The First Retrieval of a Substellar Subdwarf: A Cloud-free SDSS J125637.13–022452.4

Abstract We present the first retrieval analysis of a substellar subdwarf, SDSS J125637.13−022452.4 (SDSS J1256−0224), using the Brewster retrieval code base. We find SDSS J1256−0224 is best fit by a cloud-free model with an ion (neutral H, H−, and electron) abundance corresponding to Fe / H ion = − 1.5 . However, this model is indistinguishable from a cloud-free model with Fe / H ion = − 2.0 and a cloud-free model with Fe / H ion = − 1.5 assuming a subsolar carbon-to-oxygen ratio. We are able to constrain abundances for H2O, FeH, and CrH, with an inability to constrain any carbon-bearing species likely due to the low metallicity of SDSS J1256−0224. We also present an updated spectral energy distribution (SED) and semiempirical fundamental parameters. Our retrieval- and SED-based fundamental parameters agree with the Baraffe low-metallicity evolutionary models. From examining our “rejected” models (those with ΔBIC > 45), we find that we are able to retrieve gas abundances consistent with those of our best fitting model. We find the cloud in these poorer fitting “cloudy” models is either pushed to the bottom of the atmosphere or made optically thin.

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Big Three Dragons: A [N ii] 122 μm Constraint and New Dust-continuum Detection of a z = 7.15 Bright Lyman-break Galaxy with ALMA

The Astrophysical Journal ◽

10.3847/1538-4357/ac2a36 ◽

2021 ◽

Vol 923 (1) ◽

pp. 5

Author(s):

Yuma Sugahara ◽

Akio K. Inoue ◽

Takuya Hashimoto ◽

Satoshi Yamanaka ◽

Seiji Fujimoto ◽

...

Keyword(s):

Spectral Energy Distribution ◽

Far Infrared ◽

Abundance Ratio ◽

Continuum Emission ◽

Spectral Energy ◽

High Ionization ◽

The Galaxy ◽

Infrared Spectral ◽

Best Fit ◽

Redshift Galaxies

Abstract We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman-break galaxy at z = 7.15, B14-65666 (“Big Three Dragons”), which is an object detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum emission during the epoch of reionization. Our targets are the [N ii] 122 μm fine-structure emission line and the underlying 120 μm dust continuum. The dust continuum is detected with a ∼19σ significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 μm, we obtain a best-fit dust temperature of 40 K (79 K) and an infrared luminosity of log 10 ( L IR / L ⊙ ) = 11.6 (12.1) at the emissivity index β = 2.0 (1.0). The [N ii] 122 μm line is not detected. The 3σ upper limit of the [N ii] luminosity is 8.1 × 107 L ⊙. From the [N ii], [O iii], and [C ii] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high (Z > 0.4 Z ⊙), the ionization parameter and hydrogen density are log 10 U ≃ − 2.7 ± 0.1 and n H ≃ 50–250 cm−3, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, N/O, is constrained to be subsolar. At Z < 0.4 Z ⊙, the allowed U drastically increases as the assumed metallicity decreases. For high ionization parameters, the N/O constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.

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Near- to mid-infrared spectroscopy of the heavily obscured AGN LEDA 1712304 with AKARI/IRC

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935483 ◽

2019 ◽

Vol 626 ◽

pp. A130

Author(s):

