129 research outputs found

    An eccentric companion at the edge of the brown dwarf desert orbiting the 2.4 Msun giant star HIP67537

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    We report the discovery of a substellar companion around the giant star HIP67537. Based on precision radial velocity measurements from CHIRON and FEROS high-resolution spectroscopic data, we derived the following orbital elements for HIP67537 b\,b: mb_bsinii = 11.1−1.1+0.4^{+0.4}_{-1.1} Mjup_{\rm {\tiny jup}}, aa = 4.9−0.13+0.14^{+0.14}_{-0.13} AU and ee = 0.59−0.02+0.05^{+0.05}_{-0.02}. Considering random inclination angles, this object has ≳\gtrsim 65% probability to be above the theoretical deuterium-burning limit, thus it is one of the few known objects in the planet to brown-dwarf transition region. In addition, we analyzed the Hipparcos astrometric data of this star, from which we derived a minimum inclination angle for the companion of ∼\sim 2 deg. This value corresponds to an upper mass limit of ∼\sim 0.3 M⊙_\odot, therefore the probability that HIP67537 b\,b is stellar in nature is ≲\lesssim 7%. The large mass of the host star and the high orbital eccentricity makes HIP67537 b\,b a very interesting and rare substellar object. This is the second candidate companion in the brown dwarf desert detected in the sample of intermediate-mass stars targeted by the EXPRESS radial velocity program, which corresponds to a detection fraction of ff = 1.6−0.5+2.0^{+2.0}_{-0.5}%. This value is larger than the fraction observed in solar-type stars, providing new observational evidence of an enhanced formation efficiency of massive substellar companions in massive disks. Finally, we speculate about different formation channels for this object.Comment: Accepted for publication to A&

    Early Dust Formation and a Massive Progenitor for SN 2011ja?

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    SN 2011ja was a bright (I = -18.3) Type II supernova occurring in the nearby edge on spiral galaxy NGC 4945. Flat-topped and multi-peaked H-alpha and H-beta spectral emission lines appear between 64 - 84 days post-explosion, indicating interaction with a disc-like circumstellar medium inclined 30-45 degrees from edge-on. After day 84 an increase in the H- and K-band flux along with heavy attenuation of the red wing of the emission lines are strong indications of early dust formation, likely located in the cool dense shell created between the forward shock of the SN ejecta and the reverse shock created as the ejecta plows into the existing CSM. Radiative transfer modeling reveals both ~1.5 x 10^-4 Msun of pre-existing dust located ~ 10^16.7 cm away and ~ 5 x 10^-5 Msun of newly formed dust. Spectral observations after 1.5 years reveal the possibility that the fading SN is located within a young (3-6 Myr) massive stellar cluster, which when combined with tentative 56Ni mass estimates of 0.2 Msun may indicate a massive (> 25 Msun) progenitor for SN 2011ja.Comment: 13 pages, 8 figures, submitted to MNRAS awaiting final referee repor

    Four new planets around giant stars and the mass-metallicity correlation of planet-hosting stars

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    CONTEXT. Exoplanet searches have demonstrated that giant planets are preferentially found around metal-rich stars and that their fraction increases with the stellar mass. AIMS. During the past six years, we have conducted a radial velocity follow-up program of 166 giant stars, to detect substellar companions, and characterizing their orbital properties. Using this information, we aim to study the role of the stellar evolution in the orbital parameters of the companions, and to unveil possible correlations between the stellar properties and the occurrence rate of giant planets. METHODS. Using FEROS and CHIRON spectra, we have computed precision radial velocities and we have derived atmospheric and physical parameters for all of our targets. Additionally, velocities computed from UCLES spectra are presented here. By studying the periodic radial velocity signals, we have detected the presence of several substellar companions. RESULTS. We present four new planetary systems around the giant stars HIP8541, HIP74890, HIP84056 and HIP95124. Additionally, we find that giant planets are more frequent around metal-rich stars, reaching a peak in the detection of ff = 16.7−5.9+15.5^{+15.5}_{-5.9}% around stars with [Fe/H] ∼\sim 0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆_\star ∼\sim 1.0 -2.1 M⊙_\odot, with a maximum of ff = 13.0−4.2+10.1^{+10.1}_{-4.2}%, at M⋆_\star = 2.1 M⊙_\odot. CONCLUSIONS. We conclude that giant planets are preferentially formed around metal-rich stars. Also, we conclude that they are more efficiently formed around more massive stars, in the mass range of M⋆_\star ∼\sim 1.0 - 2.1 M⊙_\odot. These observational results confirm previous findings for solar-type and post-MS hosting stars, and provide further support to the core-accretion formation model.Comment: Accepted for publication in A&

