Strategies for prompt searches for GRB afterglows: the discovery of the GRB 001011 optical/near-infrared counterpart using colour-colour selection

We report the discovery of the optical and near-infrared counterparts to GRB 001011. The GRB 001011 error box determined by Beppo-SAX was simultaneously imaged in the near-infrared by the 3.58-m New Technology Telescope and in the optical by the 1.54-m Danish Telescope ~8 hr after the gamma-ray event. Here we implement the colour-colour discrimination technique proposed by Rhoads (2001) and extend it using near-IR data as well. We present the results provided by an automatic colour-colour discrimination pipe-line developed to discern the different populations of objects present in the GRB 001011 error box. Our software revealed three candidates based on single-epoch images. Second-epoch observations carried out ~3.2 days after the burst revealed that the most likely candidate had faded, thus identifying it with the counterpart to the GRB. In deep R-band images obtained 7 months after the burst a faint (R=25.38+/-0.25) elongated object, presumably the host galaxy of GRB 001011, was detected at the position of the afterglow. The GRB 001011 afterglow is the first discovered with the assistance of colour-colour diagram techniques. We discuss the advantages of using this method and its application to error boxes determined by future missions.Comment: Accepted for publication in Astronomy and Astrophysics, 13 pages, 16 figure

Studies of a three-stage dark matter and neutrino observatory based on multi-ton combinations of liquid xenon and liquid argon detectors

We study a three stage dark matter and neutrino observatory based on multi-ton two-phase liquid Xe and Ar detectors with sufficiently low backgrounds to be sensitive to WIMP dark matter interaction cross sections down to 10E-47 cm^2, and to provide both identification and two independent measurements of the WIMP mass through the use of the two target elements in a 5:1 mass ratio, giving an expected similarity of event numbers. The same detection systems will also allow measurement of the pp solar neutrino spectrum, the neutrino flux and temperature from a Galactic supernova, and neutrinoless double beta decay of 136Xe to the lifetime level of 10E27 - 10E28 y corresponding to the Majorana mass predicted from current neutrino oscillation data. The proposed scheme would be operated in three stages G2, G3, G4, beginning with fiducial masses 1-ton Xe + 5-ton Ar (G2), progressing to 10-ton Xe + 50-ton Ar (G3) then, dependent on results and performance of the latter, expandable to 100-ton Xe + 500-ton Ar (G4). This method of scale-up offers the advantage of utilizing the Ar vessel and ancillary systems of one stage for the Xe detector of the succeeding stage, requiring only one new detector vessel at each stage. Simulations show the feasibility of reducing or rejecting all external and internal background levels to a level <1 events per year for each succeeding mass level, by utilizing an increasing outer thickness of target material as self-shielding. The system would, with increasing mass scale, become increasingly sensitive to annual signal modulation, the agreement of Xe and Ar results confirming the Galactic origin of the signal. Dark matter sensitivities for spin-dependent and inelastic interactions are also included, and we conclude with a discussion of possible further gains from the use of Xe/Ar mixtures

Determination and evaluation of clinically efficient stopping criteria for the multiple auditory steady-state response technique

Background: Although the auditory steady-state response (ASSR) technique utilizes objective statistical detection algorithms to estimate behavioural hearing thresholds, the audiologist still has to decide when to terminate ASSR recordings introducing once more a certain degree of subjectivity. Aims: The present study aimed at establishing clinically efficient stopping criteria for a multiple 80-Hz ASSR system. Methods: In Experiment 1, data of 31 normal hearing subjects were analyzed off-line to propose stopping rules. Consequently, ASSR recordings will be stopped when (1) all 8 responses reach significance and significance can be maintained for 8 consecutive sweeps; (2) the mean noise levels were ≤ 4 nV (if at this “≤ 4-nV” criterion, p-values were between 0.05 and 0.1, measurements were extended only once by 8 sweeps); and (3) a maximum amount of 48 sweeps was attained. In Experiment 2, these stopping criteria were applied on 10 normal hearing and 10 hearing-impaired adults to asses the efficiency. Results: The application of these stopping rules resulted in ASSR threshold values that were comparable to other multiple-ASSR research with normal hearing and hearing-impaired adults. Furthermore, in 80% of the cases, ASSR thresholds could be obtained within a time-frame of 1 hour. Investigating the significant response-amplitudes of the hearing-impaired adults through cumulative curves indicated that probably a higher noise-stop criterion than “≤ 4 nV” can be used. Conclusions: The proposed stopping rules can be used in adults to determine accurate ASSR thresholds within an acceptable time-frame of about 1 hour. However, additional research with infants and adults with varying degrees and configurations of hearing loss is needed to optimize these criteria

COMPTEL solar flare observations

COMPTEL as part of a solar target of opportunity campaign observed the sun during the period of high solar activity from 7-15 Jun. 1991. Major flares were observed on 9 and 11 Jun. Although both flares were large GOES events (greater than or = X10), they were not extraordinary in terms of gamma-ray emission. Only the decay phase of the 15 Jun. flare was observed by COMPTEL. We report the preliminary analysis of data from these flares, including the first spectroscopic measurement of solar flare neutrons. The deuterium formation line at 2.223 MeV was present in both events and for at least the 9 Jun. event, was comparable to the flux in the nuclear line region of 4-8 MeV, consistent with Solar-Maximum Mission (SSM) Observations. A clear neutron signal was present in the flare of 9 Jun. with the spectrum extending up to 80 MeV and consistent in time with the emission of gamma-rays, confirming the utility of COMPTEL in measuring the solar neutron flux at low energies. The neutron flux below 100 MeV appears to be lower than that of the 3 Jun. 1982 flare by more than an order of magnitude. The neutron signal of the 11 Jun. event is under study. Severe dead time effects resulting from the intense thermal x-rays require significant corrections to the measured flux which increase the magnitude of the associated systematic uncertainties

Step size of the rotary proton motor in single FoF1-ATP synthase from a thermoalkaliphilic bacterium by DCO-ALEX FRET

Thermophilic enzymes can operate at higher temperatures but show reduced activities at room temperature. They are in general more stable during preparation and, accordingly, are considered to be more rigid in structure. Crystallization is often easier compared to proteins from bacteria growing at ambient temperatures, especially for membrane proteins. The ATP-producing enzyme FoF1-ATP synthase from thermoalkaliphilic Caldalkalibacillus thermarum strain TA2.A1 is driven by a Fo motor consisting of a ring of 13 c-subunits. We applied a single-molecule F\"orster resonance energy transfer (FRET) approach using duty cycle-optimized alternating laser excitation (DCO-ALEX) to monitor the expected 13-stepped rotary Fo motor at work. New FRET transition histograms were developed to identify the smaller step sizes compared to the 10-stepped Fo motor of the Escherichia coli enzyme. Dwell time analysis revealed the temperature and the LDAO dependence of the Fo motor activity on the single molecule level. Back-and-forth stepping of the Fo motor occurs fast indicating a high flexibility in the membrane part of this thermophilic enzyme.Comment: 14 pages, 7 figure