| 1. |
- Marleau, G.-D., et al.
(författare)
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Accreting protoplanets : Spectral signatures and magnitude of gas and dust extinction at H α
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 657
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Tidskriftsartikel (refereegranskat)abstract
- Context. Accreting planetary-mass objects have been detected at H α, but targeted searches have mainly resulted in non-detections. Accretion tracers in the planetary-mass regime could originate from the shock itself, making them particularly susceptible to extinction by the accreting material. High-resolution (R > 50 000) spectrographs operating at H α should soon enable one to study how the incoming material shapes the line profile.Aims. We calculate how much the gas and dust accreting onto a planet reduce the H α flux from the shock at the planetary surface and how they affect the line shape. We also study the absorption-modified relationship between the H α luminosity and accretion rate.Methods. We computed the high-resolution radiative transfer of the H α line using a one-dimensional velocity–density–temperature structure for the inflowing matter in three representative accretion geometries: spherical symmetry, polar inflow, and magnetospheric accretion. For each, we explored the wide relevant ranges of the accretion rate and planet mass. We used detailed gas opacities and carefully estimated possible dust opacities.Results. At accretion rates of Ṁ ≲ 3 × 10−6 MJ yr−1, gas extinction is negligible for spherical or polar inflow and at most AH α ≲ 0.5 mag for magnetospheric accretion. Up to Ṁ ≈ 3 × 10−4 MJ yr−1, the gas contributes AH α ≲ 4 mag. This contribution decreases with mass. We estimate realistic dust opacities at H α to be κ ~ 0.01–10 cm2 g−1, which is 10–104 times lower than in the interstellar medium. Extinction flattens the LH α –Ṁ relationship, which becomes non-monotonic with a maximum luminosity LH α ~ 10−4 L⊙ towards Ṁ ≈ 10−4 MJ yr−1 for a planet mass ~10 MJ. In magnetospheric accretion, the gas can introduce features in the line profile, while the velocity gradient smears them out in other geometries.Conclusions. For a wide part of parameter space, extinction by the accreting matter should be negligible, simplifying the interpretation of observations, especially for planets in gaps. At high Ṁ, strong absorption reduces the H α flux, and some measurements can be interpreted as two Ṁ values. Highly resolved line profiles (R ~ 105) can provide (complex) constraints on the thermal and dynamical structure of the accretion flow.
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| 2. |
- Chomez, A., et al.
(författare)
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An imaged 15 MJup companion within a hierarchical quadruple system
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 676, s. L10-L10
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Tidskriftsartikel (refereegranskat)abstract
- Context. Since 2019, the direct imaging B-star Exoplanet Abundance STudy (BEAST) at SPHERE@VLT has been scanning the surroundings of young B-type stars in order to ascertain the ultimate frontiers of giant planet formation. Recently, the 17+3-4 Myr HIP 81208 was found to host a close-in (∼50 au) brown dwarf and a wider (∼230 au) late M star around the central 2.6 M⊙ primary.Aims. Alongside the continuation of the survey, we are undertaking a complete reanalysis of archival data aimed at improving detection performances so as to uncover additional low-mass companions.Methods. We present here a new reduction of the observations of HIP 81208 using the patch covariance algorithm (PACO), a recent and powerful algorithm dedicated to processing high-contrast imaging datasets, as well as more classical algorithms and a dedicated point spread function subtraction approach. The combination of different techniques allowed for a reliable extraction of astrometric and photometric parameters.Results. A previously undetected source was recovered at a short separation from the C component of the system. Proper motion analysis provided robust evidence for the gravitational bond of the object to HIP 81208 C. Orbiting C at a distance of ∼20 au, this 15 MJup brown dwarf becomes the fourth object of the hierarchical HIP 81208 system.Conclusions. Among the several BEAST stars which are being found to host substellar companions, HIP 81208 stands out as a particularly striking system. As the first stellar binary system with substellar companions around each component ever found by direct imaging, it yields exquisite opportunities for thorough formation and dynamical follow-up studies.
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| 3. |
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| 4. |
- Squicciarini, V., et al.
