Change In Position Angle Research Articles

Management of overbite with the Invisalign appliance.

Most of the published literature on the management of overbite with the Invisalign appliance (Align Technology, Santa Clara, Calif) consists of case reports and case series. In this retrospective study of 120 patients, we sought to assess the nature of overbite changes with the Invisalign appliance. Records were collected from 3 practitioners, all experienced with the Invisalign technique. The patients were consecutively treated adults (>18years old) who underwent orthodontic treatment only with the Invisalign appliance. Patients with major transverse or anteroposterior changes or extraction treatment plans were excluded. The study sample included 68 patients with normal overbites, 40 with deepbites, and 12 with open bites. Their median age was 33years, and 70% of the patients were women. Cephalometric analyses indicated that the deepbite patients had a median overbite opening of 1.5mm, whereas the open bite patients had a median deepening of 1.5mm. The median change for the normal overbite patients was 0.3mm. Changes in incisor position were responsible for most of the improvements in the deepbite and open bite groups. Minimal changes in molar vertical position and mandibular plane angle were noted. The Invisalign appliance appears to manage the vertical dimension relatively well, and the primary mechanism is via incisor movements.

Location ofγ-ray emission and magnetic field strengths in OJ 287

The Gamma-ray BL Lac object OJ 287 is known to exhibit inner-parsec "jet-wobbling", high degrees of variability at all wavelengths and quasi-stationary features including an apparent (~100 deg) position angle change in projection on the sky plane. Sub-50 micro-arcsecond resolution 86 GHz observations with the global mm-VLBI array (GMVA) supplement ongoing multi-frequency VLBI blazar monitoring at lower frequencies. Using these maps together with cm/mm total intensity and Gamma-ray observations from Fermi/LAT from 2008-2014, we aimed to determine the location of Gamma-ray emission and to explain the inner-mas structural changes. Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and allow us to observe above the synchrotron self-absorption peak frequency. The jet was spectrally decomposed at multiple locations along the jet. From this we derived estimates of the magnetic field. How the field decreases down the jet allowed an estimate of the distance to the jet apex and an estimate of the magnetic field strength at the jet apex and in the broad line region. Combined with accurate kinematics we attempt to locate the site of Gamma-ray activity, radio flares and spectral changes. Strong Gamma-ray flares appeared to originate from either the "core" region, a downstream stationary feature, or both, with Gamma-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be >1.6 G in the "core" and >0.4 G in the downstream quasi-stationary feature. We therefore found upper limits on the location of the "core" as >6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss.

CONSTRAINTS ON THE ARCHITECTURE OF THE HD 95086 PLANETARY SYSTEM WITH THE GEMINI PLANET IMAGER

ABSTRACT We present astrometric monitoring of the young exoplanet HD 95086 b obtained with the Gemini Planet Imager between 2013 and 2016. A small but significant position angle change is detected at constant separation; the orbital motion is confirmed with literature measurements. Efficient Monte Carlo techniques place preliminary constraints on the orbital parameters of HD 95086 b. With 68% confidence, a semimajor axis of au and an inclination of are favored, with eccentricity less than 0.21. Under the assumption of a coplanar planet–disk system, the periastron of HD 95086 b is beyond 51 au with 68% confidence. Therefore, HD 95086 b cannot carve the entire gap inferred from the measured infrared excess in the SED of HD 95086. We use our sensitivity to additional planets to discuss specific scenarios presented in the literature to explain the geometry of the debris belts. We suggest that either two planets on moderately eccentric orbits or three to four planets with inhomogeneous masses and orbital properties are possible. The sensitivity to additional planetary companions within the observations presented in this study can be used to help further constrain future dynamical simulations of the planet–disk system.