    EPIC247098361b: a transiting warm Saturn on an eccentric P=11.2P=11.2 days orbit around a V=9.9V=9.9 star

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    We report the discovery of EPIC247098361b using photometric data of the Kepler K2 satellite coupled with ground-based spectroscopic observations. EPIC247098361b has a mass of MP=0.397±0.037_{P}=0.397\pm 0.037 MJ_J, a radius of RP=1.00±0.020_{P}=1.00 \pm 0.020 RJ_J, and a moderately low equilibrium temperature of Teq=1030±15T_{eq}=1030 \pm 15 K due to its relatively large star-planet separation of a=0.1036a=0.1036 AU. EPIC247098361b orbits its bright (V=9.9V=9.9) late F-type host star in an eccentric orbit (e=0.258±0.025e=0.258 \pm 0.025) every 11.2 days, and is one of only four well characterized warm Jupiters having hosts stars brighter than V=10V=10. We estimate a heavy element content of 20 ±\pm 7 M⊕_{\oplus} for EPIC247098361b, which is consistent with standard models of giant planet formation. The bright host star of EPIC247098361b makes this system a well suited target for detailed follow-up observations that will aid in the study of the atmospheres and orbital evolution of giant planets at moderate separations from their host stars.Comment: 11 pages, 10 figures, submitted to MNRA

    The reddest ISO-2MASS quasar

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    In the course of the NIR/MIR AGN search combining the 6.7 mu ISOCAM Parallel Survey and 2MASS we have discovered 24 type-1 quasars about a third of which are too red to be discriminated by optical/UV search techniques. Here we report on a detailed case study of the reddest type-1 quasar of our sample (J2341) at redshift z=0.236 with M_K=-25.8 and J-K=1.95. We performed spectroscopy in the optical with VLT/FORS1 and in the MIR with Spitzer as well as NIR imaging with ISPI at CTIO. The optical and NIR observations reveal a star forming emission-line galaxy at the same redshift as the quasar with a projected linear separation of 1.8 arcsec (6.7 kpc). The quasar and its companion are embedded in diffuse extended continuum emission. Compared with its companion the quasar exhibits redder optical-NIR colours, which we attribute to hot nuclear dust. The MIR spectrum shows only few emission lines superimposed on a power-law spectral energy distribution. However, the lack of strong FIR emission suggests that our potentially interacting object contains much less gas and dust and is in a stage different from dust reddened ULIRG-AGN like Mrk 231. The optical spectrum shows signatures for reddening in the emission-lines and no post-starburst stellar population is detected in the host galaxy of the quasar. The optical continuum emission of the active nucleus appears absorbed and diluted. Even the combination of absorption and host dilution is not able to match J2341 with standard quasar templates. While the BLR shows only a rather moderate absorption of E_(B-V)=0.3, the continuum shorter than 4500 AA requires strong obscuration with E_(B-V)=0.7, exceeding the constraints from the low upper limit on the 9.7 mu silicate absorption. This leads us to conclude that the continuum of J2341 is intrinsically redder than that of typical quasars.Comment: 8 pages, 9 figure

    Family doctors' knowledge and self-reported care of type 2 diabetes patients in comparison to the clinical practice guideline: cross-sectional study

