ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    Exoplanet atmosphere. Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy (2014)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2014-10-11
    Description: Exoplanets that orbit close to their host stars are much more highly irradiated than their solar system counterparts. Understanding the thermal structures and appearances of these planets requires investigating how their atmospheres respond to such extreme stellar forcing. We present spectroscopic thermal emission measurements as a function of orbital phase ("phase-curve observations") for the highly irradiated exoplanet WASP-43b spanning three full planet rotations using the Hubble Space Telescope. With these data, we construct a map of the planet's atmospheric thermal structure, from which we find large day-night temperature variations at all measured altitudes and a monotonically decreasing temperature with pressure at all longitudes. We also derive a Bond albedo of 0.18(-0.12)(+0.07) and an altitude dependence in the hot-spot offset relative to the substellar point.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stevenson, Kevin B -- Desert, Jean-Michel -- Line, Michael R -- Bean, Jacob L -- Fortney, Jonathan J -- Showman, Adam P -- Kataria, Tiffany -- Kreidberg, Laura -- McCullough, Peter R -- Henry, Gregory W -- Charbonneau, David -- Burrows, Adam -- Seager, Sara -- Madhusudhan, Nikku -- Williamson, Michael H -- Homeier, Derek -- New York, N.Y. -- Science. 2014 Nov 14;346(6211):838-41. doi: 10.1126/science.1256758. Epub 2014 Oct 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA. NASA Sagan Fellow. kbs@uchicago.edu. ; CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309, USA. ; Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA. ; Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA. ; Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, USA. ; Space Telescope Science Institute, Baltimore, MD 21218, USA. Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA. ; Center for Excellence in Information Systems, Tennessee State University, Nashville, TN 37209, USA. ; Department of Astronomy, Harvard University, Cambridge, MA 02138, USA. ; Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA. ; Department of Earth, Atmospheric, and Planetary Sciences, Department of Physics, Massachusetts Institute of Technology, 54-1718, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. ; Institute of Astronomy, University of Cambridge, Cambridge CB3 OHA, UK. ; Centre de Recherche Astrophysique de Lyon, UMR 5574, CNRS, Universite de Lyon, Ecole Normale Superieure de Lyon, 46 Allee d'Italie, F-69364 Lyon Cedex 07, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25301972" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-12-18
    Description: Thousands of transiting exoplanets have been discovered, but spectral analysis of their atmospheres has so far been dominated by a small number of exoplanets and data spanning relatively narrow wavelength ranges (such as 1.1-1.7 micrometres). Recent studies show that some hot-Jupiter exoplanets have much weaker water absorption features in their near-infrared spectra than predicted. The low amplitude of water signatures could be explained by very low water abundances, which may be a sign that water was depleted in the protoplanetary disk at the planet's formation location, but it is unclear whether this level of depletion can actually occur. Alternatively, these weak signals could be the result of obscuration by clouds or hazes, as found in some optical spectra. Here we report results from a comparative study of ten hot Jupiters covering the wavelength range 0.3-5 micrometres, which allows us to resolve both the optical scattering and infrared molecular absorption spectroscopically. Our results reveal a diverse group of hot Jupiters that exhibit a continuum from clear to cloudy atmospheres. We find that the difference between the planetary radius measured at optical and infrared wavelengths is an effective metric for distinguishing different atmosphere types. The difference correlates with the spectral strength of water, so that strong water absorption lines are seen in clear-atmosphere planets and the weakest features are associated with clouds and hazes. This result strongly suggests that primordial water depletion during formation is unlikely and that clouds and hazes are the cause of weaker spectral signatures.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sing, David K -- Fortney, Jonathan J -- Nikolov, Nikolay -- Wakeford, Hannah R -- Kataria, Tiffany -- Evans, Thomas M -- Aigrain, Suzanne -- Ballester, Gilda E -- Burrows, Adam S -- Deming, Drake -- Desert, Jean-Michel -- Gibson, Neale P -- Henry, Gregory W -- Huitson, Catherine M -- Knutson, Heather A -- des Etangs, Alain Lecavelier -- Pont, Frederic -- Showman, Adam P -- Vidal-Madjar, Alfred -- Williamson, Michael H -- Wilson, Paul A -- England -- Nature. 2016 Jan 7;529(7584):59-62. doi: 10.1038/nature16068. Epub 2015 Dec 14.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK. ; Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA. ; Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK. ; Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721, USA. ; Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, New Jersey 08544, USA. ; Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA. ; Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, Colorado 80309, USA. ; European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Munchen, Germany. ; Center of Excellence in Information Systems, Tennessee State University, Nashville, Tennessee 37209, USA. ; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA. ; CNRS, Institut dAstrophysique de Paris, UMR 7095, 98 bis boulevard Arago, 75014 Paris, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26675732" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/*chemistry ; Extraterrestrial Environment/*chemistry ; Jupiter ; *Planets ; Pressure ; Spectrophotometry, Infrared ; Telescopes ; Temperature ; Water/*analysis
