Absolute Calibration of the Infrared Array Camera on the<i>Spitzer Space Telescope</i>

Reach, W. T.; Megeath, S. Thomas; Cohen, Martin; Hora, J. L.; Carey, Sean; Surace, Jason; Willner, S. P.; Barmby, P.; Wilson, Gillian; Glaccum, W.; Lowrance, P.; Marengo, Massimo; Fazio, G. G.

doi:10.1086/432670

Cited by 559 publications

(378 citation statements)

References 9 publications

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“…A systematic offset between A-type and K-M type giant standard stars is reported by Reach et al (2005) for the calibration of the IRAC on Spitzer. We have only three A-type standard stars in our calibration for the 9 μm band and no A-type stars are used for the calibration of the 18 μm band due to the detection limit.…”

Section: Flux Calibrationmentioning

confidence: 90%

“…The conversion function from electrons to Jy is derived statistically by comparing the model fluxes with the measurements of hundreds of standard stars. The standard stars are selected from the infrared standard star network consisting of K-and Mgiants (Cohen et al 1999) and additional faint standard stars located around the north and south ecliptic poles (Reach et al 2005;Ishihara et al 2006b), which have a high visibility for the AKARI survey. The expected fluxes ( f quoted λ (λ i )) of the standard stars at the effective wavelengths (9 μm and 18 μm) are calculated for the incident spectrum of f λ ∝ λ −1 by convolving the model spectra of the standard stars ( f λ (λ)) with the relative spectral response curves (R i ) in electron units as…”

Section: Flux Calibrationmentioning

confidence: 99%

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The AKARI/IRC mid-infrared all-sky survey

Ishihara

Onaka

Kataza

et al. 2010

A&A

533

249

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Context. AKARI is the first Japanese astronomical satellite dedicated to infrared astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 μm and 200 μm during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9 μm and 18 μm bands) of the survey carried out with one of the on-board instruments, the infrared camera (IRC). Aims. We present unprecedented observational results of the 9 μm and 18 μm AKARI all-sky survey and detail the operation and data processing leading to the point source detection and measurements. Methods. The raw data are processed to produce small images for every scan, and the point sources candidates are derived above the 5σ noise level per single scan. The celestial coordinates and fluxes of the events are determined statistically and the reliability of their detections is secured through multiple detections of the same source within milli-seconds, hours, and months from each other. Results. The sky coverage is more than 90% for both bands. A total of 877 091 sources (851 189 for 9 μm, 195 893 for 18 μm) are confirmed and included in the current release of the point source catalog. The detection limit for point sources is 50 mJy and 90 mJy for the 9 μm and 18 μm bands, respectively. The position accuracy is estimated to be better than 2 . Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9 μm band and 4% for the 18 μm band. The coordinates and fluxes of detected sources in this survey are also compared with those of the IRAS survey and are found to be statistically consistent.

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Section: Flux Calibrationmentioning

confidence: 90%

Section: Flux Calibrationmentioning

confidence: 99%

The AKARI/IRC mid-infrared all-sky survey

Ishihara

Onaka

Kataza

et al. 2010

A&A

533

249

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“…The mean-weighted magnitudes were calculated for targets in which multiepoch observations are reported. Magnitudes were converted into flux densities using the zero-points of 281 ± 4 Jy, 180 ± 3 Jy, 115 ± 2 Jy and 65 ± 1 Jy at 3.6, 4.5, 5.8 and 8.0 µm respectively (Reach et al 2005), and 7.2 ± 0.1 Jy at 24 µm ). Additionally, the Wide-field Infrared Survey Explorer (WISE) All-Sky Data Release (Cutri & et al 2012) was used to extract photometry for all targets measured in the four WISE channels.…”

