Spectral Irradiance Calibration in the Infrared. XVI. Improved Accuracy in the Infrared Spectra of the Secondary and Tertiary Standard Calibration Stars

Engelke, C. W.; Price, S. D.; Kraemer, K. E.

doi:10.1086/505865

Cited by 33 publications

(46 citation statements)

References 66 publications

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“…The stellar spectra and calibration issues were discussed by Decin et al (2003), for example, who used atmospheric parameters from the literature for α Cen A and determined parameters from the infrared spectra for the other stars. These four stars, as well as β Gem, are also included in the sample of 12 standard stars used for calibration purposes in a procedure for creating template spectral energy distributions in the infrared for arbitrary effective temperatures (autoshape procedure, 1-35 µm, Engelke et al 2006). Procyon and Eri were used by Lobel (2011) to calibrate oscillator strengths of over 900 lines of neutral species in the wavelength range 400 to 680 nm.…”

Section: Sample Selectionmentioning

confidence: 99%

GaiaFGK benchmark stars: Effective temperatures and surface gravities

Heiter

Jofré

Gustafsson

et al. 2015

A&A

287

414

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Context. In the era of large Galactic stellar surveys, carefully calibrating and validating the data sets has become an important and integral part of the data analysis. Moreover, new generations of stellar atmosphere models and spectral line formation computations need to be subjected to benchmark tests to assess any progress in predicting stellar properties. Aims. We focus on cool stars and aim at establishing a sample of 34 Gaia FGK benchmark stars with a range of different metallicities. The goal was to determine the effective temperature and the surface gravity independently of spectroscopy and atmospheric models as far as possible. Most of the selected stars have been subjected to frequent spectroscopic investigations in the past, and almost all of them have previously been used as reference, calibration, or test objects. Methods. Fundamental determinations of T eff and log g were obtained in a systematic way from a compilation of angular diameter measurements and bolometric fluxes and from a homogeneous mass determination based on stellar evolution models. The derived parameters were compared to recent spectroscopic and photometric determinations and to gravity estimates based on seismic data. Results. Most of the adopted diameter measurements have formal uncertainties around 1%, which translate into uncertainties in effective temperature of 0.5%. The measurements of bolometric flux seem to be accurate to 5% or better, which contributes about 1% or less to the uncertainties in effective temperature. The comparisons of parameter determinations with the literature in general show good agreements with a few exceptions, most notably for the coolest stars and for metal-poor stars. Conclusions. The sample consists of 29 FGK-type stars and 5 M giants. Among the FGK stars, 21 have reliable parameters suitable for testing, validation, or calibration purposes. For four stars, future adjustments of the fundamental T eff are required, and for five stars the log g determination needs to be improved. Future extensions of the sample of Gaia FGK benchmark stars are required to fill gaps in parameter space, and we include a list of suggested candidates.

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Section: Sample Selectionmentioning

confidence: 99%

GaiaFGK benchmark stars: Effective temperatures and surface gravities

Heiter

Jofré

Gustafsson

et al. 2015

A&A

287

414

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“…Their spectra were published by Cohen et al (1999). For U Ari we used α Ceti, whose calibrated spectrum was published by Engelke et al (2006). Last, for RX Tau we used the IRAS LRS spectrum for 119 Tau (Beichman et al 1988).…”

