BVR_cI_c light curves of GRB970508 optical remnant and colors of underlying host galaxy

Optical observations of the GRB 970508 optical remnant were continued with the 6-m telescope of SAO RAS in standard BVRcIc bands in Oct.-Dec.1997 and in Jan. 1998. The results of the photometry of GRB970508 remnant and of three nearby galaxies are presented. The BVRcIc light curves of the GRB970508 remnant may be described by a power law plus a constant F(t)=F_0(t-t_0)^{\alpha}+C. In In parameters determination of the faint host galaxy we used the results of our BVRcIc photometry of May-August, 1997, the data of recent observations Keck-II and WHT telescopes and also the data of Rc and B bands photometry obtained by other authors based on our secondary standards. The level-off from the initial power-law decline seen in the first months after the burst observed in all bands. The effect is the most strong in Ic band. The best \chi^2-fits for Fo, \alpha, C parameters of the data in each of 4 bands point to the presence of a faint constant source with Ic=24.13\pm0.28, Rc = 25.55\pm0.19, V=25.80\pm 0.14, B=26.68\pm 0.14. The average \alpha of light curve power law is -1.23\pm0.04. The optical remnant has the power law F_\nu \nu^\beta spectrum with spectral slope = -1.10\pm0.08 and does not change after optical curve maximum. BVRcIc spectrum together with an absolute magnitude of the constant component M_B_rest=-17.5\pm0.3 and the limit of the linear size of underlying host galaxy d<1.1 kpc, calculated for z=0.835,H_0=75km s^-1 Mpc^-1, q_0=0.5, correspond to a host galaxy, such as a starburst dwarf, red starburst dwarf, irregular dwarf, HII galaxy, or blue compact dwarf galaxy. All these types of dwarf galaxies show evidence of starburst or post starburst activity. Galaxy G2 has a spectrum similar to one of the host GRB galaxy and lies at the projected distance of ~20 kpc from GRB.Comment: 8 pages, Postscript figures, Latex(aa.cls, psfig), accepted to Astronomy and Astrophysic

Current Saturation in Nonmetallic Field Emitters

It has been known for a long time that traditional semiconductor (e.g. intrinsic and doped Si and Ge or binary SiC and GaN) field emitters significantly deviate from Fowler-Nordheim (FN) law and saturate when a large current, on the order of microamperes or more, is attempted to be drawn from them. Many experiments established that the field emission current from carbonic materials, such as carbon nanotubes, amorphous carbon and polycrystalline diamond films, also deviate from FN law and saturate. These findings suggested that the saturation and departure from FN law is a broad and general phenomenon that applies to the class of nonmetallic field emitters. In this letter, we report a universal formula that describes the current saturation effect in nonmetallic field emitters. The formula accounts for material's bulk properties and field emitter geometry.Comment: 5 pages, 2 figures, 1 tabl

Field Electron Emission Induced Glow Discharge in Nanodiamond Vacuum Diode

The present letter extends the prior findings on self-induced heating of solid state field emission devices. It was found that a vacuum diode (base pressure $\sim10^{-9}$ Torr), that makes use of graphite-rich polycrystalline diamond as cathode material, can switch from diode regime to resistor regime, to glow discharge plasma regime without any external perturbation, i.e. all transitions are self-induced. Combined results of in situ field emission microscopy and ex situ electron microscopy and Raman spectroscopy suggested that the nanodiamond cathode of the diode heated to about 3000 K which caused self-induced material evaporation, ionization and eventually micro-plasma formation. Our results confirm that field emission, commonly called cold emission, is a very complex phenomenon that can cause severe thermal load. Thermal load and material runaway could be the major factors causing vacuum diode deterioration, i.e. progressive increase in turn-on field, decrease in field enhancement factor, and eventual failure.Comment: 6 pages, 5 figure

Large-Scale Fluctuations in the Number Density of Galaxies in Independent Surveys of Deep Fields

