The spectral-energy curves of subdwarfs

Johnson, H. L.; MacArthur, John W.; Mitchell, R. I.

doi:10.1086/149563

Cited by 47 publications

(30 citation statements)

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“…Sources for (b − y) and β are given in Table 14. The (R − I), (V − R), (V − I), and (V − K) colors are all in the Johnson system (Glass 1974;Johnson 1964;Johnson et al 1966Johnson et al , 1968. When only narrow-band (V − K n ) from Selby et al (1988) are available, they have been transformed to Johnson (V − K) using the relations provided by these same authors.…”

Section: Selection Of Photometry Irfm T Eff and [Fe/h] Datamentioning

confidence: 99%

A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun

Mello

Silva

et al. 2014

A&A

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Context. Solar twins and analogs are fundamental in the characterization of the Sun's place in the context of stellar measurements, as they are in understanding how typical the solar properties are in its neighborhood. They are also important for representing sunlight observable in the night sky for diverse photometric and spectroscopic tasks, besides being natural candidates for harboring planetary systems similar to ours and possibly even life-bearing environments. Aims. We report a photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun. Hipparcos absolute magnitudes and (B − V)Tycho colors were used to define a 2σ box around the solar values, where 133 stars were considered. Additional stars resembling the solar UBV colors in a broad sense, plus stars present in the lists of Hardorp, were also selected. All objects were ranked by a color-similarity index with respect to the Sun, defined by uvby and BV photometry. Methods. Moderately high-resolution, high signal-to-noise ratio spectra were used for a subsample of equatorial-southern stars to derive T eff , log g (both ionization and evolutionary), and spectroscopic [Fe/H] with average internal errors better than 50 K, 0.20 dex, and 0.08 dex, respectively. Ages and masses were estimated from theoretical HR diagrams. Results. The color-similarity index proved very successful, since none of the best solar-analog and twin candidates that were photometrically and spectroscopically found to be good solar matches differed from the Sun by more than 3σ in their colors. We identify and quantitatively rank many new excellent solar analogs, which are fit to represent the Sun in the night sky to varying degrees of accuracy and in a wide range of contexts. Some of them are faint enough (V Tycho ∼ 8.5) to be of interest for moderately large telescopes. We also identify two stars with near-UV spectra indistinguishable from the Sun's, although only HD 140690 also has atmospheric parameters matching the Sun's, besides a high degree of photometric fidelity. This object is proposed as a prime solar analog in both the UV and visible ranges, a rare object. We present five new "probable" solar twin stars, besides five new "possible" twins, the best candidates being HD 98649, HD 118598, HD 150248, and HD 164595. Masses and isochronal ages for the best solar twin candidates lie very close to the solar values within uncertainties, but chromospheric activity levels range somewhat. We propose that the solar twins be emphasized in the ongoing searches for extra-solar planets and SETI searches.

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Section: Selection Of Photometry Irfm T Eff and [Fe/h] Datamentioning

confidence: 99%

A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun

Mello

Silva

et al. 2014

A&A

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“…The two systems with G dwarf primaries have photometry in Johnson, MacArthur, & Mitchell (1968) that has been converted to the appropriate systems using calibrations in Leggett (1992). The only V photometry not available from these photometric studies or our own work, that of GJ 1081 AB, was taken from Gliese & Jahreiss (1991).…”

Section: Samplementioning

confidence: 99%

The Optical Mass‐Luminosity Relation at the End of the Main Sequence (0.08–0.20M_⊙)

Henry

Franz

Wasserman

et al. 1999

ApJ

176

198

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The empirical mass-luminosity relation at is presented for stars with masses 0.08È0.20 based M V M _ upon new observations made with Fine Guidance Sensor 3 on the Hubble Space T elescope. The targets are nearby, red dwarf multiple systems in which the magnitude di †erences are typically measured tô 0.1 mag or better. The values are generated using the best available parallaxes and are also accu-M V rate to^0.1 mag, because the errors in the magnitude di †erences are the dominant error source. In several cases this is the Ðrst time the observed sub-arcsecond multiples have been resolved at optical wavelengths. The mass-luminosity relation deÐned by these data reaches to and provides a M V \ 18.5 powerful empirical test for discriminating the lowest mass stars from high-mass brown dwarfs at wavelengths shorter than 1 km.

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“…Wooley (1970) suggests that they are members of the ζ Her moving group, which has an isochrone age of a few billion years. Da Silva & Foy (1987) measured a metallicity typical of population I stars and, therefore, criticized the hypothesis by Johnson et al (1968) that the pair is composed of subdwarfs. There is no sign of radial velocity variability in either star (da Silva & Foy 1987).…”

Section: Hd 20766 ≡ ζ 1 Ret ≡ Hr 756mentioning

confidence: 99%

Chromospherically young, kinematically old stars

Rocha-Pinto¹,

Castilho²,

Maciel³

2002

A&A

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Abstract.We have investigated a group of stars known to have low chromospheric ages, but high kinematical ages. Isochrone, chemical and lithium ages are estimated for them. The majority of stars in this group show lithium abundances much smaller than expected for their chromospheric ages, which is interpreted as an indication of their old age. Radial velocity measurements in the literature also show that they are not close binaries. The results suggest that they can be formed from the coalescence of short-period binaries. Coalescence rates, calculated taking into account several observational data and a maximum theoretical time scale for contact, in a short-period pair, predict a number of coalesced stars similar to what we have found in the solar neighbourhood.

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The spectral-energy curves of subdwarfs

Cited by 47 publications

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A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun

A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun

The Optical Mass‐Luminosity Relation at the End of the Main Sequence (0.08–0.20M_⊙)

Chromospherically young, kinematically old stars

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The spectral-energy curves of subdwarfs

Cited by 47 publications

References 0 publications

A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun

A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun

The Optical Mass‐Luminosity Relation at the End of the Main Sequence (0.08–0.20M⊙)

Chromospherically young, kinematically old stars

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Product

Resources

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The Optical Mass‐Luminosity Relation at the End of the Main Sequence (0.08–0.20M_⊙)