We present the results of N-band spectro-interferometric observations of the silicate carbon star IRAS08002-3803 with the MID-infrared Interferometric instrument (MIDI) at the Very Large Telescope ...Interferometer (VLTI) of the European Southern Observatory (ESO). The observations were carried out using two unit telescopes (UT2 and UT3) with projected baseline lengths ranging from 39 to 47 m. Our observations of IRAS08002-3803 have spatially resolved the dusty environment of a silicate carbon star for the first time and revealed an unexpected wavelength dependence of the angular size in the N band: the uniform-disk diameter is found to be constant and 636 mas (72 R*) between 8 and 10 km, while it steeply increases longward of 10 km to reach 653 mas (106 R*) at 13 km. Model calculations with our Monte Carlo radiative transfer code show that neither spherical shell models nor axisymmetric disk models consisting of silicate grains alone can simultaneously explain the observed wavelength dependence of the visibility and the spectral energy distribution (SED). We propose that the circumstellar environment of IRAS08002-3803 may consist of two grain species coexisting in the disk: silicate and a second grain species, for which we consider amorphous carbon, large silicate grains, and metallic iron grains. Comparison of the observed visibilities and SED with our models shows that such disk models can fairly - though not entirely satisfactorily - reproduce the observed SED and N-band visibilities. Our MIDI observations and the radiative transfer calculations lend support to the picture where oxygen-rich material around IRAS08002-3803 is stored in a circumbinary disk surrounding the carbon-rich primary star and its putative low-luminosity companion.
Aims. We present coordinated near-infrared K-band interferometric and optical spectroscopic observations of the M 1.5 giant \alpha Cet (Menkar) obtained with the instruments VINCI and UVES at the ...Paranal Observatory. Spherically symmetric PHOENIX stellar model atmospheres are constrained by comparison to our interferometric and spectroscopic data, and high-precision fundamental parameters of Menkar are obtained. Methods. Our high- precision VLTI/VINCI observations in the first and second lobes of the visibility function directly probe the model-predicted strength of the limb darkening effect in the K-band and the stellar angular diameter. The high spectral resolution of UVES of R=80\,000-110\,000 allows us to confront in detail observed and model-predicted profiles of atomic lines and molecular bands. Results. We show that our derived PHOENIX model atmosphere for Menkar is consistent with both the measured strength of the limb-darkening in the near-infrared K-band and the profiles of spectral bands around selected atomic lines and TiO bandheads from 370 nm to 1000 nm. At the detailed level of our high spectral resolution, however, noticeable discrepancies between observed and synthetic spectra exist. We obtain a high- precision Rosseland angular diameter of \Theta_\mathrm{Ross}=12.20 similar to {\rm mas}\pm 0.04 similar to {\rm mas}. Together with the Hipparcos parallax of 14.82 mas \pm 0.83 mas, it corresponds to a Rosseland radius of R_\mathrm{Ross}=89 \pm 5 R_\odot, and together with the bolometric flux based on available spectrophotometry, to an effective temperature of T_\mathrm{eff}=3795 similar to {\rm K} \pm 70 K. The luminosity based on these values is L=1460 similar to L_\odot \pm 300 similar to L_\odot. Relying on stellar evolutionary tracks, these values correspond to a mass M= 2.3 similar to M_\odot similar to \pm 0.2 similar to M_\odot and a surface gravity \log g=0.9 \pm 0.1 (cgs). Conclusions. Our approach illustrates the power of combining interferometry and high-resolution spectroscopy to constrain and calibrate stellar model atmospheres. The simultaneous agreement of the model atmosphere with our interferometric and spectroscopic data increases confidence in the reliability of the modelling of this star, while discrepancies at the detailed level of the high resolution spectra can be used to further improve the underlying model.
We present K-band commissioning observations of the Mira star prototype o Cet obtained at the ESO Very Large Telescope Interferometer (VLTI) with the VINCI instrument and two siderostats. The ...observations were carried out between 2001 October and December, in 2002 January and December, and in 2003 January. Rosseland angular radii are derived from the measured visibilities by fitting theoretical visibility functions obtained from center-to-limb intensity variations (CLVs) of Mira star models CITE. Using the derived Rosseland angular radii and the SEDs reconstructed from available photometric and spectrophotometric data, we find effective temperatures ranging from $T_{\rm eff}=3192 \pm 200$ K at phase $\Phi=0.13$ to $2918 \pm 183$ K at $\Phi=0.26$. Comparison of these Rosseland radii, effective temperatures, and the shape of the observed visibility functions with model predictions suggests that o Cet is a fundamental mode pulsator. Furthermore, we investigated the variation of visibility function and diameter with phase. The Rosseland angular diameter of o Cet increased from $28.9 \pm 0.3$ mas (corresponding to a Rosseland radius of $332 \pm 38~R_{\odot}$ for a distance of $D=107\pm12~{\rm pc}$) at $\Phi=0.13$ to $34.9 \pm 0.4$ mas ($402 \pm 46~R_{\odot}$) at $\Phi=0.4$. The error of the Rosseland linear radius almost entirely results from the error of the parallax, since the error of the angular diameter is only approximately 1%.
