Bennett +7
We report results of observations and analyses on the gamma-ray blazar PKS 1622-297, with emphasis on the COMPTEL data (0.75 - 30 MeV) collected between April 1991 and November 199…
The eROSITA Final Equatorial Depth Survey (eFEDS): the hard X-ray selected sample
K. Nandra, S. G. H. Waddell, T. Liu +25
During its calibration and performance verification phase, the eROSITA instrument aboard the SRG satellite performed a uniform wide--area X-ray survey of approximately 140 deg$^{2}…
The SRG/eROSITA All-Sky Survey: X-ray beacons at late cosmic dawn
J. Wolf, M. Salvato, S. Belladitta +12
The SRG/eROSITA All-Sky Survey (eRASS) is expected to contain ~100 quasars that emitted their light when the universe was less than a billion years old, i.e. at z>5.6. By selection…
BeppoSAX Observations of Centaurus A: the Hard Continuum and the Iron Line Feature
P. Grandi, M. Fiocchi, C. G. Perola +7
The radio galaxy Centaurus A was observed by the BeppoSAX satellite five times from 1997 to 2000. From July 6 1999 to August 17 1999, the source was also simultaneously pointed by…
INTEGRAL survey of the Cassiopeia region in hard X rays
P. R. den Hartog, W. Hermsen, L. Kuiper +3
We report on the results of a deep 1.6 Ms INTEGRAL observation of the Cassiopeia region performed from December 2003 to February 2004. Eleven sources were detected with the imager…
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…
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…
Investigation of the energy dependence of the orbital light curve in LS 5039
Z. Chang, S. Zhang, L. Ji +5
LS 5039 is so far the best studied -ray binary system at multi-wavelength energies. A time resolved study of its spectral energy distribution (SED) shows that above 1 keV its p…
The Soft Gamma-Ray Spectral Variability of Cygnus X-1
M. L. McConnell, A. A. Zdziarski, K. Bennett +11
We have used observations of Cygnus X-1 from the Compton Gamma-Ray Observatory (CGRO) and BeppoSAX to study the variation in the MeV gamma-ray emission between the hard and soft sp…
Spectral constraints on unidentified EGRET gamma-ray sources from COMPTEL MeV observations
S. Zhang, W. Collmar, W. Hermsen +1
We investigated the MeV properties of 173 unidentified or only tentatively identified EGRET sources listed in the third EGRET catalogue, by analyzing the simultaneously collected C…