POLARIZATION EVOLUTION OF EARLY OPTICAL AFTERGLOWS OF GAMMA-RAY BURSTS

ABSTRACT The central engine and jet composition of gamma-ray bursts (GRBs) remain mysterious. Here we suggest that observations on the polarization evolution of early optical afterglows may shed light on these questions. We first study the dynamics of a reverse shock and a forward shock that are generated during the interaction of a relativistic jet and its ambient medium. The jet is likely magnetized with a globally large-scale magnetic field from the central engine. The existence of the reverse shock requires that the magnetization degree of the jet should not be high (σ ≤ 1), so that the jet is mainly composed of baryons and leptons. We then calculate the light curves and polarization evolution of early optical afterglows and find that when the polarization position angle changes by 90° during the early afterglow, the polarization degree is zero for a toroidal magnetic field but is very likely to be nonzero for an aligned magnetic field. This result would be expected to provide a probe for the central engine of GRBs because an aligned field configuration could originate from a magnetar central engine and a toroidal field configuration could be produced from a black hole via the Blandford–Znajek mechanism. Finally, for such two kinds of magnetic field configurations, we fit the observed data of the early optical afterglow of GRB 120308A equally well.

Astrometric follow-up observations of directly imaged sub-stellar companions to young stars and brown dwarfs★

The formation of massive planetary or brown dwarf companions at large projected separations from their host star is not yet well understood. In order to put constraints on formation scenarios we search for signatures in the orbit dynamics of the systems. We are specifically interested in the eccentricities and inclinations since those parameters might tell us about the dynamic history of the systems and where to look for additional low-mass sub-stellar companions. For this purpose we utilized VLT/NACO to take several well calibrated high resolution images of 6 target systems and analyze them together with available literature data points of those systems as well as Hubble Space Telescope archival data. We used a statistical Least-Squares Monte-Carlo approach to constrain the orbit elements of all systems that showed significant differential motion of the primary star and companion. We show for the first time that the GQ Lup system shows significant change in both separation and position angle. Our analysis yields best fitting orbits for this system, which are eccentric (e between 0.21 and 0.69), but can not rule out circular orbits at high inclinations. Given our astrometry we discuss formation scenarios of the GQ Lup system. In addition, we detected an even fainter new companion candidate to GQ Lup, which is most likely a background object. We also updated the orbit constraints of the PZ Tel system, confirming that the companion is on a highly eccentric orbit with e > 0.62. Finally we show with a high significance, that there is no orbital motion observed in the cases of the DH Tau, HD 203030 and 1RXS J160929.1-210524 systems and give the most precise relative astrometric measurement of the UScoCTIO 108 system to date.

Position Angle Changes of Inner-Jets in a Sample of Blazars

We have carried out the Gaussian model-fitting to the 15 GHz VLBA cores for a sample of blazars from the MOJAVE database, analyzed the correlations in the model-fitted parameters and studied the variability properties for different group of sources. We find that the Fermi LAT-detected blazars have on average higher position angle changes of cores than the LAT non-detected blazars, and that the LAT-detected ones largely associate with more variable cores in flux density.

Changes in Polarization Position Angle across the Eclipse in the Double Pulsar System

AbstractWe investigate the changes in polarization position angle in radiation from pulsar A around the eclipse in the Double Pulsar system PSR J0737-3039A/B at the 20 cm and 50 cm wavelengths using the Parkes 64-m radio telescope. The changes are ~ 2σ during and shortly after the eclipse at 20 cm but less significant at 50 cm. We show that the changes in position angle during the eclipse can be modelled by differential synchrotron absorption in the eclipse regions. Position angle changes after the eclipse are interpreted as Faraday rotation in the magnetotail of pulsar B. Implied charge densities are consistent with the Goldreich-Julian density, suggesting that the particle energies in the magnetotail are mildly relativistic.

SUBMILLIMETER POLARIZATION OF GALACTIC CLOUDS: A COMPARISON OF 350 μm AND 850 μm DATA

The Hertz and SCUBA polarimeters, working at 350 micron and 850 micron respectively, have measured the polarized emission in scores of Galactic clouds. Of the clouds in each dataset, 17 were mapped by both instruments with good polarization signal-to-noise ratios. We present maps of each of these 17 clouds comparing the dual-wavelength polarization amplitudes and position angles at the same spatial locations. In total number of clouds compared, this is a four-fold increase over previous work. Across the entire data-set real position angle differences are seen between wavelengths. While the distribution of \phi(850)-\phi(350) is centered near zero (near-equal angles), 64% of data points with high polarization signal-to-noise (P >= 3\sigma_p) have |\phi(850)-\phi(350)| > 10 degrees. Of those data with small changes in position angle (<= 10 degrees) the median ratio of the polarization amplitudes is P(850)/P(350) = 1.7 +/- 0.6. This value is consistent with previous work performed on smaller samples and models which require mixtures of different grain properties and polarization efficiencies. Along with the polarization data we have also compiled the intensity data at both wavelengths; we find a trend of decreasing polarization with increasing 850-to-350 micron intensity ratio. All the polarization and intensity data presented here (1699 points in total) are available in electronic format.