New arguments supporting the reality of large-scale fluctuations in the density of the visible matter in deep galaxy surveys are presented. A statistical analysis of the radial distributions of galaxies in the COSMOS and HDF-N deep fields is presented. Independent spectral and photometric surveys exist for each field, carried out in different wavelength ranges and using different observing methods. Catalogs of photometric redshifts in the optical (COSMOS-Zphot) and infrared (UltraVISTA) were used for the COSMOS field in the redshift interval $0.1 < z < 3.5$, as well as the zCOSMOS (10kZ) spectroscopic survey and the XMM-COSMOS and ALHAMBRA-F4 photometric redshift surveys. The HDFN-Zphot and ALHAMBRA-F5 catalogs of photometric redshifts were used for the HDF-N field. The Pearson correlation coefficient for the fluctuations in the numbers of galaxies obtained for independent surveys of the same deep field reaches $R = 0.70 \pm 0.16$. The presence of this positive correlation supports the reality of fluctuations in the density of visible matter with sizes of up to 1 000 Mpc and amplitudes of up to 20% at redshifts $z \sim 2$. The absence of correlations between the fluctuations in different fields (the correlation coefficient between COSMOS and HDF-N is $R = -0.20 \pm 0.31$) testifies to the independence of structures visible in different directions on the celestial sphere. This also indicates an absence of any influence from universal systematic errors (such as "spectral voids"), which could imitate the detection of correlated structures.Comment: 12 pages, 13 figure

Single Crystal Diamond Refractive Lens for Focusing of X-rays in Two Dimensions

We report the fabrication and performance evaluation of single crystal diamond refractive x-ray lenses with a paraboloid of rotation form factor for focusing x-rays in two dimensions simultaneously. The lenses were manufactured using a femtosecond laser micromachining process and tested using x-ray synchrotron radiation. Such lenses were stacked together to form a standard compound refractive lens (CRL). Due to the superior physical properties of the material, diamond CRLs are enabling and indispensable wavefront-preserving primary focusing optics for x-ray free-electron lasers and the next-generation synchrotron storage rings. They can be used for highly efficient refocusing of the extremely bright x-ray sources for secondary optical schemes with limited aperture such as nanofocusing Fresnel zone plates and multilayer Laue lenses.Comment: CRL testing results were adde

High Quantum Efficiency Ultrananocrystalline Diamond Photocathode: Negative Electron Affinity Meets nn-doping

We report results of quantum efficiency (QE) measurements carried out on a 150 nm thick nitrogen-incorporated ultrananocrystalline diamond terminated with hydrogen; abbreviated as (N)UNCD:H. (N)UNCD:H demonstrated a QE of $\sim$10$^{-3}$ ($\sim$0.1%) at 254 nm. Moreover, (N)UNCD:H was sensitive in visible light with a QE of $\sim$5$\times$10$^{-8}$ at 405 nm and $\sim$5$\times$10$^{-9}$ at 436 nm. After growth and prior to QE measurements, samples were exposed to air for about 2 hours for transfer and loading. Such design takes advantage of a key combination: 1) H-termination inducing negative electron affinity (NEA) on the (N)UNCD and stabilizies its surface against air exposure; and 2) N-incorporation inducing $n$-type conductivity in intrinsically insulating UNCD.Comment: 3 pages; 3 figure

A crucial test of the phantom closed cosmological model

We suggest a crucial direct-observational test for measuring distinction between the standard $\Lambda$CDM model and recently proposed phantom dark energy positive curvature cosmological model. The test is based on the fundamental distance--flux--redshift relation for general Friedmann models. It does not depend on the CMBR data, on the large-scale structure growth models, and also on the value of the Hubble constant $H_0$. Our crucial test can be performed by future gamma-ray burst observations with THESEUS space mission and by using gravitational-wave standard siren observations with modern advanced LIGO--Virgo and also forthcoming LISA detectors.Comment: 4 pages, 1 figure, MNRAS accepted 18.09.202

