High-Frequency and Type-C QPOs from Oscillating, Precessing Hot, Thick Flow

Motivated by recent studies showing an apparent correlation between the high-frequency quasi-periodic oscillations (QPOs) and the low-frequency, type-C QPO in low-mass, black hole X-ray binaries (LMXBs), we explore a model that explains all three QPOs in terms of an oscillating, precessing hot flow in the truncated-disk geometry. Our model favors attributing the two high-frequency QPOs, often occurring in a near 3:2 frequency ratio, to the breathing and vertical epicyclic frequency modes of the hot, thick flow, although we can not rule out the Keplerian and m=-1 radial epicyclic modes. In either case, the type-C QPO is attributed to precession. The correlation of the QPOs comes from the fact that all three frequencies are associated with the same geometrical structure. While the exact QPO frequencies are sensitive to the black hole mass and spin, their evolution over the course of an outburst is mainly tied to the truncation radius between the geometrically thin, optically thick disk and the inner, hot flow. We show that, in the case of the LMXB GRO J1655-40, this model can explain the one simultaneous observation of all three QPOs and that an extrapolation of the model appears to match lower frequency observations where only two of the three components are seen. Thus, this model may be able to unify multiple QPO observations using the properties of a single, simple, geometrical model.Comment: 7 pages, 4 figures, accepted to MNRA

PACE Technical Report Series, Volume 4: Cloud Retrievals in the PACE Mission: PACE Science Team Consensus Document

Earth is a complex dynamical system exhibiting continuous change in its atmosphere, ocean,and surface elements. Nearly all (99.97%) of the energy driving these systems is linked to the Sun. Measurements of reflected sunlight contain a unique signature of wavelength-specific scattering and absorption interactions occurring between incoming solar energy and atmospheric (molecules, aerosols,clouds) and surface features Clouds can affect significantly both shortwave and long wave radiation, depending on altitude/vertical structure, thermodynamic phase, and optical properties. Low, warm, and optically thick clouds predominantly have a cooling effect, while high, cold, optically thin clouds can cause warming by absorbing warmer radiation emitted from the surface and lower atmosphere.When the net difference between outgoing and incoming solar radiation is matched by the net infrared radiation emitted to space, the Earth's climate is in radiative balance. While radiative forcing components (GHGs, aerosols - direct and indirect) contribute to a net radiative imbalance, climate sensitivity is ultimately determined by the contribution of various system feed backs. The role of cloud feedback in a warming climate is currently the largest inter-model uncertainty in climate sensitivity and therefore in climate prediction [Bony and Dufresne 2005]. A comprehensive understanding of current cloud propertiesand dynamic/microphysical processes requires a global perspective from satellites

Epicyclic oscillations of non-slender fluid tori around Kerr black holes

Considering epicyclic oscillations of pressure-supported perfect fluid tori orbiting Kerr black holes we examine non-geodesic (pressure) effects on the epicyclic modes properties. Using a perturbation method we derive fully general relativistic formulas for eigenfunctions and eigenfrequencies of the radial and vertical epicyclic modes of a slightly non-slender, constant specific angular momentum torus up to second-order accuracy with respect to the torus thickness. The behaviour of the axisymmetric and lowest-order ($m=\pm 1$) non-axisymmetric epicyclic modes is investigated. For an arbitrary black hole spin we find that, in comparison with the (axisymmetric) epicyclic frequencies of free test particles, non-slender tori receive negative pressure corrections and exhibit thus lower frequencies. Our findings are in qualitative agreement with the results of a recent pseudo-Newtonian study of analogous problem defined within the Paczy{\'n}ski-Wiita potential. Implications of our results on the high-frequency QPO models dealing with epicyclic oscillations are addressed.Comment: 24 pages, 8 figure

Improving breast cancer survivors' knowledge using a patient-centered intervention

Background Low-income, minority women with breast cancer experience a range of barriers to receiving survivorship information. Our objective was to test a novel, patient-centered intervention aimed at improving communication about survivorship care. Methods We developed a wallet card to provide oncologic and follow-up care survivorship information to breast cancer patients. We used a prospective, pre-post design to assess the intervention at a safety net hospital. The intervention was given by a patient navigator or community health worker. Results Patient knowledge (n = 130) of personal cancer history improved from baseline pretest to 1 week after the intervention for stage (66-93%; P <.05), treatment (79-92%; P <.05), and symptoms of recurrence (48-89%; P <.05), which was retained at 3 months. The intervention reduced the number of patients who were unsure when their mammogram was due (15-5% at 1 week and 6% at 3 months; P <.05). Nearly 90% reported they would be likely to share their survivorship card with their providers. Conclusion A patient-centered survivorship card improved short-term recall of key survivorship care knowledge and seems to be effective at reducing communication barriers for this population. Further studies are warranted to assess long-term retention and the impact on receipt of appropriate survivorship follow-up care

Multiple star systems in the Orion nebula

This is the author accepted manuscript. The final fersion is available from EDP Sciences via the DOI in this record.This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium cluster with the recently comissioned GRAVITY instrument. We observed a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for θ1 Ori B, θ2 Ori B, and θ2 Ori C. We determined a separation for the previously suspected companion of NU Ori. We confirm four companions for θ1 Ori A, θ1 Ori C, θ1 Ori D, and θ2 Ori A, all with substantially improved astrometry and photometric mass estimates. We refined the orbit of the eccentric high-mass binary θ1 Ori C and we are able to derive a new orbit for θ1 Ori D. We find a system mass of 21.7 M⊙ and a period of 53 days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about two, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints toward a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We excluded collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion.Marie Skłodowska-Curie Grant AgreementFCT-PortugalERC Starting Gran

Effects of entry conditions on channel flow characteristics

There have been various studies on channel flow due to its relevance in engineering applications, but the effects of the entry conditions on its flow characteristics have not been given much attention. This 2-D numerical simulation studied how the initial velocity and tripping devices at the entrance of a channel affect the mean flow structure. The CFD analysis is based on the use of COMSOL Multiphysics. The turbulent stresses in the RANS equation are closed using the k-ɛ turbulence model. Input parameters for the simulation are taken from experimental conditions in the literature, with Reynolds number ranging from 18,700 to 600, 000. The CFD strategy flow without tripping is validated against experimental results and a good agreement is achieved. The results show that the skin friction factor for the flow without tripping for Reynolds number 18,700 is 3.59x10-3. However, for the same Re, with tripping devices covering 15%, 30%, 45%, and 60% of the channel height, the skin friction factors are 3.68x10-3, 3.78x10-3, 3.82x10-3, and 3.98x10-3 respectively. Hence it has been shown the tripping devices placed at the entry of a channel increase the skin friction coefficient by values between 2% to 11% for the various conditions considered in this work