scholarly journals New Radial Velocities and the Barnes-Evans Method

1993 ◽  
Vol 139 ◽  
pp. 386-386
Author(s):  
Robert Hindsley ◽  
R.A. Bell
Keyword(s):  
Absolute Magnitude ◽  
Radial Velocities ◽  
The Absolute ◽  
Absolute Magnitudes

AbstractNew radial velocities by Butler are used to recalculate the absolute magnitudes of Eta Aquilae and X Cygni using the Barnes-Evans method. The new velocities have little effect on the result for Eta Aquilae, but the absolute magnitude of X Cygni is found to be 0.40 mag fainter than that obtained earlier.

scholarly journals The Absolute Magnitude of the Early-Type MK Standards From Hipparcos Parallaxes

1998 ◽  
Vol 11 (1) ◽  
pp. 566-566
Author(s):  
C. Jaschek ◽  
A.E. Gómez
Keyword(s):  
Main Sequence ◽  
Rotational Velocity ◽  
Wide Band ◽  
Absolute Magnitude ◽  
Interstellar Extinction ◽  
Early Type ◽  
Class V ◽  
Luminosity Class ◽  
The Absolute ◽  
Absolute Magnitudes

We have analysed the standards of the MK system in the B0-F5 spectral region with the help of Hipparcos parallaxes, using only stars for which the error on the absolute magnitude is ≤ 0.3 mag. The sample stars (about one hundred) were scrutinized for companions and for interstellar extinction. We find that the main sequence is a wide band and that, although in general giants and dwarfs have different absolute magnitudes, the separation between luminosity class V and III is not clear. We conclude that there is no strict relation between luminosity class and absolute magnitude. The relation is only a statistical one and has a large intrinsic dispersion. We have analysed similarly the system of standards defined by Garrison and Gray (1994) separating low and high rotational velocity standards. We find similar effects as in the original MK system.

scholarly journals The Luminosity Determination

1995 ◽  
Vol 10 ◽  
pp. 399-402
Author(s):  
A.E. Gómez ◽  
C. Turon
Keyword(s):  
Main Sequence ◽  
Small Volume ◽  
Absolute Magnitude ◽  
Fitting Procedure ◽  
Trigonometric Parallaxes ◽  
The Mean ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Kinematical Data ◽  
Magnitude Determination

The Hertzprung-Russel (HR) diagram luminosity calibration relies basically on three kinds of data: trigonometric parallaxes, kinematical data (proper motions and radial velocities) and cluster distances obtained by the zero-age main sequence fitting procedure. The most fundamental method to calculate the absolute magnitude is the use of trigonometric parallaxes, but up to now, accurate data only exist for stars contained in a small volume around the sun. Individual absolute magnitudes are obtained using trigonometric parallaxes or photometric and spectroscopic calibrations. In these calibrations the accuracy on the absolute magnitude determination ranges from ±0.m2 in the main sequence to ±0m5 in the giant branch. On the other hand, trigonometric parallaxes, kinematical data or cluster distances have been used to make statistical calibrations of the absolute magnitude. The standard error on the mean absolute magnitude calibrations ranges from ±0m3 to ±0m6 on the mean sequence, from ±0m5 to ±0m7 on thegiant branch and is of about 1mfor supergiants.Future improvements in the absolute magnitude determination will depend on the improvement of the basic data from the ground and space. A brief overview of the new available data is presented. In particular, the analysis of the first 30 months data of the Hipparcos mission (H30) (from the 37 months data of the whole mission) allows to perform a statistical evaluation of the improvements expected in the luminosity determination.

scholarly journals The Parallaxes of U Gem Variables

1979 ◽  
Vol 53 ◽  
pp. 494-494
Author(s):  
Karl W. Kamper
Keyword(s):  
Confidence Level ◽  
Absolute Magnitude ◽  
Weighted Mean ◽  
Quiescent Phase ◽  
A Value ◽  
The Mean ◽  
The Absolute ◽  
Absolute Magnitudes