T. Tsuchikawa ◽

H. Kaneda ◽

S. Oyabu ◽

T. Kokusho ◽

K. Morihana ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Spectral Properties ◽

Spectral Energy Distribution ◽

Galactic Nuclei ◽

Spectral Energy ◽

Absorption Feature ◽

Distribution Fitting ◽

Submillimeter Range ◽

Spectral Fitting ◽

Best Fit

Context. Although heavily obscured active galactic nuclei (AGNs) have been found by many observational studies, the properties of the surrounding dust are poorly understood. Using AKARI/IRC spectroscopy, we discovered a new heavily obscured AGN in LEDA 1712304 which shows a deep spectral absorption feature due to silicate dust. Aims. We study the infrared (IR) spectral properties of circumnuclear silicate dust in LEDA 1712304. Methods. We performed IR spectral fitting, considering silicate dust properties such as composition, porosity, size, and crystallinity. Spectral energy distribution fitting was also performed on the flux densities in the UV to submillimeter range to investigate the global spectral properties. Results. The best-fit model indicates 0.1 μm-sized porous amorphous olivine (Mg2xFe2−2xSiO4; x = 0.4) with 4% crystalline pyroxene. The optical depth is τsil ∼ 2.3, while the total IR luminosity and stellar mass are estimated to be LIR = (5 ± 1)×1010 L⊙ and Mstar = (2.7 ± 0.8)×109 M⊙, respectively. In such low LIR and Mstar ranges, there are few galaxies that show such a large τsil. Conclusion. The silicate dust in the AGN torus of LEDA 1712304 has properties that are notably similar to those in other AGNs overall, but slightly different in the wing shape of the absorption profile. The porosity of the silicate dust suggests dust coagulation or processing in the circumnuclear environments, while the crystallinity suggests that the silicate dust is relatively fresh.

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Probing midplane CO abundance and gas temperature with DCO+ in the protoplanetary disk around HD 169142

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732384 ◽

2018 ◽

Vol 614 ◽

pp. A106 ◽

Cited By ~ 15

Author(s):

M. T. Carney ◽

D. Fedele ◽

M. R. Hogerheijde ◽

C. Favre ◽

C. Walsh ◽

...

Keyword(s):

Spectral Energy Distribution ◽

Physical Structure ◽

Intensity Profile ◽

Spectral Energy ◽

Gas Temperature ◽

Broad Ring ◽

Disk Structure ◽

Outer Disk ◽

Grain Distribution ◽

Best Fit

Context. Physical and chemical processes in protoplanetary disks affect the disk structure and the midplane environment within which planets form. The simple deuterated molecular cation DCO+ has been proposed to act as a tracer of the disk midplane conditions. Aims. This work aims to understand which midplane conditions are probed by the DCO+ emission in the disk around the Herbig Ae star HD 169142. We explore the sensitivity of the DCO+ formation pathways to gas temperature and CO abundance. Methods. The DCO+ J = 3−2 transition was observed with Atacama Large Millimeter/submillimeter Array at a spatial resolution of ~0.3′′ (35 AU at 117 pc). We modeled the DCO+ emission in HD 169142 with a physical disk structure adapted from the literature, and employed a simple deuterium chemical network to investigate the formation of DCO+ through the cold deuterium fractionation pathway via H2D+. Parameterized models are used to modify the gas temperature and CO abundance structure of the disk midplane to test their effect on DCO+ production. Contributions from the warm deuterium fractionation pathway via CH2D+ are approximated using a constant abundance in the intermediate disk layers. Results. The DCO+ line is detected in the HD 169142 disk with a total integrated line flux of 730 ± 73 mJy km s−1. The radial intensity profile reveals a warm, inner component of the DCO+ emission at radii ≲30 AU and a broad, ring-like structure from ~50–230 AU with a peak at 100 AU just beyond the edge of the millimeter grain distribution. Parameterized models show that alterations to the midplane gas temperature and CO abundance are both needed to recover the observed DCO+ radial intensity profile. The alterations are relative to the fiducial physical structure of the literature model constrained by dust and CO observations. The best-fit model contains a shadowed, cold midplane in the region z∕r < 0.1 with an 8 K decrease in Tgas and a factor of five CO depletion just beyond the millimeter grains (r = 83 AU), and a 2 K decrease in Tgas for r > 120 AU. The warm deuterium fractionation pathway is implemented as a constant DCO+ abundance of 2.0 × 10−12 between 30–70 K and contributes >85% to the DCO+ emission at r < 83 AU in the best-fit model. Conclusions. The DCO+ emission probes a reservoir of cold material in the HD 169142 outer disk that is not probed by the millimeter continuum, the spectral energy distribution, nor the emission from the 12 CO, 13 CO, or C18O J = 2−1 lines. The DCO+ emission is a sensitive probe of gas temperature and CO abundance near the disk midplane and provides information about the outer disk beyond the millimeter continuum distribution that is largely absent in abundant gaseous tracers such as CO isotopologues.

