Spectral Irradiance Calibration in the Infrared.VII.New Composite Spectra, Comparison with Model Atmospheres, and Far-Infrared Extrapolations

Cohen, Martin; Witteborn, F. C.; Carbon, D. F.; Davies, John K.; Wooden, D. H.; Bregman, J. D.

doi:10.1086/118180

Cited by 91 publications

(109 citation statements)

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“…The Cohen et al (1996) models of α Ari, ε Lep, ω Cap, δ Dra and HD 41047 are well confirmed by our PACS photometry and are thus adequate representations of the stellar FIR photospheric emission. These stars together with 42 Dra and HD 152222 are good candidates to establish fainter FIR primary standards.…”

Section: Namesupporting

confidence: 76%

“…In preparation of the PACS in-flight photometric calibration, secondary standard source lists with stars described in Cohen et al (1996), Hammersley et al (1998), and Gordon et al (2007) were prepared by the PACS Instrument Control Centre (ICC) team. Depending on the source visibility during the Herschel mission, a subset of sources from these lists were observed to cover the flux range from 0.5 -2.5 Jy down to 2 -10 mJy over the three photometer wavelengths 70, 100, and 160 µm.…”

Section: Source Selectionmentioning

confidence: 99%

“…One other aspect to consider in this context is possible source variability; we investigate this for the case of β Gem: The Cohen et al (1996) FIR model SED is an extension of an absolutely calibrated 1.2 -35 µm model 5 Cohen et al (1995). In Fig.…”

Section: Stars With Fir Excessmentioning

confidence: 99%

“…For a better zoom-in over a large wavelength range, log 10 (λ 4 · f λ ) is displayed. The orange and red lines are the Cohen et al (1995) absolutely calibrated 1.2 -35 µm spectral model and the Cohen et al (1996) FIR extension, respectively. The black line represents a scaled (×0.169) fiducial star continuum model of α Boo (Dehaes et al 2011).…”

Section: Intrinsic Fir Excessmentioning

confidence: 99%

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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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Section: Namesupporting

confidence: 76%

Section: Source Selectionmentioning

confidence: 99%

Section: Stars With Fir Excessmentioning

confidence: 99%

Section: Intrinsic Fir Excessmentioning

confidence: 99%

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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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“…HIFOGS used a 3 circular aperture and a 30 chop throw. The spectra of CQ Tau were flux calibrated with the bright IR standard star α Tau, using the well determined flux spectrum by Cohen et al (1996). Differences in atmospheric transmission between CQ Tau and α Tau spectra were corrected using the ratio of telluric transmissions calculated by ATRAN (Lord 1993) for a total column of 4.5 mm of H 2 O for WIRO.…”

Section: Micron Spectrophotometrymentioning

confidence: 99%

A reconsideration of disk properties in Herbig Ae stars

Natta

Prusti

Neri

et al. 2001

A&A

331

342

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Abstract. This paper presents state-of-the-art spectral energy distributions (SEDs) of four Herbig Ae stars, based in part on new data in the mid and far-infrared and at millimeter wavelengths. The SEDs are discussed in the context of circumstellar disk models. We show that models of irradiated disks provide a good fit to the observations over the whole range of wavelengths. We offer a possible solution to the long-standing puzzle caused by the excess emission of Herbig Ae stars, where a large fraction of the stellar luminosity is re-radiated between ∼1.25 and 7 µm, with a peak at about 3 µm. We suggest that this general behaviour can be caused by dust evaporation in disks where the gas component is optically thin to the stellar radiation, as expected if the accretion rate is very low. The creation of a puffed-up inner wall of optically thick dust at the dust sublimation radius can account for the near-infrared characteristics of the SEDs. It can also naturally explain the H and K band interferometric observations of AB Aur (Millan-Gabet et al. 2001), which reveal a ring of emission of radius ∼0.3 AU. Finally, irradiated disk models can easily explain the observed intensity of the 10 µm silicate features and their variation from star to star.

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Deep Far Infrared ISOPHOT Survey in “Selected Area 57”

Linden-Vørnle

Nørgaard-Nielsen

Jørgensen³

et al. 2000

ISO Surveys of a Dusty Universe

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We present here the results of a deep survey in a 0.4 deg 2 blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observatory (ISO 1 ) at both 60 µm and 90 µm. The resulting sky maps have a spatial resolution of 15 × 23 arcsrc 2 per pixel which is much higher than the 90 × 90 arcsec 2 pixels of the IRAS All Sky Survey. We describe the main instrumental effects encountered in our data, outline our data reduction and analysis scheme and present astrometry and photometry of the detected point sources. With a formal signal to noise ratio of 6.75 we have source detection limits of 90 mJy at 60 µm and 50 mJy at 90 µm. To these limits we find cumulated number densities of 5±3.5 deg −2 at 60 µm and 14.8±5.0 deg −2 at 90 µm. These number densities of sources are found to be lower than previously reported results from ISO but the data do not allow us to discriminate between no-evolution scenarios and various evolutionary models.

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Spectral Irradiance Calibration in the Infrared.VII.New Composite Spectra, Comparison with Model Atmospheres, and Far-Infrared Extrapolations

Cited by 91 publications

References 0 publications

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

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

A reconsideration of disk properties in Herbig Ae stars

Deep Far Infrared ISOPHOT Survey in “Selected Area 57”

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