Absolute Magnitude Estimation Research Articles

Distances of absorbing features in the LDN 1622 direction

With Tycho-2 BT and VT photometry of Hipparcos stars with π 8.0 mas, /π 15% and with spectral type and luminosity classification from the Michigan Catalogues we have a presumably unreddened sample for establishing a ( main sequence relation in the range from A0 to G5. We discuss the location of the median main sequence relation relative to published ZAMS relations for the A0-G5 range in some detail since the applications of this relation will have to assume that the evolutionary status of the calibration sample is representative of the local disk. If the ZAMS is defined as the lower envelope of the class V stars the published versions we discuss seem to be too bright by about half a magnitude in the F0-G5 range. The resulting intrinsic color and absolute magnitude estimates have errors of the mean of 003 and 03–04 respectively. From this relation any given star with Tycho-2 photometry, spectral classification and luminosity class V can have its color excess and distance modulus estimated. This means that the local interstellar extinction may be estimated for the ~50% of the sky where Michigan classification presently is available. The individual color excesses and distance moduli may not be particularly accurate but we propose that they may be used to indicate extinction discontinuities caused by interstellar material at well defined distances. We have applied this new technique on stars from the Michigan Catalogue in the direction of LDN 1622 supposed to be associated to the Orion B region 400–500 pc away but color excesses exceeding start appearing already in the distance slot 160–200 pc. Presently we cannot decide whether this nearby dust is related to LDN 1622 or whether this cloud is associated to Orion B. In a final comparison we study the color excess – distance variation in a 4° region centered on LDN 1622 from Hipparcos – Tycho-1 – Michigan data and the dust at ~160 pc is confirmed.

Characterization of M, L, and T Dwarfs in the Sloan Digital Sky Survey

An extensive sample of M, L and T dwarfs identified in the Sloan Digital Sky Survey (SDSS) has been compiled. The sample of 718 dwarfs includes 677 new objects (629 M dwarfs, 48 L dwarfs) together with 41 that have been previously published. All new objects and some of the previously published ones have new optical spectra obtained either with the SDSS spectrographs or with the Apache Point Observatory 3.5m ARC telescope. Spectral types and SDSS colors are available for all objects; approximately 35% also have near-infrared magnitudes measured by 2MASS or on the Mauna Kea system. We use this sample to characterize the color--spectral type and color--color relations of late type dwarfs in the SDSS filters, and to derive spectroscopic and photometric parallax relations for use in future studies of the luminosity and mass functions based on SDSS data. We find that the (i*-z*) and (i*-J) colors provide good spectral type and absolute magnitude (M_i*) estimates for M and L dwarfs. Our distance estimates for the current sample indicate that SDSS is finding early M dwarfs out to about 1.5 kpc, L dwarfs to approximately 100 pc and T dwarfs to near 20 pc. The T dwarf photometric data show large scatter and are therefore less reliable for spectral type and distance estimation.

Estimation of size at three sites on the face

The subjective size of steel balls was judged by nine subjects using the method of Absolute Magnitude Estimation. The balls were rolled (‘‘scripted’’) over three areas of the face (forehead, cheek, and lower lip) using the right index distal finger pad. The areas were stimulated under three conditions; (1) the subjects upon themselves (intra-active touch); (2) the subjects upon another person (interactive touch); and (3) another person upon the face of the subject (interactive touch). There were significant differences among the three facial sites in the intra-active condition. When another person’s face was scripted by the subject, there were no differences among the sites. The results were mixed when another scripted upon the faces of the subjects. The results are considered in terms of tissue mechanics, mode of stimulation and representation of the sites on the somatosensory cortex. [Work supported by NIH.]

Effect of aging on the subjective magnitude of vibration

Two groups of subjects were tested using the method of Absolute Magnitude Estimation (AME) to determine the effect of age on the subjective intensity of vibration delivered to the skin of the hand. The mean age of the younger group was 23.5 years and that of the older group was 68.6 years. Average thresholds in the older group were higher in both the Pacinian (P) and non-Pacinian channel (NP II). The subjective magnitude of vibration was substantially lower at all intensities in the older group. Individual results clearly showed that the P channel saturates near the detection threshold of the NP II channel.

