S. Rosen

A short γ-ray burst apparently associated with an elliptical galaxy at redshift z = 0.225

Gamma-ray bursts (GRBs) come in two classes: long (> 2u2009s), soft-spectrum bursts and short, hard events. Most progress has been made on understanding the long GRBs, which are typically observed at high redshift (z ≈ 1) and found in subluminous star-forming host galaxies. They are likely to be produced in core-collapse explosions of massive stars. In contrast, no short GRB had been accurately (< 10″) and rapidly (minutes) located. Here we report the detection of the X-ray afterglow from—and the localization of—the short burst GRB 050509B. Its position on the sky is near a luminous, non-star-forming elliptical galaxy at a redshift of 0.225, which is the location one would expect if the origin of this GRB is through the merger of neutron-star or black-hole binaries. The X-ray afterglow was weak and faded below the detection limit within a few hours; no optical afterglow was detected to stringent limits, explaining the past difficulty in localizing short GRBs.

External electrical stimulation of the cochlea: clinical, psychophysical, speech-perceptual and histological findings.

Our progress towards the development of a particular form of cochlear implant for the totally deaf is described. A single channel stimulation at the round window or promontory is used. This involves a minimum of surgical intervention and infective risk, preserves the possibility of remission and allows the application of later developments. The signal used for stimulation is designed to be matched both to the deaf lip-readers needs and to his new, restricted, auditory ability. This is done by concentrating on the acoustic pattern components of speech which carry intonation and voiced-voiceless information. Surgical electrophysical, psychoacoustic and speech perceptual aspects of our work with twelve patients are described. The tests involve responses, for example, relating to: threshold for sinusoids; frequency difference limens; periodic -aperiodic discrimination; stress placement; and consonant labelling using combined visual and electrical inputs. Relatively extensive measurements were made with six patients. Significant individual differences were found and the sets of responses provide an essential basis for an appraisal of the potential usefulness of our work to the individual patient. Possible reasons for the individual differences are discussed. A brief indication is given of the techniques which we have developed for the future speech training and speech production evaluation of patients with electro-cochlear voice monitoring. The final section of our paper mentions our histological investigation of the effects of this type of stimulation in the guinea pig.

Swift panchromatic observations of the bright gamma-ray burst GRB 050525a

The bright gamma- ray burst GRB 050525a has been detected with the Swift observatory, providing unique multiwavelength coverage from the very earliest phases of the burst. The X- ray and optical / UV afterglow decay light curves both exhibit a steeper slope similar to 0.15 days after the burst, indicative of a jet break. This jet break time combined with the total gamma- ray energy of the burst constrains the opening angle of the jet to be 3 degrees.2. We derive an empirical `` timelag redshift from the BAT data of (z) over bar z 0: 69 +/- 0: 02, in good agreement with the spectroscopic redshift of 0.61. Prior to the jet break, the X- ray data can be modeled by a simple power law with index alpha = - 1: 2. However, after 300 s the X- ray flux brightens by about 30% compared to the power- law fit. The optical / UV data have a more complex decay, with evidence of a rapidly falling reverse shock component that dominates in the first minute or so, giving way to a flatter forward shock component at later times. The multiwavelength X- ray/ UV/ optical spectrum of the afterglow shows evidence for migration of the electron cooling frequency through the optical range within 25,000 s. The measured temporal decay and spectral indexes in the X- ray and optical/ UV regimes compare favorably with the standard fireball model for gamma- ray bursts assuming expansion into a constant- density interstellar medium.

Further calibration of the Swift ultraviolet/optical telescope

The Ultraviolet/Optical Telescope (UVOT) is one of three instruments onboard the Swift observatory. The photometric calibration has been published, and this paper follows up with details on other aspects of the calibration including a measurement of the point spread function with an assessment of the orbital variation and the effect on photometry. A correction for large-scale variations in sensitivity over the field of view is described, as well as a model of the coincidence loss which is used to assess the coincidence correction in extended regions. We have provided a correction for the detector distortion and measured the resulting internal astrometric accuracy of the UVOT, also giving the absolute accuracy with respect to the International Celestial Reference System. We have compiled statistics on the background count rates, and discuss the sources of the background, including instrumental scattered light. In each case, we describe any impact on UVOT measurements, whether any correction is applied in the standard pipeline data processing or whether further steps are recommended.

Production and perception of rise time in the voiceless affricate/fricative distinction

Rise times of voiceless affricates and fricatives were measured when the test material occurred in sentences, in isolated words, and in isolated nonsense syllables. As has been reported previously the rise times of affricates were significantly shorter than those of fricatives. Rise times varied with the type of test material and for all types of material were significantly longer than those reported by L.J. Gerstman [unpublished doctoral dissertation, New York University (1957)]. Differences in the way the previous measurements were made do not appear to explain the discrepancy. Because rise time varies with type of test material, no auditory sensitivity at a single rise time value can be responsible for the perceptual distinction between voiceless affricates and fricatives. This conclusion was also supported by the results of a perceptual experiment in which listeners were asked to label speech or nonspeech stimuli drawn from a continuum varying in rise time. Substantially different estimates of the category boundary were obtained when the range of rise times covered by the stimuli differed.