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Asteroseismological Analysis of the DAV HS 0507+0434B: The Influence of Chemical Profile on the Pulsation Periods

The Astrophysical Journal ◽

10.3847/1538-4357/ac25f1 ◽

2021 ◽

Vol 922 (2) ◽

pp. 138

Author(s):

Lin Guifang ◽

Su Jie ◽

Li Yan ◽

Fu Jianning

Keyword(s):

Iteration Method ◽

Mass Fraction ◽

Chemical Structure ◽

Inner Core ◽

Chemical Profile ◽

Fundamental Parameters ◽

Trapped Mode ◽

Core Profile ◽

Best Fitting ◽

Fitting Model

Abstract Asteroseismology is a powerful tool to infer the details of the inner chemical structure of white dwarfs. Using the nine observed frequencies of HS 0507+0434B, we explore the influence of the inner chemical profile on the pulsation periods. Based on the evolutionary C/O profile, we modify slightly the C/O core profile and make an asteroseismic analysis for HS 0507+0434B. We find that the trapped mode with the period of 445.3 s is mainly affected by the hydrogen and helium mass fraction. The inner C/O core profile has an influence on all modes extending into the inner core. When we use the iteration method with the optimal C/O core profile, the fit between the theoretical periods and observed ones is significantly improved. For the best-fitting model with the optimal parametric C/O core, there is a smaller C/O ratio and a smaller overshooting zone in the stellar interior. The fundamental parameters of the model with the optimal C/O core are M */M ⊙ ∼ 0.710 ± 0.005, T eff ∼ 12570 ± 106K, log M H / M * ∼ − 8.01 ± 0.08 , and log M He / M * ∼ − 2.51 ± 0.08 .

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The outer disk of the classical Be star ψ Per

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317003064 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 414-414

Author(s):

Robert Klement ◽

Alex C. Carciofi ◽

Thomas Rivinius ◽

Lynn D. Matthews ◽

Richard Ignace ◽

...

Keyword(s):

Monte Carlo ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Density Measurements ◽

Outer Disk ◽

Disk Size ◽

Gaussian Fit ◽

Be Star ◽

Best Fit ◽

Striking Contrast

AbstractTo this date ψ Per is the only classical Be star that was angularly resolved in radio (by the VLA at λ = 2 cm). Gaussian fit to the azimuthally averaged visibility data indicates a disk size (FWHM) of ~500 stellar radii (Dougherty & Taylor 1992). Recently, we obtained new multi-band cm flux density measurements of ψ Per from the enhanced VLA. We modeled the observed spectral energy distribution (SED) covering the interval from ultraviolet to radio using the Monte Carlo radiative transfer code HDUST (Carciofi & Bjorkman 2006). An SED turndown, that occurs between far-IR and radio wavelengths, is explained by a truncated viscous decretion disk (VDD), although the shallow slope of the radio SED suggests that the disk is not simply cut off, as is assumed in our model. The best-fit size of a truncated disk derived from the modeling of the radio SED is 100+5−15 stellar radii, which is in striking contrast with the result of Dougherty & Taylor (1992). The reasons for this discrepancy are under investigation.

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Optical and Infrared Spectroscopy of CM Draconis

Highlights of Astronomy ◽

10.1017/s1539299600021729 ◽

1998 ◽

Vol 11 (1) ◽

pp. 441-441

Author(s):

S. Viti ◽

H.R.A. Jones ◽

F. Allard ◽

A. Schweitzer ◽

P. Hauschildt

Keyword(s):