A comparison of AME and CR100 for scaling perceived exertion

In psychophysical studies of the relation between perceived magnitude and physical stimulus, interest has focused on the preciseness of growth functions. Very little interest has been devoted to natural levels of an “absolute” character and to the validity of direct measurements. In this article, the Category ( C)–Ratio ( R) (CR) scaling methodology, developed by Borg (1973, 1977, 1982) is presented together with a new CR scale: the CR100 scale. In an experiment on perceived exertion, CR100 was compared with Absolute Magnitude Estimation (AME). Perceived exertion has the advantage of having easily measured physiological variables that can function as validity criteria. 32 persons (16 men and 16 women) participated as subjects on two different occasions, and the presentation order was counterbalanced. Results from CR100 and AME could be described equally well with psychophysical functions. The exponents obtained with CR100 were n=1.60 for women and n=1.69 for men, and the corresponding exponents for AME were n=1.60 for women and n=1.46 for men (with a “noise” constant included in the function). ANOVA showed that CR100 could make the predicted differentiation between sexes, whereas AME could not. This drawback with AME was also found when using the methods to predict working capacity.

Observations of five supernovae in 1995–1997

We present the results of photometric observations of the type Ia supernovae SN 1995al, 1996bo, 1996bk, the type Ib/c supernova SN 1997X, and the type II supernova SN 1996an. The photometric characteristics of SN 1995al are close to the average for type Ia supernovae. Our analysis has revealed possible peculiarities in the light-curve shape and deviations from the average photometric parameters for SN 1996bk and 1996bo. Sn 1996an probably belongs to type IIP. The light curve of SN 1997X resembles that of the type Ic supernova SN 1994I. Light-curve parameters and absolute magnitude estimates are presented.

Loudness scaling in children

Loudness measurements in children have been carried out using different psychoacoustical methods. Besides absolute magnitude estimation (AME) and cross modality matching (CMM) category and non-category loudness scalings have been performed. However, there is a lack of systematic evaluation in loudness scalings with children. A clinically feasible categorical method is presented which was evaluated in 10 normally hearing children of 7 to 8 years. Furthermore, measurements with hearing disabled children were performed in the framework of hearing aid evaluation. Normal hearing children scaled slightly louder than a group of adult subjects with normal hearing. Regarding the shape of the loudness functions measured they were very similar. Particularly, they showed a steeper course at higher levels than for low input signals. Intraindividual scatter of the loudness judgements was larger for children than for adults. However, high correlation appeared between the data across test and retest. Hence, the outcome of the scalings appears to be sufficient reliable. Clinical measurements confirmed that the method is appropriate for children from approximately 5-10 years. Loudness judgements became more consistent and more subtly differentiated with increasing age and decreasing hearing loss. Especially with view of hearing aid evaluation the method can give valuable indications because of the possibility to directly measure individual loudness over a broad range of levels and frequencies.

Response to low-frequency HVAC noise

With the increasing use of variable air volume systems in building air-conditioning, there has been an increased occurrence of low-frequency and rumble noise problems. ASHRAE is currently funding a research program to determine the relationship between low-frequency HVAC noise and comfort in occupied spaces. A pilot psycho-acoustic study was conducted using up to nine subjects. Twelve noise stimuli representing various HVAC sounds were utilised and subjects assigned an annoyance and loudness rating using the absolute magnitude estimation technique. The results showed that for noise stimuli dominated by low-frequency energy, the annoyance was more severe than the loudness, rather than equal as has been generally assumed. The main study is currently underway and some of the results will be discussed. The subjective rating responses were correlated with the dB SPL and other noise metrics and Sound Quality metrics. The results have implications with respect to assessment of low-frequency noise in buildings and possibly to the external environment.

Sensory dissonance of two-tone complexes

Sensory dissonance, a basically unpleasant auditory sensation related to amplitude or frequency modulation of sound, is an element of a broader concept of musical dissonance. The present study was carried out to determine the magnitude of sensory dissonance produced by beats in two-tone complexes. The method of absolute magnitude estimation was employed for scaling. The measurements were obtained for tone frequencies ranging from 32 to 4000 Hz and beat frequencies ranging from 2 to 2000 Hz. The results show that at beat frequencies higher than 20 Hz, sensory dissonance is equivalent to roughness. The beat frequency at which the maximum of roughness and of sensory dissonance is observed increases with the frequency of the low tone in a complex, ranging from 20 for a 32-Hz tone to about 100 for a 4000-Hz tone. At beat frequencies lower than 20 Hz, sensory dissonance is produced by audible fluctuations of loudness. The effect of loudness fluctuations on sensory dissonance is most pronounced in the range of lowest audible frequencies.