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    BACKGROUND: It is widely believed that providing doctors with guidelines will lead to more effective clinical practice and better patient care. However, different studies have shown contradictory results in quality improvement as a result of guideline implementation. The aim of this study was to compare family doctors' knowledge and self-reported care of type 2 diabetes patients with recommendation standards of the clinical practice guideline. METHODS: In April 2003 a survey was conducted among family doctors in Estonia. The structured questionnaire focused on the knowledge and self-reported behavior of doctors regarding the guideline of type 2 diabetes. The demographic and professional data of the respondents was also provided. RESULTS: Of the 354 questionnaires distributed, 163 were returned for a response rate of 46%. Seventy-six percent of the responded doctors stated that they had a copy of the guideline available while 24% reported that they did not. Eighty-three percent of the doctors considered it applicable and 79% reported using it in daily practice. The doctors tended to start treatment with medications and were satisfied with treatment outcomes at higher fasting blood glucose levels than the levels recommended in the guideline. Doctors' self-reported performance of the tests and examinations named in the guideline, which should be performed within a certain time limit, varied from overuse to underuse. Blood pressure, serum creatinine, eye examination and checking patients' ability to manage their diabetes were the best-followed items while glycosylated hemoglobin and weight reduction were the most poorly followed. Doctors' behavior was not related to the fact of whether they had the guideline available, whether they considered it applicable, or whether they actually used it. CONCLUSION: Doctors' knowledge and self-reported behavior in patient follow-up of type 2 diabetes is very variable and is not related to the reported availability or usage of the guideline. Practice guidelines may be a useful source of information but they should not be overestimated

    Narrow-line AGN in the ISO-2MASS Survey

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    Context: A long-standing challenge of observational AGN research is to find type 2 quasars, the luminous analogues of Seyfert-2 galaxies. Aims: We search for luminous narrow-line type 2 AGN, characterise their properties, and compare them with broad-line type 1 AGN. Methods: Combining the ISOCAM parallel survey at 6.7 mu with 2MASS, we have selected AGN via near-mid-infrared colours caused by the hot nuclear dust emission. We performed spectroscopy in the optical and, for a subset of the sample, also in the mid-infrared with Spitzer. Results: We find nine type 2 AGN at redshift 0.1<z<0.5, three of them have even quasar-like [OIII] luminosities. At the given redshift and luminosity range the number of type 2 AGN is at least as high as that of type 1s. At z>0.5 we did not find type 2 AGN, probably because the hottest dust emission, still covered by the NIR filters, is obscured. The optical spectra of the type 2 host galaxies show young and old stellar populations. Only one object is an ultraluminous infrared galaxy with starburst. The 5-38 mu spectra of the two type 2 sources observed show a strong continuum with PAH emission in one case and silicate absorption in the other case. Conclusions: The near-mid-infrared selection is a successful strategy to find luminous type 2 AGN at low z. The objects exhibit a large range of properties so that it is difficult to infer details by means of popular SED fitting with simple average templates.Comment: Accepted for publication in A&

    New spectroscopic binary companions of giant stars and updated metallicity distribution for binary systems

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    We report the discovery of 24 spectroscopic binary companions to giant stars. We fully constrain the orbital solution for 6 of these systems. We cannot unambiguously derive the orbital elements for the remaining stars because the phase coverage is incomplete. Of these stars, 6 present radial velocity trends that are compatible with long-period brown dwarf companions. The orbital solutions of the 24 binary systems indicate that these giant binary systems have a wide range in orbital periods, eccentricities, and companion masses. For the binaries with restricted orbital solutions, we find a range of orbital periods of between ~97–1600 days and eccentricities of between ~0.1–0.4. In addition, we studied the metallicity distribution of single and binary giant stars. We computed the metallicity of a total of 395 evolved stars, 59 of wich are in binary systems. We find a flat distribution for these binary stars and therefore conclude that stellar binary systems, and potentially brown dwarfs, have a different formation mechanism than planets. This result is confirmed by recent works showing that extrasolar planets orbiting giants are more frequent around metal-rich stars. Finally, we investigate the eccentricity as a function of the orbital period. We analyzed a total of 130 spectroscopic binaries, including those presented here and systems from the literature. We find that most of the binary stars with periods .30 days have circular orbits, while at longer orbital periods we observe a wide spread in their eccentricities
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