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  • 1
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    The impact of the Kasatochi eruption on the Moon's illumination during the August 2008 lunar eclipse (2011)
    Wiley
    Details
    Publication Date: 2011-07-21
    Description: The Moon's changeable aspect during a lunar eclipse is largely attributable to variations in the refracted unscattered sunlight absorbed by the terrestrial atmosphere that occur as the satellite crosses the Earth's shadow. The contribution to the Moon's aspect from sunlight scattered at the Earth's terminator is generally deemed minor. However, our analysis of a published spectrum of the 16 August 2008 lunar eclipse shows that diffuse sunlight is a major component of the measured spectrum at wavelengths shorter than 600 nm. The conclusion is supported by two distinct features, namely the spectrum's tail at short wavelengths and the unequal absorption by an oxygen collisional complex at two nearby bands. Our findings are consistent with the presence of the volcanic cloud reported at high northern latitudes following the 7–8 August 2008 eruption in Alaska of the Kasatochi volcano. The cloud both attenuates the unscattered sunlight and enhances moderately the scattered component, thus modifying the contrast between the two contributions.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Discovery of young, isolated planetary mass objects in the final sigma Orionis star cluster (2000)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2000-10-06
    Description: We present the discovery by optical and near-infrared imaging of an extremely red, low-luminosity population of isolated objects in the young, nearby stellar cluster around the multiple, massive star final sigma Orionis. The proximity (352 parsecs), youth (1 million to 5 million years), and low internal extinction make this cluster an ideal site to explore the substellar domain from the hydrogen mass limit down to a few Jupiter masses. Optical and near-infrared low-resolution spectroscopy of three of these objects confirms the very cool spectral energy distribution (atmospheric effective temperatures of 1700 to 2200 kelvin) expected for cluster members with masses in the range 5 to 15 times that of Jupiter. Like the planets of the solar system, these objects are unable to sustain stable nuclear burning in their interiors, but in contrast they are not bound to stars. This new kind of isolated giant planet, which apparently forms on time scales of less than a few million years, offers a challenge to our understanding of the formation processes of planetary mass objects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zapatero Osorio, M R -- Bejar, V J -- Martin, E L -- Rebolo, R -- Barrado y Navascues, D -- Bailer-Jones, C A -- Mundt, R -- New York, N.Y. -- Science. 2000 Oct 6;290(5489):103-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife, Spain.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11021788" 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)
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  • 3
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    Decay of the GRB 990123 optical afterglow: implications for the fireball model (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-03-26
    Description: Broad-band (ultraviolet to near-infrared) observations of the intense gamma ray burst GRB 990123 started approximately 8.5 hours after the event and continued until 18 February 1999. When combined with other data, in particular from the Robotic Telescope and Transient Source Experiment (ROTSE) and the Hubble Space Telescope (HST), evidence emerges for a smoothly declining light curve, suggesting some color dependence that could be related to a cooling break passing the ultraviolet-optical band at about 1 day after the high-energy event. The steeper decline rate seen after 1.5 to 2 days may be evidence for a collimated jet pointing toward the observer.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Castro-Tirado -- Zapatero-Osorio -- Caon -- Cairos -- Hjorth -- Pedersen -- Andersen -- Gorosabel -- Bartolini -- Guarnieri -- Piccioni -- Frontera -- Masetti -- Palazzi -- Pian -- Greiner -- Hudec -- Sagar -- Pandey -- Mohan V -- Yadav -- Nilakshi -- Bjornsson -- Jakobsson -- Burud I -- et -- New York, N.Y. -- Science. 1999 Mar 26;283(5410):2069-73.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Instituto de Astrofisica de Andalucia, IAA-CSIC, Granada, Spain. Instituto de Astrofisica de Canarias, La Laguna, Tenerife, Spain. Astronomical Observatory, University of Copenhagen, Copenhagen, Denmark. Nordic Optical Telescope, La Palma, T.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10092226" 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)
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  • 4
    Electronic Resource
    Electronic Resource
    Discovery of a brown dwarf in the Pleiades star cluster (1995)
    [s.l.] : Nature Publishing Group
    Nature 377 (1995), S. 129-131 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Only about half a dozen extremely cool dwarfs with spectral types M9 or later have been identified5. At present they are the best candidates for brown dwarfs. Their mass-luminosity and mass-spectral-type relationships6'7 show that these objects are indeed very close to the substellar limit, but ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/377129a0