Subjective magnitude of tactile roughness

The subjective experience of tactile roughness was judged by subjects using the method of absolute magnitude estimation (AME). The stimuli were 11 grades of sandpaper having particle diameters ranging from 16 to 905 mum. All of the estimates resulted in power functions when assigned numbers were plotted as a function of particle diameter. It was determined that on the finger pad of the index finger and the thumb there was no difference between the active and passive modes of stimulation and that there was no difference in roughness estimates made on the finger and on the thumb. When the finger and thumb were stimulated simultaneously, higher numbers were assigned for a given stimulus indicating the presence of a form of spatial summation at these sites. The pleasantness of the tactile sensation, as assessed using AME, was inversely related to the roughness estimates. Furthermore, hydration of the stratum corneum with water and three concentrations of surfactant solutions reduced the sensation of roughness below that of normally hydrated skin.

Absolute magnitude estimation of pitch

The pitch of 24 pure tones covering a frequency range of 63–12 500 Hz in 1/3-oct. steps was measured by absolute magnitude estimation. The tones were presented monaurally at a loudness level of 60 phons. Tone duration was 1 s. Sixteen music students, not possessing absolute pitch served as subjects. The experiment was carried out in individual listening sessions. The subjects were instructed to assign a number to the tone in such a way that their impression of how large the number was matched their impression of the pitch of the tone. The results show that the pitch function plotted in log–log coordinates against frequency is considerably steeper below than above 250 Hz. A similar shape of the pitch function was found in a previous study in which narrow-band noises were used [A. Rakowski, Proc. Fechner Day ’97, pp. 91–96]. It is hypothesized that the change of the pitch function steepness at 250 Hz may also be observed in the perception of musical intervals. Intervals in low pitch registers may be perceived larger than those corresponding to the same frequency ratios in high-pitch registers.

Tactile estimation of roughness and size

Subjects estimated the subjective magnitude of roughness and the size of steel balls by the method of absolute magnitude estimation. Using the index finger and thumb, estimates were made of 11 grades of sandpaper with particle diameters ranging from 16–905 μm. The results describe a power function and show spatial summation when stimuli are applied simultaneously to two sites (finger and thumb). The same subjects judged the size of nine steel balls ranging in diameter from 0.4–6.4 mm. Estimates were made with combinations of the index finger, volar forearm, and thumb. Again, all of the results were power functions and spatial summation of tactile stimulation was evident. The results are discussed in terms of theoretical considerations and practical application. [Work supported by Unilever and NIH, PO1DC00380].

Hipparcos absolute magnitudes for metal-rich K giants and the calibration of DDO photometry

Parallaxes for 581 bright K giants have been determined using the Hipparcos satellite. We combine the trigonometric parallaxes with ground-based photometric data to determine the K giant absolute magnitudes. For all these giants, absolute magnitude estimates can also be made using the intermediate-band photometric David Dunlop Observatory (DDO) system. We compare the DDO absolute magnitudes with the very accurate Hipparcos absolute magnitudes, finding various systematic offsets in the DDO system. These systematic effects can be corrected, and we provide a new calibration of the DDO system allowing absolute magnitude to be determined with an accuracy of 0.35 mag in the range 2 > Mv > −1. The new calibration performs well when tested on K giants with DDO photometry in a selection of low-reddening open clusters with well-measured distance moduli.

Intensity resolution and subjective magnitude in psychophysical scaling.

