# Spectroscopy of the HR 8799 system

## Spectroscopy of the HR 8799 system

VLT Captures First Direct Spectrum of an Exoplanet

http://www.eso.org/public/news/eso1002/

(assuming HR8799c is an exoplanet)

A link to the paper is provided at the end of the press release.

exoplanet
Planetesimal

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## Re: Spectroscopy of the HR 8799 system

Moving further into the era of exoplanetary characterisation. This system is also valuable as there are multiple, presumably roughly coeval planets: wonder if there are going to be significant differences in the spectra. Also good to get data on planets in a different range of irradiation than the hot Jupiters which have been the best characterised planets up to now.

(I would think it is rather difficult to argue against HR 8799 c being a planet given the configuration of the entire system.)

Lazarus
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## Direct Imaging of the Spectrum of HR8799c

Lazarus wrote:(I would think it is rather difficult to argue against HR 8799 c being a planet given the configuration of the entire system.)

Yes, quite true. Just teasing a little
A common origin based on a protoplanetary disc is more likely.

exoplanet
Planetesimal

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## Re: Spectroscopy of the HR 8799 system

Less methane and more carbon monoxide than expected?

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Sirius_Alpha

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## Re: Spectroscopy of the HR 8799 system

Here's the paper.

Spatially resolved spectroscopy of the exoplanet HR 8799 c
http://arxiv.org/abs/1001.2017

Abstract wrote:HR 8799 is a multi-planet system detected in direct imaging, with three companions known so far. Here, we present spatially resolved VLT/NACO 3.88--4.10 micron spectroscopy of the middle planet, HR 8799 c, which has an estimated mass of ~10 Mjup, temperature of ~1100 K and projected separation of 38 AU. The spectrum shows some differences in the continuum from existing theoretical models, particularly longwards of 4 microns, implying that detailed cloud structure or non-equilibrium conditions may play an important role in the physics of young exoplanetary atmospheres.

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Sirius_Alpha

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## VLT Captures First Direct Spectrum of an Exoplanet (HR 8799)

Now this is interesting guys.
By studying a triple planetary system that resembles a scaled-up
version of our own Sun’s family of planets, astronomers have been able
to obtain the first direct spectrum — the “chemical fingerprint” — of a planet orbiting a distant star ,
thus bringing new insights into the planet's formation and composition.
The result represents a milestone in the search for life elsewhere in
the Universe.

Ryag Han
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## Re: Spectroscopy of the HR 8799 system

Edit (Aug 20, 2010): Threads merged.

Last edited by Sirius_Alpha on 30th August 2010, 5:51 pm; edited 1 time in total

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Sirius_Alpha

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## Re: Spectroscopy of the HR 8799 system

ops...anyway,that one was on the exoplanetary news and discoveries,
this one is for discussing the issue scientifically.

Ryag Han
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## IR Spectroscopy of HR 8799 b

Near-Infrared Spectroscopy of the Extrasolar Planet HR 8799 b
http://arxiv.org/abs/1008.4582

Abstract wrote:We present 2.12-2.23 um high contrast integral field spectroscopy of the extrasolar planet HR 8799 b. Our observations were obtained with OSIRIS on the Keck II telescope and sample the 2.2 um CH4 feature, which is useful for spectral classification and as a temperature diagnostic for ultracool objects. The spectrum of HR 8799 b is relatively featureless, with little or no methane absorption, and does not exhibit the strong CH4 seen in T dwarfs of similar absolute magnitudes. Overall, we find that HR 8799 b has a spectral type consistent with L5-T2, although its SED is atypical compared to most field objects. We fit the 2.2 um spectrum and the infrared SED using the Hubeny & Burrows, Burrows et al., and Ames-Dusty model atmosphere grids, which incorporate nonequilibrium chemistry, non-solar metallicities, and clear and cloudy variants. No models agree with all of the data, but those with intermediate clouds produce significantly better fits. The largest discrepancy occurs in the J-band, which is highly suppressed in HR 8799 b. The best-fitting effective temperatures range from 1300-1700 K with radii between ~0.3-0.5 RJup. These values are inconsistent with evolutionary model-derived values of 800-900 K and 1.1-1.3 RJup based on the luminosity of HR 8799 b and the age of HR 8799, a discrepancy that probably results from imperfect atmospheric models or the limited range of physical parameters covered by the models. The low temperature inferred from evolutionary models indicates that HR 8799 b is ~400 K cooler than field L/T transition objects, providing further evidence that the L/T transition is gravity-dependent. With an unusually dusty photosphere, an exceptionally low luminosity for its spectral type, and hints of extreme secondary physical parameters, HR 8799 b appears to be unlike any class of field brown dwarf currently known.