Study of Faint Galaxies in the Field of GRB 021004

We present an analysis of BVRcIc observations of the field sized around 4' x 4' centered at the host galaxy of the gamma-ray burst GRB 021004 with the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We measured the magnitudes and constructed the color diagrams for 311 galaxies detected in the field (S/N > 3). The differential and integral counts of galaxies up to the limit, corresponding to 28.5 (B), 28.0 (V), 27.0 (Rc), 26.5 (Ic) were computed. We compiled the galaxy catalog, consisting of 183 objects, for which the photometric redshifts up to the limiting magnitudes 26.0 (B), 25.5 (V), 25.0 (Rc), 24.5 (Ic) were determined using the HyperZ code. We then examined the radial distribution of galaxies based on the z estimates. We have built the curves expected in the case of a uniform distribution of galaxies in space, and obtained the estimates for the size and contrast of the possible super-large-scale structures, which are accessible with the observations of this type.Comment: 15 pages, 7 figures, 2 tables, to be published in Astrophysical Bulletin 65, 311-325 (2010

Properties of the host galaxy of the gamma-ray burst 970508 and local star-forming galaxies

Late-time observations of GRB970508 with the SAO-RAS 6-m telescope in July-August 1998 show that the optical transient (OT) varies very little since November 1997. Here we report the $BVR_cI_c$ light-curves behaviour up to 470 days from the GRB occurence with independent $BVR_cI_c$ power-law fits. After ~=200 days the power-law decay has ceased and the OT contamination to the host galaxy flux is already less than the observational errors of the brightness estimates. Spectral energy distribution for the host galaxy alone (without OT) and comparison of its broad-band spectrum to the average continuum spectra of different Hubble types galaxies are shown. The best fits to the BVR_cI_c spectral energy distribution of the GRB host with local starburst galaxies are found for the blue compact S0 dwarf galaxy NGC1510, the Scd starburst HII galaxy NGC7793 and the blue compact galaxy Mrk 1267. Position of the host galaxy in the M_B vs. log(D_25) diagram for local late-type LEDA galaxies allows us to attribute GRB970508 host galaxy to the blue compact galaxies.Comment: 8 pages, Latex, 6 PS figures, requires aa.cls, accepted for publication on Astronomy and Astrophysic

High resolution SIMS depth profiling of nanolayers

We report results of high-resolution TOF SIMS (time of flight secondary ion mass spectrometry) depth profiling experiments on a nanolayered structure, a stack of 16 alternating MgO and ZnO ~5.5 nm layers grown on a Si substrate by atomic layer deposition. The measurements were performed using a newly developed approach implementing a low energy direct current normally incident Ar+ ion beam for sample material removal by sputtering (250 eV and 500 eV energy), in combination with a pulsed 5 keV Ar+ ion beam at 60{\deg} incidence for TOF SIMS analysis. By this optimized arrangement, a noticeably improved version of known dual-beam (DB) approach to TOF SIMS depth profiling is introduced, which can be called gentleDB. We apply the mixing-roughness-information model to detailed analysis of experimental results. It reveals that the gentleDB approach allows ultimate depth resolution by confining the ion beam mixing length to about 2 monolayers. This corresponds to the escape depth of secondary ions, the fundamental depth resolution limitation in SIMS. Other parameters deduced from the measured depth profiles indicate that a single layer thickness equals to 6 nm so that "flat" layer thickness d is of 3 nm and interfacial roughness {\sigma} is of 1.5 nm thus yielding d+2\bullet{\sigma}=6 nm. In essence, we have demonstrated that the gentleDB TOF SIMS depth profiling with noble gas ion beams is capable of revealing structural features of a stack of nanolayers, resolving its original surface and estimating the roughness of interlayer interfaces, which is difficult to obtain by traditional approaches.Comment: 7 pages and 4 figure