An Allegheny parallax series of SS Cyg, consisting of 52 exposures obtained on 15 nights, was recently measured on the PDS microphotometer at the David Dunlap Observatory, and a value of (m.e.) derived for the absolute parallax. This is close to the mean of the two previous discordant measures for this star given in the table below. The weighted mean of the three determinations implies that the absolute magnitude, at quiescent phase, of the star is between 7.0 and 9.0 formally at a 90% confidence level. Recent parallax determinations made at Lick by Vasilevskls et al. (1975) for three other stars, listed below along with the Mt. Wilson value for U Gem, imply even fainter absolute magnitudes.

scholarly journals The Absolute Magnitudes of RR Lyrae Stars and the Age of the Galaxy

1989 ◽  
Vol 111 ◽  
pp. 121-140
Author(s):  
Allan Sandage
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
Cluster System ◽  
Apparent Magnitude ◽  
Rr Lyrae ◽  
Globular Cluster System ◽  
The Absolute ◽  
Absolute Magnitudes

AbstractIt is shown that the intrinsic spread in the absolute magnitudes of the RR Lyrae variables in a given globular cluster can reach 0.5 magnitudes at a given period or at a given color, due to luminosity evolution away from the zero age horizontal (ZAHB). The size of this intrinsic luminosity spread is largest in clusters of the highest metallicity.The absolute magnitude of the ZAHB itself also differs from cluster to cluster as a function of metallicity, being brightest in clusters of the lowest metallicity. Three independent methods of calibrating the ZAHB RR Lyrae luminosities each show a strong variation of MV(RR) with [Fe/H]. The pulsation equation of P<ρ>0.5 = Q(M,Te, L) used with the observed periods, temperatures, and masses of field and of cluster RR Lyraes gives the very steep luminosity-metallicity dependence of dMv(RR)/d[Fe/H] = 0.42. Main sequence fitting of the color-magnitude diagrams of clusters which have modern main-sequence photometry gives a confirming steep slope of 0.39. A summary of Baade-Wesselink MV(RR) values for field stars determined in four independent recent studies also shows a luminosity-metallicity dependence, but less steep with a slope of dMV(RR)/d[Fe/H] = 0.21.Observations show that the magnitude difference between the main sequence turn-off point and the ZAHB in a number of well observed globular clusters is independent of [Fe/H], and has a stable value of dV = 3.54 with a disperion of only 0.1 magnitudes. Using this fact, the absolute magnitude of the main sequence turn-off is determined in any given globular cluster from the observed apparent magnitude of the ZAHB by adopting any particular MV(RR) = f([Fe/H]) calibration.Ages of the clusters are shown to vary with [Fe/H] by amounts that depend upon the slopes of the MV(RR) = f([Fe/H]) calibrations. The calibrations show that there would be a steep dependence of the age on [Fe/H] if MV(RR) does not depend on [Fe/H]. No dependence of age on metallicity exists if the RR Lyrae luminosities depend on [Fe/H] as dMV(RR)/d[Fe/H] = 0.37. If Oxygen is not enhanced as [Fe/H] decreases, the absolute average age of the globular cluster system is 16 Gyr, independent of [Fe/H], using the steep MV(RR)/[Fe/H] calibration that is favored. If Oxygen is enhanced by [O/Fe] = – 0.14 [Fe/H] + 0.40 for [Fe/H] < –1.0, as suggested from the observations of field subdwarfs, then the age of the globular cluster system decreases to 13 Gyr, again independent of [Fe/H], if the RR Lyrae ZAHB luminosities have a metallicity dependence of dMV(RR)/d[Fe/H] = 0.37.

scholarly journals TAMS companions of classical cepheids

1994 ◽  
Vol 162 ◽  
pp. 51-52 ◽  
Author(s):  
Nancy Remage Evans
Keyword(s):  
Absolute Magnitude ◽  
Low Resolution ◽  
Classical Cepheids ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Magnitude Difference

IUE low resolution spectra are an excellent way to determine the temperatures of the hot companions of binary Cepheids. The spectral types of the companions are derived by comparing the spectra with the spectra of standard stars. Absolute magnitudes are calculated from the magnitude difference between the two stars and the absolute magnitude of the Cepheid. In this study, eight binaries containing a Cepheid and a hot companion evolved beyond the ZAMS are discussed.

