V. P. Fomin

On the periodical very high energy gamma-ray emission from Cyg X-3

The period of very high energy (E>2×1012 eV) gamma-ray emission of Cyg X-3 by using the data of observations of the source made during 6 years, 1972–1977, was specified. The value of the period is equal to 0.199 683±1×10−6 days. Phase histogram reveals two peaks, one lagging the other by 0.6 of the period. The averaged 6 year data amounts to 1.8×10−10 quanta cm−2 s−1 (peak intensity). It corresponds to luminosity of about 1.2×1037 erg s−1 if one assumes that an emission is isotropical and the distance is equal to 10 kpc.АбстрактПо данным наблюдения гамма-излучения E>2×1012 эв источника Cyg X-3 за. шесть лет 1972–1977 гг. получено численое значение периода гамма-излучения T=0,199 683 суток±10−6 суток. Световая кривая периолической составляющей имеет импульсный харахтер с двумя пиками, разнесенными на 0,6 периода. Средняя за все годы величина потока равна 1,8×10−10 кв см−2 сек−1 (пиковое знааение), что в чредположении изотропности излуения соответствует 1,2×1037 эгр/сек при расстоянии до ицточника 10 кпс.

BL Lac: A new ultrahigh-energy gamma-ray source

The active galactic nucleus BL Lac was observed with the GT-48 atmospheric Cherenkov detector of the Crimean Astrophysical Observatory from July 23–September 1, 1998, in order to search for ultrahighenergy gamma-ray (>1 TeV) emission. The object was in the field of view of the detector for more than 24 hours. The source was detected with a high level of confidence (7.2 σ) with a flux equal to (2.1±0.4)×10−11 photons cm−2 s−1.

Observations of the Flux of Very-High-Energy Gamma Rays from the Blazar 3C 66A

Measurements of the flux of very-high-energy (>1 TeV) gamma rays from the blazar 3C 66A obtained over four years are presented. The mean flux over the four-year period was (2.8±0.4)×10−11 cm−2 s−1. There is a correlation between the season-averaged flux of very-high-energy gamma rays and the observed optical radiation.

A search for discrete gamma-ray sources of energy greater than 21012 eV

The results of the observations to search gamma-ray sources with the energy greater than 2×1012 eV, which were made in Crimean Astrophysical Observatory during the years 1969–73 are presented. A technique of the detection of the EAS Cerenkov flashes was used.The quality of the data obtained is analysed. The criteria for the selection of the data free from meteorological variations are considered.It was shown that two objects, namely, Cyg X-3 and Cas γ-1, may be the sources of high-energy gamma quanta. It is probable that the object with the coordinates α=05h15m, δ=+1° is the source of gamma-rays as well. An unidentified object Cas γ-1 is variable: gamma-ray flux was observed twice — in Sepember–October 1971 and in December 1972. It is possible that the flux from Cyg X-3 has a period of 4.8 hr.АбстрктПриводятся результатьI четьIреклетних наблюдений, проводимйIх в КрйIмской асторфизической обсерватории АН СССР, с целью поиска источнков гамма-квантов С цнергией>2.1012 цв. Наблудения Проводились методом регистрации черенковских вспьппек широких атмосферньIх ливней.Приводятся результатьI анализа качества получного материала, на основе которого вьIводятся критерии для отбора данньIх, свободньIх от метеовариаций.Показано, что два объекта-Саγ γ-1 и Су Cyg Х-3-могут считаться источниками гамма-квантоввьIсокой энергии. Очень вероятно, что объект с координатами α=05н15м и ·=+1° также является источником гамма-излучения.НеотождествленньIй объект саγ γ-1 является переменньIм: обнаруженньIй поток квантов набJнодался дваждьI-в сентябре-окябре 1971 года и в декабе 1972 года. Рентгеновский источник Су Cyg Х-3, по всей видимоссти, является периодческим источнком гамма-квантов сT=4.8 часа.

Observations of the gamma-ray flux from the galaxy Mk 501

We present two-year-long observations of the flux of very-high-energy (∼1012 eV) gamma rays from the active galactic nucleus Mk 501 performed with a Cherenkov detector at the Crimean Astrophysical Observatory. A gamma-ray flux from the object was shown to exist at confidence levels of 11 and 7 standard deviations for 1997 and 1998, respectively. The flux varied over a wide range. The mean flux at energies >1012 eV, as inferred from the 1997 and 1998 data, is (5.0±0.6)×10−11 and (3.7±0.6)×10−11 cm−2 s−1, respectively. The errors are the sum of statistical observational and modeling errors. The mean power released in the form of gamma rays is ∼2×1043 erg s−1 sr−1.

Observations of active galactic nuclei with the GT-48 CrAO gamma-ray telescope in 2004

Observations of several active galactic nuclei were performed with the GT-48 gamma-ray telescope at CrAO in 2004: 3C 66A, Mk 421, Mk 501, 1H 1426, 1ES 1959, and BL Lac. Very-high-energy (E ≥ 1012 eV) gamma-ray fluxes were recorded from 3C 66A, Mk 421, Mk 501, and 1H 1426 at a confidence level of more than 4σ. Upper limits for the flux of very-high-energy gamma rays are presented for 1ES 1959 and BL Lac. The 2004 observational data for 3C 66A (z = 0.44) confirm the results obtained previously at CrAO.

Results of observation of Cyg γ-2, BL Lac, 3C66A, Mk 501, and the Crab nebula by the GT-48 gamma-ray telescope in 2006

The active galactic nuclei BL Lac, 3C66A, and Mk501, as well as the Crab nebula and the Cyg γ-2 source were observed in 2006 at the Crimean Astrophysical Observatory using the GT-48 gamma-ray telescope. Very high energy (VHE) gamma-ray fluxes at a high confidence level (Q > 4) were detected from the active galactic nuclei and the Crab nebula. VHE gamma-ray fluxes from the unidentified gamma-ray source Cyg γ-2 and the X-ray source Cyg X-3 were recorded during observations of Cyg γ-2.

Observations of the gamma-ray flux from the X-ray source Cyg X-3 in 1994–1995

We present the observations of Cygnus X-3 carried out with the GT-48 gamma-ray telescope at the Crimean Astrophysical Observatory in 1994–1995. The mean gamma-ray flux at energy E>1012 eV is shown to be approximately equal to 1.3×10−11 cm−2 s−1. The flux in 1994 was much lower than that in 1995, being (6.2±2.6)×10−12 cm−2 s−1; i.e., it was statistically insignificant. The flux in 1995 was (2.7±0.7)×10−11 cm−2 s−1. Thus, the very high energy gamma-ray emission from Cyg X-3 is variable. These measurement results can be used to obtain upper limits on the flux from Cyg X-3 in 1994–1995.

Long-term observations of galaxy 3C 66A

Monitoring of the active galaxy nucleus 3C 66A in the VHE γ-ray and analysis of data in X-rays and optical ranges over the period 1996–2009 were carried out. The nature of processes responsible for one or another type of radiation appeared to be very complicated since, at certain periods of time, an either positive or negative correlation may be observed between different types of radiation. Period of radiation P = 365 days in the X-ray range was found.

Ultrahigh-energy gamma-ray emission from the Geminga pulsar

In 1996–1997, the Geminga pulsar was observed at the Crimean Astrophysical Observatory with a ground-based gamma-ray telescope. An analysis of the observational data suggests that this object is a source of ultrahigh-energy gamma rays. An analysis of the temporal distribution of gamma-ray photons by an epoch-folding technique reveals a periodicity in the gamma-ray emission with a period of 0.237 s.