CHANGES IN POLARIZATION POSITION ANGLE ACROSS THE ECLIPSE IN THE DOUBLE PULSAR SYSTEM

We investigate the changes in polarization position angle in radiation from pulsar A around the eclipse in the Double Pulsar system PSR J0737-3039A/B at the 20 cm and 50 cm wavelengths using the Parkes 64-m telescope. The changes are ~2\sigma\ during and shortly after the eclipse at 20 cm but less significant at 50 cm. We show that the changes in position angle during the eclipse can be modelled by differential synchrotron absorption in the eclipse regions. Position angle changes after the eclipse are interpreted as Faraday rotation in the magnetotail of pulsar B. Implied charge densities are consistent with the Goldreich-Julian density, suggesting that the particle energies in the magnetotail are mildly relativistic.

VII Zw 403: H I STRUCTURE IN A BLUE COMPACT DWARF GALAXY

We present optical (UBVJ), ultraviolet (FUV, NUV), and high resolution atomic hydrogen (HI) observations of the nearby blue compact dwarf (BCD), VII Zw 403. We find that VII Zw 403 has a relatively high HI mass-to-light ratio for a BCD. The rotation velocity is nominally 10-15 km/s, but rises to ~20 km/s after correction for the ~8-10 km/s random motions present in the gas. The velocity field is complex; including a variation in the position angle of the major axis going from the NE to the SW parts of the galaxy. Our high resolution HI maps reveal structure in the central gas, including a large, low-density HI depression or hole between the southern and northern halves of the galaxy, coincident with an unresolved x-ray source. Although interactions have been proposed as the triggering mechanism for the vigorous star formation occurring in BCDs, VII Zw 403 does not seem to have been tidally triggered by an external interaction, as we have found no nearby possible perturbers. It also doesn't appear to fall in the set of galaxies that exhibit a strong central mass density concentration, as its optical scale length is large in comparison to similar systems. However, there are some features that are compatible with an accretion event: optical/HI axis misalignment, a change in position angle of the kinematic axis, and a complex velocity field.

Further deep imaging of HR 7329 A (η Tel A) and its brown dwarf companion B★

About 4" south of the young A0-type star HR 7329, a faint companion candidate was found by Lowrance et al. (2000). Its spectral type of M7-8 is consistent with a young brown dwarf companion. Here, we report ten new astrometric imaging observations of the pair HR 7329 A and B, obtained with the Hubble Space Telescope and the Very Large Telescope, aimed at showing common proper motion with high significance and possible orbital motion of B around A. With 11 yrs of epoch difference between the first and our last image, we can reject by more than 21 sigma that B would be a non-moving background object unrelated to A. We detect no change in position angle and small or no change in separation (2.91 +/- 2.41 mas/yr), so that the orbit of HR 7329 B around A is inclined and/or eccentric and/or the orbital motion is currently only in radial direction. If HR 7329 B is responsible for the outer radius of the debris disk around HR 7329 A being 24 AU, and if HR 7329 B currently is at its apastron at 200 AU (4.2" at 47.7 pc), we determine its pericenter distance to be 71 AU, its semi-major axis to be 136 AU, and its eccentricity to be e=0.47. From the magnitude differences between HR 7329 A and B and the 2MASS magnitudes for the HR 7329 A+B system, we can estimate the magnitudes of HR 7329 B (J=12.06+/-0.19, H=11.75+/-0.10, Ks=11.6+/-0.1, L=11.1+/-0.2 mag) and then, with a few otherwise known parameters, its luminosity and mass (20-50 Jupiter masses). In the deepest images available, we did not detect any additional companion candidates up to <=9", but determine upper limits in the planetary mass regime.