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Sirius_Alpha

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## Re: Spectroscopy of the HR 8799 system

Well that is weird, definitely poking some holes into theoretical models of such objects, and given the masses are determined from these models, it raises the question of just how far they can be trusted.

(Incidentally it might be worth merging this with the two threads on the spectrum of HR 8799 c?)

Lazarus
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## Re: Spectroscopy of the HR 8799 system

Lazarus wrote:(Incidentally it might be worth merging this with the two threads on the spectrum of HR 8799 c?)
That's a great idea

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## Re: Spectroscopy of the HR 8799 system

A Combined Subaru/VLT/MMT 1--5 Micron Study of Planets Orbiting HR 8799: Implications for Atmospheric Properties, Masses, and Formation
http://arxiv.org/abs/1101.1973

We present new 1--1.25 $\mu m$ (z and J band) Subaru/IRCS and 2 $\mu m$ (K band) VLT/NaCo data for HR 8799 and a rereduction of the 3--5 $\mu m$ MMT/Clio data first presented by citet{Hinz2010}. Our VLT/NaCo data yields a detection of a fourth planet at a projected separation of $\sim$ 15 AU -- "HR 8799e". We also report new, albeit weak detections of HR 8799b at 1.03 $\mu m$ and 3.3 $\mu m$. Empirical comparisons to field brown dwarfs show that at least HR 8799b and HR8799c, and possibly HR 8799d, have near-to-mid IR colors/magnitudes significantly discrepant from the L/T dwarf sequence. Standard cloud deck atmosphere models appropriate for brown dwarfs provide only (marginally) statistically meaningful fits to HR 8799b and c for unphysically small radii. Models with thicker cloud layers not present in brown dwarfs reproduce the planets' SEDs far more accurately and without the need for rescaling the planets' radii. Our preliminary modeling suggests that HR 8799b has log(g) = 4--4.5, T$_{eff}$ = 900K, while HR 8799c, d, and (by inference) e have log(g) = 4--4.5, T$_{eff}$ = 1000--1200K. Combining results from planet evolution models and new dynamical stability limits implies that the masses of HR 8799b, c, d, and e are 6--7 M$_{J}$, 7--10 M$_{J}$, 7--10 M$_{J}$ and 7--10 M$_{J}$. 'Patchy" cloud prescriptions may provide even better fits to the data and may lower the estimated surface gravities and masses. Finally, contrary to some recent claims, forming the HR 8799 planets by core accretion is still plausible, although such systems are likely rare.

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Sirius_Alpha

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## Re: Spectroscopy of the HR 8799 system

Best of all, it was possible to confirm the fourth planet. Keck and VLT telescopes is the best telescops for photographing.

Borislav
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## Re: Spectroscopy of the HR 8799 system

Wonder if the HR 8799 planets are sufficiently different from brown dwarfs to warrant a new spectral type (Y?). The bit about core accretion is interesting, wouldn't be surprised if this debate goes on for a while...

Lazarus
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## Re: Spectroscopy of the HR 8799 system

More modelling, seems that thick clouds (thicker than those on typical brown dwarfs) might be to blame for the weird spectra.

Furthermore the spectral type sequence L/T may not be so useful for planets...