Section: Construction Of Spectral Energy Distributionsmentioning

confidence: 99%

The Taurus Boundary of Stellar/Substellar (TBOSS) Survey

Bulger

Patience

Ward-Duong

et al. 2014

A&A

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With the PACS instrument on Herschel, 134 low mass members of the Taurus star-forming region spanning the M4-L0 spectral type range and covering the transition from low mass stars to brown dwarfs were observed. Combining the new Herschel results with other Herschel programs, a total of 150 of the 154 M4-L0 Taurus members have observations, and we have added an additional 3 targets from Spitzer to form the 153-object TBOSS (Taurus Boundary of Stellar/Substellar) sample, a 99% complete study. Among the 150 targets, 70 µm flux densities were measured for 7 of the 7 Class I objects, 48 of the 67 Class II objects, and 3 of the 76 Class III objects. For the detected Class II objects, the median 70 µm flux density level declines with spectral type; however, the distribution of excess relative to central object flux density does not change across the stellar/substellar boundary in the M4-L0 range. Connecting the 70 µm TBOSS values with the results from K0-M3 Class II members results in the first comprehensive census of far-IR emission across the full mass spectrum of the stellar and substellar population of a star-forming region, and the median flux density declines with spectral type in a trend analogous to the flux density decline expected for the central objects. Spectral energy distributions (SEDs) were constructed for all TBOSS targets covering the optical to far-IR range and extending to the submm/mm for a subset of sources with longer wavelength data. Based on an initial exploration of the impact of different physical parameters on the Herschel flux densities, geometrical factors such as inclination and structural parameters such as scale height and flaring have the largest influence on the flux densities in the PACS bands. From the 24 µm to 70 µm spectral index of the SEDs, 5 new candidate transition disks were identified. Considering the previously known and new candidate transition disks, the spectral indices over longer wavelengths (≥70 µm) are not distinct from those of the full Class II population, suggesting that the outer regions of the transition disks are similar to Class II disks. The steep 24 µm to 70 µm slope for a subset of 8 TBOSS targets may be an indication of truncated disks in these systems, however additional measurements are required to establish the outer radii of these disks conclusively. From existing high angular resolution companion search observations, two examples of mixed pair systems that include secondaries with disks were measured in the Herschel data. Finally, comparing the TBOSS results with a Herschel study of Ophiuchus brown dwarfs reveals a lower fraction of disks around the Taurus substellar population with flux densities comparable to the Ophiuchus disks.

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“…However, the infrared (IR) observations are affected by systematic effects that may compromise the measurements because these effects induce flux variations comparable to the depth of a planetary transit. For example, the 3.6 and 4.5 μm Spitzer/IRAC channels (InSb detectors) are affected by the pixel-phase effect (Reach et al 2005;Charbonneau et al 2005;MoralesCalderón et al 2006;Knutson et al 2008) due to the telescope jitter and intra-pixel variation in the sensitivity of the detector, which may cause a flux peak-to-peak amplitude of up to ∼1% (Beaulieu et al 2008;Hébrard et al 2010) or even higher (Désert et al 2011b;Fressin et al 2011), according to the exposure time. The light curves of the 5.8 and 8.0 μm channels (Si:As detectors) follow non-linear trends with time, called the ramp effect Knutson et al 2007a), caused by the trapping of electrons by the detector impurities (see Agol et al 2010 for further details), which produce mmag level flux variations in photometry.…”

Section: Influence Of Stellar Activity On Stellar Colours and The Chamentioning

confidence: 99%

Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits

Ballerini

Micela

Lanza

et al. 2012

A&A

102

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Stellar magnetic activity is a source of noise in the study of the transits of extrasolar planets. It induces flux variations that significantly affect the transit depth determination and the derivations of planetary and stellar parameters. Furthermore, the colour dependence of stellar activity may significantly influence the characterization of planetary atmospheres. Here we present a systematic approach to quantify the corresponding stellar flux variations as a function of wavelength bands. We consider a star with spots covering a given fraction of its disc and model the variability in both the UBVRIJHK photometric system and the Spitzer/IRAC wavebands for dwarf stars from G to M spectral types. We compare activity-induced flux variations in different passbands with planetary transits and quantify how they affect the determination of the planetary radius and the analysis of the transmission spectroscopy in the study of planetary atmospheres. We suggest that the monitoring of the systems by using broad-band photometry, from visible to infrared, helps us to constrain activity effects. The ratio of the relative variations in the stellar fluxes at short wavelength optical bands (e.g., U or B) to near-infrared ones (e.g., J or K) can be used to distinguish starspot brightness dips from planetary transits in a stellar light curve. In addition to the perturbations in the measurement of the planetary radius, we find that starspots can affect the determinations of both the relative semimajor axis and the inclination of the planetary orbit, which have a significant impact on the derivation of the stellar density from the transit light curves.

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Absolute Calibration of the Infrared Array Camera on theSpitzer Space Telescope

Cited by 559 publications

References 9 publications

The AKARI/IRC mid-infrared all-sky survey

The AKARI/IRC mid-infrared all-sky survey

The Taurus Boundary of Stellar/Substellar (TBOSS) Survey

Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits

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