A discussion on infared astronomy - Near infrared photometry of late-type stars

1969 ◽  
Vol 264 (1150) ◽  
pp. 209-225 ◽  
Keyword(s):  
Spectral Type ◽  
Near Infrared ◽  
Model Atmosphere ◽  
Spectral Irradiance ◽  
Photometric Method ◽  
Infrared Photometry ◽  
Late Type ◽  
Stellar Diameters ◽  
Effective Temperatures ◽  
The Absolute

A multi-band photoelectric photometer for observations in the ultraviolet, blue and visible and the infrared bands W (1.06μm), X (1.13 μm, Y (1.63 μm) and Z (2.21 μm) has been constructed and applied to both stellar and planetary observations. The results of photometry obtained for 61 stars are presented. The observations at λ = 1.63 μm are shown to exhibit an excess flux due to a minimum in the H opacity in accordance with the predictions of model atmosphere studies. Bolometric corrections are derived for stars of late spectral type from integration of the observed absolute spectral irradiance curve. A simple photometric method for the measurement of stellar diameters is proposed based upon the absolute irradiance observed at 2.21 μm and the 2.21 μm flux at the surface of the star calculated from model atmospheres. Angular diameters derived by this technique are consistent with interferometric results; and, when combined with the bolometric corrections, effective temperatures are found.

scholarly journals Abundance Effects in the Classification of K Stars

1976 ◽  
Vol 72 ◽  
pp. 87-90
Author(s):  
P. M. Williams
Keyword(s):  
Spectral Type ◽  
Near Infrared ◽  
Narrow Band ◽  
Infrared Photometry ◽  
Metal Abundance ◽  
Metal Abundances ◽  
Effective Temperatures

The influence of metal abundance and gravity on the relation between spectral type and effective temperatures of late G and K type stars is investigated and calibrated using metal abundances from narrow-band photometry, near infrared photometry and independent luminosity estimates.

scholarly journals The Absolute Calibration of the HR Diagram: Fundamental Effective Temperatures and Bolometric Corrections

1978 ◽  
Vol 80 ◽  
pp. 65-76 ◽  
Author(s):  
D. S. Hayes
Keyword(s):  
Spectral Type ◽  
Absolute Calibration ◽  
Effective Temperatures ◽  
The Absolute ◽  
Hr Diagram

Scales of fundamental bolometric connections (B.C.) and effective temperatures (Teff) as a function of spectral type or color are necessary for the comparison of observations and theory in the HR diagram.

scholarly journals Discovery of a Tight Brown Dwarf Companion to the Low Mass Star LHS 2397a

2003 ◽  
Vol 211 ◽  
pp. 261-264 ◽  
Author(s):  
Melanie Freed ◽  
Laird M. Close ◽  
Nick Siegler
Keyword(s):  
Adaptive Optics ◽  
Spectral Type ◽  
Proper Motion ◽  
Near Infrared ◽  
Mass Star ◽  
Infrared Photometry ◽  
Brown Dwarf ◽  
Dynamical Mass ◽  
Low Mass ◽  
Adaptive Optics System

Using the adaptive optics system, Hōkūpa'a, at Gemini-North, we have directly imaged a companion around the UKIRT faint standard M8 star, LHS 2397a (FS 129) at a separation of 2.96 AU. Near-Infrared photometry obtained on the companion has shown it to be an L7.5 brown dwarf and confirmed the spectral type of the primary to be an M8. We also derive a substellar mass of the companion of 0.068M⊙, although masses in the range (0.061 – 0.069) are possible, and the primary mass as 0.090M⊙ (0.089 – 0.094). Reanalysis of archival imaging from HST has confirmed the secondary as a common proper motion object. This binary represents the first clear example of a brown dwarf companion within 4 AU of a low mass star, and should be the first L7.5 to have a dynamical mass. As part of a larger survey of M8-M9 stars, this object may indicate that there is no “brown dwarf desert” around low mass primaries.