Therefore, our analysis predicts that the near-IR SEDs of many soon-to-be imaged planets will not track the L/T dwarf sequence. Rather, like the HR 8799 planets and 2M1207b, they will track a distinguishable “planet locus” following an extension of the L dwarf sequence, diverging from the L/T dwarf sequence for field brown dwarfs at the L/T transition, and extending to systematically fainter and redder color-magnitude positions.

Lazarus
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## Re: Spectroscopy of the HR 8799 system

Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b
http://arxiv.org/abs/1103.3895

Using the integral field spectrograph OSIRIS, on the Keck II telescope, broad near-infrared H and K-band spectra of the young exoplanet HR8799b have been obtained. In addition, six new narrow-band photometric measurements have been taken across the H and K bands. These data are combined with previously published photometry for an analysis of the planet's atmospheric properties. Thick photospheric dust cloud opacity is invoked to explain the planet's red near-IR colors and relatively smooth near-IR spectrum. Strong water absorption is detected, indicating a Hydrogen-rich atmosphere. Only weak CH4 absorption is detected at K band, indicating efficient vertical mixing and a disequilibrium CO/CH4 ratio at photospheric depths. The H-band spectrum has a distinct triangular shape consistent with low surface gravity. New giant planet atmosphere models are compared to these data with best fitting bulk parameters, Teff = 1100K +- 100 and log(g) = 3.5 +-0.5 (for solar composition). Given the observed luminosity, log(Lobs/Lsun) ~ -5.1, these values correspond to a radius of 0.75 Rjup (+0.17, -0.12) and mass ~ 0.72 Mjup (+2.6,-0.6) -- strikingly inconsistent with interior/evolution models. Enhanced metallicity (up to ~ 10 times that of the Sun) along with thick clouds and non-equilibrium chemistry are likely required to reproduce the complete ensemble of spectroscopic and photometric data and the low effective temperatures (< 1000K) required by the evolution models.

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## Re: Spectroscopy of the HR 8799 system

Reconnaissance of the HR 8799 Exosolar System I: Near IR Spectroscopy
http://arxiv.org/abs/1303.2627

We obtained spectra, in the wavelength range \lambda = 995 - 1769 nm, of all four known planets orbiting the star HR 8799. Using the suite of instrumentation known as Project 1640 on the Palomar 5-m Hale Telescope, we acquired data at two epochs. This allowed for multiple imaging detections of the companions and multiple extractions of low-resolution (R ~ 35) spectra. Data reduction employed two different methods of speckle suppression and spectrum extraction, both yielding results that agree. The spectra do not directly correspond to those of any known objects, although similarities with L and T-dwarfs are present, as well as some characteristics similar to planets such as Saturn. We tentatively identify the presence of CH_4 along with NH_3 and/or C_2H_2, and possibly CO_2 or HCN in varying amounts in each component of the system. Other studies suggested red colors for these faint companions, and our data confirm those observations. Cloudy models, based on previous photometric observations, may provide the best explanation for the new data presented here. Notable in our data is that these presumably co-eval objects of similar luminosity have significantly different spectra; the diversity of planets may be greater than previously thought. The techniques and methods employed in this paper represent a new capability to observe and rapidly characterize exoplanetary systems in a routine manner over a broad range of planet masses and separations. These are the first simultaneous spectroscopic observations of multiple planets in a planetary system other than our own.

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## Re: Spectroscopy of the HR 8799 system

Notable in our data is that these presumably co-eval objects of similar luminosity have significantly different spectra; the diversity of planets may be greater than previously thought.
Makes you wonder how well we should expect the class I-V system of Sudarsky et al. (2000) to hold up, once giant planets in the relevant distance ranges are observed.

I expect surprises.

Lazarus
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## Re: Spectroscopy of the HR 8799 system

The C/O ratio has been determined for HR 8799 c. The atmospheric C/O is consistent with core accretion formation.

Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere
http://arxiv.org/abs/1303.3280

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