Spectral Energy Distribution ◽

Systematic Errors ◽

Spectral Energy ◽

Space Motion ◽

Optical Region ◽

Rich Solution ◽

Low Metallicity ◽

Atomic Lines ◽

High Space ◽

Infrared Sed

Abstract We compare observations of the binary system CM Draconis with synthetic spectra. Spectroscopic observations from 0.40 to 2.41μm, combined with photometry and the accurately known surface gravity enable us to estimate the temperature and metallicity using detailed spectra synthesis. We find discrepancies between the analysis of the infrared and optical spectrum: while the optical spectral energy distribution (SED) yields a metal-rich solution with Teff = 3000K, the infrared SED yields around 3200K and —0.8 ≤ [M/H] ≤ —0.6 compatible with the high space motion of the system. The low-metallicity characteristics of the infrared SED could be real and is partly supported by the detailed analysis of the atomic lines in the optical region. Although, the known incompleteness of the TiO and H2O line lists in the models may cause substantial systematic errors.

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A dust radiative transfer study of the edge-on spiral galaxy NGC 5908

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314010059 ◽

2014 ◽

Vol 10 (S309) ◽

pp. 309-309 ◽

Cited By ~ 1

Author(s):

G. De Geyter ◽

M. Baes ◽

P. Camps ◽

J. Fritz ◽

S. Viaene

Keyword(s):

Radiative Transfer ◽

Spiral Galaxy ◽

Spectral Energy Distribution ◽

Radiative Transfer Model ◽

Spectral Energy ◽

Transfer Model ◽

Double Exponential ◽

Best Fitting ◽

Dust Distribution ◽

Transfer Study

AbstractWe present a dust radiative transfer analysis of the edge-on spiral galaxy NGC 5908. In our previous analysis, it was found that the standard assumption of a double-exponential dust distribution resulted in a poor fit. We investigate the possibility of the dust being distributed in one or more rings. The parameters are constrained using FitSKIRT, a code used to automatically determine the best fitting radiative transfer model given a set of observations. We discuss the possible implications of this dust distribution on the predicted spectral energy distribution.

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The GRAVITY young stellar object survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038249 ◽

2020 ◽

Vol 642 ◽

pp. A162

Author(s):

◽

Y.-I. Bouarour ◽

K. Perraut ◽

F. Ménard ◽

W. Brandner ◽

...

Keyword(s):

Near Infrared ◽

Gravity Data ◽

Spectral Energy Distribution ◽

Central Star ◽

High Resolution Spectroscopy ◽

Spectral Energy ◽

Disk Model ◽

Stellar Radius ◽

Fundamental Parameters ◽

Outer Disk

Context. Studies of the dust distribution, composition, and evolution of protoplanetary disks provide clues for understanding planet formation. However, little is known about the innermost regions of disks where telluric planets are expected to form. Aims. We aim constrain the geometry of the inner disk of the T Tauri star RY Lup by combining spectro-photometric data and interferometric observations in the near-infrared (NIR) collected at the Very Large Telescope Interferometer. We use PIONIER data from the ESO archive and GRAVITY data that were obtained in June 2017 with the four 8m telescopes. Methods. We use a parametric disk model and the 3D radiative transfer code MCFOST to reproduce the spectral energy distribution (SED) and match the interferometric observations. MCFOST produces synthetic SEDs and intensity maps at different wavelengths from which we compute the modeled interferometric visibilities and closure phases through Fourier transform. Results. To match the SED from the blue to the millimetric range, our model requires a stellar luminosity of 2.5 L⊙, higher than any previously determined values. Such a high value is needed to accommodate the circumstellar extinction caused by the highly inclined disk, which has been neglected in previous studies. While using an effective temperature of 4800 K determined through high-resolution spectroscopy, we derive a stellar radius of 2.29 R⊙. These revised fundamental parameters, when combined with the mass estimates available (in the range 1.3–1.5 M⊙), lead to an age of 0.5–2.0 Ma for RY Lup, in better agreement with the age of the Lupus association than previous determinations. Our disk model (that has a transition disk geometry) nicely reproduces the interferometric GRAVITY data and is in good agreement with the PIONIER ones. We derive an inner rim location at 0.12 au from the central star. This model corresponds to an inclination of the inner disk of 50°, which is in mild tension with previous determinations of a more inclined outer disk from SPHERE (70° in NIR) and ALMA (67 ± 5°) images, but consistent with the inclination determination from the ALMA CO spectra (55 ± 5°). Increasing the inclination of the inner disk to 70° leads to a higher line-of-sight extinction and therefore requires a higher stellar luminosity of 4.65 L⊙ to match the observed flux levels. This luminosity would translate to a stellar radius of 3.13 R⊙, leading to an age of 2–3 Ma, and a stellarmass of about 2 M⊙, in disagreement with the observed dynamical mass estimate of 1.3–1.5 M⊙. Critically, this high-inclination inner disk model also fails to reproduce the visibilities observed with GRAVITY. Conclusions. The inner dust disk, as traced by the GRAVITY data, is located at a radius in agreement with the dust sublimation radius. An ambiguity remains regarding the respective orientations of the inner and outer disk, coplanar and mildly misaligned, respectively.As our datasets are not contemporary and the star is strongly variable, a deeper investigation will require a dedicated multi-technique observing campaign.

