Results of the search for inspiraling compact star binaries from TAMA300's observation in 2000-2004

We analyze the data of TAMA300 detector to search for gravitational waves from inspiraling compact star binaries with masses of the component stars in the range 1-3Msolar. In this analysis, 2705 hours of data, taken during the years 2000-2004, are used for the event search. We combine the results of different observation runs, and obtained a single upper limit on the rate of the coalescence of compact binaries in our Galaxy of 20 per year at a 90% confidence level. In this upper limit, the effect of various systematic errors such like the uncertainty of the background estimation and the calibration of the detector's sensitivity are included.Comment: 8 pages, 4 Postscript figures, uses revtex4.sty The author list was correcte

Observation results by the TAMA300 detector on gravitational wave bursts from stellar-core collapses

We present data-analysis schemes and results of observations with the TAMA300 gravitational-wave detector, targeting burst signals from stellar-core collapse events. In analyses for burst gravitational waves, the detection and fake-reduction schemes are different from well-investigated ones for a chirp-wave analysis, because precise waveform templates are not available. We used an excess-power filter for the extraction of gravitational-wave candidates, and developed two methods for the reduction of fake events caused by non-stationary noises of the detector. These analysis schemes were applied to real data from the TAMA300 interferometric gravitational wave detector. As a result, fake events were reduced by a factor of about 1000 in the best cases. The resultant event candidates were interpreted from an astronomical viewpoint. We set an upper limit of 2.2x10^3 events/sec on the burst gravitational-wave event rate in our Galaxy with a confidence level of 90%. This work sets a milestone and prospects on the search for burst gravitational waves, by establishing an analysis scheme for the observation data from an interferometric gravitational wave detector

Pressure-induced unusual metallic state in EuNiO3

The perovskite antiferromagnetic (TN∼220K) insulator EuNiO3 undergoes at ambient pressure a metal-to-insulator transition at TMI=460K which is associated with a simultaneous orthorhombic-to-monoclinic distortion, leading to charge disproportionation. We have investigated the change of the structural and magnetic properties of EuNiO3 with pressure (up to ∼20GPa) across its quantum critical point (QCP) using low-temperature synchrotron angle-resolved x-ray diffraction and 151Eu nuclear forward scattering of synchrotron radiation, respectively. With increasing pressure, we find that after a small increase of TN (p≤2GPa) and the induced magnetic hyperfine field Bhf at the 151Eu nucleus (p≤9.7GPa), both TN and Bhf are strongly reduced and finally disappear at pc≅10.5GPa, indicating a magnetic QCP at pc. The analysis of the structural parameters up to 10.5 GPa reveals no change of the lattice symmetry within the experimental resolution. Since the pressure-induced insulator-to-metal transition occurs at pIM≅6GPa, this result implies the existence of an antiferromagnetic metallic state between 6 and 10.5 GPa. We further show from the analysis of the reported high-pressure electrical resistance data on EuNiO3 at low temperatures that in the vicinity of the QCP the system behaves as non-Fermi-liquid, with the resistance changing as Tn, with n=1.6, whereas it becomes a normal Fermi liquid, n=2, for pressures above ∼15GPa. On the basis of the obtained data, a magnetic phase diagram in the (p, T) space is suggested.The 151Eu NFS and x-ray diffraction experiments under pressure were performed at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposals No. 2010A1517, No. 2008B1460, and No. 2007A1450). M.M.A. and D.K. would like to thank the Deutsche Forschungsgemeinschaft (DFG) for the support through SFB 608. The work of D.K. was supported by the German project FOR 1346 and by Cologne University within the German Excellence Initiative