Investigating γ- and X-ray properties of GRBs using multivariate statistics

We propose to study the interrelation between the γ- (Fluence, 1sec Peakflux, duration) and X-ray (early X flux, 24 h X flux, X decay index, X spectral index, X HI column density) properties using the canonical correlation method. Computing the canonical correlations and variables we show that there is a significant interrelation between the γ- and X-ray data. Using the canonical variables from the analysis, we computed their correlations (canonical loadings) with the original ones. The canonical loadings revealed that the γ-ray fluence and the early X-ray flux give the strongest contribution to the correlation in contrast to the X-ray decay index and spectral index. An interesting new result appears to be the strong contribution of the HI column density to the correlation. Accepting the collapsar model of long GRBs this effect may be interpreted as an indication for the ejection of an HI envelope by the progenitor in the course of producing the GRB.     

The INTEGRAL view of Gamma-Ray Bursts

After more than six and half years in orbit, the ESA space observatory INTEGRAL has provided new, exciting results in the soft gamma-ray energy range (from a few keV to a few MeV). With the discovery of about 700 hard X-Ray sources, it has changed our previous view of a sky composed of peculiar and “monster” sources. The new high energy sky is in fact full of a large variety of normal, very energetic emitters, characterized by new accretion and acceleration processes (see also IBIS cat4 (Bird et al., 2010). At the same time, about one GRB/month is detected and imaged by the two main gamma-ray instruments on board: IBIS and SPI. In this paper, we review the major achievements of the INTEGRAL observatory in the field of Gamma-Ray Bursts. We summarize the global properties of Gamma-Ray Bursts detected by INTEGRAL, with respect to their duration, spectral index, and peak flux distributions. We recall INTEGRAL results on the spectral lag analysis, showing how long-lag GRBs appear to form a separate population at low peak fluxes. We review the outcome of polarisation studies performed by using INTEGRAL data. Finally, concerning single GRB studies, we highlight the properties of particularly interesting Gamma-Ray Bursts in the INTEGRAL sample.     

Real time localization of gamma ray bursts with INTEGRAL

The INTEGRAL satellite has been successfully launched in October 2002 and has recently started its operational phase. The INTEGRAL burst alert system (IBAS) will distribute in real time the coordinates of the gamma ray bursts (GRBs) detected with INTEGRAL. After a brief introduction on the INTEGRAL instruments, we describe the main IBAS characteristics and report on the initial results. During the initial performance and verification phase of the INTEGRAL mission, which lasted about two months, two GRBs have been localized with accuracy of 2–4 arcmin. These observations have allowed us to validate the IBAS software, which is now expected to provide quick (few seconds delay) and precise (few arcmin) localization for 10–15 GRBs per year.     

A possible redshift evolution of the time-lag and variability luminosity relations for long gamma-ray bursts

Several luminosity relations currently exist for long gamma-ray bursts (GRBs). Some were derived from the light curves; others were obtained from the spectra. In this study, we consider two of these luminosity relations: the time-lag, _τlag${\tau }_{\mathit{lag}}$, relation and the variability, V, relation and investigate their possible dependence on (or “evolution” with) the redshift, z.     

REM/ROSS: a powerful tool for monitoring the prompt afterglow of γ-ray bursts

Observations of the prompt afterglow of γ-ray burst events are unanimously considered of paramount importance for GRB science and cosmology. Such observations at NIR wavelengths are even more promising allowing the monitoring of high-z Ly- absorbed bursts as well as events occurring in dusty star-forming regions. In these pages we present rapid eye mount (REM), a fully robotized fast slewing telescope equipped with a high throughput NIR (Z, J, H, K) camera dedicated to detecting the prompt IR afterglow. REM can discover objects at extremely high redshift and trigger large telescopes to observe them. The REM telescope will simultaneously feed REM optical slitless spectrograph (ROSS) via a dichroic. ROSS will intensively monitor the prompt optical continuum of GRB afterglows. The synergy between the REM-IR camera and the ROSS spectrograph makes REM a powerful observing tool for any kind of fast transient phenomena. Beside its ambitious scientific goals, REM is also technically challenging since it represent the first attempt to locate a NIR camera on a small telescope providing, with ROSS, unprecedented simultaneous wavelength coverage on a telescope of this size.     