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Warm ice giant GJ 3470b - II. Revised planetary and stellar parameters from optical to near-infrared transit photometry (2014)
    Oxford University Press
    Details
    Publication Date: 2014-07-27
    Description: It is important to explore the diversity of characteristics of low-mass, low-density planets to understand the nature and evolution of this class of planets. We present a homogeneous analysis of 12 new and 9 previously published broad-band photometric observations of the Uranus-sized extrasolar planet GJ 3470b, which belongs to the growing sample of sub-Jovian bodies orbiting M dwarfs. The consistency of our analysis explains some of the discrepancies between previously published results and provides updated constraints on the planetary parameters. Our data are also consistent with previous transit observations of this system. The physical properties of the transiting system can only be constrained as well as the host star is characterized, so we provide new spectroscopic measurements of GJ 3470 from 0.33 to 2.42 μm to aid our analysis. We find R * = 0.48 ± 0.04 R , M * = 0.51 ± 0.06 M , and T eff = 3652 ± 50K for GJ 3470, along with a rotation period of 20.70 ± 0.15 d and an R -band amplitude of 0.01 mag, which is small enough that current transit measurements should not be strongly affected by stellar variability. However, to report definitively whether stellar activity has a significant effect on the light curves, this requires future multiwavelength, multi-epoch studies of GJ 3470. We also present the most precise orbital ephemeris for this system: T o = 2455983.70472 ± 0.00021BJD TDB , P = 3.336 6487 $^{+0.000\,0043}_{-0.000\,0033}$ d, and we see no evidence for transit timing variations greater than 1 min. Our reported planet to star radius ratio is 0.076 42 ± 0.000 37. The physical parameters of this planet are R p = 3.88 ± 0.32 R and M p = 13.73 ± 1.61 M . Because of our revised stellar parameters, the planetary radius we present is smaller than previously reported values. We also perform a second analysis of the transmission spectrum of the entire ensemble of transit observations to date, supporting the existence of an H 2 -dominated atmosphere exhibiting a strong Rayleigh scattering slope.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Hubble Space Telescope hot Jupiter transmission spectral survey: a detection of Na and strong optical absorption in HAT-P-1b (2013)
    Oxford University Press
    Details
    Publication Date: 2013-12-06
    Description: We present an optical to near-infrared transmission spectrum of the hot Jupiter HAT-P-1b, based on Hubble Space Telescope observations, covering the spectral regime from 0.29 to 1.027 μm with Space Telescope Imaging Spectrograph (STIS), which is coupled with a recent Wide Field Camera 3 (WFC3) transit (1.087 to 1.687 μm). We derive refined physical parameters of the HAT-P-1 system, including an improved orbital ephemeris. The transmission spectrum shows a strong absorption signature shortward of 0.55 μm, with a strong blueward slope into the near-ultraviolet. We detect atmospheric sodium absorption at a 3.3 significance level, but find no evidence for the potassium feature. The red data imply a marginally flat spectrum with a tentative absorption enhancement at wavelength longer than ~ 0.85 μm. The STIS and WFC3 spectra differ significantly in absolute radius level (4.3 ± 1.6 pressure scaleheights), implying strong optical absorption in the atmosphere of HAT-P-1b. The optical to near-infrared difference cannot be explained by stellar activity, as simultaneous stellar activity monitoring of the G0V HAT-P-1b host star and its identical companion show no significant activity that could explain the result. We compare the complete STIS and WFC3 transmission spectrum with theoretical atmospheric models which include haze, sodium and an extra optical absorber. We find that both an optical absorber and a supersolar sodium to water abundance ratio might be a scenario explaining the HAT-P-1b observations. Our results suggest that strong optical absorbers may be a dominant atmospheric feature in some hot Jupiter exoplanets.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering (2014)
    Oxford University Press
    Details
    Publication Date: 2014-11-29