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Modeling circumstellar envelope with advanced numerical codes

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311006867 ◽

2010 ◽

Vol 6 (S274) ◽

pp. 175-177

Author(s):

P. Procopio ◽

A. De Rosa ◽

C. Burigana ◽

G. Umana ◽

C. Trigilio

Keyword(s):

Monte Carlo ◽

Markov Chain ◽

Scientific Community ◽

Spectral Synthesis ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Circumstellar Envelope ◽

Circumstellar Envelopes ◽

Formation And Evolution ◽

Best Fit

AbstractWe propose a modeling study on the formation and evolution of the Circumstellar Envelopes (CSEs) of a sample of selected radio-loud objects, based on an innovative interaction between two codes widely used by the scientific community, but in different fields. CLOUDY (Ferland et al. 1998) is a widely used code to model the spectral energy distribution (SED) of the several objects characterized by clouds of gas heated and ionized by a central object. CosmoMC (Lewis & Bridle 2002) instead is usually used for exploring cosmological parameter space. We investigate here on the exploitation of the sampling performance of the Markov-Chain Monte-Carlo (MCMC) engine of CosmoMC to search for a best fit model of the considered objects through the spectral synthesis capacity of CLOUDY.

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What Powers the 2006 Outburst of the Symbiotic Star BF Cygni?

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2015.02.0277 ◽

2015 ◽

Vol 2 (1) ◽

pp. 277-281 ◽

Cited By ~ 1

Author(s):

A. Skopal ◽

M. Sekeráš ◽

N. A. Tomov ◽

M. T. Tomova ◽

T. N. Tarasova ◽

...

Keyword(s):

Spectral Energy Distribution ◽

Emission Measure ◽

Active Phase ◽

Spectral Energy ◽

Active Object ◽

Low Resolution ◽

Radiation Emission ◽

Fundamental Parameters ◽

Optical Light Curve ◽

High Level

BF Cygni is a classical symbiotic binary. Its optical light curve occasionally shows outbursts of the Z And-type, whose nature is not well understood. During the 2006 August, BF Cyg underwent the recent outburst, and continues its active phase to the present. The aim of this contribution is to determine the fundamental parameters of the hot component in the binary during the active phase. For this purpose we used a high- and low-resolution optical spectroscopy and the multicolour UBV RCIC photometry. Our photometric monitoring revealed that a high level of the star’s brightness lasts for unusually long time of > 7 years. A sharp violet-shifted absorption component and broad emission wings in the Hα profile developed during the whole active phase. From 2009, our spectra revealed a bipolar ejection from the white dwarf (WD). Modelling the spectral energy distribution (SED) of the low-resolution spectra showed simultaneous presence of a warm (< 10 000 K) disk-like pseudophotosphere and a strong nebular component of radiation (emission measure of ~1061 cm−3). The luminosity of the hot active object was estimated to > 5−8×103 Lʘ. Such high luminosity, sustained for the time of years, can be understood as a result of an enhanced transient accretion rate throughout a large disk, leading also to formation of collimated ejection from the WD.

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