scholarly journals Observed Relations Between Physical Properties and MK Classification as Functions of Metal Abundance for F5-K4 Stars

1976 ◽  
Vol 72 ◽  
pp. 75-78
Author(s):  
M. Grenon
Keyword(s):  
Physical Properties ◽  
Spectral Range ◽  
Spectral Type ◽  
Photometric System ◽  
Luminosity Class ◽  
Empirical Relations ◽  
Metal Abundance ◽  
Systematic Effects ◽  
The Absolute ◽  
Absolute Magnitudes

The Geneva photometric system has been calibrated in terms of [M/H], θeff, Mv in the spectral range F5 to K4. As the spectral type is a datum generally available, we derive empirical relations showing the coupling of θeff and [M/H] at given spectral type and luminosity class. Similar relations are offered for the absolute magnitudes and provide a more accurate means for deriving spectroscopic parallaxes. Systematic effects on the estimation of the luminosity class are also shown.

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 Hipparcos Positions of B/Be Stars on the HR Diagram

2000 ◽  
Vol 175 ◽  
pp. 117-128 ◽  
Author(s):  
Danielle Briot ◽  
Noel Robichon
Keyword(s):  
Spectral Type ◽  
Rotational Velocity ◽  
Absolute Magnitude ◽  
Be Stars ◽  
Class V ◽  
B Stars ◽  
Luminosity Class ◽  
The Mean ◽  
Absolute Magnitudes ◽  
Hipparcos Parallax

AbstractAbsolute magnitudes of Be and B stars are computed for each spectral type and luminosity class V and IV, using the Hipparcos parallax measurements. Some simulations have been carried out in order to estimate the effects which could bias the mean absolute magnitude calculations. As a result, only stars with σπ/π < 15% have been used. A first result is that B stars are fainter than previous estimations by about 0.5 magnitude on average. We then observe that on average Be stars are brighter than B stars of the same spectral type and this over-luminosity increases with the spectral type. A possible interpretation is proposed based on the fact that the rotational velocity of the late Be stars is near the critical rotational velocity.

scholarly journals The Absolute Magnitudes of the Nearby Stars: Calibrations of mean luminosity relations

1985 ◽  
Vol 111 ◽  
pp. 369-372
Author(s):  
W. Gliese ◽  
H. Jahreiss
Keyword(s):  
Spectral Type ◽  
Trigonometric Parallaxes ◽  
Preliminary Version ◽  
Nearby Stars ◽  
The Absolute ◽  
Absolute Magnitudes

The nearby stars are most favored for determining precise absolute magnitudes and for calibrating spectral-type, luminosity relations and color, luminosity relations. To demonstrate the main problems we discuss the (Mv,B-V) relation since (B-V) data are available for most of our candidates. At Yale Observatory van Altena is compiling a new catalog of trigonometric parallaxes. We feel deeply indebted to van Altena for making available to us a preliminary version of this catalog.

scholarly journals The Zero-Point of the Cepheid Luminosity Scale from a Calibration of the Luminosities of Early-Type Stars

1985 ◽  
Vol 82 ◽  
pp. 201-202
Author(s):  
L. A. Balona ◽  
R. R. Shobbrook
Keyword(s):  
Zero Point ◽  
Photometric System ◽  
Early Type ◽  
Early Type Stars ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Zero Points

AbstractA new calibration of the absolute magnitudes of early-type stars in terms of the (β, c0) photometric system is used to establish the distance moduli of clusters containing Cepheids. The zero points of the period – luminosity and period – luminosity – colour relations are calculated and compared to previous determinations.

scholarly journals Long-term photometric monitoring of the dwarf planet (136472) Makemake

2019 ◽  
Vol 625 ◽  
pp. A46 ◽  
Author(s):  
T. A. Hromakina ◽  
I. N. Belskaya ◽  
Yu. N. Krugly ◽  
V. G. Shevchenko ◽  
J. L. Ortiz ◽  
...  
Keyword(s):  
Broad Band ◽  
Spherical Shape ◽  
Absolute Magnitude ◽  
Photometric System ◽  
Small Peak ◽  
Photometric Observations ◽  
The Absolute ◽  
Photometric Monitoring ◽  
Absolute Magnitudes

Aims. We studied the rotational properties of the dwarf planet Makemake. Methods. The photometric observations were carried out at different telescopes between 2006 and 2017. Most of the measurements were acquired in BVRI broad-band filters of a standard Johnson-Cousins photometric system. Results. We found that Makemake rotates more slowly than was previously reported. A possible lightcurve asymmetry suggests a double-peaked period of P = 22.8266 ± 0.0001 h. A small peak-to-peak lightcurve amplitude in R-filter A = 0.032 ± 0.005 mag implies an almost spherical shape or near pole-on orientation. We also measured BVRI colours and the R-filter phase-angle slope and revised the absolute magnitudes. The absolute magnitude of Makemake has remained unchanged since its discovery in 2005. No direct evidence of a newly discovered satellite was found in our photometric data; however, we discuss the possible existence of another larger satellite.

scholarly journals Shell Stars in the Geneva Photometric System

1987 ◽  
Vol 92 ◽  
pp. 523-525
Author(s):  
B. Hauck
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Photometric System ◽  
Be Stars ◽  
Main Sequence Stars ◽  
Class V ◽  
Luminosity Class ◽  
Be Star ◽  
Shell Star

L. Divan (1979) showed that the Balmer jump is greater in a Be-shell star than in a star of same spectral type and we will consider if this property is also present in A and F-shell stars by studying their data in the Geneva photometric system. Two photometric parameters in this system are correlated with the Balmer jump: d=(U-Bl) -1.430 (B1-B2) and Δ=(U-B2) -0.832 (B2-G). In addition to the Balmer jump, Δ is also sensitive to blanketing. Both parameters are reddening free. A study of the Be stars of luminosity class V or IV classified by Slettebak (1982) shows that, in a d vs Δ diagram, they are in the area of main sequence stars or a little above, while the majority of Be-shell stars are above the Be star sequence. Pleione is well known for presenting a Be phase followed by a shell phase.

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 ABSOLUTE MAGNITUDES OF TYPE Ia SUPERNOVAE IN THE ULTRAVIOLET

2010 ◽  
Vol 721 (2) ◽  
pp. 1608-1626 ◽  
Author(s):  
Peter J. Brown ◽  
Peter W. A. Roming ◽  
Peter Milne ◽  
Filomena Bufano ◽  
Robin Ciardullo ◽  
...  
Keyword(s):  
Type Ia Supernovae ◽  
Type Ia ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Ia Supernovae
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