    Description: We present Hubble Space Telescope optical and near-IR transmission spectra of the transiting hot-Jupiter WASP-31b. The spectrum covers 0.3–1.7 μm at a resolution R  ~ 70, which we combine with Spitzer photometry to cover the full-optical to IR. The spectrum is dominated by a cloud deck with a flat transmission spectrum which is apparent at wavelengths 〉 0.52 μm. The cloud deck is present at high altitudes and low pressures, as it covers the majority of the expected optical Na line and near-IR H 2 O features. While Na  i absorption is not clearly identified, the resulting spectrum does show a very strong potassium feature detected at the 4.2 confidence level. Broadened alkali wings are not detected, indicating pressures below ~10 mbar. The lack of Na and strong K is the first indication of a sub-solar Na/K abundance ratio in a planetary atmosphere (ln[Na/K] = –3.3 ± 2.8), which could potentially be explained by Na condensation on the planet's night side, or primordial abundance variations. A strong Rayleigh scattering signature is detected at short wavelengths, with a 4 significant slope. Two distinct aerosol size populations can explain the spectra, with a smaller sub-micron size grain population reaching high altitudes producing a blue Rayleigh scattering signature on top of a larger, lower lying population responsible for the flat cloud deck at longer wavelengths. We estimate that the atmospheric circulation is sufficiently strong to mix micron size particles upwards to the required 1–10 mbar pressures, necessary to explain the cloud deck. These results further confirm the importance of clouds in hot Jupiters, which can potentially dominate the overall spectra and may alter the abundances of key gaseous species.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    HST hot-Jupiter transmission spectral survey: haze in the atmosphere of WASP-6b (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-20
    Description: We report Hubble Space Telescope optical to near-infrared transmission spectroscopy of the hot-Jupiter WASP-6b, measured with the Space Telescope Imaging Spectrograph and Spitzer's InfraRed Array Camera. The resulting spectrum covers the range 0.29–4.5 μm. We find evidence for modest stellar activity of WASP-6 and take it into account in the transmission spectrum. The overall main characteristic of the spectrum is an increasing radius as a function of decreasing wavelength corresponding to a change of ( R p / R * ) = 0.0071 from 0.33 to 4.5 μm. The spectrum suggests an effective extinction cross-section with a power law of index consistent with Rayleigh scattering, with temperatures of 973 ± 144 K at the planetary terminator. We compare the transmission spectrum with hot-Jupiter atmospheric models including condensate-free and aerosol-dominated models incorporating Mie theory. While none of the clear-atmosphere models is found to be in good agreement with the data, we find that the complete spectrum can be described by models that include significant opacity from aerosols including Fe-poor Mg 2 SiO 4 , MgSiO 3 , KCl and Na 2 S dust condensates. WASP-6b is the second planet after HD 189733b which has equilibrium temperatures near ~1200 K and shows prominent atmospheric scattering in the optical.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    Extensive study of HD 25558, a long-period double-lined binary with two SPB components (2014)
    Oxford University Press
    Details
    Publication Date: 2014-02-20
    Description: We carried out an extensive observational study of the Slowly Pulsating B (SPB) star, HD 25558. The 2000 spectra obtained at different observatories, the ground-based and MOST satellite light curves revealed that this object is a double-lined spectroscopic binary with an orbital period of about nine years. The observations do not allow the inference of an orbital solution. We determined the physical parameters of the components, and found that both lie within the SPB instability strip. Accordingly, both show line-profile variations due to stellar pulsations. 11 independent frequencies were identified in the data. All the frequencies were attributed to one of the two components based on pixel-by-pixel variability analysis of the line profiles. Spectroscopic and photometric mode identification was also performed for the frequencies of both stars. These results suggest that the inclination and rotation of the two components are rather different. The primary is a slow rotator with 6 d period, seen at 60° inclination, while the secondary rotates fast with 1.2 d period, and is seen at 20° inclination. Spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field can be detected in the primary.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    HST hot-Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b (2013)
    Oxford University Press
    Details
    Publication Date: 2013-11-30
