We introduce the Galactic Bulge Survey (GBS) and we provide the Chandra source list for the region that has been observed to date. Among the goals of the GBS are constraining the neutron star (NS) ...equation of state and the black hole (BH) mass distribution via the identification of eclipsing NS and BH low-mass X-ray binaries (LMXBs). The latter goal will, in addition, be obtained by significantly enlarging the number of BH systems for which a BH mass can be derived. Further goals include constraining X-ray binary formation scenarios, in particular the common envelope phase and the occurrence of kicks, via source-type number counts and an investigation of the spatial distribution of X-ray binaries, respectively. The GBS targets two strips of 6? X 1? (12 deg2 in total), one above (1? < b < 2?) and one below (--2? < b < --1?) the Galactic plane in the direction of the Galactic center at both X-ray and optical wavelengths. By avoiding the Galactic plane (--1? < b < 1?) we limit the influence of extinction on the X-ray and optical emission but still sample relatively large number densities of sources. The survey is designed such that a large fraction of the X-ray sources can be identified from their optical spectra. The X-ray survey, by design, covers a large area on the sky while the depth is shallow using 2 ks per Chandra pointing. In this way we maximize the predicted number ratio of (quiescent) LMXBs to cataclysmic variables. The survey is approximately homogeneous in depth to a 0.5-10 keV flux of 7.7 X 10--14 erg cm--2 s--1. So far, we have covered about two-thirds (8.3 deg2) of the projected survey area with Chandra providing over 1200 unique X-ray sources. We discuss the characteristics and the variability of the brightest of these sources.
We present optical light curves, spectroscopy, and classification of five X-ray sources in the Chandra Galactic Bulge Survey (CXOGBS J174009.1-284725 (CX5), CXOGBS J173935.7-272935 (CX18), CXOGBS ...J173946.9-271809 (CX28), CXOGBS J173729.1-292804 (CX37), CXOGBS J174607.6-261547 (CX561)). These objects were selected based on bright optical counterparts which were quickly found to have emission lines in their optical spectra. This paper presents an illustration of GBS optical follow-up, targeting emission line objects. Of these five objects, four exhibit photometric variability in the Sloan r' band. CX5 shows a tentative period of 2.1 hr and is clearly an intermediate polar (IP). CX28 and CX37 both exhibit flickering with no clear period. Both are also suggested to be IPs. CX18 was observed to undergo two dwarf nova outbursts. Finally, CX561 shows no detectable variability, although its characteristics would be consistent with either a quiescent low-mass X-ray binary or cataclysmic variable.
We present phase-resolved spectroscopy and photometry of a source discovered with the Chandra Galactic Bulge Survey (GBS), CXOGBS J174444.7−260330 (aka CX93 and CX153 in the previously published GBS ...list). We find two possible values for the orbital period P, differing from each other by ∼13 s. The most likely solution is P = 5.690 14(6) h. The optical lightcurves show ellipsoidal modulations, whose modelling provides an inclination of 32±1° for the most likely P. The spectra are dominated by a K5 V companion star (the disc veiling is 5 per cent). Broad and structured emission from the Balmer lines is also detected, as well as fainter emission from He i. From the absorption lines we measure K
2 = 117 ± 8 km s− 1 and v sin i = 69 ± 7 km s− 1. By solving the system mass function we find M
1 = 0.8 ± 0.2 M for the favoured P and i, consistent with a white dwarf accretor, and M
2 = 0.6 ± 0.2 M. We estimate a distance in the range 400-700 pc. Although in a low accretion state, both spectroscopy and photometry provide evidence of variability on a time-scale of months or faster. Besides finding a new, long orbital period cataclysmic variable (CV) in a low accretion state, this work shows that the design of the GBS works efficiently to find accreting X-ray binaries in quiescence, highlighting that the spectra of CVs in a low accretion state can at times appear suggestive of a quiescent neutron star or a black hole system.
We present optical light curves of variable stars consistent with the positions of X-ray sources identified with the Chandra X-ray Observatory for the Chandra Galactic Bulge Survey (GBS). Using data ...from the Mosaic-II instrument on the Blanco 4 m Telescope at CTIO, we gathered time-resolved photometric data on timescales from ~2 hr to 8 days over the 3/4 of the X-ray survey containing sources from the initial GBS catalog. Among the light curve morphologies we identify are flickering in interacting binaries, eclipsing sources, dwarf nova outbursts, ellipsoidal variations, long period variables, spotted stars, and flare stars. Eighty-seven percent of X-ray sources have at least one potential optical counterpart. Twenty-seven percent of these candidate counterparts are detectably variable; a much greater fraction than expected for randomly selected field stars, which suggests that most of these variables are real counterparts. We discuss individual sources of interest, provide variability information on candidate counterparts, and discuss the characteristics of the variable population.
Sustainable management of oil and gas resources implies solving environmental problems pertinent to all sectors of the oil and gas complex. Progress in this area associated with advanced technologies ...for reducing crude oil production and transportation losses, improving the environmental safety of petroleum products and their production processes, and recycling waste petrochemicals has been discussed.
Problems of environmental catalysis related to the use of nanotechnologies, as well as examples of resource-saving and environmentally-friendly technologies in catalysis, have been discussed. ...Particular attention has been given to works on the use of alternative components of catalytic systems and the implementation of new environmentally clean materials and methods of synthesis of catalysts that improve the quality of fuels obtained with their use. Processes for upgrading straight-run gasoline have been discussed in detail as the most environmentally and economically sound ones.
The results of two procedures for determining total oil products in soil by infrared (IR) spectrometry were compared. The steps of extracting oil products from the soil according to standard ...procedures were studied step-by-step using gravimetry and IR spectrometry, and the effect of micellar structures in dispersed oil systems on the recovery of oil hydrocarbons was determined.
It was shown by IR spectroscopy that 2,2′-methylenebis(4-methyl-6-
tert
-butylphenol) (BP) forms associates with intra-and intermolecular hydrogen bonds in the presence of chlorinated and aromatic ...solvents. As the polarity of the chlorinated solvents increases, the proportion of BP with intermolecular hydrogen bonding both between the BP hydroxyl groups and between the BP hydroxyl groups and acidic protons of the chlorinated hydrocarbons increases. In aromatic solvents, intramolecularly hydrogen-bonded PB prevails. In addition, intermolecularly hydrogen-bonded BP and a BP associate with the π-electron system of aromatic hydrocarbons were found, with the OH...π interaction increasing in the order C
6
H
6
< C
9
H
12
< C
7
H
8
, a result that is due to the spatial effect of the methyl groups of isopropylbenzene.
We present optical lightcurves of variable stars consistent with the positions of X-ray sources identified with the Chandra X-ray Observatory for the Chandra Galactic Bulge Survey. Using data from ...the Mosaic-II instrument on the Blanco 4m Telescope at CTIO, we gathered time-resolved photometric data on timescales from \(\sim2\) hr to 8 days over the \(\frac{3}{4}\) of the X-ray survey containing sources from the initial GBS catalog. Among the lightcurve morphologies we identify are flickering in interacting binaries, eclipsing sources, dwarf nova outbursts, ellipsoidal variations, long period variables, spotted stars, and flare stars. \(87\%\) of X-ray sources have at least one potential optical counterpart. \(24\%\) of these candidate counterparts are detectably variable; a much greater fraction than expected for randomly selected field stars, which suggests that most of these variables are real counterparts. We discuss individual sources of interest, provide variability information on candidate counterparts, and discuss the characteristics of the variable population.
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