196,811 research outputs found
A probable close brown dwarf companion to GJ 1046 (M 2.5V)
No full textContext: Brown dwarf companions to stars at separations of a few AU or less are rare objects, and none have been found so far around early-type M dwarfs (M 0V-M 5V). With GJ 1046 (M 2.5V), a strong candidate for such a system with a separation of 0.42 AU is presented. Aims: We aim at constraining the mass of the companion in order to decide whether it is a brown dwarf or a low-mass star. Methods: We employed precision RV measurements to determine the orbital parameters and the minimum companion mass. We then derived an upper limit to the companion mass from the lack of disturbances of the RV measurements by a secondary spectrum. An even tighter upper limit is subsequently established by combining the RV-derived orbital parameters with the recent new version of the Hipparcos Intermediate Astrometric Data. Results: For the mass of the companion, we derive m >= 26.9 {M}_Jup from the RV data. Based on the RV data alone, the probability that the companion exceeds the stellar mass threshold is just 6.2% . The absence of effects from the secondary spectrum lets us constrain the companion mass to m <= 229 {M}_Jup. The combination of RV and Hipparcos data yields a 3sigma upper mass limit to the companion mass of 112 {M}_Jup with a formal optimum value at m=47.2 {M}_Jup. From the combination of RV and astrometric data, the chance probability that the companion is a star is 2.9% . Conclusions: We have found a low-mass, close companion to an early-type M dwarf. While the most likely interpretation of this object is that it is a brown dwarf, a low-mass stellar companion is not fully excluded. Based on observations collected at the European Southern Observatory, Paranal, Chile, programmes 173.C-0606 and 078.C-0829
The M dwarf planet search programme at the ESO VLT + UVES. A search for terrestrial planets in the habitable zone of M dwarfs
No full textWe present radial velocity (RV) measurements of our sample of 40 M dwarfs from our planet search programme with VLT+UVES begun in 2000. Although with our RV precision down to 2-2.5 m/s and timebase line of up to 7 years, we are capable of finding planets of a few Earth masses in the close-in habitable zones of M dwarfs, there is no detection of a planetary companion. To demonstrate this we present mass detection limits allowing us to exclude Jupiter-mass planets up to 1 AU for most of our sample stars. We identified 6 M dwarfs that host a brown dwarf or low-mass stellar companion. With the exception of these, all other sample stars show low RV variability with an rms <20 m/s. Some high proper motion stars exhibit a linear RV trend consistent with their secular acceleration. Furthermore, we examine our data sets for a possible correlation between RVs and stellar activity as seen in variations of the Halpha line strength. For Barnard's star we found a significant anticorrelation, but most of the sample stars do not show such a correlation. Based on observations collected at the European Southern Observatory, Paranal Chile, ESO programmes 65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415, 69.C-0722, 70.C-0044, 71.C-0498, 072.C-0495, 173.C-0606, 078.C-0829. Radial velocity data are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/85
Toward detection of terrestrial planets in the habitable zone of our closest neighbor: proxima Centauri
No full textContext: The precision of radial velocity (RV) measurements to detect indirectly planetary companions of nearby stars has improved to enable the discovery of extrasolar planets in the Neptune and Super-Earth mass range. Detections of extremely low mass planets, even as small as 1 Earth mass or below, in short-period orbits now appears conceivable in ongoing RV planet searches. Discoveries of these Earth-like planets by means of ground-based RV programs will help to determine the parameter etaâŠâ¢, the frequency of potentially habitable planets around other stars. Aims: In search of low-mass planetary companions we monitored Proxima Centauri (M5V) as part of our M dwarf program. In the absence of a significant detection, we use these data to demonstrate the general capability of the RV method in finding terrestrial planets. For late M dwarfs the classic liquid surface water habitable zone (HZ) is located close to the star, in which