Broadband observations of the X-ray burster 4U 1705-44 with BeppoSAX

4U 1705-44 is one of the most-studied type I X-ray burster and Atoll sources. This source represents a perfect candidate to test different models proposed to self-consistently track the physical changes occurring between different spectral states because it shows clear spectral state transitions. The broadband coverage, the sensitivity and energy resolution of the BeppoSAX satellite offers the opportunity to disentangle the components that form the total X-ray spectrum and to study their changes according to the spectral state. Using two BeppoSAX observations carried out in August and October 2000, respectively, for a total effective exposure time of about 100 ks, we study the spectral evolution of the source from a soft to hard state. Energy spectra are selected according to the source position in the color-color diagram (CCD) Results. We succeeded in modeling the spectra of the source using a physical self-consistent scenario for both the island and banana branches (the double Comptonization scenario). The components observed are the soft Comptonization and hard Comptonization, the blackbody, and a reflection component with a broad iron line. When the source moves from the banana state to the island state, the parameters of the two Comptonization components change significantly and the blackbody component becomes too weak to be detected. We interpret the soft Comptonization component as emission from the hot plasma surrounding the neutron star, hard Comptonization as emission from the disk region, and the blackbody component as emission from the inner accretion disk. The broad feature in the iron line region is compatible with reflection from the inner accretion disk.Comment: 8 pages, 10 figures, accepted for publication by A&

INTEGRAL spectral variability study of the atoll 4U 1820-30: first detection of hard X-ray emission

We study the 4-200 keV spectral and temporal behaviour of the low mass X-ray binary 4U 1820-30 with INTEGRAL during 2003-2005. This source as been observed in both the soft (banana) and hard (island) spectral states. A high energy tail, above 50 keV, in the hard state has been observed for the first time. This places the source in the category of X-ray bursters showing high-energy emission. The tail can be modeled as a soft power law component, with the photon index of ~2.4, on top of thermal Comptonization emission from a plasma with the electron temperature of kT_e~6 keV and optical depth of \tau~4. Alternatively, but at a lower goodness of the fit, the hard-state broad band spectrum can be accounted for by emission from a hybrid, thermal-nonthermal, plasma. During this monitoring the source spent most of the time in the soft state, usual for this source, and the >~4 keV spectra are represented by thermal Comptonization with kT_e~3 keV and \tau~6-7.Comment: 14 pages, 4 figures, accepted for publication by Ap

BeppoSAX observations of the atoll x-ray binary 4U0614+091

We report the first simultaneous measurement of the broad band X-ray (0.3-150 keV) spectrum of the neutron star x-ray binary 4U0614+091. Our data confirm the presence of a hard x-ray tail that can be modeled as thermal Comptonization of low-energy photons on electrons having a very high temperature, greater than 220 keV, or as a non-thermal powerlaw. We detected a spectral feature that can be interpreted as reprocessing, via Compton reflection, of the direct emission by an optically-thick disk and found a correlation between the photon index of the power-law tail and the fraction of radiation reflected which is similar to the correlation found for black hole candidate x-ray binaries and Seyfert galaxies

A relativistic iron emission line from the neutron star low-mass X-ray binary GX 3+1

We present the results of a spectroscopic study of the Fe K{\alpha} emission of the persistent neutron-star atoll low-mass X-ray binary and type I X-ray burster GX 3+1 with the EPIC-PN on board XMM-Newton. The source shows a flux modulation over several years and we observed it during its fainter phase, which corresponds to an X-ray luminosity of Lx~10^37 ergs/s. When fitted with a two-component model, the X-ray spectrum shows broad residuals at \sim6-7 keV that can be ascribed to an iron K{\alpha} fluorescence line. In addition, lower energy features are observed at \sim3.3 keV, \sim3.9 keV and might originate from Ar XVIII and Ca XIX. The broad iron line feature is well fitted with a relativistically smeared profile. This result is robust against possible systematics caused by instrumental pile-up effects. Assuming that the line is produced by reflection from the inner accretion disk, we infer an inner disk radius of \sim25 Rg and a disk inclination of 35{\deg} < i < 44{\deg}.Comment: 4 pages, 3 figures Accepted for publication in Astronomy and Astrophysic