scholarly journals Revised Empirical Formulae for the Absolute Magnitudes and Intrinsic Colors of RRab Stars

2000 ◽  
Vol 176 ◽  
pp. 268-268 ◽  
Author(s):  
A. R. Walker ◽  
G. Kovács
Keyword(s):  
Light Curve ◽  
Absolute Magnitude ◽  
Large Datasets ◽  
Light Curves ◽  
Linear Functions ◽  
Physical Parameters ◽  
Fourier Amplitude ◽  
Color Indices ◽  
The Absolute ◽  
Absolute Magnitudes

AbstractThe relations between the physical parameters of the RRab stars and the Fourier parameters of their light curves have been reanalyzed on the basis of new CCD data. We show that the absolute magnitude MV and the dereddened color indices (B − V)0, (V − I)0 are linear functions of the period and of the A1 Fourier amplitude of the V light curve. Due to the large datasets, we are able to test the consistency of the formulae on independent sets. The present results are in good or fair agreement with our previous studies, despite the fewer number of significant parameters entering in the revised formulae.

scholarly journals Absolute Magnitude Calibration for Dwarfs Based on the Colour–Magnitude Diagrams of Galactic Clusters

2014 ◽  
Vol 31 ◽  
Author(s):  
S. Karaali ◽  
E. Yaz Gökçe ◽  
S. Bilir ◽  
S. Tunçel Güçtekin
Keyword(s):  
Standard Deviation ◽  
Absolute Magnitude ◽  
Derived Relations ◽  
Two Systems ◽  
Galactic Clusters ◽  
Solar Metallicity ◽  
The Mean ◽  
The Absolute ◽  
Absolute Magnitudes

AbstractWe present two absolute magnitude calibrations for dwarfs based on colour–magnitude diagrams of Galactic clusters. The combination of the Mg absolute magnitudes of the dwarf fiducial sequences of the clusters M92, M13, M5, NGC 2420, M67, and NGC 6791 with the corresponding metallicities provides absolute magnitude calibration for a given (g − r)0 colour. The calibration is defined in the colour interval 0.25 ≤ (g − r)0 ≤ 1.25 mag and it covers the metallicity interval − 2.15 ≤ [Fe/H] ≤ +0.37 dex. The absolute magnitude residuals obtained by the application of the procedure to another set of Galactic clusters lie in the interval − 0.15 ≤ ΔMg ≤ +0.12 mag. The mean and standard deviation of the residuals are < ΔMg > = − 0.002 and σ = 0.065 mag, respectively. The calibration of the MJ absolute magnitude in terms of metallicity is carried out by using the fiducial sequences of the clusters M92, M13, 47 Tuc, NGC 2158, and NGC 6791. It is defined in the colour interval 0.90 ≤ (V − J)0 ≤ 1.75 mag and it covers the same metallicity interval of the Mg calibration. The absolute magnitude residuals obtained by the application of the procedure to the cluster M5 ([Fe/H] = −1.40 dex) and 46 solar metallicity, − 0.45 ≤ [Fe/H] ≤ +0.35 dex, field stars lie in the interval − 0.29 and + 0.35 mag. However, the range of 87% of them is rather shorter, − 0.20 ≤ ΔMJ ≤ +0.20 mag. The mean and standard deviation of all residuals are < ΔMJ > =0.05 and σ = 0.13 mag, respectively. The derived relations are applicable to stars older than 4 Gyr for the Mg calibration, and older than 2 Gyr for the MJ calibration. The cited limits are the ages of the youngest calibration clusters in the two systems.

scholarly journals A New Procedure for the Photometric Parallax Estimation

2003 ◽  
Vol 20 (3) ◽  
pp. 270-278 ◽  
Author(s):  
S. Karaali ◽  
Y. Karataş ◽  
S. Bilir ◽  
S. G. Ak ◽  
E. Hamzaoğlu
Keyword(s):  
Main Sequence ◽  
Large Range ◽  
Absolute Magnitude ◽  
Colour Index ◽  
Ultraviolet Excess ◽  
Magnitude Diagram ◽  
Single Colour ◽  
The Mean ◽  
The Absolute ◽  
Absolute Magnitudes

