The very faint hard state of the persistent neutron star X-ray binary SLX 1737-282 near the Galactic centre

We report on a detailed study of the spectral and temporal properties of the neutron star low mass X-ray binary SLX 1737-282, which is located only ~1degr away from Sgr A. The system is expected to have a short orbital period, even within the ultra-compact regime, given its persistent nature at low X-ray luminosities and the long duration thermonuclear burst that it has displayed. We have analysed a Suzaku (18 ks) observation and an XMM-Newton (39 ks) observation taken 7 years apart. We infer (0.5-10 keV) X-ray luminosities in the range 3-6 x10^35erg s-1, in agreement with previous findings. The spectra are well described by a relatively cool (kTbb = 0.5 keV) black body component plus a Comptonized emission component with {\Gamma} ~1.5-1.7. These values are consistent with the source being in a faint hard state, as confirmed by the ~ 20 per cent fractional root mean square amplitude of the fast variability (0.1 - 7 Hz) inferred from the XMM-Newton data. The electron temperature of the corona is >7 keV for the Suzaku observation, but it is measured to be as low as ~2 keV in the XMM-Newton data at higher flux. The latter is significantly lower than expected for systems in the hard state. We searched for X-ray pulsations and imposed an upper limit to their semi-amplitude of 2 per cent (0.001 - 7 Hz). Finally, we investigated the origin of the low frequency variability emission present in the XMM-Newton data and ruled out an absorption dip origin. This constraint the orbital inclination of the system to 65 degr unless the orbital period is longer than 11 hr (i.e. the length of the XMM-Newton observation).Comment: 7 pages, 4 figures, 1 table. Accepted for publication in MNRA

TeV Burst of Gamma-Ray Bursts and Ultra High Energy Cosmic Rays

Some recent experiments detecting very high energy (VHE) gamma-rays above 10-20 TeV independently reported VHE bursts for some of bright gamma-ray bursts (GRBs). If these signals are truly from GRBs, these GRBs must emit a much larger amount of energy as VHE gamma-rays than in the ordinary photon energy range of GRBs (keV-MeV). We show that such extreme phenomena can be reasonably explained by synchrotron radiation of protons accelerated to \sim 10^{20-21} eV, which has been predicted by Totani (1998a). Protons seem to carry about (m_p/m_e) times larger energy than electrons, and hence the total energy liberated by one GRB becomes as large as \sim 10^{56} (\Delta \Omega / 4 \pi) ergs. Therefore a strong beaming of GRB emission is highly likely. Extension of the VHE spectrum beyond 20 TeV gives a nearly model-independent lower limit of the Lorentz factor of GRBs, as \gamma \gtilde 500. Furthermore, our model gives the correct energy range and time variability of ordinary keV-MeV gamma-rays of GRBs by synchrotron radiation of electrons. Therefore the VHE bursts of GRBs strongly support the hypothesis that ultra high energy cosmic rays observed on the Earth are produced by GRBs.Comment: Final version to appear in ApJ Lett. Emphasizing that the extremely large energy required in this model is not theoretically impossible if GRB emission is strongly beamed. References update

Aportes polínicos invernales en colmenas de Sierra Morena (Córdoba, España)

Se ha rcal~do un esaudio de aportes polfnkos invernales en colmc.nas de b SM:.rra (C6<doba, EspañJ). Adcmis de les p61cnes descrito; oon an1erioridad pan b tcmporad.l alla de recolecci6o, apartccn ellos tipoc poUnicas ca elcv.Jdas proporciones: Composirat, Oxalis pc;.oprat, PhiUyuo fJIIfUtlfolia, CoryfttSll\'ttfana. Elica arboru, cte. l...3.s ,¡gnirfcativas difc· rencias aparecidas tnlrc b.s colmenas CSiudladas en tuii.DlO a la participación de farniliM polínic: as.. apoyarian la tcoria de que el compDrt3mienro recolc:ctor de polen enApi: mtU1Tm: s.igue el modelo de. la •constancia individuar.Wintcr pcllimfcrous sourC from thc Sierra (Cérdoba, Spain) wcre Sludicd, Be· sides thc pollens previousJy dtSCribcd for thC higb harv<:SI sea.c;on, Lhe follow1ng WCIC found in ~ignifi cant proportions.: Composiroe, OxoiiJ pes-caproe, Phillytta anguJri{rHia, C01ylus D\-tllona, Erica arborta, etc. Thc signilic.3. nl differences betwec:n hivt:S ~lb rcspcctto ttlc ~n icipation of ttle pollinic fam.ilics, suppon ttlc "indhidual constanc}"' theory ia the pollen b;m.'CSicr bcha\oiGT of A pis melliftrQ