A GIANT GLITCH IN PSR J1718–3718

Radio timing observations of the high-magnetic-field pulsar PSR J1718-3718 have shown that it suffered a large glitch with Dnu_g/nu = (33.25 +/- 0.01) x 10^{-6} between 2007 September (MJD 54336) and 2009 January (MJD 54855). This is the largest pulsar glitch ever observed. As is common, there was a small increase in braking torque at the time of the glitch but, unlike all other pulsars, the braking torque has continued to increase over the two years since the glitch. Polarization observations show that the mean pulse profile has about 30% linear polarization with a smooth change of position angle through the pulse and give a rotation measure of -160 +/- 22 rad m^{-2}. There was no detectable change in pulse profile at the time of the glitch. The timing observations also gave an improved dispersion measure of 371.1 +/- 1.7 cm^{-3}pc.

WE‐E‐BRB‐07: EPID Based Verification of Delivered Fluence for VMAT with High Angular Resolution

Purpose: In VMAT, the dose rate, MLC position, and gantry angle change simultaneously, it is important they follow their predefined trajectories to ensure correct dose delivery. Our purpose is to develop an efficient VMAT QA strategy using EPID that is capable of quantifying delivery errors per gantry angle. Methods: For the QA procedure, portal images are acquired continuously during VMAT delivery. The plan is modified automatically so that the two most inferior MLC leaf pairs are open at all control points. A custom built phantom is positioned via image guidance to be visible in all projections of the opened leaf pairs, and is used to measure the angular fraction through which each portal image is acquired. Expected values of delivered MU and beginning and ending MLC positions are calculated from the plan using the measured start and stop gantry angles per image. They are used to compute a predicted detector response using the treatment planning software (Portal Dosimetry, Varian). The calculated portal response is further analyzed against the EPID images in 3D. We performed the QA procedure for a clinical VMAT 170° arc. Results: The mean gantry angle and angular width of each portal image measured using the phantom was shown to be accurate to within 0.06°±0.14° and 0.59°±0.36°, respectively. Conversely, the angle recorded with each portal image had a larger error of 1.04°±0.84°. QA analysis consisted of projecting the measured and predicted data into 3 planes: leaf motion axis vs. cross leaf axis, leaf motion vs. gantry angle, and cross leaf vs. gantry. In each plane intensities are defined by dose, dose rate, MLC positioning, and gantry angle, thereby allowing verification of all essential machine parameters. Conclusions: Accurate and efficient VMAT QA can be performed using EPID and customized phantom and software that provides verification of all plan parameters.

SPECTRAL POLARIZATION OF THE REDSHIFTED 21 cm ABSORPTION LINE TOWARD 3C 286

A re-analysis of the Stokes-parameter spectra obtained of the z=0.692 21 cm absorption line toward 3C 286 shows that our original claimed detection of Zeeman splitting by a line-of-sight magnetic field, B_los = 87 microgauss is incorrect. Because of an insidious software error, what we reported as Stokes V is actually Stokes U: the revised Stokes V spectrum indicates a 3-sigma upper limit of B_los < 17 microgauss. The correct analysis reveals an absorption feature in fractional polarization that is offset in velocity from the Stokes I spectrum by -1.9 km/s. The polarization position-angle spectrum shows a dip that is also significantly offset from the Stokes I feature, but at a velocity that differs slightly from the absorption feature in fractional polarization. We model the absorption feature with 3 velocity components against the core-jet structure of 3C 286. Our chisquare minimization fitting results in components with differing (1) ratios of H I column density to spin temperature, (2) velocity centroids, and (3) velocity dispersions. The change in polarization position angle with frequency implies incomplete coverage of the background jet source by the absorber. It also implies a spatial variation of the polarization position angle across the jet source, which is observed at frequencies higher than the 839.4 MHz absorption frequency. The multi-component structure of the gas is best understood in terms of components with spatial scales of ~100 pc comprised of hundreds of low-temperature (T < 200 K) clouds with linear dimensions of about 1 pc.