    Description: We present Hubble Space Telescope ( HST ) optical transmission spectra of the transiting hot-Jupiter WASP-12b, taken with the Space Telescope Imaging Spectrograph instrument. The resulting spectra cover the range 2900–10 300 Swhich we combined with archival Wide Field Camera 3 spectra and Spitzer photometry to cover the full optical to infrared wavelength regions. With high spatial resolution, we are able to resolve WASP-12A's stellar companion in both our images and spectra, revealing that the companion is in fact a close binary M0V pair, with the three stars forming a triple-star configuration. We derive refined physical parameters of the WASP-12 system, including the orbital ephemeris, finding the exoplanet's density is ~20 per cent lower than previously estimated. From the transmission spectra, we are able to decisively rule out prominent absorption by TiO in the exoplanet's atmosphere, as there are no signs of the molecule's characteristic broad features nor individual bandheads. Strong pressure-broadened Na and K absorption signatures are also excluded, as are significant metal-hydride features. We compare our combined broad-band spectrum to a wide variety of existing aerosol-free atmospheric models, though none are satisfactory fits. However, we do find that the full transmission spectrum can be described by models which include significant opacity from aerosols: including Rayleigh scattering, Mie scattering, tholin haze and settling dust profiles. The transmission spectrum follows an effective extinction cross-section with a power law of index α, with the slope of the transmission spectrum constraining the quantity α T  = –3528 ± 660 K, where T is the atmospheric temperature. Rayleigh scattering (α = –4) is among the best-fitting models, though requires low terminator temperatures near 900 K. Sub-micron size aerosol particles can provide equally good fits to the entire transmission spectrum for a wide range of temperatures, and we explore corundum as a plausible dust aerosol. The presence of atmospheric aerosols also helps to explain the modestly bright albedo implied by Spitzer observations, as well as the near blackbody nature of the emission spectrum. Ti-bearing condensates on the cooler night-side is the most natural explanation for the overall lack of TiO signatures in WASP-12b, indicating the day/night cold trap is an important effect for very hot Jupiters. These findings indicate that aerosols can play a significant atmospheric role for the entire wide range of hot-Jupiter atmospheres, potentially affecting their overall spectrum and energy balance.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 9
    facet.materialart.
    Unknown
    Torsional oscillations and observed rotational period variations in early-type stars (2016)
    Oxford University Press
    Details
    Publication Date: 2016-10-21
    Description: Some chemically peculiar stars in the upper main sequence show rotational period variations of unknown origin. We propose that these variations are a consequence of the propagation of internal waves in magnetic rotating stars that lead to the torsional oscillations of the star. We simulate the magnetohydrodynamic waves and calculate resonant frequencies for two stars that show rotational variations: CU Vir and HD 37776. We provide updated analyses of rotational period variations in these stars and compare our results with numerical models. For CU Vir, the length of the observed rotational period cycle, $\mathit {\Pi }=67.6(5)$  yr, can be well reproduced by the models, which predict a cycle length of 51 yr. However, for HD 37776, the observed lower limit of the cycle length, $\mathit {\Pi }\ge 100$  yr, is significantly longer than the numerical models predict. We conclude that torsional oscillations provide a reasonable explanation at least for the observed period variations in CU Vir.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b: detection of atmospheric water and likely absence of TiO (2013)
    Oxford University Press
    Details
    Publication Date: 2013-09-06
    Description: We measure the transmission spectrum of WASP-19b from three transits using low-resolution optical spectroscopy from the Hubble Space Telescope ( HST ) Space Telescope Imaging Spectrograph (STIS). The STIS spectra cover a wavelength range of 0.29–1.03 μm, with resolving power R  = 500. The optical data are combined with archival near-infrared data from the HST Wide Field Camera 3 (WFC3) G 141 grism, covering the wavelength range from 1.087 to 1.687 μm, with resolving power R  = 130. We reach signal-to-noise levels between 3000 and 11 000 in 0.1 μm bins when measuring the transmission spectra from 0.53–1.687 μm. WASP-19 is known to be a very active star, with the optical stellar flux varying by a few per cent over time. We correct the transit light curves for the effects of stellar activity using ground-based activity monitoring with the Cerro Tololo Inter-American Observatory. While we were not able to construct a transmission spectrum using the blue optical data because of the presence of large occulted starspots, we were able to use the spot crossings to help constrain the mean stellar spot temperature. To search for predicted features in the hot-Jupiter atmosphere, in addition to the transmission spectrum we also define spectral indices for differential radius ( R P / R * ) measurements to specifically search for the presence of TiO and alkali line features. Our measurements rule out TiO features predicted for a planet of WASP-19b's equilibrium temperature (2050 K) in the transmission spectrum at the 2.7–2.9 confidence level, depending on atmospheric model formalism. The WFC3 transmission spectrum shows strong absorption features due to the presence of H 2 O, which is detected at the 4 confidence level between 1.1 and 1.4 μm. The transmission spectra results indicate that WASP-19b is a planet with no or low levels of TiO and without a high C/O ratio. The lack of observable TiO features are possibly due to rainout, breakdown from stellar activity or the presence of other absorbers in the optical.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...