scholarly journals The role of cold gas on the stellar mass - metallicity relation of nearby galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 336-336
Author(s):  
Thomas M. Hughes
Keyword(s):  
Near Infrared ◽  
Stellar Mass ◽  
Gas Content ◽  
Infrared Photometry ◽  
Late Type ◽  
Limited Sample ◽  
Nearby Galaxies ◽  
The Relationship ◽  
Gas Fractions

AbstractWe investigate the relationship between stellar mass, metallicity and gas content for a magnitude- and volume-limited sample of 260 nearby late-type galaxies in different environments. Combining new oxygen abundance measurements with ultraviolet to near-infrared photometry and Hi 21 cm line observations, we observe the relationship between stellar mass and metallicity. We also find that, at fixed stellar mass, galaxies with lower gas fractions typically possess higher oxygen abundances. Gas-poor galaxies are typically more metal-rich. Our results indicate that internal evolutionary processes, rather than environmental effects, play a key role in shaping the stellar mass-metallicity relation.

scholarly journals Molecular Bands in the 1.1-1.4 μm Spectra of M-S-C stars

1989 ◽  
Vol 106 ◽  
pp. 61-61
Author(s):  
Kenneth H. Hinkle ◽  
David L. Lambert ◽  
Robert F. Wing
Keyword(s):  
Spectral Type ◽  
Short Wavelength ◽  
Near Infrared ◽  
Laboratory Work ◽  
Band Spectrum ◽  
Spectral Features ◽  
Late Type ◽  
Minimum Light ◽  
Considerable Range

Spectra are presented in the J band (7400 to 9700 cm-1) for four Miras ranging in spectral type from M through C. All the program stars have been observed near minimum light. The program stars cover a considerable range in C/0 and the spectral features exhibit a progression as a function of C/0. The S-type stars contain strong bands not previously reported. Especially striking are two sets of triple-headed bands in the J-band spectrum of the S-type Mira R And. The bandheads, which are degraded to longer wavelengths, are at 7877, 7957, 8030 cm-1 and 8379, 8459, 8530 cm-1. The former triplet, which is the stronger of the two, also is present in the mild S star × Cyg but not in the M star R Cas. Additional heads are found in R And at 7477 cm-1, near the short wavelength edge of strong telluric absorption, and at 8968, 9031, 9063 cm-1. The bands are identified as the Δv = -1, 0, 1, and 2 sequences of a predicted (3II-3Δ) transition of ZrS. Additional conspicuous features in the spectra of × Cyg and R Cas are identified with V0, TiO, and H20 bands. These observations provide additional evidence that ZrS is responsible for the majority of the Keenan-Wing bands in the near infrared (0.7-1.1 μ). With additional laboratory work, the ZrS bands will provide an opportunity to measure sulfur abundances in late-type stellar photospheres.

K–Type Supergiants in the Large Magellanic Cloud

2018 ◽  
Vol 14 (S343) ◽  
pp. 544-545
Author(s):  
Robert F. Wing
Keyword(s):  
Spectral Type ◽  
Near Infrared ◽  
Narrow Band ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Photometric System ◽  
Two Dimensional ◽  
Late Type ◽  
Type K ◽  
Lower Luminosity

AbstractTwo-dimensional spectral classifications, on a narrow-band photometric system that measures near-infrared bands of TiO and CN, are being obtained for several hundred previously unclassified “suspected late-type supergiants” in the Large Magellanic Cloud. The objective is to identify supergiants of spectral type K, which are known to be plentiful in the Small Magellanic Cloud but were thought to be rare in the LMC. In the fields examined to date, 35 % of the targets are found to be K-type supergiants, while 25 % are early-M supergiants and 40 % are foreground stars of lower luminosity.

scholarly journals Infrared studies of symbiotic stars

1982 ◽  
Vol 70 ◽  
pp. 27-42 ◽  
Author(s):  
David A. Allen
Keyword(s):  
Spectral Type ◽  
Dust Emission ◽  
Circumstellar Dust ◽  
Symbiotic Stars ◽  
Infrared Photometry ◽  
Late Type ◽  
Cool Component ◽  
Mira Variables ◽  
Infrared Studies