Radiosensitivity to high energy iron ions is influenced by heterozygosity for Atm, Rad9 and Brca1

Loss of function of DNA repair genes has been implicated in the development of many types of cancer. In the last several years, heterozygosity leading to haploinsufficiency for proteins involved in DNA repair was shown to play a role in genomic instability and carcinogenesis after DNA damage is induced, for example by ionizing radiation. Since the effect of heterozygosity for one gene is relatively small, we hypothesize that predisposition to cancer could be a result of the additive effect of heterozygosity for two or more genes critical to pathways that control DNA damage signaling, repair or apoptosis. We investigated the role of heterozygosity for Atm, Rad9 and Brca1 on cell oncogenic transformation and cell survival induced by 1 GeV/n⁵⁶Fe ions. Our results show that cells heterozygous for both Atm and Rad9 or Atm and Brca1 have high survival rates and are more sensitive to transformation by high energy iron ions when compared with wild-type controls or cells haploinsufficient for only one of these proteins. Since mutations or polymorphisms for similar genes exist in a small percentage of the human population, we have identified a radiosensitive sub-population. This finding has several implications. First, the existence of a radiosensitive sub-population may distort the shape of the dose–response relationship. Second, it would not be ethical to put exceptionally radiosensitive individuals into a setting where they may potentially be exposed to substantial doses of radiation.     

Potential of salt-accumulating and salt-secreting halophytic plants for recycling sodium chloride in human urine in bioregenerative life support systems

This study addresses the possibility of growing different halophytic plants on mineralized human urine as a way to recycle NaCl from human wastes in a bioregenerative life support system (BLSS). Two halophytic plant species were studied: the salt-accumulating Salicornia europaea and the salt-secreting Limonium gmelinii. During the first two weeks, plants were grown on Knop’s solution, then an average daily amount of urine produced by one human, which had been preliminarily mineralized, was gradually added to the experimental solutions. Nutrient solutions simulating urine mineral composition were gradually added to control solutions. NaCl concentrations in the stock solutions added to the experimental and control solutions were 9 g/L in the first treatment and 20 g/L in the second treatment. The mineralized human urine showed some inhibitory effects on S. europaea and L. gmelinii. The biomass yield of experimental plants was lower than that of control ones. If calculated for the same time period (120 d) and area (1 m²), the amount of sodium chloride taken up by S. europaea plants would be 11.7 times larger than the amount taken up by L. gmelinii plants (486 g/m² vs. 41 g/m²). Thus, S. europaea is the better choice of halophyte for recycling sodium chloride from human wastes in BLSS.     

Comparing IRI and a regional model with ionosonde measurements in Pakistan

We have used the technique of expansion in Empirical Orthogonal Functions (EOFs) to develop regional models of the critical frequencies of E and F₂ layers (f_oE, f_oF₂), peak height (h_mF₂), and semi-thickness of F₂ layer (Y_mF₂) over Pakistan. In the present study levels of solar activity specified by Smoothed Sunspot Number (R) from 10 to 200 are taken into account. The magnetic dip angle for the model ranges from 30° to 60°. We have compared the regional model and the International Reference Ionosphere (IRI) with measurements of three ionosondes in Pakistan. The model parameters f_oE and f_oF₂ are found overall comparable to the observed hourly median values during daytime at Karachi (geographic latitude = 24.95°N, longitude = 67.13°E, magnetic inclination = 37°), Multan (30.18°N, 71.48°E, 45°) and Islamabad (33.75°N, 73.13°E, 51.5°) during the years 1988, 1996 and 2000. For h_mF₂ the computed values by regional and IRI model for the year 1995 are found close to each other. However, for Y_mF₂the results are better during daytime as compared to nighttime.     

Validation of B0 and B1 in the IRI 2001 model at low solar activity for Ilorin an equatorial station

A new set of data obtained at low solar activity from Ilorin, Nigeria (geog. latitude 8.5°N, geog longitude, 4.6°E, dip 4.1°S) is used to validate the IRI 2001 model at low solar activity. The results show in general a good agreement between model and observed B0 at night but an over estimation during daytime. The overestimation is greatest during the morning period (0600LT–1000LT). The model prediction for B1 is fairly good at night and during the day. A dependence of B0 on solar zenith angle χ is observed during the daytime. A formulation of the form B0 = A[cos(χ)ⁿ] is therefore proposed. Values of the constants n and A were determined for the period of low solar activity for this station.     

