scholarly journals Absolute Magnitude Calibration for Giants Based on the Colour–Magnitude Diagrams of Galactic Clusters. II. Calibration with SDSS

2013 ◽  
Vol 30 ◽  
Author(s):  
S. Karaali ◽  
S. Bilir ◽  
E. Yaz Gökçe
Keyword(s):  
Standard Deviation ◽  
Magnitude Estimation ◽  
Absolute Magnitude ◽  
Red Giants ◽  
Derived Relations ◽  
Galactic Clusters ◽  
The Mean ◽  
The Absolute ◽  
Red Giant ◽  
Absolute Magnitudes

AbstractWe present an absolute magnitude calibration for red giants with the colour–magnitude diagrams of six Galactic clusters with different metallicities, i.e. M92, M13, M3, M71, NGC 6791, and NGC 2158. The combination of the absolute magnitudes of the red giant sequences with the corresponding metallicities provides calibration for absolute magnitude estimation for red giants for a given (g − r)0 colour. The calibration is defined in the colour interval 0.45 ≤ (g − r)0 ≤ 1.30 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 −0.28 < ΔM ≤ +0.43 mag. However, the range of 94% of the residuals is shorter, −0.1 < ΔM ≤ +0.4 mag. The mean and the standard deviation of (all) residuals are 0.169 and 0.140 mag, respectively. The derived relations are applicable to stars older than 2 Gyr, the age of the youngest calibrating cluster.

scholarly journals Absolute Magnitude Calibration for Red Giants Based on the Colour–Magnitude Diagrams of Galactic Clusters. III. Calibration with 2MASS

2013 ◽  
Vol 30 ◽  
Author(s):  
S. Karaali ◽  
S. Bilir ◽  
E. Yaz Gökçe
Keyword(s):  
Magnitude Estimation ◽  
Absolute Magnitude ◽  
Red Giants ◽  
Derived Relations ◽  
Galactic Clusters ◽  
The Absolute ◽  
Standard Deviations ◽  
Red Giant ◽  
Absolute Magnitudes

AbstractWe present two absolute magnitude calibrations, MJ and MKs, for red giants with the colour–magnitude diagrams of five Galactic clusters with different metallicities, i.e. M92, M13, M71, M67, and NGC 6791. The combination of the absolute magnitudes of the red giant sequences with the corresponding metallicities provides calibration for absolute magnitude estimation for red giants for a given colour. The calibrations for MJ and MKs are defined in the colour intervals 1.3≤(V−J)0≤2.8 and 1.75≤(V−Ks)0≤3.80 mag, respectively, and they cover 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 intervals −0.08<ΔMJ≤+0.34 and -0.10< Δ MKs≤ +0.27 mag for MJ and MKs, respectively. The means and standard deviations of the residuals are 〈ΔMJ〉=0.137 and σMJ=0.080, and $〈 Δ MKs〉 =0.109 and σMKs=0.123 mag. The derived relations are applicable to stars older than 4 Gyr, the age of the youngest calibrating cluster.

scholarly journals Absolute-Magnitude Calibration for Red Giants Based on Colour–Magnitude Diagrams of Galactic Clusters: I. Calibration in V and B–V

2012 ◽  
Vol 29 (4) ◽  
pp. 509-522 ◽  
Author(s):  
S. Karaali ◽  
S. Bilir ◽  
E. Yaz Gökçe
Keyword(s):  
Standard Deviation ◽  
Magnitude Estimation ◽  
Absolute Magnitude ◽  
Red Giants ◽  
Degree Polynomial ◽  
Derived Relations ◽  
Galactic Clusters ◽  
The Mean ◽  
The Absolute ◽  
Effect Of Age

AbstractWe present an absolute-magnitude calibration for red giants using the colour–magnitude diagrams of six Galactic clusters with different metallicities: M92, M13, M5, 47 Tuc, M67 and NGC 6791. The combination of the absolute magnitude offset from the fiducial of giant sequence of the cluster M5 with the corresponding metallicity offset provides a calibration estimation for the absolute magnitude of red giants for a given (B – V)0 colour. The calibration is defined in the colour interval 0.75 ≤ (B – V)0 ≤ 1.50 mag and it covers the metal licity interval −2.15 > [Fe/H]≤+0.37 dex. 91% of the absolute magnitude residuals obtained by the application of the procedure to another set of Galactic clusters lie in the interval −0.40 < ΔM≤+0.40 mag. The mean and the standard deviation of the residuals are 0.05 and 0.19 mag, respectively. We fitted the absolute magnitude also to metallicity and age for a limited sub-sample of (B – V)0 colour, just to test the effect of age in absolute-magnitude calibration. Comparison of the mean and the standard deviation of the residuals evaluated by this procedure with the corresponding ones provided by the procedure where the absolute magnitude fitted to a third degree polynomial of metallicity show that the age parameter may be omitted in absolute magnitude estimation of red giants. The derived relations are applicable to stars older than 4 Gyr, the age of the youngest calibrating cluster.