Orbital motion of the young brown dwarf companion TWA 5 B

With more adaptive optics images available, we aim at detecting orbital motion for the first time in the system TWA 5 A+B. We measured separation and position angle between TWA 5 A and B in each high-resolution image available and followed their change in time, because B should orbit around A. The astrometric measurement precision is about one milli arc sec. With ten year difference in epoch, we can clearly detect orbital motion of B around A, a decrease in separation by ~ 0.0054 arc sec per year and a decrease in position angle by ~ 0.26 degrees per year. TWA 5 B is a brown dwarf with ~ 25 Jupiter masses (Neuh\"auser et al. 2000), but having large error bars (4 to 145 Jupiter masses, Neuh\"auser et al. 2009). Given its large projected separation from the primary star, ~ 86 AU, and its young age ~ 10 Myrs), it has probably formed star-like, and would then be a brown dwarf companion. Given the relatively large changes in separation and position angle between TWA 5 A and B, we can conclude that they orbit around each other on an eccentric orbit. Some evidence is found for a curvature in the orbital motion of B around A - most consistent with an elliptic (e=0.45) orbit. Residuals around the best-fit ellipse are detected and show a small-amplitude (~ 18 mas) periodic sinusoid with ~ 5.7 yr period, i.e., fully consistent with the orbit of the inner close pair TWA 5 Aa+b. Measuring these residuals caused by the photocenter wobble - even in unresolved images - can yield the total mass of the inner pair, so can test theoretical pre-main sequence models.

Very Long Baseline Array observations of the intraday variable source J1128+592

Short time-scale flux density variations of flat spectrum radio sources are often explained by the scattering of radio waves in the turbulent, ionized Interstellar Matter of the Milky Way. One of the most convincing observational arguments in favor of this is the annual modulation of the variability time-scale caused by the Earth orbital motion around the Sun. J1128+592 is an IDV source with a possible annual modulation in its variability time-scale. We observed the source in 6 epochs with the VLBA at 5, 8 and 15 GHz in total intensity and polarization. The VLBA observations revealed an east-west oriented core-jet structure. Its position angle agrees with the angle of anisotropy derived from the annual modulation model. No significant long-term structural changes were observed with VLBI on mas-scales, however, compared to archival data, the VLBI core size is expanded. This expansion offers a possible explanation to the observed decrease of the strength of IDV. VLBI polarimetry revealed significant changes in the electric vector position angle and Rotation Measure of the core and jet. Part of the observed RM variability could be attributed to a scattering screen (37 pc distance), which covers the source (core and jet) and which may be responsible for the IDV. Superposition of polarized sub-components below the angular resolution limit may affect the observed RM as well.

Galaxy populations in the Antlia cluster - II. Compact elliptical galaxy candidates★

Continuing our study of galaxy populations in the Antlia cluster, we present a photometric analysis of four galaxies classified as compact elliptical (cE) galaxies in the 1990 Antlia Group catalogue of Ferguson and Sandage. Until now, there have been only six known members of this rare type of galaxy. Using data from various photometric systems (Washington C, KronCousins R, Bessel V and I, Hubble Space Telesecope F814W and F435W), we measured the brightness and colour profiles, as well as the structural parameters. By comparing these with those of other galaxies in the Antlia cluster, as well as with confirmed cE galaxies from the literature, we found that two of the cE candidates, although spectroscopically confirmed Antlia members, are not cE galaxies. However, one of these objects presents strong ellipticity and position angle variations that resemble those already reported for M32, leading us to speculate about this type of object being a progenitor of a cE galaxy. The other two cE candidates, for which radial velocities are not available, match some features typical of cE galaxies, such as being close in projection to a larger galaxy, displaying flat colour profiles, and having a high degree of compactness. Only one of the remaining cE candidates shows a high central surface brightness, two components in its brightness profile and distinct changes in ellipticity and position angle where the outer component begins to dominate. It seems to follow the same trend as other confirmed cE galaxies in a luminosity versus mean effective surface brightness diagram. Moreover, it shows a distorted inner structure with similar characteristics to those found by simulations of interacting galaxies. Also, an extremely faint structure, which seems to link this object with one of the Antlia dominant galaxies, has been detected in images from the Cerro Tololo Inter-American Observatory MOSAIC, the Very Large Telescope FORS 1 and the Hubble Space Telescope Advanced Camera for Surveys. The cE nature of this galaxy and the possible interaction with its bright companion still have to be confirmed using spectroscopy.

