Exocometary Gas in the HD 181327 Debris Ring Marino, S.; Matra, L.; Stark, C. ...
Monthly notices of the Royal Astronomical Society,
08/2016, Volume:
460, Issue:
3
Journal Article
Peer reviewed
Open access
An increasing number of observations have shown that gaseous debris discs are not an exception. However, until now, we only knew of cases around A stars. Here we present the first detection of 12CO ...(2-1) disc emission around an F star, HD 181327, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with radiative transfer calculations, we study the dust and CO mass distribution. We find the dust is distributed in a ring with a radius of 86.0 +/- 0.4 au and a radial width of 23.2 +/- 1.0 au. At this frequency, the ring radius is smaller than in the optical, revealing grain size segregation expected due to radiation pressure. We also report on the detection of low-level continuum emission beyond the main ring out to approximately 200 au. We model the CO emission in the non-local thermodynamic equilibrium regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging between 1.2 x 10(exp -6) solar mass and 2.9 x 10(exp -6) solar mass, depending on the gas kinetic temperature and collisional partners densities. The CO densities and location suggest a secondary origin, i.e. released from icy planetesimals in the ring. We derive a CO+CO2 cometary composition that is consistent with Solar system comets. Due to the low gas densities, it is unlikely that the gas is shaping the dust distribution.
ABSTRACT
Spatially resolved images of debris discs are necessary to determine disc morphological properties and the scattering phase function (SPF) thatantifies the brightness of scattered light as a ...function of phase angle. Current high-contrast imaging instruments have successfully resolved several dozens of debris discs around other stars, but few studies have investigated trends in the scattered-light, resolved population of debris discs in a uniform and consistent manner. We have combined Karhunen-Loeve Image Projection (KLIP) with radiative-transfer disc forward modelling in order to obtain the highest-quality image reductions and constrain disc morphological properties of eight debris discs imaged by the Gemini Planet Imager at H-band with a consistent and uniformly applied approach. In describing the scattering properties of our models, we assume a common SPF informed from solar system dust scattering measurements and apply it to all systems. We identify a diverse range of dust density properties among the sample, including critical radius, radial width, and vertical width. We also identify radially narrow and vertically extended discs that may have resulted from substellar companion perturbations, along with a tentative positive trend in disc eccentricity with relative disc width. We also find that using a common SPF can achieve reasonable model fits for discs that are axisymmetric and asymmetric when fitting models to each side of the disc independently, suggesting that scattering behaviour from debris discs may be similar to Solar system dust.
Several technologies have been proposed for deflecting a hazardous Solar System object on a trajectory that would otherwise impact the Earth. The effectiveness of each technology depends on several ...characteristics of the given object, including its orbit and size. The distribution of these parameters in the likely population of Earth-impacting objects can thus determine which of the technologies are most likely to be useful in preventing a collision with the Earth. None of the proposed deflection technologies has been developed and fully tested in space. Developing every proposed technology is currently prohibitively expensive, so determining now which technologies are most likely to be effective would allow us to prioritize a subset of proposed deflection technologies for funding and development. We present a new model, the Deflector Selector, that takes as its input the characteristics of a hazardous object or population of such objects and predicts which technology would be able to perform a successful deflection. The model consists of a machine-learning algorithm trained on data produced by N-body integrations simulating the deflections. We describe the model and present the results of tests of the effectiveness of nuclear explosives, kinetic impactors, and gravity tractors on three simulated populations of hazardous objects.
•Discovery time significantly constrains the probability of deflection success.•Object semi-major axis has the largest effect on the success of a deflection attempt.•Chance of success of a deflection technology varies with object population parameters.•Machine learning can accelerate predictions of deflection technology success.
An increasing number of observations have shown that gaseous debris discs are not an exception. However, until now we only knew of cases around A stars. Here we present the first detection of 12CO ...(2-1) disc emission around an F star, HD 181327, obtained with ALMA observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with radiative transfer calculations we study the dust and CO mass distribution. We find the dust is distributed in a ring with a radius of 86.0 +- 0.4 AU and a radial width of 23.2 +- 1.0 AU. At this frequency the ring radius is smaller than in the optical, revealing grain size segregation expected due to radiation pressure. We also report on the detection of low level continuum emission beyond the main ring out to ~200 AU. We model the CO emission in the non-LTE regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging between 1.2x10^-6 Mearth and 2.9x10^-6 Mearth, depending on the gas kinetic temperature and collisional partners densities. The CO densities and location suggest a secondary origin, i.e. released from icy planetesimals in the ring. We derive a CO+CO2 cometary composition that is consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is shaping the dust distribution.
An increasing number of observations have shown that gaseous debris discs are not an exception. However, until now, we only knew of cases around A stars. Here we present the first detection of ...(CO)-C-12 (2-1) disc emission around an F star, HD 181327, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with radiative transfer calculations, we study the dust and CO mass distribution. We find the dust is distributed in a ring with a radius of 86.0 +/- 0.4 au and a radial width of 23.2 +/- 1.0 au. At this frequency, the ring radius is smaller than in the optical, revealing grain size segregation expected due to radiation pressure. We also report on the detection of low-level continuum emission beyond the main ring out to similar to 200 au. We model the CO emission in the non-local thermodynamic equilibrium regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging between 1.2 x 10(-6) M-aS center dot and 2.9 x 10(-6) M-aS center dot, depending on the gas kinetic temperature and collisional partners densities. The CO densities and location suggest a secondary origin, i.e. released from icy planetesimals in the ring. We derive a CO+CO2 cometary composition that is consistent with Solar system comets. Due to the low gas densities, it is unlikely that the gas is shaping the dust distribution.