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  • 5
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    Characterization of the K2-38 planetary system (2020)
    EDP Sciences
    Details
    Publication Date: 2020-09-01
    Description: Context. An accurate characterization of the known exoplanet population is key to understanding the origin and evolution of planetary systems. Determining true planetary masses through the radial velocity (RV) method is expected to experience a great improvement thanks to the availability of ultra-stable echelle spectrographs. Aims. We took advantage of the extreme precision of the new-generation echelle spectrograph ESPRESSO to characterize the transiting planetary system orbiting the G2V star K2-38 located at 194 pc from the Sun with V ~ 11.4. This system is particularly interesting because it could contain the densest planet detected to date. Methods. We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets, K2-38b and K2-38c, with Pb = 4.01593 ± 0.00050 d and Pc = 10.56103 ± 0.00090 d, respectively. Using 43 ESPRESSO high-precision RV measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a Markov chain Monte Carlo analysis, significantly improving their mass measurements. Results. Using ESPRESSO spectra, we derived the stellar parameters, Teff = 5731 ± 66, log g = 4.38 ± 0.11 dex, and [Fe/H] = 0.26 ± 0.05 dex, and thus the mass and radius of K2-38, M⋆ = 1.03−0.02+0.04 M⊕ and R⋆ = 1.06−0.06+0.09 R⊕. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with RP = 1.54 ± 0.14 R⊕ and Mp = 7.3−1.0+1.1 M⊕, and K2-38c as a sub-Neptune with RP = 2.29 ± 0.26 R⊕ and Mp = 8.3−1.3+1.3 M⊕. Combining the radius and mass measurements, we derived a mean density of ρp = 11.0−2.8+4.1 g cm−3 for K2-38b and ρp = 3.8−1.1+1.8 g cm−3 for K2-38c, confirming K2-38b as one of the densest planets known to date. Conclusions. The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky-model with H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the RV time-series whose origin could be linked to a 0.25–3 MJ planet or stellar activity.
    Print ISSN: 0004-6361
    Electronic ISSN: 1432-0746
    Topics: Physics
    Published by EDP Sciences
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  • 6
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    ExELS: an exoplanet legacy science proposal for the ESA Euclid mission - II. Hot exoplanets and sub-stellar systems (2014)
    Oxford University Press
    Details
    Publication Date: 2014-11-06
    Description: The Exoplanet Euclid Legacy Survey (ExELS) proposes to determine the frequency of cold exoplanets down to Earth mass from host separations of ~1 au out to the free-floating regime by detecting microlensing events in Galactic bulge. We show that ExELS can also detect large numbers of hot, transiting exoplanets in the same population. The combined microlensing+transit survey would allow the first self-consistent estimate of the relative frequencies of hot and cold sub-stellar companions, reducing biases in comparing ‘near-field’ radial velocity and transiting exoplanets with ‘far-field’ microlensing exoplanets. The age of the bulge and its spread in metallicity further allows ExELS to better constrain both the variation of companion frequency with metallicity and statistically explore the strength of star–planet tides. We conservatively estimate that ExELS will detect ~4100 sub-stellar objects, with sensitivity typically reaching down to Neptune-mass planets. Of these, ~600 will be detectable in both Euclid's VIS (optical) channel and Near Infrared Spectrometer and Photometer (NISP)- H -band imager, with ~90 per cent of detections being hot Jupiters. Likely scenarios predict a range of 2900–7000 for VIS and 400–1600 for H band. Twice as many can be expected in VIS if the cadence can be increased to match the 20-min H -band cadence. The separation of planets from brown dwarfs via Doppler boosting or ellipsoidal variability will be possible in a handful of cases. Radial velocity confirmation should be possible in some cases, using 30 m-class telescopes. We expect secondary eclipses, and reflection and emission from planets to be detectable in up to ~100 systems in both VIS and NISP- H . Transits of ~500 planetary-radius companions will be characterized with two-colour photometry and ~40 with four-colour photometry (VIS, YJH ), and the albedo of (and emission from) a large sample of hot Jupiters in the H band can be explored statistically.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    HORuS transmission spectroscopy of 55 Cnc e (2020)
    Oxford University Press
    Details
    Publication Date: 2020-08-26
