A massive, dusty toroid with large grains in the pre-planetary nebula IRAS22036+5306

Using the Submillimeter Array (SMA), we have obtained high angular-resolution (∼1″) interferometric maps of the submillimeter (0.88 mm) continuum and CO J=3–2 line from IRAS 22036+5306 (I 22036), a bipolar pre-planetary nebula (PPN) with knotty jets discovered in our HST SNAPshot survey of young PPNe. In addition, we have obtained supporting lower-resolution (∼10″) 2.6 mm continuum and CO, ¹³CO J=1–0 observations with the Owens Valley Radio Observatory (OVRO) interferometer. We find an unresolved source of submillimeter (and millimeter-wave) continuum emission in I 22036, implying a very substantial mass (0.02–0.04M _⊙) of large (i.e., radius ≳1 mm), cold (≲50 K) dust grains associated with I 22036’s toroidal waist. The CO J=3–2 observations show the presence of a very fast (∼220 km s⁻¹), highly collimated, massive (0.03M _⊙) bipolar outflow with a very large scalar momentum (about 10³⁹ g cm s⁻¹), and the characteristic spatio-kinematic structure of bow-shocks at the tips of this outflow. The fast outflow in I 22036, as in most PPNe, cannot be driven by radiation pressure. The large mass of the torus suggests that it has most likely resulted from common-envelope evolution in a binary, however it remains to be seen whether or not the time-scales required for the growth of grains to millimeter sizes in the torus are commensurate with such a formation scenario. The presence of the torus should facilitate the formation of the accretion disk needed to launch the jet. We also find that the ¹³C/¹²C ratio in I 22036 is very high (0.16), close to the maximum value achieved in equilibrium CNO-nucleosynthesis (0.33). The combination of the high circumstellar mass (i.e., in the torus and an extended dust shell inferred from ISO far-infrared spectra) and the high ¹³C/¹²C ratio in I 22036 provides strong support for this object having evolved from a massive (≳4M _⊙) progenitor in which hot-bottom-burning has occurred.     

The Radio Recombination Line Intensities Of Atoms And Ions: Helium,Carbon And Oxygen

The radio recombination line intensities of heavy elements of helium, carbon and oxygen are calculated with accounting for dielectronic recombination. Dielectronic recombination rates are determined accurate to the second order of a perturbation theory and the rates are described as function of principal quantum number for helium-like atom or ion. Balance equations are solved for the departure coefficients from LTE b_n. The collision and spontaneous transition rates are accounted for the balance equations, in which non-equilibrium distribution source is dielectronic recombination. Non-equilibrium amplification coefficients are found as functions of a medium temperature, density and ion charge z = 1–3 for radio recombination lines. Optical depths are calculated for the heavy element low-frequency lines with the numbers 300 > n > 1200. For the chosen electronic temperatures and densities T_e = 0.8× 10⁴–10× 10⁴ K, N_e = 0.05–0.1 cm⁻³ the line optical depth is determined by the values τ_L∼ 0.1× 10⁻⁴–100× 10⁻⁴. Calculated for free-free transition rates, the optical depth is given by using the value τ_ff∼ 10⁻²τ_L.     

GMRTHI observations of the Eridanus group of galaxies

The GMRTHI 21 cm-line observations of galaxies in the Eridanus group are presented. The Eridanus group, at a distance of ≈ 23 Mpc, is a loose group of ≈200 galaxies. The group extends to more than 10 Mpc in projection. The velocity dispersion of the galaxies in the group is ≈240 km s⁻¹. The galaxies are clustered into different sub-groups. The overall population mix of the group is 30% (E + S0) and 70% (Sp + Irr). The observations of 57 Eridanus galaxies were carried out with the GMRT for ≈ 200 h. HI emission was detected from 31 galaxies. The channel rms of ≈ 1 mJy beam⁻¹ was achieved for most of the image-cubes made with 4 h of data. The corresponding HI column density sensitivity (3σ) is ≈ 1 × 10²⁰ cm⁻² for a velocity-width of ≈ 13.4 km s⁻¹. The 3σ detection limit of HI mass is ≈ 1.2 X 10⁷ Mpd for a line-width of 50 km s⁻¹. Total HI images, HI velocity fields, global HI line profiles, HI mass surface densities, HI disk parameters and HI rotation curves are presented. The velocity fields are analysed separately for the approaching and the receding sides of the galaxies. These data will be used to study the HI and the radio continuum properties, the Tully-Fisher relations, the dark matter halos, and the kinematical and HI lopsidedness in galaxies.     

