ABSTRACT
Using general relativistic magnetohydrodynamic simulations of accreting black holes, we show that a suitable subtraction of the linear polarization per pixel from total intensity images can ...enhance the photon ring feature. We find that the photon ring is typically a factor of ≃2 less polarized than the rest of the image. This is due to a combination of plasma and general relativistic effects, as well as magnetic turbulence. When there are no other persistently depolarized image features, adding the subtracted residuals over time results in a sharp image of the photon ring. We show that the method works well for sample, viable GRMHD models of Sgr A* and M87*, where measurements of the photon ring properties would provide new measurements of black hole mass and spin, and potentially allow for tests of the ‘no-hair’ theorem of general relativity.
Abstract
Background
Concerns regarding reduced fetal movements (RFM) are reported in 5–15% of pregnancies, and RFM are associated with adverse pregnancy outcomes including fetal growth restriction ...and stillbirth. Studies have aimed to improve pregnancy outcomes by evaluating interventions to raise awareness of RFM in pregnancy, such as kick counting, evaluating interventions for the clinical management of RFM, or both. However, there is not currently a core outcome set (COS) for studies of RFM. This study aims to create a COS for use in research studies that aim to raise awareness of RFM and/or evaluate interventions for the clinical management of RFM.
Methods
A systematic review will be conducted, to identify outcomes used in randomised and non-randomised studies with control groups that aimed to raise awareness of RFM (for example by using mindfulness techniques, fetal movement counting, or other tools such as leaflets or mobile phone applications) and/or that evaluated the clinical management of RFM.
An international Delphi consensus will then be used whereby stakeholders will rate the importance of the outcomes identified in the systematic review in (i) awareness and (ii) clinical management studies. The preliminary lists of outcomes will be discussed at a consensus meeting where one final COS for awareness and management, or two discrete COS (one for awareness and one for management), will be agreed upon.
Discussion
A well-developed COS will provide researchers with the minimum set of outcomes that should be measured and reported in studies that aim to quantify the effects of interventions.
We study the young S-stars within a distance of 0.04 pc from the supermassive black hole in the center of our Galaxy. Given how inhospitable the region is for star formation, their presence is more ...puzzling the younger we estimate their ages. In this study, we analyze the result of 12 years of high-resolution spectroscopy within the central arcsecond of the Galactic Center (GC). By co-adding between 55 and 105 hr of spectra we have obtained high signal-to-noise H- and K-band spectra of eight stars orbiting the central supermassive black hole. Using deep H-band spectra, we show that these stars must be high surface gravity (dwarf) stars. We compare these deep spectra to detailed model atmospheres and stellar evolution models to infer the stellar parameters. Our analysis reveals an effective temperature of 21,000-28,500 K, a rotational velocity of 60-170 km s−1, and a surface gravity of 4.1-4.2. These parameters imply a spectral type of B0-B3V for these stars. The inferred masses lie within 8-14 . We derive an age of Myr for the star S2, which is compatible with the age of the clockwise-rotating young stellar disk in the GC. We estimate the ages of all other studied S-stars to be less than 15 Myr, which is compatible with the age of S2 within the uncertainties. The relatively low ages for these S-stars favor a scenario in which the stars formed in a local disk rather than a field binary-disruption scenario that occurred over a longer period of time.
Transition of newly received feedlot cattle from a forage- to grain-based diet is challenging, and the appropriate roughage level in receiving diets is debatable. Nutritionists must consider the ...paradox of dietary transition and roughage level to mitigate ruminal acidosis, yet concomitantly low feed intake presents difficulty in achieving nutrient requirements when metabolic demand is increased due to inherent stress and disease challenge during the receiving period. Previous research suggests that performance is improved at the expense of increased morbidity for newly received cattle consuming diets with less roughage and greater starch concentration. The clinical signs of bovine respiratory disease (BRD) and acute acidosis are analogous; therefore, it is probable that acidotic cattle are incorrectly diagnosed with BRD in both research and production settings. Additional research efforts have attempted to elucidate alterations in microbial populations and digestion, physiological response to inflammatory challenge, and immunological response to infectious bovine rhinotracheitis virus challenge in cattle consuming diets of various roughage levels. Furthermore, our understanding of the rumen microbiome is improving rapidly with culture-independent assays, products such as direct-fed microbials are available, and increased availability and use of fibrous byproduct ingredients requires further attention. Beef cattle nutritionists and producers should consider that the health benefit of receiving diets containing greater levels of roughage and lower energy may not compensate for the reduction in performance compared with feeding receiving diets with lower roughage and greater energy.