    Description: The High Optical Resolution Spectrograph (HORuS) is a new high-resolution echelle spectrograph available on the 10.4-m Gran Telescopio Canarias (GTC). We report on the first HORuS observations of a transit of the super-Earth planet 55 Cnc e. We investigate the presence of Na i and Hα in its transmission spectrum and explore the capabilities of HORuS for planetary transmission spectroscopy. Our methodology leads to residuals in the difference spectrum between the in-transit and out-of-transit spectra for the Na i doublet lines of (3.4 ± 0.4) × 10−4, which sets an upper limit to the detection of line absorption from the planetary atmosphere that is one order of magnitude more stringent that those reported in the literature. We demonstrate that we are able to reach the photon-noise limit in the residual spectra using HORuS to a degree that we would be able to easily detect giant planets with larger atmospheres. In addition, we modelled the structure, chemistry, and transmission spectrum of 55 Cnc e using state-of-the-art open source tools.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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  • 8
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    Constraints on the substellar companions in wide orbits around the Barnard's Star from CanariCam mid-infrared imaging (2015)
    Oxford University Press
    Details
    Publication Date: 2015-07-18
    Description: We have performed mid-infrared imaging of Barnard's Star, one of the nearest stars to the Sun, using CanariCam on the 10.4 m Gran Telescopio Canarias. We aim to investigate an area within 1–10 arcsec separations, which for the 1.83 pc distance of the star translates to projected orbital separations of 1.8–18 au ( P  〉 12 yr), which have not been explored yet with astrometry or radial velocity programs. It is therefore an opportunity to enter the domain of distances where most giant planets are expected to form. We performed deep imaging in the N -band window (Si-2 filter, 8.7 μm) reaching a 3 detection limit of 0.85 ± 0.18 mJy and angular resolution of 0.24 arcsec, close to the diffraction limit of the telescope at this wavelength. A total of 80 min on-source integration time data were collected and combined for the deepest image. We achieved a dynamical range of 8.0 ± 0.1 mag in the 8.7 μm band, at angular separations from ~2 to 10 arcsec and of ~6–8 mag at 1–2 arcsec. No additional sources were found. Our detectability limits provide further constraints to the presence of substellar companions of the Barnard's Star. According to solar metallicity evolutionary models, we can exclude companions of masses larger than 15 M Jup ( T eff  〉 400 K), ages of a few Gyr, and located in ~3.6–18 au orbits with a 3 confidence level. This minimum mass is approximately 5 M Jup smaller than any previous imaging survey that explored the surroundings of Barnard's Star could restrict.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-12-21
    Description: Hot gas giant exoplanets can lose part of their atmosphere due to strong stellar irradiation, and these losses can affect their physical and chemical evolution. Studies of atmospheric escape from exoplanets have mostly relied on space-based observations of the hydrogen Lyman-α line in the far ultraviolet region, which is strongly affected by interstellar absorption. Using ground-based high-resolution spectroscopy, we detected excess absorption in the helium triplet at 1083 nanometers during the transit of the Saturn-mass exoplanet WASP-69b, at a signal-to-noise ratio of 18. We measured line blueshifts of several kilometers per second and posttransit absorption, which we interpret as the escape of part of the atmosphere trailing behind the planet in comet-like form.
    Keywords: Astronomy, Geochemistry, Geophysics, Planetary Science
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Spectral energy distribution simulations of a possible ring structure around the young, red brown dwarf G 196-3 B (2016)
    Oxford University Press
    Details
    Publication Date: 2016-10-23
    Description: The origin of the very red optical and infrared colours of intermediate-age (~10–500 Myr) L-type dwarfs remains unknown. It has been suggested that low-gravity atmospheres containing large amounts of dust may account for the observed reddish nature. We explored an alternative scenario by simulating debris disc around G 196-3 B, which is an L3 young brown dwarf with a mass of ~15 M Jup and an age in the interval 20–300 Myr. The best-fit solution to G 196-3 B's photometric spectral energy distribution from optical wavelengths through 24 μm corresponds to the combination of an unreddened L3 atmosphere ( T eff 1870 K) and a warm (1280 K), narrow (0.07–0.11 R ) debris disc located at very close distances (0.12–0.20 R ) from the central brown dwarf. This putative, optically thick, dusty belt, whose presence is compatible with the relatively young system age, would have a mass ≥7  x  10 –10 M comprised of submicron/micron characteristic dusty particles with temperatures close to the sublimation threshold of silicates. Considering the derived global properties of the belt and the disc-to-brown dwarf mass ratio, the dusty ring around G 196-3 B may resemble the rings of Neptune and Jupiter, except for its high temperature and thick vertical height (6  x  10 3 km). Our inferred debris disc model is able to reproduce G 196-3 B's spectral energy distribution to a satisfactory level of achievement.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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