Context. IRC +10420 is a massive evolved star belonging to the group of yellow hypergiants. Currently, this star is rapidly evolving through the Hertzprung-Russell diagram, crossing the so-called ...yellow void. IRC +10420 is suffering from intensive mass loss which led to the formation of an extended dust shell. Moreover, the dense stellar wind of IRC +10420 is subject to strong line emission. Aims. Our goal was to probe the photosphere and the innermost circumstellar environment of IRC +10420, to measure the size of its continuum- as well as the Br$\gamma\,$line-emitting region on milliarcsecond scales, and to search for evidence of an asymmetric distribution of IRC +10420's dense, circumstellar gas. Methods. We obtained near-infrared long-baseline interferometry of IRC +10420 with the AMBER instrument of ESO's Very Large Telescope Interferometer (VLTI). The measurements were carried out in May/June 2007 and May 2008 in low-spectral resolution mode in the JHK bands using three auxillary telescopes (ATs) at projected baselines ranging from 30 to 96 m, and in October 2008 in high-spectral resolution mode in the K band around the Br$\gamma\,$emission line using three unit telescopes (UTs) with projected baselines between 54 and 129 m. The high-spectral resolution mode observations were analyzed by means of radiative transfer modeling using CMFGEN and the 2D Busche & Hillier codes. Results. For the first time, we have been able to absolutely calibrate the H- and K-band data and, thus, to determine the angular size of IRC+10420's continuum- and Brγ line-emitting regions. We found that both the low resolution differential and closure phases are zero within the uncertainty limits across all three bands. In the high-spectral resolution observations, the visibilities show a noticeable drop across the Brγ line on all three baselines. We found differential phases up to -25° in the redshifted part of the Brγ line and a non-zero closure phase close to the line center. The calibrated visibilities were corrected for AMBER's limited field-of-view to appropriately account for the flux contribution of IRC +10420's extended dust shell. From our low-spectral resolution AMBER data we derived FWHM Gaussian sizes of 1.05±0.07 and 0.98±0.10 mas for IRC +10420's continuum-emitting region in the H and K bands, respectively. From the high-spectral resolution data, we obtained a FWHM Gaussian size of 1.014±0.010 mas in the K-band continuum. The Br$\gamma\,$-emitting region can be fitted with a geometric ring model with a diameter of $4.18^{\rm +0.19}_{-0.09}~$mas, which is approximately 4 times the stellar size. The geometric model also provides some evidence that the Br$\gamma\,$line-emitting region is elongated towards a position angle of 36°, well aligned with the symmetry axis of the outer reflection nebula. Assuming an unclumped wind and a luminosity of 6$\times$105${\,{L}_{\odot}}$, the spherical radiative transfer modeling with CMGFEN yields a current mass-loss rate of 1.5–2.0$\times$10-5${\,{M}_{\odot}\,{\rm yr}^{-1}}$ based on the Br$\gamma\,$equivalent width. However, the spherical CMFGEN model poorly reproduces the observed line shape, blueshift, and extension, definitively showing that the IRC +10420 outflow is asymmetric. Our 2D radiative transfer modeling shows that the blueshifted Br$\gamma\,$emission and the shape of the visibility across the emission line can be explained with an asymmetric bipolar outflow with a high density contrast from pole to equator (8–16), where the redshifted light is substantially diminished.
We present results of high-precision timing measurements of the binary millisecond pulsar PSR J2145-0750. Combining 10 yrs of radio timing data obtained with the Effelsberg 100-m radio telescope and ...the Lovell 76-m radio telescope we measure a significant timing parallax of 2.0(6) mas placing the system at 500 pc distance to the solar system. The detected secular change of the projected semi-major axis of the orbit x = 1.8(6) x 10 super(-14) It-s s super(-1), where x = (a sub(p) sin i)/c, is caused by the proper motion of the system. With this measurement we can constrain the orbital inclination angle to i < 61 degree , with a median likelihood value of 46 degree which is consistent with results from polarimetric studies of the pulsar magnetosphere. This constraint together with the non-detection of Shapiro delay rules out certain combinations of the companion mass, m sub(2), and the inclination, i. For typical neutron star masses and using optical observations of the carbon/oxygen-core white dwarf we derive a mass range for the companion of 0.7 M sub( ) less than or equal to m sub(2) less than or equal to 1.0 M sub( ). We apply evolutionary white dwarf cooling models to revisit the cooling age of the companion. Our analysis reveals that the companion has an effective temperature of T sub(eff) = 5750 plus or minus 600 K and a cooling age of tau sub(cool) = 3.6(2) Gyr, which is roughly a factor of three lower than the pulsar's characteristic age of 10.4 Gyr. The cooling age implies an initial spin period of P sub(0) = 13.0(5) ms, which is very close to the current period.