Several successful theories of psychophysical judgment imply that exponents of power functions in scaling tasks should covary with measures of intensity resolution such as d' in the same tasks, whereas the prevailing metatheory of ideal psychophysical scaling asserts the independence of the two. In a direct test of this relationship, three prominent psychophysical scaling paradigms were studied: category judgment without an identification function, absolute magnitude estimation, and cross-modality matching with light intensity as the response continuum. Separate groups of subjects for each scaling paradigm made repeated judgments of the loudnesses of the pure tones that constituted each of two stimulus ensembles. The narrow- and wide-range ensembles shared six identical stimulus intensities in the middle of each set. Intensity resolution, as measured by d'-like distances, of these physically identical stimuli was significantly worse for the wide-range set for all three methods. Exponents of power functions fitted to geometric mean responses, and in magnitude estimation and cross-modality matching the geometric mean responses themselves, were also significantly smaller in the wide-range condition. The variation of power function exponents, and of psychophysical scale values, for stimulus intensities that were identical in the two stimulus sets with the intensities of other members of the ensembles is inconsistent with the metatheory on which modern psychophysical scaling practice is based, although it is consistent with other useful approaches to measurement of psychological magnitudes.

The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The Northern M Dwarfs -Bandstrengths and Kinematics

view Abstract Citations (564) References (69) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The Northern M Dwarfs -Bandstrengths and Kinematics Reid, I. Neill ; Hawley, Suzanne L. ; Gizis, John E. Abstract The Third Catalogue of Nearby Stars (Gliese & Jahreiss Preliminary Version of the third Catalogue of Nearby Stars, 1991) includes over 1850 stars which lie north of δ 30° and are either identified as spectral type M, or are unclassified but with an absolute visual magnitude estimate MV>+8.O. Although there is no uniformity in selection criteria, and many of the stars lack basic data (radial velocities, spectral types, accurate photometry), the observational properties of these stars underlie most estimates of the fundamental characteristics of the Galactic Disk. We have obtained optical spectroscopy of 1746 of the 1876 stars-the remaining 130 are binary companions of brighter stars and inaccessible to our observations. These spectra allow us, first, to exclude 61 stars as either degenerates or as misclassified earlier-type (B - K) stars lying beyond the 25 pc limit; to establish radial velocities accurate to ±10 km s-1 for all stars confirmed as late-type dwarfs; to determine spectral types and absolute magnitudes from the TiO bandstrength, allowing more accurate distance estimates for stars with inaccurate (or no) trigonometric parallax measurements; and to identify stars with Ha emission (chromospherically active stars) and with strong CaH absorption (perhaps including some metal-poor disk subdwarfs). We have determined the nearby-star luminosity function from complete samples derived by applying both the distance limits defined by Wielen (1974) and by using limits derived from our own analysis. In both cases, we find good agreement with Wielen's results to MV ∼+11, but lower densities at the maximum (MV∼+12). The latter analysis results in a luminosity function, ΦCNS, which closely matches photometric parallax analyses for MV<+11 and MV>+14 -- we do not recover the apparent excess of low-luminosity stars inferred from analysis of the 5 pc sample. However, ΦCNS does lie below Φphot at the peak (MV∼12), and we suggest that this offset is caused by the inclusion of unrecognized binaries in the photometric surveys. We have also reanalyzed the local stellar kinematics using the complete sample and find that the velocity distributions show significant departures from single Gaussian velocity dispersions. Publication: The Astronomical Journal Pub Date: October 1995 DOI: 10.1086/117655 Bibcode: 1995AJ....110.1838R Keywords: STARS: FUNDAMENTAL PARAMETERS; SURVEYS; STARS: PECULIAR; STARS: LUMINOSITY FUNCTION full text sources ADS | data products SIMBAD (1848) CDS (2) Related Materials (2) Catalog: 1997yCat.3198....0R Part 2: 1996AJ....112.2799H

Relation between the growth of loudness and high-frequency excitation.

To test the conjecture that cochlear impairment and a masking noise in normal ears produce analogous effects on the growth of loudness, loudness was measured for 21 listeners, all with bilateral symmetrical high-frequency cochlear losses. Beyond the normal-hearing region, thresholds increased by 30-49 dB/octave for 10 listeners in group I and by 51-71 + dB/octave for 11 listeners in group II. Measured by absolute magnitude estimation and production at two frequencies where thresholds were normal, the dynamic range over which loudness grows was not altered by the adjacent hearing loss. This was not true however, for the slope. Whereas the overall shape and slope of the loudness functions were essentially the same for group I, the mid-to-high level slope for group II was noticeably flatter for a tone at the cutoff frequency than for a lower-frequency tone. In contrast, markedly steeper loudness functions, characteristic of loudness recruitment, were obtained for both groups at a frequency in the region of impaired hearing. The reduced rate of loudness growth observed in the region of normal hearing for listeners with steep low-pass losses, like the reduction usually found for a tone masked by an adjacent high-frequency noise, is ascribed to the tone's restricted excitation pattern. These results indicate that high-frequency auditory cues are effectively eliminated by a steeply sloping high-frequency hearing loss just as they are eliminated by the addition of an external noise.

