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  • 1
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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)
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    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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  • 2
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    The CARMENES search for exoplanets around M dwarfs (2020)
    EDP Sciences
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    Publication Date: 2020-09-01
    Description: Context. Variability caused by stellar activity represents a challenge to the discovery and characterization of terrestrial exoplanets and complicates the interpretation of atmospheric planetary signals. Aims. We aim to use a detailed modeling tool to reproduce the effect of active regions on radial velocity measurements, which aids the identification of the key parameters that have an impact on the induced variability. Methods. We analyzed the effect of stellar activity on radial velocities as a function of wavelength by simulating the impact of the properties of spots, shifts induced by convective motions, and rotation. We focused our modeling effort on the active star YZ CMi (GJ 285), which was photometrically and spectroscopically monitored with CARMENES and the Telescopi Joan Oró. Results. We demonstrate that radial velocity curves at different wavelengths yield determinations of key properties of active regions, including spot-filling factor, temperature contrast, and location, thus solving the degeneracy between them. Most notably, our model is also sensitive to convective motions. Results indicate a reduced convective shift for M dwarfs when compared to solar-type stars (in agreement with theoretical extrapolations) and points to a small global convective redshift instead of blueshift. Conclusions. Using a novel approach based on simultaneous chromatic radial velocities and light curves, we can set strong constraints on stellar activity, including an elusive parameter such as the net convective motion effect.
    Print ISSN: 0004-6361
    Electronic ISSN: 1432-0746
    Topics: Physics
    Published by EDP Sciences
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  • 3
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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
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    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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  • 4
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    Spectroscopy of Hyades L dwarf candidates (2014)
    Oxford University Press
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    Publication Date: 2014-11-02
    Description: We present the results of photometric, astrometric, and spectroscopic follow-up of L dwarf candidates identified in the Hyades cluster by Hogan et al. We obtained low-resolution optical spectroscopy with the Optical System for Imaging and low-intermediate Resolution Integrated Spectroscopy spectrograph on the Gran Telescopio de Canarias for all 12 L dwarf candidates as well as new J -band imaging for a subsample of 8 to confirm their proper motion. We also present mid-infrared photometry from the Wide Field Infrared Survey Explorer for the Hyades L and T dwarf candidates and estimate their spectroscopic distances, effective temperatures, and masses. We confirm the cool nature of several L dwarf candidates and confirm astrometrically their membership, bridging the gap between the coolest M dwarfs and the two T dwarfs previously reported in the Hyades cluster. These members represent valuable spectral templates at an age of 625 Myr and slightly supersolar metallicity (Fe/H = +0.13). We update the Hyades mass function across the hydrogen-burning limit and in the substellar regime. We confirm a small number numbers of very low mass members below ~0.1 M belonging to the Hyades cluster.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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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
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    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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  • 6
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    A deep WISE search for very late type objects and the discovery of two halo/thick-disc T dwarfs: WISE 0013+0634 and WISE 0833+0052 (2013)
    Oxford University Press
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    Publication Date: 2013-12-18
    Description: A method is defined for identifying late-T and Y dwarfs in WISE down to low values of signal-to-noise. This requires a WISE detection only in the W 2-band and uses the statistical properties of the WISE multiframe measurements and profile fit photometry to reject contamination resulting from non-point-like objects, variables and moving sources. To trace our desired parameter space, we use a control sample of isolated non-moving non-variable point sources from the Sloan Digital Sky Survey (SDSS), and identify a sample of 158 WISE W 2-only candidates down to a signal-to-noise limit of eight. For signal-to-noise ranges 〉10 and 8–10, respectively, ~45 and ~90 per cent of our sample fall outside the selection criteria published by the WISE team, mainly due to the type of constraints placed on the number of individual W 2 detections. We present follow-up of eight candidates and identify WISE 0013+0634 and WISE 0833+0052, T8 and T9 dwarfs with high proper motion (~1.3 and ~1.8 arcsec yr –1 ). Both objects show a mid-infrared/near-infrared excess of ~1–1.5 mag and are K band suppressed. Distance estimates lead to space motion constraints that suggest halo (or at least thick disc) kinematics. We then assess the reduced proper motion diagram of WISE ultracool dwarfs, which suggests that late-T and Y dwarfs may have a higher thick-disc/halo population fraction than earlier objects.
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    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    Multiple water band detections in the CARMENES near-infrared transmission spectrum of HD 189733 b (2019)
    EDP Sciences
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    Publication Date: 2019-01-01
    Description: Aims. We explore the capabilities of CARMENES for characterising hot-Jupiter atmospheres by targeting multiple water bands, in particular, those at 1.15 and 1.4 μm. Hubble Space Telescope observations suggest that this wavelength region is relevant for distinguishing between hazy and/or cloudy and clear atmospheres. Methods. We observed one transit of the hot Jupiter HD 189733 b with CARMENES. Telluric and stellar absorption lines were removed using SYSREM, which performs a principal component analysis including proper error propagation. The residual spectra were analysed for water absorption with cross-correlation techniques using synthetic atmospheric absorption models. Results. We report a cross-correlation peak at a signal-to-noise ratio (S/N) of 6.6, revealing the presence of water in the transmission spectrum of HD 189733 b. The absorption signal appeared slightly blueshifted at –3.9 ± 1.3 km s−1. We measured the individual cross-correlation signals of the water bands at 1.15 and 1.4 μm, finding cross-correlation peaks at S/N of 4.9 and 4.4, respectively. The 1.4 μm feature is consistent with that observed with the Hubble Space Telescope. Conclusions. The water bands studied in this work have been mainly observed in a handful of planets from space. Being able also to detect them individually from the ground at higher spectral resolution can provide insightful information to constrain the properties of exoplanet atmospheres. Although the current multi-band detections can not yet constrain atmospheric haze models for HD 189733 b, future observations at higher S/N could provide an alternative way to achieve this aim.