Use of dairy and non-dairy Lactobacillus plantarum, Lactobacillus paraplantarum and Lactobacillus pentosus strains as adjuncts in cheddar cheese

Lactobacilli have been used as adjunct cultures in the manufacture of different cheeses with the objective of accelerating ripening and/or improving cheese quality, but no studies have been conducted with strains from non-dairy origins. A miniature cheddar-type cheese model was used to screen ten dairy and non-dairy Lactobacillus plantarum, Lactobacillus paraplantarum and Lactobacillus pentosus strains for their performances as adjuncts in cheese manufacture. All strains were able to grow and survive in the cheese environment and produced only minor, although statistically significant, changes in gross cheese composition. Adjuncts affected secondary proteolysis causing differences in the levels of free amino groups, total free amino acids and reversed-phase HPLC (RP-HPLC) profiles of pH 4.6-soluble extract. Three strains were selected on the basis of differences in proteolysis pattern and used in a pilot-plant production of cheddar cheese, which was ripened for 180 days. The results confirmed that use of L. plantarum adjuncts significantly affected secondary proteolysis as measured by free amino acid production with minor impact on gross composition and primary starter performance, but the impact on RP- HPLC profiles of pH 4.6-soluble extracts was not statistically significant. The use of a strain originally isolated from olive brine fermentation, L. plantarum P1.5, resulted in significantly improved preference scores over the control

Strong Field Gravity and X-Ray Observations of 4U1820-30

The behavior of quasi-periodic oscillations (QPOs) at frequencies near 1 kHz in the x-ray emission from the neutron star x-ray binary 4U1820-30 has been interpreted as evidence for the existence of the marginally stable orbit, a key prediction of strong-field general relativity. The signature of the marginally stable orbit is a saturation in QPO frequency, assumed to track inner disk radius, versus mass accretion rate. Previous studies of 4U1820-30 have used x-ray count rate as an indicator of mass accretion rate. However, x-ray count rate is known to not correlate robustly with mass accretion rate or QPO frequency in other sources. Here, we examine the QPO frequency dependence on two other indicators of mass accretion rate: energy flux and x-ray spectral shape. Using either of these indicators, we find that the QPO frequency saturates at high mass accretion rates. We interpret this as strong evidence for the existence of the marginally stable orbit.Comment: accepted to the Astrophysical Journal Letters, 7 page

Dendroecology of Aspidosperma polyneuron Müll. Arg. (Apocynaceae) trees in two different geomorphological growth conditions in Atlantic forests, Paraná State, Brazil.

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Spectral states evolution of 4U 1728-34 observed by INTEGRAL and RXTE: non-thermal component detection

We report results of a one-year monitoring of the low mass X-ray binary (LMXB) source (atoll type) 4U 1728-34 with INTEGRAL and RXTE. Three time intervals were covered by INTEGRAL, during which the source showed strong spectral evolution. We studied the broad-band X-ray spectra in detail by fitting several models in the different sections of the hardness-intensity diagram. The soft states are characterised by prominent blackbody emission plus a contribution from a Comptonized emission. The hard states are characterised by the presence of an excess flux with respect to the Comptonization model above 50 keV while the soft component is fainter. To obtain an acceptable fit to the data this excess is modeled either with a power law with photon index Gamma ~ 2 or a Comptonization (CompPS) spectrum implying the presence of hybrid thermal and non-thermal electrons in a corona. This makes 4U 1728-34 one of the few LMXBs of atoll type showing non-thermal emission at high energy. From our analysis, it is also apparent that the presence of the hard tail is more prominent as the overall spectrum becames harder. We discuss also alternative models which can discribe these hard states.Comment: Accepted for publication in MNRAS (accepted 2011 April 20. Received 2011 April 20; in original form 2010 December 07); 9 pages, 7 figure