Acoustic Events in the Solar Atmosphere from <Emphasis Type="Italic">Hinode</Emphasis>/SOT NFI Observations

We investigate the properties of acoustic events (AEs), defined as spatially concentrated and short duration energy flux, in the quiet Sun, using observations of a 2D field of view (FOV) with high spatial and temporal resolution provided by the Solar Optical Telescope (SOT) onboard Hinode. Line profiles of Fe i 557.6 nm were recorded by the Narrow-band Filter Imager (NFI) on a 82″×82″ FOV during 75 min with a time step of 28.75 s and 0.08″ pixel size. Vertical velocities were computed at three atmospheric levels (80, 130, and 180 km) using the bisector technique, allowing the determination of energy flux to be made in the range 3 – 10 mHz using two complementary methods (Hilbert transform and Fourier power spectrum). Horizontal velocities were computed using local correlation tracking (LCT) of continuum intensities providing divergences. We found that the net energy flux is upward. In the range 3 – 10 mHz, a full FOV space and time averaged flux of 2700 W m⁻² (lower layer 80 – 130 km) and 2000 W m⁻² (upper layer 130 – 180 km) is concentrated in less than 1 % of the solar surface in the form of narrow (0.3″) AE. Their total duration (including rise and decay) is of the order of 10³ s. Inside each AE, the mean flux is 1.6×10⁵ W m⁻² (lower layer) and 1.2×10⁵ W m⁻² (upper). Each event carries an average energy (flux integrated over space and time) of 2.5×10¹⁹ J (lower layer) to 1.9×10¹⁹ J (upper). More than 10⁶ events could exist permanently on the Sun, with a birth and decay rate of 3500 s⁻¹. Most events occur in intergranular lanes, downward velocity regions, and areas of converging motions.     

Stability of strange dwarfs II. Computational results

The stability of strange dwarfs for quark cores with M _0core /M _⨀ = 10⁻⁴, has been studied by calculating, in each individual case, a series of strange dwarfs with configurations in which 5 ⋅ 10⁻⁴, 10⁻³, 5 ⋅ 10⁻³, 10⁻², 1.31 ⋅ 10⁻², 1.6 ⋅ 10⁻², 1.7 ⋅ 10⁻², 2 ⋅ 10⁻², ranges from the values in white dwarfs to ρ _drip = 4.3 ⋅ 10¹¹ g/cm³, at which free neutrons are produced in the crust. For the series with M _0core /M _⨀ < 0.0131, stability is lost when ρ _tr < ρ _drip . For the series with M _0core /M _⨀ > 0.0131, the equality ρ _tr = ρ _drip is reached before the strange dwarf attains its maximum mass. Although the frequency of the radial pulsations in the fundamental mode obeys ω₀² > 0 for these configurations, they are unstable with respect to transitions into a strange star state with the same total number of baryons and a radius on the order of that of neutron stars. An energy on the order of the energy in a supernova explosion is released during these transitions. It is shown that the gravitational red shift of white and strange dwarfs are substantially different for low and limiting (high) masses.     