A Statistical Description of AGN Jet Evolution from the VLBA Imaging and Polarimetry Survey (VIPS)

A detailed analysis of the evolution of the properties of core-jet systems within the VLBA Imaging and Polarimetry Survey (VIPS) is presented. We find a power-law relationship between jet intensity and width that suggests that for the typical jet, little if any energy is lost as it moves away from its core. Using VLA images at 1.5 GHz, we have found evidence that parsec-scale jets tend to be aligned with the direction of emission on kiloparsec scales. We also found that this alignment improves as the jets move farther from their cores on projected scales as small as ~50-100 pc. This suggests that realignment of jets on these projected scales is relatively common. We typically find a modest amount of bending (a change in jet position angle of ~5°) on these scales, suggesting that this realignment may typically occur relatively gradually.

An assessment of interfractional uterine and cervical motion: Implications for radiotherapy target volume definition in gynaecological cancer

Purpose To assess interfractional movement of the uterus and cervix in patients with gynaecological cancer to aid selection of the internal margin for radiotherapy target volumes. Methods and materials Thirty-three patients with gynaecological cancer had an MRI scan performed on two consecutive days. The two sets of T2-weighted axial images were co-registered, and the uterus and cervix outlined on each scan. Points were identified on the anterior uterine body (Point U), posterior cervix (Point C) and upper vagina (Point V). The displacement of each point in the antero-posterior (AP), supero-inferior (SI) and lateral directions between the two scans was measured. The changes in point position and uterine body angle were correlated with bladder volume and rectal diameter. Results The mean difference (±1SD) in Point U position was 7 mm (±9.0) in the AP direction, 7.1 mm (±6.8) SI and 0.8 mm (±1.3) laterally. Mean Point C displacement was 4.1 mm (±4.4) SI, 2.7 mm (±2.8) AP, 0.3 (±0.8) laterally, and Point V was 2.6 mm (±3.0) AP and 0.3 mm (±1.0) laterally. There was correlation for uterine SI movement in relation to bladder filling, and for cervical and vaginal AP movement in relation to rectal filling. Conclusion Large movements of the uterus can occur, particularly in the superior–inferior and anterior–posterior directions, but cervical displacement is less marked. Rectal filling may affect cervical position, while bladder filling has more impact on uterine body position, highlighting the need for specific instructions on bladder and rectal filling for treatment. We propose an asymmetrical margin with CTV–PTV expansion of the uterus, cervix and upper vagina of 15 mm AP, 15 mm SI and 7 mm laterally and expansion of the nodal regions and parametria by 7 mm in all directions.

Resolving LB 11146 withHubble Space Telescope's Fine Guidance Sensor

On the basis of its observed spectra, LB 11146 was identified as a binary system composed of pair of massive (∼0.9 M⊙) white dwarf stars. However, observations with the Hubble Space Telescope (HST) Faint Object Camera did not resolve the system, and searches for radial velocity variations yielded null results. Subsequent observations of LB 11146 with the HST's Fine Guidance Sensor have resolved the system at three epochs spanning 295 days, thereby confirming the binary nature of this object. We find a nearly constant component separation of approximately 15 mas and a large change in position angle, consistent with a low-inclination, low-eccentricity orbit with a period of approximately 130 days. At a distance of 40 pc, this corresponds to a component separation of about 0.6 AU, which in turn also results in a Keplerian orbit with a period of about 130 days, assuming the spectroscopic masses of the white dwarfs. The size of the orbit is significantly smaller than the size of the progenitor stars as they evolved through the asymptotic giant branch, so one or more phases of binary star evolution is likely to have occurred. LB 11146 joins PG 1115+116, but in a more extreme sense, as an example of a close binary composed of massive white dwarfs that did not evolve to become a short-period system, thereby providing an additional key observational test for models of binary star evolution.