Tune Recognition with Reduced Pitch and Interval Information

Twenty subjects were tested on their ability to recognize simple tunes from which rhythm information had been removed. Only the first phrase of each tune was presented. The purpose of the experiment was (a) to determine whether stimuli containing only high harmonics can evoke a sense of musical pitch, and (b) to provide a set of data in normal subjects with which the performance of deaf subjects whose auditory nerve is stimulated electrically can be compared. Each subject was tested on five sets of stimuli presented in a counterbalanced order. These stimuli were (I) pulse trains high-pass filtered at 2 kHz, with repetition rates in the range of 100–200 p.p.s.; (2) as in (I) but high-pass filtered at 4 kHz; (3) sinusoids with musical intervals compressed, so that the “octave” was a ratio of I:I·3; (4) sinusoids with the musical intervals expanded, so that the “octave” was a ratio of I:4; (5) sinusoids of a constant frequency in which the normal frequency changes were translated into intensity changes, each semitone being represented by a 3 dB change in level. The results indicate that a pattern of intensity changes does not support tune recognition, and that, although the pitch contour alone allows reasonable performance, subjects do use musical interval information in recognizing tunes. Stimuli containing only high harmonics can provide such interval information, and thus can evoke a sense of musical pitch. Preliminary results from a deaf subject stimulated electrically with an electrode on the surface of the cochlea indicate that such stimulation can also evoke a sense of musical pitch. It is concluded that musical pitch information can be carried in the time-pattern of nerve impulses in the auditory nerve.

Plucks and bows are not categorically perceived.

Cutting and Rosner (Perception & Psychophysics, 1974, 16, 564–570) reported that nonspeech stimuli differing in rise time were categorically perceived in the same way as speech sounds. With two independently generated sets of stimuli essentially the same as those described by Cutting and Rosner, we were unable to replicate their finding that discrimination measured in an ABX task was best around 40 msec, the category boundary. We found discrimination always best at the shortest rise times, decreasing monotonically with increasing rise time. Oscillographic traces of Cutting and Rosner’s original stimuli showed them not to have the intended rise times. Instead of starting with a rise of 0 msec and increasing linearly in 10-msec steps to 80 msec, the measured rise times were approximately 4, 6, 15, 19, 37, 43, 57, 66, and 76 msec, respectively. A set of stimuli having these rise times was generated. Two distinct patterns of response emerged from the discrimination task. Most subjects now showed best discrimination around 40 msec, but a few still performed best at the shortest rise times.

Optical, Infrared, and Ultraviolet Observations of the X-Ray Flash XRF 050416A

We present ultraviolet, optical, and infrared photometry of the afterglow of the X-ray flash XRF 050416A taken between approximately 100 s and 36 days after the burst. We find an intrinsic spectral slope between 1930 and 22200 ? of ? = -1.14 ? 0.20 and a decay rate of ? = -0.86 ? 0.15. There is no evidence for a change in the decay rate between approximately 0.7 and 4.7 days after the burst. Our data imply that there is no spectral break between the optical and X-ray bands between 0.7 and 4.7 days after the burst and are consistent with the cooling break being redward of the Ks band (22200 ?) at 0.7 days. The combined ultraviolet/optical/infrared spectral energy distribution shows no evidence for a significant amount of extinction in the host galaxy along the line of sight to XRF 050416A. Our data suggest that the extragalactic extinction along the line of sight to the burst is only approximately AV = 0.2 mag, which is significantly less than the extinction expected from the hydrogen column density inferred from X-ray observations of XRF 050416A assuming a dust-to-gas ratio similar to what is found for the Milky Way. The observed extinction, however, is consistent with the dust-to-gas ratio seen in the Small Magellanic Cloud. We suggest that XRF 050416A may have a two-component jet similar to what has been proposed for GRB 030329. If this is the case, the lack of an observed jet break between 0.7 and 42 days is an illusion due to emission from the wide jet dominating the afterglow after approximately 1.5 days.

Prompt optical observations of GRB 050319 with the Swift UVOT

The UVOT telescope on the Swift observatory has detected optical afterglow emission from GRB 050319. The flux declined with a power-law slope of alpha = -0.57 between the start of observations some 230 s after the burst onset (90 s after the burst trigger) until it faded below the sensitivity threshold of the instrument after similar to 5 x 10(4) s. There is no evidence for the rapidly declining component in the early light curve that is seen at the same time in the X-ray band. The afterglow is not detected in UVOT shortward of the B band, suggesting a redshift of about 3.5. The optical V-band emission lies on the extension of the X-ray spectrum, with an optical-to-X-ray slope of beta = 0.8. The relatively flat decay rate of the burst suggests that the central engine continues to inject energy into the fireball for as long as a few x 10(4) s after the burst.

Natural auditory sensitivities as universal determiners of phonemic contrasts

Are there acoustic invariants that mediate the perception of phonemes? If there were, they might be shared by a number of languages. But this acoustic-phonemic relationship does not occur in a simple way for any of the languages that have been examined. Has, then, such an approach to speech perception been abandoned? Not entirely; some theorists argue that there are invariant acoustic properties which occur whatever context a phoneme is spoken in. On the other hand, some have considered that the speech signal is inherently variable and the invariant relations only occur at higher levels of processing (Liberman et al. 1967; Liberman and Studdert-Kennedy 1978). Stevens has been the main protagonist of the view that the signal contains invariant acoustic correlates of phonemic categories (Stevens 1975, 1981; Stevens and Klatt 1976; Halle and Stevens 1980). He has considered all the problems that need to be accounted for by a theory which holds that acoustic invariants exist in the signal — how these invariant relations arise in speech production, what factors make it difficult to isolate them from acoustic records, and what evidence there is that these acoustic relations are used for the purpose of perceiving phonemic categories. Other workers have taken a similar theoretical line in explaining phonemic perception. For example, Kuhl and Miller (1975) have reported that chinchillas label synthetic speech in a remarkably similar way to English-speaking humans. This finding has been interpreted as showing that the animals are responding to acoustic factors in these sounds which underlie the phoneme categories common to the languages of the world. In this chapter we will assess whether invariant auditory factors can mediate perception of phonemic categories within and across the worlds languages. The invariant acoustic factors associated with phonemes are supposed to give rise to the phenomena of categorical perception whether it occurs in human or other mammalian