    Print ISSN: 0004-6361
    Electronic ISSN: 1432-0746
    Topics: Physics
    Published by EDP Sciences
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  • 8
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    The CARMENES search for exoplanets around M dwarfs (2019)
    EDP Sciences
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    Publication Date: 2019-07-01
    Description: We present precise photospheric parameters of 282 M dwarfs determined from fitting the most recent version of PHOENIX models to high-resolution CARMENES spectra in the visible (0.52–0.96 μm) and NIR wavelength range (0.96–1.71 μm). With its aim to search for habitable planets around M dwarfs, several planets of different masses have been detected. The characterization of the target sample is important for the ability to derive and constrain the physical properties of any planetary systems that are detected. As a continuation of previous work in this context, we derived the fundamental stellar parameters effective temperature, surface gravity, and metallicity of the CARMENES M-dwarf targets from PHOENIX model fits using a χ2 method. We calculated updated PHOENIX stellar atmosphere models that include a new equation of state to especially account for spectral features of low-temperature stellar atmospheres as well as new atomic and molecular line lists. We show the importance of selecting magnetically insensitive lines for fitting to avoid effects of stellar activity in the line profiles. For the first time, we directly compare stellar parameters derived from multiwavelength range spectra, simultaneously observed for the same star. In comparison with literature values we show that fundamental parameters derived from visible spectra and visible and NIR spectra combined are in better agreement than those derived from the same spectra in the NIR alone.
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    Electronic ISSN: 1432-0746
    Topics: Physics
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  • 9
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    Detection of He I λ10830 Å absorption on HD 189733 b with CARMENES high-resolution transmission spectroscopy (2018)
    EDP Sciences
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    Publication Date: 2018-12-01
    Description: We present three transit observations of HD 189733 b obtained with the high-resolution spectrograph CARMENES at Calar Alto. A strong absorption signal is detected in the near-infrared He I triplet at 10830 Å in all three transits. During mid-transit, the mean absorption level is 0.88 ± 0.04% measured in a ±10 km s−1 range at a net blueshift of − 3.5 ± 0.4 km s−1 (10829.84–10830.57 Å). The absorption signal exhibits radial velocities of + 6.5 ± 3.1 km s−1 and − 12.6 ± 1.0 km s−1 during ingress and egress, respectively; all radial velocities are measured in the planetary rest frame. We show that stellar activity related pseudo-signals interfere with the planetary atmospheric absorption signal. They could contribute as much as 80% of the observed signal and might also affect the observed radial velocity signature, but pseudo-signals are very unlikely to explain the entire signal. The observed line ratio between the two unresolved and the third line of the He I triplet is 2.8 ± 0.2, which strongly deviates from the value expected for an optically thin atmospheres. When interpreted in terms of absorption in the planetary atmosphere, this favors a compact helium atmosphere with an extent of only 0.2 planetary radii and a substantial column density on the order of 4 × 1012 cm−2. The observed radial velocities can be understood either in terms of atmospheric circulation with equatorial superrotation or as a sign of an asymmetric atmospheric component of evaporating material. We detect no clear signature of ongoing evaporation, like pre- or post-transit absorption, which could indicate material beyond the planetary Roche lobe, or radial velocities in excess of the escape velocity. These findings do not contradict planetary evaporation, but only show that the detected helium absorption in HD 189733 b does not trace the atmospheric layers that show pronounced escape signatures.
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    Electronic ISSN: 1432-0746
    Topics: Physics
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  • 10
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    Water vapor detection in the transmission spectra of HD 209458 b with the CARMENES NIR channel (2019)
    EDP Sciences
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    Publication Date: 2019-09-23
    Description: Aims. We aim at detecting water vapor in the atmosphere of the hot Jupiter HD 209458 b and perform a multi-band study in the near infrared with CARMENES. Methods. The water vapor absorption lines from the atmosphere of the planet are Doppler-shifted due to the large change in its radial velocity during transit. This shift is of the order of tens of km s−1, whilst the Earth’s telluric and the stellar lines can be considered quasi-static. We took advantage of this shift to remove the telluric and stellar lines using SYSREM, which performs a principal component analysis including proper error propagation. The residual spectra contain the signal from thousands of planetary molecular lines well below the noise level. We retrieve the information from those lines by cross-correlating the residual spectra with models of the atmospheric absorption of the planet. Results. We find a cross-correlation signal with a signal-to-noise ratio (S/N) of 6.4, revealing H2O in HD 209458 b. We obtain a net blueshift of the signal of –5.2 −1.3+2.6 km s−1 that, despite the large error bars, is a firm indication of day- to night-side winds at the terminator of this hot Jupiter. Additionally, we performed a multi-band study for the detection of H2O individually from the three near infrared bands covered by CARMENES. We detect H2O from its 0.96–1.06 μm band with a S/N of 5.8, and also find hints of a detection from the 1.06–1.26 μm band, with a low S/N of 2.8. No clear planetary signal is found from the 1.26–1.62 μm band. Conclusions. Our significant H2O signal at 0.96–1.06 μm in HD 209458 b represents the first detection of H2O from this band individually, the bluest one to date. The unfavorable observational conditions might be the reason for the inconclusive detection from the stronger 1.15 and 1.4 μm bands. H2O is detected from the 0.96–1.06 μm band in HD 209458 b, but hardly in HD 189733 b, which supports a stronger aerosol extinction in the latter, in line with previous studies. Future data gathered at more stable conditions and with larger S/N at both optical and near-infrared wavelengths could help to characterize the presence of aerosols in HD 209458 b and other planets.
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    Electronic ISSN: 1432-0746
    Topics: Physics
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