The shape of the vibrotactile loudness function: the effect of stimulus repetition and skin-contactor coupling.

In the psychophysical literature describing the relationships between physical and psychological magnitudes, as physical intensity increases, perceived intensity often grows much faster near threshold than at higher levels. In this laboratory, however, the loudness curve for sinusoidal vibrotactile stimuli was best fit by a single-limbed function rather than by the expected two-limbed function. In the present study, we measured the growth of vibrotactile loudness of 250-Hz sinusoidal stimuli by the method of absolute magnitude estimation to explore the source of the one- versus two-limbed discrepancy. The number of times that the stimulus was presented was varied, as well as whether the stimulator contacted the skin with constant force or constant penetration. Neither of these manipulations affected the shape of the loudness function consistently. Number of repetitions influenced the shapes of the magnitude estimation functions, but only for a few individuals. Skin-contactor coupling did not affect the shapes of the functions, although the absolute level (vibrotactile loudness) was consistently greater for constant indentation.

Dichotic loudness of tone-noise complexes

The overall loudness of dichotic sounds composed of a tone to one ear and a low- or high-pass noise to the other ear, was determined by absolute magnitude estimation for groups of ten listeners with normal hearing. Within a 30-dB range above 70 dB, the sound pressure levels (SPL) of the tone and noise were independently varied in 5-dB steps. Results showed that total loudness was generally a nonmonotonic function of the overall SPL of the complex. Moreover, the obtained loudness functions were steeper than those typically measured separately for pure tones and broadband noise. Instead of the standard slope of 0.60 (log loudness as a function of SPL), overall slopes ranged from 0.75 to 0.86. For a given complex, the rate of loudness growth was dependent on the relative loudness of the component stimuli. Loudness increased more rapidly with overall SPL when the tone and noise were nearly equal in loudness than when they were markedly unequal. In contrast to earlier results for the same stimuli presented together binaurally [R. P. Hellman, J. Acoust. Soc. Am. 75, 209–218 (1984)], the current findings suggest that dichotic loudness is mainly based on the summed output from each ear without the effects of intraaural interactions. [Work supported by NIH.]

Context effects in judging taste intensity: a comparison of variable line and category rating methods.

The effect of stimulus range and stimulus spacing was examined when subjects registered the perceived intensity of sweet liquids using either a matching procedure (Experiment 1) or category rating (Experiment 2). The matching procedure is conceptually similar to absolute magnitude estimation, whereby subjects match their impression of number size to their impression of the subjective magnitude of a stimulus. In Experiment 1, subjects matched their impression of the stimulus to their impression of the magnitude of the length of a continuously variable line under their control. In Experiment 2, subjects rated perceived sweetness on a vertical 13-point scale with five equally spaced verbal labels. In both experiments, three sets of four sucrose concentrations were employed. In two of these sets, a set of weaker solutions and a set of stronger solutions, concentrations were separated by 0.25 log units. In a third set, which spanned the range of concentrations used in the other two sets (0.87 to 27.36% w/v), solutions were separated by 0.5 log units. An examination of both individual and group data showed the matching procedure to be less susceptible to a range bias than the rating procedure. In particular, a single intensity function accommodated data from individual ranges better when the matching procedure was used than when the rating procedure was used. No effect of stimulus spacing was evident in the data from either procedure.

The estimation of absolute magnitude and distance from the Tully-Fisher relation

Several aspects of using the Tully-Fisher relation to estimate magnitudes and distances are examined, in particular the effect of the luminosity function on the theoretical estimation of regression parameters, unbiased estimates of absolute magnitude, and the Malmquist bias of field galaxies. With respect to observations of clusters of galaxies, if the limiting absolute magnitude is close to or brighter than the Schecter magnitude M * there is a significant difference in the slopes and offsets of the regression of magnitude upon log (line width) as calculated from Gaussian and Schecter functions