Location of type I radio continuum and bursts on Yohkoh soft X-ray maps

A solar type I noise storm was observed on 30 July, 1992 with the radio spectrometer Phoenix of ETH Zürich, the Very Large Array (VLA) and the soft X-ray (SXR) telescope on board theYohkoh satellite. The spectrogram was used to identify the type I noise storm. In the VLA images at 333 MHz a fully left circular polarized (100% LCP) continuum source and several highly polarized (70% to 100% LCP) burst sources have been located. The continuum and the bursts are spatially separated by about 100 and apparently lie on different loops as outlined by the SXR. Continuum and bursts are separated in the perpendicular direction to the magnetic field configuration. Between the periods of strong burst activities, burst-like emissions are also superimposed on the continuum source. There is no obvious correlation between the flux density of the continuum and the bursts. The burst sources have no systematic motion, whereas the the continuum source shows a small drift of 0.2 min^–1 along the X-ray loop in the long-time evolution. The VLA maps at higher frequency (1446 MHz) show no source corresponding to the type I event. The soft X-ray emission measure and temperature were calculated. The type I continuum source is located (in projection) in a region with enhanced SXR emission, a loop having a mean density of n _e = (1.5 ± 0.4) × 10⁹ cm^–3 and a temperature ofT = (2.1 ± 0.1) × 10⁶ K. The centroid positions of the left and right circularly polarized components of the burst sources are separated by 15–50 and seem to be on different loops. These observations contradict the predictions of existing type I theories.Presented at the CESRA-Workshop on Coronal Magnetic Energy Release at Caputh near Potsdam in May 1994.     

Galactic kinematics from OB3 stars with distances determined from interstellar Ca II lines

Based on data for 102 OB3 stars with known proper motions and radial velocities, we have tested the distances derived by Megier et al. from interstellar Ca II spectral lines. The internal reconciliation of the distance scales using the first derivative of the angular velocity of Galactic rotation Ω′₀ and the external reconciliation with Humphreys’s distance scale for OB associations refined by Mel’nik and Dambis show that the initial distances should be reduced by ≈20%. Given this correction, the heliocentric distances of these stars lie within the range 0.6–2.6 kpc. A kinematic analysis of these stars at a fixed Galactocentric distance of the Sun, R ₀ = 8 kpc, has allowed the following parameters to be determined: (1) the solar peculiar velocity components (u _⊙, v _⊙, ω _⊙) = (8.9, 10.3, 6.8) ± (0.6, 1.0, 0.4) km s⁻¹; (2) the Galactic rotation parameters Ω₀ = −31.5 ± 0.9 km s⁻¹ kpc⁻¹, Ω′₀ = +4.49 ± 0.12 km s⁻¹ kpc⁻², Ω″₀ = −1.05 ± 0.38 km s⁻¹ kpc⁻³ (the corresponding Oort constants are A = 17.9 ± 0.5 km s⁻¹ kpc⁻¹, B = −13.6 ± 1.0 km s⁻¹ kpc⁻¹ and the circular rotation velocity of the solar neighborhood is |V ₀| = 252 ± 14 km s⁻¹); (3) the spiral density wave parameters, namely: the perturbation amplitudes for the radial and azimuthal velocity components, respectively, f _R = −12.5±1.1 km s⁻¹ and f _ϑ = 2.0 ± 1.6 km s⁻¹; the pitch angle for the two-armed spiral pattern i = −5.3° ± 0.3°, with the wavelength of the spiral density wave at the solar distance being λ = 2.3 ± 0.2 kpc; the Sun’s phase in the spiral wave x _⊙ = −91° ± 4°.     

On most general exact solution for Vaidya-Tikekar isentropicsuperdense star

The energy density of Vaidya-Tikekar isentropic superdense star is found to be decreasing away from the center, only if the parameter K is negative. The most general exact solution for the star is derived for all negative values of K in terms of circular and inverse circular functions. Which can further be expressed in terms of algebraic functions for K = 2-(n/δ)² < 0 (n being integer andδ = 1,2,3 4). The energy conditions 0 ≤ p ≤ αρc ², (α = 1 or 1/3) and adiabatic sound speed conditiondp dρ ≤ c ², when applied at the center and at the boundary, restricted the parameters K and α such that .18 < −K −2287 and.004 ≤ α ≤ .86. The maximum mass of the star satisfying the strong energy condition (SEC), (α = 1/3) is found to be3.82 Mq_· at K=−2/3, while the same for the weak energy condition (WEC), (α =1) is 4.57 M_ _⊙ atK=−>5/2. In each case the surface density is assumed to be 2 × 10¹⁴ gm cm^-3. The solutions corresponding to K>0 (in fact K>1) are also made meaningful by considering the hypersurfaces t= constant as 3-hyperboloid by replacing the parameter R ² by −R² in Vaidya-Tikekar formalism. The solutions for the later case are also expressible in terms of algebraic functions for K=2-(n/δ² > 1 (n being integer or zero and δ =1,2,3 4). The cases for which 0 < K < 1 do not possess negative energy density gradient and therefore are incapable of representing any physically plausible star model. In totality the article provides all the physically plausible exact solutions for the Buchdahl static perfect fluid spheres. This revised version was published online in July 2006 with corrections to the Cover Date.     

