A new extensive library of PHOENIX stellar atmospheres and synthetic spectra

Husser, Tim-Oliver; Berg, S.; Dreizler, S.; Homeier, D.; Reiners, A.; Barman, Travis; Hauschildt, P. H.

doi:10.1051/0004-6361/201219058

Cited by 1,642 publications

(1,624 citation statements)

References 46 publications

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“…In the first approach we fixed the limb darkening coefficients w 1 and w 2 during the MCMC analysis to the values from the PHOENIX atmospheric model (Husser et al 2013). In the second we utilized the triangular sampling method proposed by Kipping (2013 3 ).…”

Section: Other Limb Darkening Prescriptionsmentioning

confidence: 99%

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ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Rackham

Espinoza

Apai

et al. 2017

ApJ

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GJ1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanetʼs atmosphere, either equilibrium condensate clouds or photochemical hazes. Many photometric observations have been reported in the optical by different groups, though simultaneous measurements spanning the entire optical regime are lacking. We present an optical transmission spectrum (4500-9260Å) of GJ1214b in 14 bins, measured with Magellan/IMACS repeatedly over three transits. We measure a mean planet-to-star radius ratio of ( ) in the spectral bins. The optical transit depths are shallower on average than observed in the near-infrared. We present a model for jointly incorporating the effects of a composite photosphere and atmospheric transmission through the exoplanetʼs limb (the CPAT model), and use it to examine the cases of absorber and temperature heterogeneities in the stellar photosphere. We find the optical and near-infrared measurements are best explained by the combination of (1) photochemical haze in the exoplanetary atmosphere with a mode particle size r=0.1μm and haze-forming efficiency = f 10% haze and (2) faculae in the unocculted stellar disk with a temperature contrast D = -+ T 354 46 46 K, assuming 3.2% surface coverage. The CPAT model can be used to assess potential contributions of heterogeneous stellar photospheres to observations of exoplanet transmission spectra, which will be important for searches for spectral features in the optical.

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Section: Other Limb Darkening Prescriptionsmentioning

confidence: 99%

“…We utilize PHOENIX model stellar spectra (Husser et al 2013) We employ an MCMC approach to find the best-fitting CPAT-absorber model. We conduct an MCMC optimization for each of the exoplanet atmosphere models in the grids of cloudy and hazy models described in Section 6.2.…”

Section: Cpat Model For Absorber Heterogeneitiesmentioning

confidence: 99%

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Rackham

Espinoza

Apai

et al. 2017

ApJ

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“…Data from literature and the corresponding fits to a black body. The blue dots represents a PHOENIX stellar atmosphere similar to Fomalhaut (Husser et al 2013). The black dashed line is the best fit black body for all data points with T B = 8647 K. The green dashed line is the 870 µm -6600 µm data with T B = 5540 K. The Herschel data are denoted as red X's because they are not direct measurements of the star.…”

Section: Discussionmentioning

confidence: 99%

“…7 shows all of the stellar flux data from Table 3, along with two black bodies with TB = 8600 K (the photosphere) and TB = 5540 K (from millimetre data). A PHOENIX Stellar atmosphere model similar to that of Fomalhaut (Husser et al 2013) is also shown. The Herschel data from 70-500 µm are not a direct measurement of the stellar emission, but instead are the estimated stellar contribution to the unresolved central emission at each corresponding wavelength.…”

Section: What Can the Observations Tell Us About A Possible Close In mentioning

confidence: 94%

1.3 mm ALMA Observations of the Fomalhaut Debris System

White¹,

Boley²,

Dent³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present ALMA Band 6 observations (1.3 mm/233 GHz) of Fomalhaut and its debris disc. The observations achieve a sensitivity of 17 µJy and a resolution of 0.28 arcsec (2.1 au at a distance of 7.66 pc), which are the highest resolution observations to date of the millimetre grains in Fomalhaut's main debris ring. The ring is tightly constrained to 139 +2 −3 au with a FWHM of 13 ± 3 au, following a Gaussian profile. The millimetre spectral index is constrained to α mm = −2.73 ± 0.13. We explore fitting debris disc models in the image plane, as well as fitting models using visibility data directly. The results are compared and the potential advantages/disadvantages of each approach are discussed.The detected central emission is indistinguishable from a point source, with a most probable flux of 0.90±0.12 mJy (including calibration uncertainties). This implies that any inner debris structure, as was inferred from far-Infrared observations, must contribute little to the total central emission. Moreover, the stellar flux is less than 70% of that predicted by extrapolating a black body from the constrained stellar photosphere temperature. This result emphasizes that unresolved inner debris components cannot be fully characterized until the behaviour of the host star's intrinsic stellar emission at millimetre wavelengths is properly understood.

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“…Subscript 1 refers to the hot subdwarf, for which the models included H, He, C, N, O, Mg, Si and Fe opacities. Subscript 2 refers to the cool companions for which models were extracted from the P spectral library (Husser et al 2013 of the systems in order to be able to use multiple telescopes in the radial velocity follow-up and obtain a high enough signal-to-noise for abundance analysis. High resolution optical spectra have been obtained with the VLT-UVES spectrograph on a time-span comparable to the long orbital period (Chen et al 2013 predict 400 < P orb < 1600 d) of these binaries.…”

Section: Pb 3877 -A Hypervelocity Sdb Binarymentioning

confidence: 99%

Astroserver – Research Services in the Stellar Webshop

Németh¹

2017

Open Astronomy

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Abstract:A quick look at research and development in astronomy shows that we live in exciting times. Exoplanetary systems, supernovae, and merging binary black holes were far out of reach for observers two decades ago and now such phenomena are recorded routinely. This quick development would not have been possible without the ability for researchers to be connected, to think globally and to be mobile. Classical short-term positions are not always suitable to support these conditions and freelancing may be a viable alternative. We introduce the Astroserver framework, which is a new freelancing platform for scientists, and demonstrate through examples how it contributed to some recent projects related to hot subdwarf stars and binaries. These contributions, which included spectroscopic data mining, computing services and observing services, as well as artwork, allowed a deeper look into the investigated systems. The work on composite spectra binaries provided new details for the hypervelocity wide subdwarf binary PB 3877 and found diverse and rare systems with sub-giant companions in high-resolution spectroscopic surveys. The models for the peculiar abundance pattern of the evolved compact star LP 40-365 showed it to be a bound hypervelocity remnant of a supernova Iax event. Some of these works also included data visualizations to help presenting the new results. Such services may be of interest for many researchers.

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A new extensive library of PHOENIX stellar atmospheres and synthetic spectra

Cited by 1,642 publications

References 46 publications

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

1.3 mm ALMA Observations of the Fomalhaut Debris System

Astroserver – Research Services in the Stellar Webshop

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