AbstractInfrared photometry and spectroscopy of symbiotic stars is reviewed. It is shown that at wavelengths beyond lym these systems are generally dominated by the cool star’s photosphere and, indeed, are indistinguishable from ordinary late-type giants. About 25% of symbiotic stars exhibit additional emission due to circumstellar dust. Most of the dusty systems probably involve Mira variables, the dust forming in the atmospheres of the Miras. In a few cases the dust is much cooler and the cool component hotter; the dust must then form in distant gas shielded from the hot component, perhaps by an acccretion disk.Spectroscopy at 2μm can be used to spectral type the cool components, even in the presence of some dust emission. Distances may thereby be estimated, though with some uncertainty.Spectroscopy at longer wavelengths reveals information about the dust itself. In most cases this dust appears to include silicate grains, which form in the oxygen-rich envelope of an M star. In the case of HD 330036, however, different emission features are found which suggest a carbon-rich environment.

scholarly journals Applications of Narrow-Band Photometry in the Study of Peculiar Red Giants

2000 ◽  
Vol 177 ◽  
pp. 127-140
Author(s):  
Robert F. Wing
Keyword(s):  
Near Infrared ◽  
Narrow Band ◽  
Red Giants ◽  
Late Type ◽  
Energy Distributions ◽  
Synthetic Spectra ◽  
Continuum Energy ◽  
Qualitative Classification ◽  
Effective Temperatures ◽  
Classification Recognition

Narrow-band photometry, carried out with filters or spectrum scanners, is useful for measuring molecular bandstrengths and continuum energy distributions in late-type stars. This review emphasizes observations by the writer on three different multicolor photometric systems in the near infrared (0.75 − 4.0 μm); a summary of available data is given. While applications to date have been primarily qualitative (classification, recognition of peculiarities, relative temperatures), future applications are expected to be quantitative (determinations of effective temperatures, luminosities, and abundances) and based upon comparison with synthetic spectra.

scholarly journals Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation

2018 ◽  
Vol 615 ◽  
pp. A139 ◽  
Author(s):  
A. M. Amarsi ◽  
T. Nordlander ◽  
P. S. Barklem ◽  
M. Asplund ◽  
R. Collet ◽  
...  
Keyword(s):  
Effective Temperature ◽  
3D Models ◽  
Balmer Line ◽  
Late Type ◽  
Balmer Lines ◽  
3D Effects ◽  
Hydrostatic Model ◽  
Effective Temperatures ◽  
The Absolute ◽  
First Time

Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, reliable inferences require accurate model spectra, and the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and local thermodynamic equilibrium (LTE) is still unclear. To investigate this, we carry out 3D non-LTE calculations for the Balmer lines, performed, for the first time, over an extensive grid of 3D hydrodynamic STAGGER model atmospheres. For Hα, Hβ, and Hγ we find significant 1D non-LTE versus 3D non-LTE differences (3D effects): the outer wings tend to be stronger in 3D models, particularly for Hγ, while the inner wings can be weaker in 3D models, particularly for Hα. For Hα, we also find significant 3D LTE versus 3D non-LTE differences (non-LTE effects): in warmer stars (Teff ≈ 6500 K) the inner wings tend to be weaker in non-LTE models, while at lower effective temperatures (Teff ≈ 4500 K) the inner wings can be stronger in non-LTE models; the non-LTE effects are more severe at lower metallicities. We test our 3D non-LTE models against observations of well-studied benchmark stars. For the Sun, we infer concordant effective temperatures from Hα, Hβ, and Hγ; however the value is too low by around 50 K which could signal residual modelling shortcomings. For other benchmark stars, our 3D non-LTE models generally reproduce the effective temperatures to within 1σ uncertainties. For Hα, the absolute 3D effects and non-LTE effects can separately reach around 100 K, in terms of inferred effective temperatures. For metal-poor turn-off stars, 1D LTE models of Hα can underestimate effective temperatures by around 150 K. Our 3D non-LTE model spectra are publicly available, and can be used for more reliable spectroscopic effective temperature determinations.

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