Millimeter and Submillimeter Emissions from Galactic and Extragalactic Photodissociation Regions

The galactic and Extragalactic photodissociation regions are primarily heated by photoelectrons ejected from the surface of interstellar dust grains by Far-ultraviolet (FUV) photons. But there is no direct mechanism to measure the photoelectric heating efficiency. To understand the role of dust grains in processing the Interstellar Radiation Field (ISRF) and heating the gas, we compare the intensities I _CII, I _CO and I _FIR for (² P _3/2→² P _1/2) & (J = 1→ 0) line emission of CII & CO at 158 μm & 2.6 mm and integrated far-infrared from number of photodissociation regions, HII regions, planetary nebulae, reflection nebulae and high latitude translucent clouds (HLCs). It is found that I _CII is linearly correlated with I _FIR. In the cold medium where cloud is exposed to weak radiations temperature is low and most of the cooling is due to [CII] emissions. As a result the ratio of I _CII/I _FIR provide indirect method to evaluate the photoelectric heating efficiency. For the neutral cold medium it is evaluated to be ∼0.028. The FUV radiation field G ₀ are estimated through the model calculation of I _CII and I _CO for different galactic and photodissociation regions. The intensity of FIR radiation I _FIR are well represented as 1.23×10⁻⁴ G ₀(ergs cm⁻² s⁻¹ sr⁻¹) almost same as estimated for HLCs by Ingalls et al (2002). Hydrogen density for each source has also been estimated.     

Observations of Powerful Type III Bursts in the Frequency Range 10 – 30 MHz

The properties of powerful (flux >10⁻¹⁹ W m⁻² Hz⁻¹) type III bursts observed in July – August 2002 by the radio telescope UTR-2 at frequencies 10 – 30 MHz are analyzed. Most bursts have been registered when the active regions associated to these bursts were located near the central meridian or at 40° – 60° to the East or West from it. All powerful type III bursts drift from high to low frequencies with frequency drift rates 1 – 2.5 MHz s⁻¹. It is important to emphasize that according to our observations the drift rate is linearly increasing with frequency. The duration of the bursts changes mainly from 6 s at frequency 30 MHz up to 12 s at 10 MHz. The instantaneous frequency bandwidth does not depend on the day of observations, i.e. on the disk location of the source active region, and is increasing with frequency.     

Galactic rotation curve from the space velocities of selected masers

Based on currently available observations of 28 maser sources in 25 star-forming regions with measured trigonometric parallaxes, proper motions, and radial velocities, we have constructed the rotation curve of the Galaxy. Taking different distances to the Galactic center R ₀, we have estimated the peculiar velocity of the Sun, the angular velocity of Galactic rotation, and its three derivatives. For R ₀ = 8 kpc, we have found the circular velocity of the Sun to be V ₀ = 243 ± 16 km s⁻¹, which corresponds to a revolution period of 202 ± 10 Myr. We have obtained the Oort constants A = 16.9 ± 1.2 km s⁻¹ kpc⁻¹ and B = −13.5 ± 1.4 km s⁻¹ kpc⁻¹. Our simulation of the influence of a spiral density wave has shown that the peculiar velocity of the Sun with respect to the local standard of rest and the component (V _⊙)_LSR depend significantly on the Sun’s phase in the spiral wave.     

