Spectral Irradiance Calibration in the Infrared. X. A Self-Consistent Radiometric All-Sky Network of Absolutely Calibrated Stellar Spectra

Cohen, Martin; Walker, Russell G.; Carter, Brian S.; Hammersley, P. L.; Kidger, M.; Noguchi, Kunio

doi:10.1086/300813

Cited by 480 publications

(560 citation statements)

References 39 publications

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“…The PSF calibrator (HD 70555) was chosen in the spectrophotometric catalogue assembled by Cohen et al (1999). This gives us the possibility to use it as a convenient photometric reference to convert the measured ratio with RS Pup into magnitude.…”

Section: Psf Subtraction and Photometry Of Rs Pupmentioning

confidence: 99%

The long-period Galactic Cepheid RS Puppis

Kervella¹,

Mérand

Szabados

et al. 2008

A&A

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Context. The bright southern Cepheid RS Pup is surrounded by a circumstellar nebula reflecting the light from the central star. The propagation of the light variations from the Cepheid inside the dusty nebula creates spectacular light echoes that can be observed up to large distances from the star itself. This phenomenon is currently unique in this class of stars. Aims. For this relatively distant star, the trigonometric parallax available from Hipparcos has a low accuracy. A careful observation of the light echoes has the potential to provide a very accurate, geometric distance to RS Pup. Methods. We obtained a series of CCD images of RS Pup with the NTT/EMMI instrument covering the variation period of the star (P = 41.4 d), allowing us to track the progression of the light wavefronts over the nebular features surrounding the star. We measured precisely the phase lag of the photometric variation in several regions of the circumstellar nebula. Results. From our phase lag measurements, we derive a geometric distance of 1992 ± 28 pc to RS Pup. This distance is affected by a total uncertainty of 1.4%, and corresponds to a parallax of π = 0.502 ± 0.007 mas and a distance modulus of µ = 11.50 ± 0.03. Conclusions. The geometric distance we derive is by far the most accurate to a Cepheid, and among the most accurate to any star. RS Pup appears both as somewhat neglected and particularly promising to investigate the mass-loss history of Cepheids. Thanks to its highly accurate distance, it is also bound to become an important luminosity fiducial for the long period part of the period-luminosity diagram.

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Section: Psf Subtraction and Photometry Of Rs Pupmentioning

confidence: 99%

The long-period Galactic Cepheid RS Puppis

Kervella¹,

Mérand

Szabados

et al. 2008

A&A

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“…This is a primary ISO calibration standard star and is described in detail at the TIMMI2 webpage 1 . The synthetic calibrated spectrum for this standard star is given by Cohen et al (1999). The data processing included the removal of bad frames and the coaddition of all chopping and nodding pairs.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

High spatial resolution mid-infrared spectroscopy of NGC 5253: The stellar content of the embedded super-star cluster

Martín-Hernández

Schaerer

Sauvage³

2004

A&A

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Abstract. We present the N-band (8-13 µm) spectrum of the hidden compact radio super-star cluster in NGC 5253, C2, obtained with TIMMI2 on the ESO 3.6 m telescope. The spectrum is characterised by a rising continuum due to warm dust, a silicate absorption and a strong [S ] line at 10.5 µm. Weaker lines of [Ar ] at 9.0 µm and [Ne ] at 12.8 µm are also present.The continuum can be modelled by an optically thick emission from hot (T d = 253 ± 1 K) dust emission extinguished by a cold foreground dust screen and a silicate absorption feature with A sil = 0.73 ± 0.05 mag. We show how the spatial scale of the observations greatly determine the mid-IR appearance of NGC 5253 and the important implications that this has on the interpretation of line fluxes in terms of the properties (age, IMF, etc.) of the embedded cluster. We have modelled the observed line fluxes towards C2 using photoionisation models with the most recent spectral energy distributions available to describe the integrated properties of the stellar cluster. The detailed dependence of the mid-IR lines on parameters such as the cluster age, upper mass cutoff and power law index of the IMF, as well as the local abundance, the presence of internal dust and the density structure is largely discussed. Strong constraints on the geometry based on high spatial resolution observations at different wavelengths -near-IR (HST and Keck), mid-IR (TIMMI2) and radio (VLA) -allows us to restrain the ionisation parameters to values log U ≥ −0.5 dex. This constraint on U leads to two possible solutions for the age and upper mass cutoff of C2: 1) a young (<4 Myr) cluster with a "non-standard" IMF having a low upper mass cutoff M up < 50 M ; and 2) a cluster of ∼5−6 Myr with a standard high upper mass cutoff (M up ∼ 100 M ). A young age of <4 Myr would agree with the lack of supernovae signatures in C2 and in case of being confirmed, would be the first indication for a "non-standard", low upper mass cutoff of the IMF for an individual massive cluster. An older age of ∼5-6 Myr would imply that it is possible to "contain" and hide such a compact cluster for a longer time that what it is generally thought. Arguments in favour and against these two scenarios are presented.The origin of the [O ] 25.9 µm emission measured by ISO and the possible presence of an intermediate mass black hole inside C2 are also addressed.