Section: Spectrum Calibrationmentioning

confidence: 99%

High-resolution IR and radio observations of AGB stars

Perrin

Cotton

Millan-Gabet

et al. 2015

A&A

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Aims. We present the results of observations with interferometers of a sample of pulsating asymptotic giant branch (AGB) stars in the infrared and at radio wavelengths. The goal of these observations is to explore the extended stellar atmospheres and to establish links between the spatial scales of molecular envelopes and of the dust shell. This is the key to better understand the process of dust formation and therefore of mass loss. Methods. We used the ESO VLTI/MIDI interferometer in the N band, the Keck Interferometer in the K band, and NRAO VLBA observations of SiO masers at 7 mm wavelength of a sample of AGB stars: U Ari, W Cnc, RX Tau, RT Tau, RT Aql, S Ser, and V Mon. The various instruments probe different altitudes of the atmosphere of the AGB stars. They are sensitive to regions below the silicate dust condensation distance and provide the opportunity of finding hints about how dust and its precursors form in the extended atmosphere of an AGB star. The K-band observations are sensitive to water and carbon-monoxyde vapors. Unfortunately, we were only able to observe S Ser in this wavelength range. Results. We find a ratio of 2.2 between the molecular envelope radius and the photospheric size, which is consistent with previous results. The N-band observations are mostly sensitive to vapors of SiO and water and to dust (alumina and silicate). The silicate dust shell is fully resolved, and no precise parameters can be deduced from the N-band observations other than a spatial extension of at least 12-16 R for our sample. The sizes found for the SiO region are consistent with the radii of the SiO maser rings provided by the VLBA observations. The sizes of the alumina and water vapor regions are systematically found to be larger. There is clear evidence that SiO is absent from regions farther from the star where silicate dust condenses. Conclusions. These observations support a possible scenario in which SiO is adsorbed by species such as corundum. An alternative explanation could be that SiO has chemically disappeared at this range of distances.

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“…However, a care was taken not to doublecount the flux component in the extended shell part that is accounted for as part of the core emission via aperture correction. For each flux value obtained for the core and shell, we independently applied color correction and obtained the final flux values, which are listed in Table 1. For PSF calibration purposes, we also observed an M5 III giant β Gru (Engelke et al 2006) with AKARI on 2006 November 16 and an asteroid Ceres (Müller & Lagerros 2002) with Spitzer on 2008 February 17. The same instrumental/mapping set-up was used for both PSF observations, except for Spitzer observations, for which the photometry/movingcluster-offset mode was used because Ceres is a moving target.…”

Section: Photometry and Deconvolutionmentioning

confidence: 99%

The interface between the stellar wind and interstellar medium around R Cassiopeiae revealed by far-infrared imaging

Ueta¹,

Stencel²,

Yamamura

et al. 2010

A&A

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Aims. The circumstellar dust shells of intermediate initial-mass (∼1 to 8 M ) evolved stars are generated by copious mass loss during the asymptotic giant branch phase. The density structure of their circumstellar shell is the direct evidence of mass loss processes, from which we can investigate the nature of mass loss. Methods. We used the AKARI infrared astronomy satellite and the Spitzer space telescope to obtain the surface brightness maps of an evolved star R Cas at far-infrared wavelengths, since the temperature of dust decreases as the distance from the star increases and one needs to probe dust at lower temperatures, i.e., at longer wavelengths. The observed shell structure and the star's known proper motion suggest that the structure represents the interface regions between the dusty wind and the interstellar medium. The deconvolved structures are fitted with the analytic bow shock structure to determine the inclination angle of the bow shock cone. Results. Our data show that (1) the bow shock cone of 1−5 × 10 −5 M dust mass is inclined at 68 • with respect to the plane of the sky; and (2) the dust temperature in the bow shock cone is raised to more than 20 K by collisional shock interaction in addition to the ambient interstellar radiation field. By comparison between the apex vector of the bow shock and space motion vector of the star we infer that there is a flow of interstellar medium local to R Cas whose flow velocity is at least 55.6 km s −1 , consistent with an environment conducive to dust heating by shock interactions.

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Spectral Irradiance Calibration in the Infrared. XVI. Improved Accuracy in the Infrared Spectra of the Secondary and Tertiary Standard Calibration Stars

Cited by 33 publications

References 66 publications

GaiaFGK benchmark stars: Effective temperatures and surface gravities

GaiaFGK benchmark stars: Effective temperatures and surface gravities

High-resolution IR and radio observations of AGB stars

The interface between the stellar wind and interstellar medium around R Cassiopeiae revealed by far-infrared imaging

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