InFOCμS Hard X-ray Imaging Telescope

InFOCμS is a new generation balloon-borne hard X-ray telescope with focusing optics and spectroscopy. We had a successful 22.5-hour flight from Fort Sumner, NM on September 16,17, 2004. In this paper, we present the performance of the hard X-ray telescope, which consists of a depth-graded platinum/carbon multilayer mirror and a CdZnTe detector. The telescope has an effective area of 49 cm² at 30 keV, an angular resolution of 2.4 arcmin (HPD), and a field of view of 11 arcmin (FWHM) depending on energies. The CdZnTe detector is configured with a 12 × 12 segmented array of detector pixels. The pixels are 2 mm square, and are placed on 2.1 mm centers. An averaged energy resolution is 4.4 keV at 60 keV and its standard deviation is 0.36 keV over 128 pixels. The detector is surrounded by a 3-cm thick CsI anti coincidence shield to reduce background from particles and photons not incident along the mirror focal direction. The inflight background is 2.9 × 10⁻⁴ cts cm⁻² sec⁻¹ keV⁻¹ in the 20–50 keV band.     

Spectroscopy and photometry of the protoplanetary nebula candidate stHα62 = IRAS 07171+1823

We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 Å spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V _r 〉 = +45 ± 1 and +52 ± 1 km s^?1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s^?1. The He I λ5876 Å line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s^?1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N _e = 3.1 × 10³ cm^?3 and T _e ～ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 ? spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V _r 〉 = +45 ± 1 and +52 ± 1 km s⁻¹, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s⁻¹. The He I λ5876 ? line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s⁻¹. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N _e = 3.1 × 10³ cm⁻³ and T _e ∼ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = , ΔB = , and ΔU = and no color-magnitude correlation. We estimate the total extinction for the star from our photometric observations as A _v = . Near-IR observations have revealed dust radiation with a temperature of ∼1300 K. We estimate the distance to StHα62 to be r = 5.2 ± 1.2 kpc by assuming that the star is a low-mass (M = 0.55 ± 0.05 M _⊙) protoplanetary nebula. Original Russian Text ? V.P. Arkhipova, V.G. Klochkova, E.L. Chentsov, V.F. Esipov, N.P. Ikonnikova, G.V. Komissarova, 2006, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 10, pp. 737–747.     

Upper limits on neutrino fluxes from point-like sources with AMANDA-II

The AMANDA-II telescope, operated by the IceCube collaboration, is currently the world’s most sensitive telescope to fluxes of neutrinos from individual sources. A data sample of 4282 neutrino induced events collected in 1001 days of detector livetime during the years 2000–2004 have now been analyzed looking for a neutrino signal from point-like sources. A sensitivity to fluxes of of d Φ/dE=1.0×10⁻¹⁰(E/TeV)⁻² TeV⁻¹ cm⁻²s⁻¹ was reached in the energy range between 1.7 TeV and 2.4 PeV. So far no statistically significant localized excess of events over the background of atmospheric neutrinos has been found, which would be ascribed to a neutrino source. However, the flux upper limits derived from the non-observation of a signal are comparable to observed fluxes of high energy gamma rays from blazars and within the range of current models for neutrino emission from selected sources. Possible constraints on these models are discussed.      

WR 140 (=V1687 Cyg): Infrared photometry, 2001–2010

We present the results of our infrared observations of WR 140 (=V1687 Cyg) in 2001–2010. Analysis of the observations has shown that the J brightness at maximum increased near the periastron by about 0 ^m .3; the M brightness increased by ∼2 ^m in less than 50 days. The minimum J brightness and the minimum L and M brightnesses were observed 550–600 and 1300–1400 days after the maximum, respectively. The JHKLM brightness minimum was observed in the range of orbital phases 0.7–0.9. The parameters of the primary O5 component of the binary have been estimated to be the following: R(O5) ≈ 24.7R _⊙, L(O5) ≈ 8 × 10⁵ L _⊙, and M _bol(O5) ≈ −10 ^m . At the infrared brightness minimum, T _g ∼ 820–880 K, R _g ≈ 2.6 × 10⁵ R _⊙, the optical depth of the shell at 3.5 μm is ∼5.3 × 10⁻⁶, and its mass is ≈1.4 × 10⁻⁸ M _⊙. At the maximum, the corresponding parameters are ∼1300 K, 8.6 × 10⁴ R _⊙, ∼2 × 10⁻⁴, and ∼6 × 10⁻⁸ M _⊙; the mean rate of dust inflow (condensation) into the dust structure is ∼3.3 × 10⁻⁸ M _⊙ yr⁻¹. The mean escape velocity of the shell from the heating source is ∼10³ km s⁻¹ and the mean dispersal rate of the shell is ∼1.1 × 10⁻⁸ M _⊙ yr⁻¹.     

