Results 51 to 60 of about 277 (132)

ROSAT Observations of BL Lacertae Objects

, 1996
We present soft X-ray spectra of 74 BL Lacertae objects observed with the PSPC detector on board of the ROSAT satellite. The sample contains all BL Lac objects detected during the pointed observation phase as a target or serendipitously. We have investigated the soft X-ray and broad band spectral properties and discuss the consequences for the X-ray ...
Lamer, G., Brunner, H., Staubert, R.
openaire   +2 more sources

Classification of Fermi BCUs Using Machine Learning

The Astrophysical Journal, 2023
The Fermi Large Area Telescope (LAT) has detected 6659 γ -ray sources in the incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi-LAT catalog of γ -ray sources and 3743 of them are blazars, including 1517 blazar candidates of uncertain ...
Pei-yu Xiao, Rui-Feng Xie, Xiang-Tao Zeng, Yin Chen, Jia-Hui Chen, Yin-Yi Huo, Tian-Hang Liu, Jin-Liang Shi, Ying Wei, Zhuang Zhang, Zi-An Su, Hu-Bing Xiao, Jun-Hui Fan   +12 more
doaj   +1 more source

Multi-Band Optical Variability of Blazar 1ES 2344+514 on Diverse Time-Scales

Journal of Advanced Research in Natural and Applied Sciences
This study presents the results of multi-band observations from 2022 to 2024 and Zwicky Transient Facility (ZTF) observations from 2018 to 2023, examining the flux variability of the blazar 1ES 2344+514 on diverse time-scales in the optical bands.
Aykut Özdönmez
doaj   +1 more source

HESS J1943+213: a candidate extreme BL Lacertae object [PDF]

Astronomy & Astrophysics, 2011
We report on a newly detected point-like source, HESS J1943+213 located in the Galactic plane. This source coincides with an unidentified hard X-ray source IGR J19443+2117, which was proposed to have radio and infrared counterparts. HESS J1943+213 is detected at the significance level of 7.9 σ(post-trials) at RA(J2000)=19h 43m 55s +- 1s (stat) +- 1s ...
Collaboration, H. E. S. S., Abramowski, A., Acero, F., Aharonian, F., Akhperjanian, A. G., Anton, G., Balzer, A., Barnacka, A., de Almeida, U. Barres, Bazer-Bachi, A. R., Becherini, Y., Becker, J., Behera, B., Bernlöhr, K., Bochow, A., Boisson, C., Bolmont, J., Bordas, P., Borrel, V., Brucker, J., Brun, F., Brun, P., Bulik, T., Büsching, I., Carrigan, S., Casanova, S., Cerruti, M., Chadwick, P. M., Charbonnier, A., Chaves, R. C. G., Cheesebrough, A., Chounet, L. -M., Clapson, A. C., Coignet, G., Colom, P., Conrad, J., Dalton, M., Daniel, M. K., Davids, I. D., Degrange, B., Deil, C., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., Drury, L. O'C., Dubois, F., Dubus, G., Dyks, J., Dyrda, M., Egberts, K., Eger, P., Espigat, P., Fallon, L., Farnier, C., Fegan, S., Feinstein, F., Fernandes, M. V., Fiasson, A., Fontaine, G., Förster, A., Füßling, M., Gallant, Y. A., Gast, H., Gérard, L., Gerbig, D., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Göring, D., Häffner, S., Hague, J. D., Hampf, D., Hauser, M., Heinz, S., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Hofverberg, P., Holler, M., Horns, D., Jacholkowska, A., de Jager, O. C., Jahn, C., Jamrozy, M., Jung, I., Kastendieck, M. A., Katarzyński, K., Katz, U., Kaufmann, S., Keogh, D., Khangulyan, D., Khélifi, B., Klochkov, D., Kluźniak, W., Kneiske, T., Komin, Nu., Kosack, K., Kossakowski, R., Laffon, H., Lamanna, G., Lennarz, D., Lohse, T., Lopatin, A., Lu, C. -C., Marandon, V., Marcowith, A., Masbou, J., Maurin, D., Maxted, N., McComb, T. J. L., Medina, M. C., Méhault, J., Nguyen, N., Moderski, R., Moulin, E., Naumann, C. L., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Nicholas, B., Niemiec, J., Nolan, S. J., Ohm, S., Olive, J-F., Wilhelmi, E. de Oña, Opitz, B., Ostrowski, M., Panter, M., Arribas, M. Paz, Pedaletti, G., Pelletier, G., Petrucci, P. -O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raue, M., Rayner, S. M., Reimer, A., Reimer, O., Renaud, M., Reyes, R. de los, Rieger, F., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Rulten, C. B., Ruppel, J., Ryde, F., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schönwald, A., Schulz, A., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sikora, M., Skilton, J. L., Sol, H., Spengler, G., Stawarz, Ł., Steenkamp, R., Stegmann, C., Stinzing, F., Stycz, K., Sushch, I., Szostek, A., Tavernet, J. -P., Terrier, R., Tibolla, O., Tluczykont, M., Valerius, K., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Viana, A., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Vorobiov, S., Vorster, M., Wagner, S. J., Ward, M., Wierzcholska, A., Zajczyk, A., Zdziarski, A. A., Zech, A., Zechlin, H. -S., Hill, A. B.   +200 more
openaire   +6 more sources