circumstances the RV method is most effective. We want to demonstrate that late M dwarfs are ideal targets for the search of terrestrial planets with the RV technique. Methods: Using the iodine cell technique we obtained differential RV measurements of Proxima Cen over a time span of 7 years with the UVES spectrograph at the ESO VLT. We determine upper limits to the masses of companions in circular orbits by means of numerical simulations. Results: The RV data of Proxima Cen have a total rms scatter of 3.1~m s-1 and a period search does not reveal any significant signals. In contrast to our earlier results for Barnard's star, the RV results for the active M dwarf Proxima Cen are only weakly correlated with Halpha line index measurements. As a result of our companion limit calculations, we find that we successfully recover all test signals with RV amplitudes corresponding to planets with m sin i >= 2-3 M_âŠ⢠residing inside the HZ of Proxima Cen with a statistical significance of >99%. Over the same period range, we can recover 50% of the test planets with masses of m sin i >= 1.5-2.5~M_âŠâ¢. Based on our simulations, we exclude the presence of any planet in a circular orbit with m sin i >= 1~M_Neptune at separations of a <= 1 AU. Based on observations collected at the European Southern Observatory, Paranal, Chile, programmes 65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415, 69.C-0722, 70.C-0044, 71.C-0498, 072.C-0495, 173.C-0606 and 078.C-0829. Table 1 is only available in electronic form at http://www.aanda.or
A giant planet in the triple system HD 132563
No full textAs part of our radial velocity planet-search survey performed with SARG at TNG, we monitored the components of HD 132563 for ten years. It is a binary system formed by two rather similar solar type stars with a projected separation of 4.1 arcsec, which corresponds to 400 AU at the distance of 96 pc. The two components are moderately metal-poor ([Fe/H] = -0.19), and the age of the system is about 5 Gyr. We detected RV variations of HD 132563B with period of 1544 days and semi-amplitude of 26 m/s. From the star characteristics and line profile measurements, we infer their Keplerian origin. Therefore HD 132563B turns out to host a planet with a projected mass m sin i = 1.49 M-J at 2.6 AU with a moderately eccentric orbit (e = 0.22). The planet around HD 132563B is one of the few that are known in triple stellar systems, as we found that the primary HD 132563A is itself a spectroscopic binary with a period longer than 15 years and an eccentricity higher than 0.65. The spectroscopic component was not detected in adaptive-optics images taken with the instrument AdOpt mounted at the TNG, since it expected at a projected separation that was smaller than 0.2 arcsec at the time of our observations. A small excess in K band difference between the components with respect to the difference in V band is compatible with a companion of about 0.55 M-circle dot. A preliminary statistical analysis of when planets occur in triple systems indicate a similar frequency of planets around the isolated component in a triple system, components of wide binaries and single stars. There is no significant iron abundance difference between the components. The lack of stars in binary systems and open clusters showing strong enhancements of iron abundance, which are comparable to the typical metallicity difference between stars with and without giant planets, agrees with the idea that accretion of planetary material producing iron abundance anomalies over 0.1 dex is rare.PRIN-INAF 2008Astronom
Popowia pisocarpa Endl.
No full textPopowia cf. pisocarpa (Blume) Endl. Regional distribution Solomon Archipelago (BSIP 11563, BSIP 11686). Notes The presence of Popowia in the Solomon Islands can be confirmed from the herbarium material available. These specimens have previously been assigned to Popowia pisocarpa. Moeljono (2012) did not record Popowia pisocarpa from mainland New Guinea or from the Pacific Islands, so the identity of the plant from the Solomons remains doubtful.Published as part of Turner, Ian M. & Utteridge, Timothy M. A., 2017, Annonaceae in the Western Pacific: geographic patterns and four new species, pp. 1-44 in European Journal of Taxonomy 339 on pages 32-33, DOI: 10.5852/ejt.2017.339, http://zenodo.org/record/383250
Nothofagus pumilio (Poepp. et Endl.) Krasser, (1838) 1896.