(författare)
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A scaled-up planetary system around a supernova progenitor
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 664
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Tidskriftsartikel (refereegranskat)abstract
- Context. Virtually all known exoplanets reside around stars with M < 2.3 M⊙ either due to the rapid evaporation of the protostellar disks or to selection effects impeding detections around more massive stellar hosts.Aims. To clarify if this dearth of planets is real or a selection effect, we launched the planet-hunting B-star Exoplanet Abundance STudy (BEAST) survey targeting B stars (M > 2.4 M⊙) in the young (5-20 Myr) Scorpius-Centaurus association by means of the high-contrast spectro-imager SPHERE at the Very Large Telescope.Methods. In this paper we present the analysis of high-contrast images of the massive (M - 9 M⊙) star μ2 Sco obtained within BEAST. We carefully examined the properties of this star, combining data from Gaia and from the literature, and used state-of-the-art algorithms for the reduction and analysis of our observations.Results. Based on kinematic information, we found that μ2 Sco is a member of a small group which we label Eastern Lower Scorpius within the Scorpius-Centaurus association. We were thus able to constrain its distance, refining in turn the precision on stellar parameters. Around this star we identify a robustly detected substellar companion (14.4 ± 0.8 MJ)at a projected separation of 290 ± 10 au, and a probable second similar object (18.5 ± 1.5 MJ) at 21 ± 1 au. The planet-to-star mass ratios of these objects are similar to that of Jupiter to the Sun, and the flux they receive from the star is similar to those of Jupiter and Mercury, respectively.Conclusions. The robust and the probable companions of μ2 Sco are naturally added to the giant 10.9 MJ planet recently discovered by BEAST around the binary b Cen system. While these objects are slightly more massive than the deuterium burning limit, their properties are similar to those of giant planets around less massive stars and they are better reproduced by assuming that they formed under a planet-like, rather than a star-like scenario. Irrespective of the (needed) confirmation of the inner companion, μ2 Sco is the first star that would end its life as a supernova that hosts such a system. The tentative high frequency of BEAST discoveries is unexpected, and it shows that systems with giant planets or small-mass brown dwarfs can form around B stars. When putting this finding in the context of core accretion and gravitational instability formation scenarios, we conclude that the current modeling of both mechanisms is not able to produce this kind of companion. The completion of BEAST will pave the way for the first time to an extension of these models to intermediate and massive stars.
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| 7. |
- Andersson, Lars-Göran, et al.
(författare)
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Thallium-201 Myocardial Imaging at Rest in Male Orienteers and Other Endurance Athletes
- 2001
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Ingår i: Upsala Journal of Medical Sciences. - : Uppsala Medical Society. - 0300-9734 .- 2000-1967. ; 106:1, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- During the period 1979 to 1992, 16 sudden unexpected cardiac deaths were known to have occurred in young Swedish orienteers. Autopsy indicated myocarditis to be the most frequent finding, most often combined with extensive myocardial fibrosis. The aim of the present investigation was to explore whether young male orienteers show a higher frequency than other young elite endurance athletes (controls) in the occurrence of Thallium-201 myocardial perfusion defects at rest, suggestive of fibrosis evoked by myocarditis. Thallium-201 perfusion abnormalities at rest were more frequently found in the controls than in the orienteers (26% vs. 12%, p=0.03). Uneven Tl-201 perfusion was associated with left ventricular mass (r=0.32, r=0.24, p<0.01, p=0.02) and body weight (r=0.30, r=0.31, p<0.01, p=0.03) in orienteers and controls, respectively. Echocardiographic left ventricular wall motion abnormalities were found in 11 athletes (9 orienteers and 2 controls) but only two displayed an abnormal Thallium-201 perfusion scan at rest. Perfusion abnormalities at rest did not occur more frequently in the orienteers but were commonly found in both groups of apparently healthy athletes making it futile to discern abnormals from normals. Thallium-201 perfusion aberrations were not associated with left ventricular wall motion abnormalities obtained by echocardiography.
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| 8. |
- Enochsson, L, et al.