X-ray absorption effects due to intergalactic abundance of carbon

The absorption effects at the soft X-ray and hard ultraviolet wavelengths due to some model abundance of intergalactic carbon material have been investigated for different cosmologies. Even though the local density, 2 × 10⁹ <ϱ ₀ = 1.0 × 10⁻³⁴ g cm⁻³ of the absorbing component of the intergalactic material in the form of carbon is not adequate for the thermalization of the discrete background radiation, the amount of absorption in the X-rays up to the Hubble radius is not negligible.     

Dynamical fine structure of a quiescent filament

A quiescent filament was observed near the center of the disk (N5, W5) with the MSDP spectrograph of the 50 cm refractor of the Pic-du-Midi Observatory on June 17, 1986. We focus our study on the statistical moments of the Dopplershift,V ₁, and the intensity,I ₁, at the center of a chord of the Hα profile (±0.256 Å), versus the minimum intensityI ₀. We use a statistical model simulating a numbern _max of threads (of optical thicknessτ ₀ and source functionS ₀), seen over the chromosphere. The threadsj along the same line-of-sighti are identical except for the velocityv _j (gaussian distributionv ₀,σ _v). We search for the best fit between the observed and simulated quantities:V ₁,σ (V ₁),I ₁,σ(I ₁), and the histogram of theI ₀ values over the field of view. A good fit is obtained with: (a) threads characterized byτ ₀ = 0.2,S ₀ = 0.06 (unit of the continuum at disk center), mean upward velocityv ₀ = 1.7 km s⁻¹ and gaussian-type velocity distributionσ _v = 3.5 km s⁻¹. Other possible values ofτ ₀ andσ _v are discussed; (b) underlying chromosphere deduced from observed quiet Sun (outside the filament) by modifying the chromospheric velocities: additional mean upward velocity 0.7 km s⁻¹, standard deviation reduced by a factorF _c ∼ 0.7. The results are discussed in connection with the values deduced from prominence observations.     

Non-Integrability of the Generalized Two Fixed Centres Problem

We consider two fixed centres attracting a third body. Each centre is the source of a force field with potential V=−ar ⁻²ⁿ , where n is a real number. We prove that this generalization of the classical two fixed centres problem is non-integrable except when n= 0, 1/2, −1 and −2. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cooling of magnetars with internal layer heating

We model thermal evolution of magnetars with a phenomenological heat source in a spherical internal layer and compare the results with observations of persistent thermal radiation from magnetars. We show that the heat source should be located in the outer magnetar’s crust, at densities ρ≲5×10¹¹ g cm⁻³, and the heating rate should be ∼10²⁰ erg cm⁻³ s⁻¹. Heating deeper layers is extremely inefficient because the thermal energy is mainly radiated away by neutrinos and does not warm up the surface to the magnetar’s level. This deep heating requires too much energy; it is inconsistent with the energy budget of neutron stars.      

Search for ultrahigh-energy cosmic gamma-ray bursts on the Baksan underground scintillation telescope

Based on data from the Baksan underground scintillation telescope (BUST) for the period 2001–2004, we searched for cosmic gamma-ray bursts (GRBs) at primary photon energies of 0.5 TeV or higher. We obtained constraints on the rate of bursts with durations of 1–10 s for fluences within the range 4.6 × 10⁻³-1.8 × 10⁻² erg cm⁻² in the declination band 30° ≤ δ ≤ 80°. We searched for ultrahigh-energy gamma rays from GRBs detected on spacecraft during and within ±2 h of the burst. No statistically significant excesses above the background of random coincidences were found. The derived constraints on the ultrahigh-energy gamma-ray fluence during GRBs lie within the range 4.6 × 10⁻³-3.7 × 10⁻² erg cm⁻².