Abstract
Debris disks are dusty, optically thin structures around main-sequence stars. HD 106906AB is a short-period stellar binary, host to a wide-separation planet, HD 106906b, and a debris disk. ...Only a few known systems include a debris disk and a directly imaged planet, and HD 106906 is the only one in which the planet is exterior to the disk. The debris disk is edge-on and highly asymmetric in scattered light. Here we resolve the disk structure at a resolution of 0.″38 (39 au) with the Atacama Large Millimeter/submillimeter Array (ALMA) at a wavelength of 1.3 mm. We model the disk with both a narrow and broad ring of material, and find that a radially broad, axisymmetric disk between radii of ∼50–100 au is able to capture the structure of the observations without evidence of any asymmetry or eccentricity, other than a tentative stellocentric offset. We place stringent upper limits on both the gas and dust contents of a putative circumplanetary disk. We interpret the ALMA data in concert with scattered-light observations of the inner ring and astrometric constraints on the planet’s orbit, and find that the observations are consistent with a large-separation, low-eccentricity orbit for the planet. A dynamical analysis indicates that the central binary can efficiently stabilize planetesimal orbits interior to ∼100 au, which somewhat relaxes the constraints on the eccentricity and semimajor axis. The observational constraints are consistent with in-situ formation via gravitational instability but cannot rule out a scattering event as the origin for HD 106906b’s current orbit.
Meditation practices are in use for relaxation and stress reduction. Some studies indicate beneficial cardiovascular health effects of meditation. The effects on the autonomous nervous system seem to ...vary among techniques. The purpose of the present study was to identify autonomic nerve activity changes during nondirective meditation.
Heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) were monitored in 27 middle-aged healthy participants of both genders, first during 20 min regular rest with eyes closed, thereafter practising Acem meditation for 20 min. Haemodynamic and autonomic data were collected continuously (beat-to-beat) and non-invasively. HRV and BPV parameters were estimated by power spectral analyses, computed by an autoregressive model. Spontaneous activity of baroreceptors were determined by the sequence method. Primary outcomes were changes in HRV, BPV, and BRS between rest and meditation.
HRV increased in the low-frequency (LF) and high-frequency (HF) bands during meditation, compared with rest (p = 0.014, 0.013, respectively). Power spectral density of the RR-intervals increased as well (p = 0.012). LF/HF ratio decreased non-significantly, and a reduction of LF-BPV power was observed during meditation (p < 0.001). There was no significant difference in BRS. Respiration and heart rates remained unchanged. Blood pressure increased slightly during meditation.
There is an increased parasympathetic and reduced sympathetic nerve activity and increased overall HRV, while practising the technique. Hence, nondirective meditation by the middle aged may contribute towards a reduction of cardiovascular risk.
The American Lung Association of Minnesota (ALAMN) was granted access to a 2004 administrative claims data from an upper mid-Western, independent practice association model health plan. Claims ...information, including demographics, prevalence, medication and oxygen therapy, and health care utilization, was extracted for 7,782 patients with COPD who were 40 years of age and older. In addition, ALAMN conducted a survey of 1,911 patients from Minnesota diagnosed with COPD. The survey queried the patients about demographics, treatment, medications, limitations, wants, and needs. This article compares and contrasts the information gained through the health plan administrative claims database with the findings from the COPD patient survey in areas of age, gender, types of provider primarily responsible for COPD care, spirometry use, medication therapy, pulmonary rehabilitation, oxygen therapy, and health care utilization. Primary care practitioners provided a majority of the COPD-related care. The claims evidence of spirometry use was 16%-62% of COPD patients had claims evidence of COPD-related medications. 25% of patients reported, and 23% of patients had claims evidence of, a hospitalization during the observation year. 16% of patients reported using pulmonary rehabilitation programs. The results indicate there is an opportunity to improve COPD diagnosis and management.
Jill Heins-Nesvold1, Angeline Carlson2, Leslie King-Schultz3, Kenneth E Joslyn41American Lung Association of Minnesota, St. Paul, MN, USA; 2Data Intelligence Consultants, LLC, Eden Prairie, MN, USA; ...3Mayo Medical School, Rochester, MN, USA; 4Medica Health Plan, Minnetonka, MN, USAAbstract: The American Lung Association of Minnesota (ALAMN) was granted access to a 2004 administrative claims data from an upper mid-Western, independent practice association model health plan. Claims information, including demographics, prevalence, medication and oxygen therapy, and health care utilization, was extracted for 7,782 patients with COPD who were 40 years of age and older. In addition, ALAMN conducted a survey of 1,911 patients from Minnesota diagnosed with COPD. The survey queried the patients about demographics, treatment, medications, limitations, wants, and needs. This article compares and contrasts the information gained through the health plan administrative claims database with the findings from the COPD patient survey in areas of age, gender, types of provider primarily responsible for COPD care, spirometry use, medication therapy, pulmonary rehabilitation, oxygen therapy, and health care utilization. Primary care practitioners provided a majority of the COPD-related care. The claims evidence of spirometry use was 16%-62% of COPD patients had claims evidence of COPD-related medications. 25% of patients reported, and 23% of patients had claims evidence of, a hospitalization during the observation year. 16% of patients reported using pulmonary rehabilitation programs. The results indicate there is an opportunity to improve COPD diagnosis and management.Keywords: chronic obstructive pulmonary disease, oxygen therapy, medication therapy, spirometry, chronic care, assessment
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