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“…The OBSID combinations of the deepest maps are used for this investigation. f 160,excess is estimated as the difference of the measured f 160 minus model f model flux from Cohen et al (1999), Selby et al (1988)) as represented by the violet square symbol. Dark-blue squares, light-blue diamonds, and green triangles represent IRAS FSC, PACS, and ISOPHOT HPDP photometry and their respective uncertainties.…”

Section: Intrinsic Fir Excessmentioning

confidence: 99%

Herschel-PACS photometry of faint stars for sensitivity performance assessment and establishment of faint FIR primary photometric standards

Klaas

Balog

Nielbock

et al. 2018

A&A

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Aims. Our aims are to determine flux densities and their photometric accuracy for a set of seventeen stars that range in flux from intermediately bright ( 2.5 Jy) to faint ( 5 mJy) in the far-infrared (FIR). We also aim to derive signal-to-noise dependence with flux and time, and compare the results with predictions from the Herschel exposure-time calculation tool. Methods. We obtain aperture photometry from Herschel-PACS high-pass-filtered scan maps and chop/nod observations of the faint stars. The issues of detection limits and sky confusion noise are addressed by comparison of the field-of-view at different wavelengths, by multi-aperture photometry, by special processing of the maps to preserve extended emission, and with the help of large-scale absolute sky brightness maps from AKARI. This photometry is compared with flux-density predictions based on photospheric models for these stars. We obtain a robust noise estimate by fitting the flux distribution per map pixel histogram for the area around the stars, scaling it for the applied aperture size and correcting for noise correlation.Results. For 15 stars we obtain reliable photometry in at least one PACS filter, and for 11 stars we achieve this in all three PACS filters (70, 100, 160 µm). Faintest fluxes, for which the photometry still has good quality, are about 10 -20 mJy with scan map photometry. The photometry of seven stars is consistent with models or flux predictions for pure photospheric emission, making them good primary standard candidates. Two stars exhibit source-intrinsic far-infrared excess: β Gem (Pollux), being the host star of a confirmed Jupiter-size exoplanet, due to emission of an associated dust disk, and η Dra due to dust emission in a binary system with a K1 dwarf. The investigation of the 160 µm sky background and environment of four sources reveals significant sky confusion prohibiting the determination of an accurate stellar flux at this wavelength. As a good model approximation, for nine stars we obtain scaling factors of the continuum flux models of four PACS fiducial standards with the same or quite similar spectral type. We can verify a linear dependence of signal-to-noise ratio (S/N) with flux and with square root of time over significant ranges. At 160 µm the latter relation is, however, affected by confusion noise. Conclusions. The PACS faint star sample has allowed a comprehensive sensitivity assessment of the PACS photometer. Accurate photometry allows us to establish a set of five FIR primary standard candidates, namely α Ari, ε Lep, ω Cap, HD 41047 and 42 Dra, which are 2 -20 times fainter than the faintest PACS fiducial standard (γ Dra) with absolute accuracy of <6%. For three of these primary standard candidates, essential stellar parameters are known, meaning that a dedicated flux model code may be run.

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Spectral Irradiance Calibration in the Infrared. X. A Self-Consistent Radiometric All-Sky Network of Absolutely Calibrated Stellar Spectra

Cited by 480 publications

References 39 publications

The long-period Galactic Cepheid RS Puppis

The long-period Galactic Cepheid RS Puppis

High spatial resolution mid-infrared spectroscopy of NGC 5253: The stellar content of the embedded super-star cluster

Herschel-PACS photometry of faint stars for sensitivity performance assessment and establishment of faint FIR primary photometric standards

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