On the Cosmological Evolution of BL Lacertae Objects

The Astrophysical Journal, 2002
We study the cosmological evolution of BL Lac objects by applying the Ve/Va analysis to a new sample of 55 objects, presented for the first time in this paper. This sample has been selected from the 239 sources with the brightest X-ray flux (≥4 × 10-13 ergs s-1 cm-2) and relatively bright optical counterparts (B ≤ 20.5) among the ~1600 objects included
A. Caccianiga, T. Maccacaro, A. Wolter, R. Della Ceca, I. M. Gioia   +4 more
openaire   +1 more source

VLBI Observations of Nearby HBLs: Physical Implications

Galaxies
We review the jet kinematics of HBL blazars based on results of the MOJAVE survey, which obtained images of active galactic nuclei with the Very Long Baseline Array (VLBA) at 15 GHz, and the VLBA-BU-BLAZAR program as well as its successor BEAM-ME program,
Svetlana G. Jorstad, Alan P. Marscher, José L. Gómez   +2 more
doaj   +1 more source

The Radio Properties of BL Lacertae Objects [PDF]

Symposium - International Astronomical Union, 1980
A recent study of the properties of BL Lacertae Objects at λλ6 and 21 cm by K.J. Johnston and myself has shown:
openaire   +1 more source

Multiwavelength Variability and Jet Properties of Low-synchrotron-peaked BL Lacertae Objects

The Astrophysical Journal
Low-synchrotron-peaked BL Lac objects (LBLs) are promising candidates for masquerading BL Lacs, and the mechanism responsible for their high-energy γ -ray emission still requires further investigation.
R. X. Zhou, S. M. Hu, K. R. Zhu, S. J. Kang, Y. G. Zheng   +4 more
doaj   +1 more source

The Study of Radio Flux Density Variations of the Quasar OJ 287 by the Wavelet and the Singular Spectrum Methods

Open Astronomy, 2016
Flux density variations of the extragalactic radio source OJ 287 are studied by applying the wavelet and the singular spectrum methods to the long-term monitoring data at 14.5, 8.0 and 4.8 GHz acquired at the University of Michigan Radio Astronomy ...
Donskykh Ganna
doaj   +1 more source

The Cosmological Evolution of BL Lacertae Objects

, 2000
We review the main results from several radio, X-ray and multi-frequency surveys on the topic of cosmological evolution of BL Lacertae objects. Updated findings on BL Lac evolution following the recent identification of many sources in the ``Sedentary Multi-Frequency survey'' are also discussed.
Giommi, P., Pellizzoni, A., Perri, M., Padovani, P.   +3 more
openaire   +2 more sources