AbstractWe present a new procedure for photometric parallax estimation. The data for 1236 stars provide calibrations between the absolute magnitude offset from the Hyades main-sequence and the ultraviolet-excess for eight different (B–V)0 colour-index intervals, (0.3 0.4), (0.4 0.5), (0.5 0.6), (0.6 0.7), (0.7 0.8), (0.8 0.9), (0.9 1.0) and (1.0 1.1). The mean difference between the original and estimated absolute magnitudes and the corresponding standard deviation are rather small, +0.0002 and ±0.0613 mag. The procedure has been adapted to the Sloan photometry by means of colour equations and applied to a set of artificial stars with different metallicities. The comparison of the absolute magnitudes estimated by the new procedure and the canonical one indicates that a single colour–magnitude diagram does not supply reliable absolute magnitudes for stars with large range of metallicity.

scholarly journals A New Method for Evaluating the Hubble Constant

1983 ◽  
Vol 6 ◽  
pp. 288-288 ◽  
Author(s):  
Vera C. Rubin ◽  
Norbert Thonnard
Keyword(s):  
Rotation Curve ◽  
Optical Rotation ◽  
Hubble Constant ◽  
Absolute Magnitude ◽  
New Method ◽  
Rotation Curves ◽  
The Absolute ◽  
Absolute Magnitudes

We have devised a procedure for evaluating the absolute magnitudes of galaxies from their optical rotation curves, as an extention of the conventional Fisher-Tully method. We describe here how this method can be employed to evaluate the Hubble constant. From observations of 23 Sb field galaxies with luminosities ranging from –19.5 to –23.0 (adopting H=50 km s–1 Mpc–1), we have produced synthetic rotation curves showing the systematic progression toward increasing velocity with increasing luminosity within a given Hubble type. (See Thonnard and Rubin, Carnegie Yrbk 80, p. 551 for details of producing such a set of curves). By matching even a small portion of a rotation curve with these curves, the absolute magnitude of an Sb galaxy can be estimated to about ±0.5 mag. This magnitude, of course, is based on an assumed value for H.

scholarly journals A UV and optical study of 18 old novae with Gaia DR2 distances: mass accretion rates, physical parameters, and MMRD

2019 ◽  
Vol 622 ◽  
pp. A186 ◽  
Author(s):  
Pierluigi Selvelli ◽  
Roberto Gilmozzi
Keyword(s):  
Accretion Rate ◽  
Functional Dependence ◽  
Absolute Magnitude ◽  
Physical Parameters ◽  
Maximum Magnitude ◽  
Mass Accretion Rate ◽  
Accretion Rates ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
The Individual

We combine the results of our earlier study of the UV characteristics of 18 classical novae (CNe) with data from the literature and with the recent precise distance determinations from the Gaia satellite to investigate the statistical properties of old novae. All final parameters for the sample include a detailed treatment of the errors and their propagation. The physical properties reported here include the absolute magnitudes at maximum and minimum, a new maximum magnitude versus rate of decline (MMRD) relation, and the inclination-corrected 1100–6000 Å accretion disk luminosity. Most importantly, these data have allowed us to derive a homogenous set of accretion rates in quiescence for the 18 novae. All novae in the sample were super-Eddington during outburst, with an average absolute magnitude at maximum of −7.5 ± 1.0. The average absolute magnitude at minimum corrected for inclination is 3.9 ± 1.0. The median mass accretion rate is log Ṁ1 M⊙ = −8.52 (using 1 M⊙ as WD mass for all novae) or log ṀMWD = −8.48 (using the individual WD masses). These values are lower than those assumed in studies of CNe evolution and appear to attenuate the need for a hibernation hypothesis to interpret the nova phenomenon. We identified a number of correlations among the physical parameters of the quiescent and eruptive phases, some already known but others new and even surprising. Several quantities correlate with the speed class t3 including, unexpectedly, the mass accretion rate (Ṁ). This rate correlates also with the absolute magnitude at minimum corrected for inclination, and with the outburst amplitude, providing new and simple ways to estimate Ṁ through its functional dependence on (more) easily observed quantities. There is no correlation between Ṁ and the orbital period.

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