GRB 000301C: a possible short/intermediate duration burst connected to a DLA system

We discuss two main aspects of the GRB 000301C afterglow (Fynbo et al. 2000, Jensen et al. 2000); its short duration and its possible connection with a Damped Ly-alpha Absorber (DLA). GRB 000301C falls in the short class of bursts, though it is consistent with belonging to the proposed intermediate class or the extreme short end of the distribution of long-duration GRBs. Based on two VLT spectra we estimate the HI column density to be Log(N(HI))=21.2+/-0.5. This is the first direct indication of a connection between GRB host galaxies and Damped Ly-alpha Absorbers.Comment: 3 pages, 3 postscript figures. To appear in the proceedings of the October 2000 Rome Workshop on ``Gamma-Ray Bursts in the Afterglow Era'

Multi-Wavelength Studies of the Optically Dark Gamma-Ray Burst 001025A

We identify the fading X-ray afterglow of GRB 001025A from XMM-Newton observations obtained 1.9-2.3 days, 2 years, and 2.5 years after the burst. The non-detection of an optical counterpart to an upper limit of R=25.5, 1.20 days after the burst, makes GRB 001025A a ``dark'' burst. Based on the X-ray afterglow spectral properties of GRB 001025A, we argue that some bursts appear optically dark because their afterglow is faint and their cooling frequency is close to the X-ray band. This interpretation is applicable to several of the few other dark bursts where the X-ray spectral index has been measured. The X-ray afterglow flux of GRB 001025A is an order of magnitude lower than for typical long-duration gamma-ray bursts. The spectrum of the X-ray afterglow can be fitted with an absorbed synchrotron emission model, an absorbed thermal plasma model, or a combination thereof. For the latter, an extrapolation to optical wavelengths can be reconciled with the R-band upper limit on the afterglow, without invoking any optical circumburst absorption, provided the cooling frequency is close to the X-ray band. Alternatively, if the X-ray afterglow is due to synchrotron emission only, seven magnitudes of extinction in the observed R-band is required to meet the R-band upper limit, making GRB 001025A much more obscured than bursts with detected optical afterglows. Based on the column density of X-ray absorbing circumburst matter, an SMC gas-to-dust ratio is insufficient to produce this amount of extinction. The X-ray tail of the prompt emission enters a steep temporal decay excluding that the tail of the prompt emission is the onset of the afterglow (abridged).Comment: 32 pages, 8 figures, ApJ in pres

A Numerical Model of an Acoustic Metamaterial Using the Boundary Element Method Including Viscous and Thermal Losses

[EN] In recent years, boundary element method (BEM) and finite element method (FEM) implementations of acoustics in fluids with viscous and thermal losses have been developed. They are based on the linearized Navier¿Stokes equations with no flow. In this paper, such models with acoustic losses are applied to an acoustic metamaterial. Metamaterials are structures formed by smaller, usually periodic, units showing remarkable physical properties when observed as a whole. Acoustic losses are relevant in metamaterials in the millimeter scale. In addition, their geometry is intricate and challenging for numerical implementation. The results are compared with existing measurements.The authors wish to thank Mads J. Herring Jensen, from the company COMSOL, for his support in setting up the FEM model of the metamaterial. J. Sanchez-Dehesa acknowledges the support by the Spanish Ministerio de Economia y Competitividad, and the European Union Fondo Europeo de Desarrollo Regional (FEDER) through Project No. TEC2014-53088-C3-1-R.Cutanda-Henriquez, V.; Andersen, PR.; Jensen, JS.; Juhl, PM.; Sánchez-Dehesa Moreno-Cid, J. (2017). A Numerical Model of an Acoustic Metamaterial Using the Boundary Element Method Including Viscous and Thermal Losses. Journal of Computational Acoustics. 25(4):1750006-1-1750006-11. doi:10.1142/S0218396X17500060S1750006-11750006-11254Craster, R. V., & Guenneau, S. (Eds.). (2013). Acoustic Metamaterials. Springer Series in Materials Science. doi:10.1007/978-94-007-4813-2Cummer, S. A., Christensen, J., & Alù, A. (2016). Controlling sound with acoustic metamaterials. Nature Reviews Materials, 1(3). doi:10.1038/natrevmats.2016.1Cutanda-Henríquez, V., & Juhl, P. M. (2013). An axisymmetric boundary element formulation of sound wave propagation in fluids including viscous and thermal losses. The Journal of the Acoustical Society of America, 134(5), 3409-3418. doi:10.1121/1.4823840Bruneau, M., Herzog, P., Kergomard, J., & Polack, J. D. (1989). General formulation of the dispersion equation in bounded visco-thermal fluid, and application to some simple geometries. Wave Motion, 11(5), 441-451. doi:10.1016/0165-2125(89)90018-8Kampinga, W. R., Wijnant, Y. H., & de Boer, A. (2010). Performance of Several Viscothermal Acoustic Finite Elements. Acta Acustica united with Acustica, 96(1), 115-124. doi:10.3813/aaa.918262Kampinga, W. R., Wijnant, Y. H., & de Boer, A. (2011). An Efficient Finite Element Model for Viscothermal Acoustics. Acta Acustica united with Acustica, 97(4), 618-631. doi:10.3813/aaa.918442BELTMAN, W. M. (1999). VISCOTHERMAL WAVE PROPAGATION INCLUDING ACOUSTO-ELASTIC INTERACTION, PART I: THEORY. Journal of Sound and Vibration, 227(3), 555-586. doi:10.1006/jsvi.1999.2355Graciá-Salgado, R., García-Chocano, V. M., Torrent, D., & Sánchez-Dehesa, J. (2013). Negative mass density andρ-near-zero quasi-two-dimensional metamaterials: Design and applications. Physical Review B, 88(22). doi:10.1103/physrevb.88.224305Homentcovschi, D., & Miles, R. N. (2011). An analytical-numerical method for determining the mechanical response of a condenser microphone. The Journal of the Acoustical Society of America, 130(6), 3698-3705. doi:10.1121/1.3652853Geuzaine, C., & Remacle, J.-F. (2009). Gmsh: A 3-D finite element mesh generator with built-in pre- and post-processing facilities. International Journal for Numerical Methods in Engineering, 79(11), 1309-1331. doi:10.1002/nme.257