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 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 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 Empirical photometric calibration of the Gaia red clump: Colours, effective temperature, and absolute magnitude

2018 ◽  
Vol 609 ◽  
pp. A116 ◽  
Author(s):  
L. Ruiz-Dern ◽  
C. Babusiaux ◽  
F. Arenou ◽  
C. Turon ◽  
R. Lallement
Keyword(s):  
Effective Temperature ◽  
Absolute Magnitude ◽  
Interstellar Extinction ◽  
Red Giants ◽  
Photometric Calibration ◽  
Empirical Calibration ◽  
Data Release ◽  
Red Clump ◽  
Red Giant ◽  
Absolute Magnitudes

Context. Gaia Data Release 1 allows the recalibration of standard candles such as the red clump stars. To use those stars, they first need to be accurately characterised. In particular, colours are needed to derive interstellar extinction. As no filter is available for the first Gaia data release and to avoid the atmosphere model mismatch, an empirical calibration is unavoidable. Aims. The purpose of this work is to provide the first complete and robust photometric empirical calibration of the Gaia red clump stars of the solar neighbourhood through colour–colour, effective temperature–colour, and absolute magnitude–colour relations from the Gaia, Johnson, 2MASS, Hipparcos, Tycho-2, APASS-SLOAN, and WISE photometric systems, and the APOGEE DR13 spectroscopic temperatures. Methods. We used a 3D extinction map to select low reddening red giants. To calibrate the colour–colour and the effective temperature–colour relations, we developed a MCMC method that accounts for all variable uncertainties and selects the best model for each photometric relation. We estimated the red clump absolute magnitude through the mode of a kernel-based distribution function. Results. We provide 20 colour versus G−Ks relations and the first Teff versus G−Ks calibration. We obtained the red clump absolute magnitudes for 15 photometric bands with, in particular, MKs = (−1.606 ± 0.009) and MG = (0.495 ± 0.009) + (1.121 ± 0.128)(G−Ks−2.1). We present a dereddened Gaia-TGAS HR diagram and use the calibrations to compare its red clump and its red giant branch bump with Padova isochrones.

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 Core rotation braking on the red giant branch for various mass ranges

2018 ◽  
Vol 616 ◽  
pp. A24 ◽  
Author(s):  
C Gehan ◽  
B. Mosser ◽  
E. Michel ◽  
R. Samadi ◽  
T. Kallinger
Keyword(s):  
Angular Momentum ◽  
Red Giants ◽  
Regular Pattern ◽  
Convective Envelope ◽  
Large Sample ◽  
The Mean ◽  
Mixed Modes ◽  
Red Giant ◽  
Core Rotation ◽  
Dipole Gravity

Context. Asteroseismology allows us to probe stellar interiors. In the case of red giant stars, conditions in the stellar interior are such as to allow for the existence of mixed modes, consisting in a coupling between gravity waves in the radiative interior and pressure waves in the convective envelope. Mixed modes can thus be used to probe the physical conditions in red giant cores. However, we still need to identify the physical mechanisms that transport angular momentum inside red giants, leading to the slow-down observed for red giant core rotation. Thus large-scale measurements of red giant core rotation are of prime importance to obtain tighter constraints on the efficiency of the internal angular momentum transport, and to study how this efficiency changes with stellar parameters. Aims. This work aims at identifying the components of the rotational multiplets for dipole mixed modes in a large number of red giant oscillation spectra observed by Kepler. Such identification provides us with a direct measurement of the red giant mean core rotation. Methods. We compute stretched spectra that mimic the regular pattern of pure dipole gravity modes. Mixed modes with the same azimuthal order are expected to be almost equally spaced in stretched period, with a spacing equal to the pure dipole gravity mode period spacing. The departure from this regular pattern allows us to disentangle the various rotational components and therefore to determine the mean core rotation rates of red giants. Results. We automatically identify the rotational multiplet components of 1183 stars on the red giant branch with a success rate of 69% with respect to our initial sample. As no information on the internal rotation can be deduced for stars seen pole-on, we obtain mean core rotation measurements for 875 red giant branch stars. This large sample includes stars with a mass as large as 2.5 M⊙, allowing us to test the dependence of the core slow-down rate on the stellar mass. Conclusions. Disentangling rotational splittings from mixed modes is now possible in an automated way for stars on the red giant branch, even for the most complicated cases, where the rotational splittings exceed half the mixed-mode spacing. This work on a large sample allows us to refine previous measurements of the evolution of the mean core rotation on the red giant branch. Rather than a slight slow-down, our results suggest rotation is constant along the red giant branch, with values independent of the mass.

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.

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