(författare)
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Laparoscopic vs open appendectomy in overweight patients
- 2001
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Ingår i: Surgical Endoscopy. - : Springer Science and Business Media LLC. - 0930-2794 .- 1432-2218. ; 15:4, s. 387-392
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Tidskriftsartikel (refereegranskat)abstract
- Background: Laparoscopic appendectomy (LA) has been associated with a faster recovery and less postoperative pain than the open technique. However, few data are available on the clinical outcome of LA in overweight patients. Methods: A group of 106 patients with a body mass index (BMI) > 26.4, representing the upper quintile of 500 prospectively randomized patients, were included in the study. They were randomized to undergo either laparoscopic or open appendectomy (OA). Operating and anesthesia times, postoperative pain, complications, hospital stay, functional index (1 week postoperatively), sick leave, and time to full recovery were documented. Results: In OA, the operating time for overweight patients was significantly longer than that for patients in the normal weight range (40 vs 35 min, p < 0.05). In LA, there was no difference in operating time between the normal and overweight patients. Overweight patients who underwent LA had longer operating and anesthesia times than their OA counterparts (55 vs 40 min, p < 0.001, and 125 vs 100 min, p < 0.001, respectively). Postoperative pain was significantly greater in overweight patients who underwent OA than in those treated with the laparoscopic technique. Postoperative pain was also significantly greater in overweight patients subjected to OA than in patients of normal weight after 4 weeks, the clinical significance may, however, be of less importance since the values are low (0.26 vs 0.09, p < 0.05). There were no significant differences between the two operating techniques in terms of complications. Hospital stay was longer for overweight patients than for normal-weight patients undergoing OA (3.0 vs 2.0, p < 0.01). The functional index did not differ between any group of patients. Sick leave was longer for overweight patients who underwent OA than for normal-weight patients treated with the same technique (17 vs 13 days, p < 0.01). In the laparoscopic group, however, there were no differences between the overweight and normal-weight patients. Time to full recovery was greater in overweight patients subjected to OA than in the overweight patients in the LA group (22 vs 15 days, p < 0.001). Conclusion: In this study, overweight patients who were submitted to LA had less postoperative pain and a faster postoperative recovery than overweight patients who had OA. LA also abolished some of the negative effects that overweight had on operating time, hospital stay, and sick leave with the open technique. However, anesthesia and operating times were significantly longer in LA for both overweight patients and those with a normal BMI.
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| 9. |
- Enochsson, L, et al.
(författare)
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The Fenyo-Lindberg scoring system for appendicitis increases positive predictive value in fertile women - A prospective study in 455 patients randomized to either laparoscopic or open appendectomy
- 2004
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Ingår i: Surgical Endoscopy. - : Springer Science and Business Media LLC. - 0930-2794 .- 1432-2218. ; 18:10, s. 1509-1513
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Tidskriftsartikel (refereegranskat)abstract
- Background: Suspected appendicitis is one of the most common indications for acute laparotomy or laparoscopy. The negative laparotomy and laparoscopy rates are high, often in the range of 15-30%, and especially high in some groups of patients such as women of child-bearing age and young patients. Different scoring systems have been introduced in order to improve diagnostic accuracy. The aim of the present study was to analyse the outcome of the Fenyo-Lindberg scoring system in a prospectively randomized multicenter trial and to analyze how well the score performed in stratified subgroups. Methods: The variables of the Fenyo-Lindberg scoring system were collected in a prospective study comparing laparoscopic and open surgery in suspected appendicitis and with four participating centers. None of the hospitals had used the scoring system previously. Since surgeons were unfamiliar with the score, they could not use it as a diagnostic aid. When comparing the score with the clinical outcome, retrospectively, the investigators interpreting the score were blinded regarding the surgical outcome. Results: Positive predictive value (PPV) of the Fenyo-Lindberg score was higher than that of the surgeon's clinical diagnosis in the patient cohort [0.90 vs 0.79 (p < 0.001)]. The score demonstrated an improvement of PPV in women [0.83 vs 0.70 (p < 0.01)]. PPV was increased in women between 15 and 50 years of age. In women aged 15-30 years and 31-50 years PPV increased from 0.69 to 0.82 and 0.68 to 0.86, respectively (p < 0.01). Both the sensitivity (0.77) and the specificity (0.69) of the score were, however, low. Conclusion: The Fenyo-Lindberg score is an inexpensive clinical tool that may improve the diagnostic accuracy for acute appendicitis in women of childbearing age, which is a group of patients where the diagnostic accuracy usually is low and where the arsenal of diagnostic tools such Lis Computed tomography is limited because of radiation. The low specificity of the score in women of childbearing age must, however, be kept in mind.
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