No full textWeber, M., Bava, J. (2009): Nothofagus pumilio (Poepp. et Endl.) Krasser. In: Roloff, A.; Weisgerber, H.; Lang, U. M.; Stimm, B. (Hrsg.): Enzyklopädie der Holzgewächse: Handbuch und Atlas der Dendrologie. 53. ErgWILEY-VCH.. Lfg. 9/09, 1-1
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An M Sin I=24 M-Circle Plus Planetary Companion To The Nearby M Dwarf Gj 176
No full textWe report the detection of a planetary companion with a minimum mass of m sin i 0.0771 M-Jup 24.5 M-circle plus to the nearby (d 9.4 pc) M2.5 V star GJ 176. The star was observed as part of our M dwarf planet search at the Hobby-Eberly Telescope (HET). The detection is based on 5 years of high-precision differential radial velocity (RV) measurements using the High-Resolution Spectrograph (HRS). The orbital period of the planet is 10.24 days. GJ 176 thus joins the small (but increasing) sample of M dwarfs hosting short-period planets with minimum masses in the Neptune-mass range. Low-mass planets could be relatively common around M dwarfs, and the current detections might represent the tip of a rocky planet population.NASA NNG04G141G NNG05G107GTerrestrial Planet Finderr Foundation Science Program NNX07AL70GMcDonald Observator
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The Discovery Of Stellar Oscillations In The K Giant Iota Draconis
No full textiota Dra (HIP 75458) is a well-known example of a K giant hosting a substellar companion. We present radial velocity measurements of this star from observations taken with three different instruments spanning nearly 8 years. They show more clearly that the RV period is long-lived and coherent thus supporting the companion hypothesis. The longer time baseline now allows for a more accurate determination of the orbit with a revised period of P = 511 d and an additional small linear trend, indicative of another companion in a wide orbit. Moreover we show that the star exhibits low amplitude, solar-like oscillations with frequencies around 3-4 d(-1) (34.7-46.3 mu Hz).Astronom
THE PAN-PACIFIC PLANET SEARCH. I. A GIANT PLANET ORBITING 7 CMa
No full textWe introduce the Pan-Pacific Planet Search, a survey of 170 metal-rich Southern Hemisphere subgiants using the 3.9 m Anglo-Australian Telescope. We report the first discovery from this program, a giant planet orbiting 7 CMa (HD 47205) with a period of 763 +/- 17 days, eccentricity e = 0.14 +/- 0.06, and msin i = 2.6 +/- 0.6 M(Jup). The host star is a K giant with a mass of 1.5 +/- 0.3M(circle dot) and metallicity [Fe/H] = 0.21 +/- 0.10. The mass and period of 7 CMa b are typical of planets which have been found to orbit intermediate-mass stars (M(*) > 1.3M(circle dot)). Hipparcos photometry shows this star to be stable to 0.0004 mag on the radial-velocity period, giving confidence that this signal can be attributed to reflex motion caused by an orbiting planet.The Pan-Pacific Planet Search. I. A Giant Planet Orbiting 7 CMAMcDonald Observator
News From The Gamma Cephei Planetary System
No full textThe gamma Cephei planetary system is one of the most interesting systems due to several reasons: I.) it is the first planet candidate detected by precise radial velocity (RV) measurements that was discussed in the literature (Campbell et al. 1988); 2.) it is a tight binary system with a approximate to 20 AU; and 3.) the planet host star is an evolved K-type star. In Hatzcs et al. (2003) we confirmed the presence of the planetary companion with a minimum mass of 1.7 M-Jup at 2 AU. In this paper we present additional eight years of precise RV data from the Harlan J. Smith 2.7 m Telescope and its Tull Coude spectrograph at McDonald Observatory. The 900 d signal, that is interpreted as the presence of the giant planetary companion, is strongly confirmed by adding the new data. We present an updated orbital solution for the planet, which shows that the planet is slightly more massive and the orbit more circular than previous results have suggested. An intensive high-cadence week of RV observations in 2007 revealed that gamma Cep A is a multi-periodic pulsator. We discuss this issue within the context of searching for additional planets in this system.McDonald Observator
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