Study on the system of night hours for decoding Korean astronomical records of 1625–1787

This paper presents a study of the dates and times of astrophysical phenomena seen in the night time hours in Korea between 1625 and 1787. This is a period when two different calendars were used and it is important to know which calendar was used to record events such as lunar eclipses. It is known that the Joseon court adopted Shixianli (a Chinese calendar of Adam Schall) in 1654, the fifth reign of King Hyojong. However, the year when the court introduced the calendar into the system of night hours has not yet been determined. To know the enforcement year is very important for studies on astronomical events that are presented in Korean historical documents. From Seungjeongwon Ilgi (Daily Records of the Royal Secretariat), we compile a total of 90 lunar eclipse records referring to the observation time of the eclipses and calculate the times of occurrence of the eclipses with respect to the calendrical methods: Chiljeongsan Naepyeon (a Korean calendar) and Shixianli. As a result, we find that the system of night hours by the former calendrical method was used in the Joseon dynasty until as late as 1710. We also verify that the times of sunrise and sunset were considered as the moments when the center of the Sun reached the horizon according to Chiljeongsan Naepyeon at least. Therefore, we think that this study will contribute to the studies on astronomical phenomena of the Joseon dynasty, particularly on the estimate of the observation time.     

Rotational constants of linear and/or bent Cn+1H and CnN(n = 1–6): A DFT study

The geometries, dipole moments, and rotational constants for the linear and/or bent cations, C_n+1H⁺ and C_nN⁺(n = 1–6), were studied by the B3LYP method with the modest basis sets. For C_nH⁺(n = odd; 3, 5, 7) and C_nN⁺(n = even; 2, 4, 6), the theoretical rotational constants (B_es) of closed-shell singlet C₃H⁺, C₅H⁺, C₇H⁺, CCN⁺, C₄N⁺, and C₆N⁺ were calculated to be about 11,244, 2420, 885.2, 11,970, 2439, and 880.8 MHz, respectively. By contrast, the triplets are stable than the corresponding singlets for C_nH⁺(n = odd; 2, 4, 6) and C_nN⁺(n = even; 3, 5) except CN⁺.     

Is the North Atlantic Oscillation modulated by solar and lunar cycles? Some evidences from Hurst autocorrelation analysis

Several studies have suggested that the Sun and Moon cycles affect the Earth climatic dynamics. Nevertheless, there is a long-standing controversy whether solar variability and tides can significantly generate climate change, and how this may occur. Spectral analysis of climatic indices has provided only indirect evidences of the effects of solar–tidal periodicities in the Earth climate. This work addresses the issue by considering the dynamics of the daily North Atlantic Oscillation index over the period from 1950 to 2009. In contrast to previous studies, this work proposes that external cycles can be detected in the autocorrelation dynamics rather than in the raw North Atlantic Oscillation index series. Here, the R/S-scaling analysis is used to quantify, via the so-called Hurst exponent, the presence of autocorrelations along the studied years. Fourier analysis scan of the autocorrelation series thus show two prominent spectral components near (±3%) the lunar tidal 4.425 and the solar 11 years cycles. Intermediate spectral components near 6.4, 7.75 and 8.9 years are proposed to be, at least partially, a result of energy capture from internal mechanisms into cycles resulting from the nonlinear resonance of the fundamental solar–tidal cycles. The dominant effect of the solar variability is clarified by showing that in about 70% of the studied period the sunspot number and the Hurst exponent phases are synchronized, indicating that a higher solar activity enhances the North Atlantic Oscillation index predictability.     

Acoustic κ-density fluctuation waves in suprathermal κ function fluids

We describe a new wave mode similar to the acoustic wave in which both density and velocity fluctuate. Unlike the acoustic wave in which the underlying distribution is Maxwellian, this new wave mode occurs when the underlying distribution is a suprathermal κ-function and involves fluctuations in the power law index, κ. This wave mode always propagates faster than the acoustic wave with an equivalent effective temperature and becomes the acoustic wave in the Maxwellian limit as κ → ∞.     

Korean space food development: Ready-to-eat Kimchi, a traditional Korean fermented vegetable,sterilized with high-dose gamma irradiation

Addition of calcium lactate and vitamin C, a mild heating, deep-freezing, and gamma irradiation at 25 kGy were conducted to prepare Kimchi as a ready-to-eat space food. It was confirmed that the space food was sterilized by an irradiation at 25 kGy through incubation at 37 °C for 30 days. The hardness of the Space Kimchi (SK) was lower than the untreated Kimchi (CON), but higher than the irradiated Kimchi (IR). Also, this result was supported by the scanning electron microscopic observation. Sensory attributes of the SK were similar to CON, and maintained during preservation at 35 °C for 30 days. According to the Ames test, Kimchi sterilized with a high-dose irradiation exerted no mutagenic activity in the bacterial strains of Salmonella typhimurium. And, the SK was certificated for use in space flight conditions during 30 days by the Russian Institute of Biomedical Problems.