In early 2014, the fast-moving near-infrared source G2 reached its closest approach to the supermassive black hole Sgr A* in the Galactic center. We report on the evolution of the ionized gaseous ...component and the dusty component of G2 immediately after this event, revealed by new observations obtained in 2015 and 2016 with the SINFONI integral field spectrograph and the NACO imager at the ESO VLT. The spatially resolved dynamics of the Brγ line emission can be accounted for by the ballistic motion and tidal shearing of a test-particle cloud that has followed a highly eccentric Keplerian orbit around the black hole for the last 12 years. The non-detection of a drag force or any strong hydrodynamic interaction with the hot gas in the inner accretion zone limits the ambient density to less than a few at the distance of closest approach ( ), assuming G2 is a spherical cloud moving through a stationary and homogeneous atmosphere. The dust continuum emission is unresolved in L′-band, but stays consistent with the location of the Brγ emission. The total luminosity of the Brγ and L′ emission has remained constant to within the measurement uncertainty. The nature and origin of G2 are likely related to that of the precursor source G1, since their orbital evolution is similar, though not identical. Both objects are also likely related to a trailing tail structure, which is continuously connected to G2 over a large range in position and radial velocity.
Objective
This study aimed to create core outcome sets (COSs) for use in research studies relating to the awareness and clinical management of reduced fetal movement (RFM).
Design
Delphi survey and ...consensus process.
Setting
International.
Population
A total of 128 participants (40 parents, 19 researchers and 65 clinicians) from 16 countries.
Methods
A systematic literature review was conducted to identify outcomes in studies of interventions relating to the awareness and the clinical management of RFM. Using these outcomes as a preliminary list, stakeholders rated the importance of these outcomes for inclusion in COSs for studies of: (i) awareness of RFM; and (ii) clinical management of RFM.
Main outcome measures
Preliminary lists of outcomes were discussed at consensus meetings where two COSs (one for studies of RFM awareness and one for studies of clinical management of RFM).
Results
The first round of the Delphi survey was completed by 128 participants, 66% of whom (n = 84) completed all three rounds. Fifty outcomes identified by the systematic review, after multiple definitions were combined, were voted on in round one. Two outcomes were added in round one, and as such 52 outcomes were voted on in two lists in rounds two and three. The COSs for studies of RFM awareness and clinical management are comprised of eight outcomes (four maternal and four neonatal) and 10 outcomes (two maternal and eight neonatal), respectively.
Conclusions
These COSs provide researchers with the minimum set of outcomes to be measured and reported in studies relating to the awareness and the clinical management of RFM.
We present the first systematic analysis of the X-ray variability of Sgr A* during the Chandra X-ray Observatory's 2012 Sgr A* X-ray Visionary Project. With 38 High Energy Transmission Grating ...Spectrometer observations spaced an average of 7 days apart, this unprecedented campaign enables detailed study of the X-ray emission from this supermassive black hole at high spatial, spectral and timing resolution. In 3 Ms of observations, we detect 39 X-ray flares from Sgr A*, lasting from a few hundred seconds to approximately 8 ks, and ranging in 2-10 keV luminosity from ~10 super(34) erg s super(-1) to 2 x 10 super(35) erg s super(-1). Despite tentative evidence for a gap in the distribution of flare peak count rates, there is no evidence for X-ray color differences between faint and bright flares. Our preliminary X-ray flare luminosity distribution dN/dL is consistent with a power law with index -19 super(+0.3) sub(-0.4); this is similar to some estimates of Sgr A*'s near-IR flux distribution. The observed flares contribute one-third of the total X-ray output of Sgr A* during the campaign, and as much as 10% of the quiescent X-ray emission could be comprised of weak, undetected flares, which may also contribute high-frequency variability. We argue that flares may be the only source of X-ray emission from the inner accretion flow.