VLT identification of the optical afterglow of the gamma-ray burst GRB 000131 at z=4.50

We report the discovery of the gamma-ray burst GRB 000131 and its optical afterglow. The optical identification was made with the VLT 84 hours after the burst following a BATSE detection and an Inter Planetary Network localization. GRB 000131 was a bright, long-duration GRB, with an apparent precursor signal 62 s prior to trigger. The afterglow was detected in ESO VLT, NTT, and DK1.54m follow-up observations. Broad-band and spectroscopic observations of the spectral energy distribution reveals a sharp break at optical wavelengths which is interpreted as a Ly-alpha absorption edge at 6700 A. This places GRB 000131 at a redshift of 4.500 +/- 0.015. The inferred isotropic energy release in gamma rays alone was approximately 10^54 erg (depending on the assumed cosmology). The rapid power-law decay of the afterglow (index alpha=2.25, similar to bursts with a prior break in the lightcurve), however, indicates collimated outflow, which relaxes the energy requirements by a factor of < 200. The afterglow of GRB 000131 is the first to be identified with an 8-m class telescope.Comment: 8 pages, 7 figures, accepted to A&A Letter

The bright Gamma-Ray Burst of February 10, 2000: a case study of an optically dark GRB

The gamma-ray burst GRB000210 had the highest gamma-ray peak flux of any event localized by BeppoSAX as yet but it did not have a detected optical afterglow. It is therefore one of the events recently classified as dark GRBs or GHOST (GRB Hiding Optical Source Transient), whose origin is still unclear. Chandra observations allowed us to localize this GRB within ~1" and a radio transient was detected with the VLA. We identify the likely (P=0.01) host galaxy of this burst at z=0.846. The X-ray spectrum of the afterglow shows intrinsic absorption N_H=5x10**21 cm-2. The amount of dust needed to absorb the optical flux of this object is consistent with the above HI column density, given a dust-to-gas ratio similar to that of our Galaxy. We do not find evidence for a partially ionized absorber expected if the absorption takes place in a Giant Molecular Cloud. We therefore conclude that either the gas is local to the GRB, but is condensed in small-scale high-density (n>~10**9 cm-3) clouds, or that the GRB is located in a dusty, gas-rich region of the galaxy. Finally, if GRB000210 lies at z>5, its X-ray absorbing medium would have to be substantially different from that observed in GRBs with optical afterglows.Comment: 29 pages, 7 fig.s, some revisions, ApJ, in pres

Mirroring everyday clinical practice in clinical trial design: a new concept to improve the external validity of randomized double-blind placebo-controlled trials in the pharmacological treatment of major depression

Background: Randomized, double-blind, placebo-controlled trials constitute the gold standard in clinical research when testing the efficacy of new psychopharmacological interventions in the treatment of major depression. However, the blinded use of placebo has been found to influence clinical trial outcomes and may bias patient selection. Discussion: To improve clinical trial design in major depression so as to reflect clinical practice more closely we propose to present patients with a balanced view of the benefits of study participation irrespective of their assignment to placebo or active treatment. In addition every participant should be given the option to finally receive the active medication. A research agenda is outlined to evaluate the impact of the proposed changes on the efficacy of the drug to be evaluated and on the demographic and clinical characteristics of the enrollment fraction with regard to its representativeness of the eligible population. Summary: We propose a list of measures to be taken to improve the external validity of double-blind, placebocontrolled trials in major depression. The recommended changes to clinical trial design may also be relevant for other psychiatric as well as medical disorders in which expectations regarding treatment outcome may affect the outcome itself

The GRB-SN connection: GRB030329 and XRF030723

The attempt to secure conclusive, spectroscopic evidence for the GRB/SN connection has been a central theme in most GRB observing time proposals since the discovery of the very unusual GRB980425 associated with the peculiar type Ib/c SN1998bw. GRB030329 provided this evidence to everybody's satisfaction. In this contribution we show the results of a spectroscopic campaign of the supernova associated with GRB030329 carried out at ESOs Very Large Telescope. We also present preliminary results from a photometric and spectroscopic campaign targeting the X-ray Flash of July 23.Comment: 6 pages, 3 figures, to appear in the Santa Fe GRB Conference Proceedings, 200

On the Afterglow of the X-ray Flash of 2003 July 23: Photometric evdence for an Off-Axis Gamma-Ray burst with an Associated Supernova

Peer reviewe

City dynamics: mobility and livelihoods of urban residents

City dynamics: mobility and livelihoods of urban resident