Using VLTI/GRAVITY and SINFONI data, we investigate the subparsec gas and dust structure around the nearby type 1 active galactic nucleus (AGN) hosted by NGC 3783. The
K
-band coverage of GRAVITY ...uniquely allows simultaneous analysis of the size and kinematics of the broad line region (BLR), the size and structure of the near-infrared(near-IR)-continuum-emitting hot dust, and the size of the coronal line region (CLR). We find the BLR, probed through broad Br
γ
emission, to be well described by a rotating, thick disc with a radial distribution of clouds peaking in the inner region. In our BLR model, the physical mean radius of 16 light-days is nearly twice the ten-day time-lag that would be measured, which closely matches the ten-day time-lag that has been measured by reverberation mapping. We measure a hot dust full-width at half-maximum (FWHM) size of 0.74 mas (0.14 pc) and further reconstruct an image of the hot dust, which reveals a faint (5% of the total flux) offset cloud that we interpret as an accreting or outflowing cloud heated by the central AGN. Finally, we directly measure the FWHM size of the nuclear CLR as traced by the Ca
VIII
and narrow Br
γ
line. We find a FWHM size of 2.2 mas (0.4 pc), fully in line with the expectation of the CLR located between the BLR and narrow line region. Combining all of these measurements together with larger scale near-IR integral field unit and mid-IR interferometry data, we are able to comprehensively map the structure and dynamics of gas and dust from 0.01 to 100 pc.
We present new near-infrared VLTI/GRAVITY interferometric spectra that spatially resolve the broad Br
γ
emission line in the nucleus of the active galaxy IRAS 09149−6206. We use these data to measure ...the size of the broad line region (BLR) and estimate the mass of the central black hole. Using an improved phase calibration method that reduces the differential phase uncertainty to 0.05° per baseline across the spectrum, we detect a differential phase signal that reaches a maximum of ∼0.5° between the line and continuum. This represents an offset of ∼120
μ
as (0.14 pc) between the BLR and the centroid of the hot dust distribution traced by the 2.3
μ
m continuum. The offset is well within the dust sublimation region, which matches the measured ∼0.6 mas (0.7 pc) diameter of the continuum. A clear velocity gradient, almost perpendicular to the offset, is traced by the reconstructed photocentres of the spectral channels of the Br
γ
line. We infer the radius of the BLR to be ∼65
μ
as (0.075 pc), which is consistent with the radius–luminosity relation of nearby active galactic nuclei derived based on the time lag of the H
β
line from reverberation mapping campaigns. Our dynamical modelling indicates the black hole mass is ∼1 × 10
8
M
⊙
, which is a little below, but consistent with, the standard
M
BH
–
σ
*
relation.
Abstract
We use VLBA+VLA observations to measure the sizes of the scatter-broadened images of six of the most heavily scattered known pulsars: three within the Galactic Centre (GC) and three ...elsewhere in the inner Galactic plane (Δl < 20°). By combining the measured sizes with temporal pulse broadening data from the literature and using the thin-screen approximation, we locate the scattering medium along the line of sight to these six pulsars. At least two scattering screens are needed to explain the observations of the GC sample. We show that the screen inferred by previous observations of SGR J1745−2900 and Sgr A*, which must be located far from the GC, falls off in strength on scales ≲0
$_{.}^{\circ}$
2. A second scattering component closer to (Δ < 2 kpc) or even (tentatively) within (Δ < 700 pc) the GC produces most or all of the temporal broadening observed in the other GC pulsars. Outside the GC, the scattering locations for all three pulsars are ≃2 kpc from Earth, consistent with the distance of the Carina-Sagittarius or Scutum spiral arm. For each object the 3D scattering origin coincides with a known H ii region (and in one case also a supernova remnant), suggesting that such objects preferentially cause the intense interstellar scattering seen towards the Galactic plane. We show that the H ii regions should contribute ≳25 per cent of the total dispersion measure (DM) towards these pulsars, and calculate reduced DM distances. Those distances for other pulsars lying behind H ii regions may be similarly overestimated.
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