We present the results of the first mid-infrared interferometric observations of the Mira variable RR Sco with the MID-infrared Interferometer (MIDI) coupled to the European Southern Observatory's ...(ESO) Very Large Telescope Interferometer (VLTI), together with K-band observations using VLTI VINCI. The observations were carried out in June 2003, when the variability phase of the object was 0.6, using two unit telescopes (UT1 and UT3), as part of the Science Demonstration Time (SDT) program of the instrument. Projected baseline lengths ranged from 73 to 102 m, and a spectral resolution of 30 was employed in the observations, which enabled us to obtain the wavelength dependence of the visibility in the region between 8 and 13 mu m. The uniform-disk diameter was found to be 18 mas between 8 and 10 mu m, while it gradually increases at wavelengths longer than 10 mu m to reach 24 mas at 13 mu m. The uniform-disk diameter between 8 and 13 mu m is significantly larger than the K-band uniform-disk diameter of 10.2 plus or minus 0.5 mas measured using VLTI VINCI with projected baseline lengths of 15-16 m, three weeks after the MIDI observations. Our model calculations show that optically thick emission from a warm molecular envelope consisting of H sub(2)O and SiO can cause the apparent mid-infrared diameter to be much larger than the continuum diameter. We find that the warm molecular envelope model extending to similar to 2.3 R* with a temperature of similar to 1400 K and column densities of H sub(2)O and SiO of 3 x 10 super(21) cm super(-2) and 1 x 10 super(20) cm super(-2), respectively, can reproduce the observed uniform-disk diameters between 8 and 10 mu m. The observed increase of the uniform-disk diameter longward of 10 mu m can be explained by an optically thin dust shell consisting of silicate and corundum grains. The inner radius of the optically thin dust shell is derived to be 7-8 R* with a temperature of similar to 700 K, and the optical depth at 10 mu m is found to be similar to 0.025.
Context. Be supergiants are luminous, massive post-main sequence stars exhibiting non-spherical winds, forbidden lines, and hot dust in a disc-like structure. The physical properties of their rich ...and complex circumstellar environment (CSE) are not well understood, partly because these CSE cannot be easily resolved at the large distances found for Be supergiants (typically ≳1 kpc). Aims. From mid-IR spectro-interferometric observations obtained with VLTI/MIDI we seek to resolve and study the CSE of the Galactic Be supergiant CPD-57° 2874. Methods. For a physical interpretation of the observables (visibilities and spectrum) we use our ray-tracing radiative transfer code (FRACS), which is optimised for thermal spectro-interferometric observations. Results. Thanks to the short computing time required by FRACS (<10 s per monochromatic model), best-fit parameters and uncertainties for several physical quantities of CPD-57° 2874 were obtained, such as inner dust radius, relative flux contribution of the central source and of the dusty CSE, dust temperature profile, and disc inclination. Conclusions. The analysis of VLTI/MIDI data with FRACS allowed one of the first direct determinations of physical parameters of the dusty CSE of a Be supergiant based on interferometric data and using a full model-fitting approach. In a larger context, the study of Be supergiants is important for a deeper understanding of the complex structure and evolution of hot, massive stars.
To investigate intraocular pressure (IOP) control and corneal graft survival rates in eyes with glaucoma drainage device (GDD) implantation and penetrating keratoplasty (PK) and 5 years of follow-up ...data.
Retrospective review.
We performed a review of records of all patients who underwent both GDD placement and PK at our institution between January 1, 1988 and December 31, 2003. Twenty-eight eyes of 27 patients were studied. Glaucoma outcome was assessed by postoperative IOP, number of glaucoma medications, and need for further glaucoma surgery. Corneal grafts were assessed for clarity.
All eyes had GDD placement in the anterior chamber. The mean pre-GDD IOP was 28.8 ± 10.3 mm Hg on a mean of 2.6 ± 0.8 glaucoma medications. At 5-year follow-up, the mean IOP was 13.0 ± 5.9 mm Hg on a mean of 0.9 ± 1.0 glaucoma medications. GDD implantation successfully controlled glaucoma in 96%, 86%, 79%, 75%, and 71% of eyes at 1, 2, 3, 4, and 5 years, respectively. Grafts remained clear in 96%, 82%, 75%, 57%, and 54% of eyes at 1, 2, 3, 4, and 5 years, respectively. Failure of glaucoma outcome or graft survival was associated with prior intraocular surgeries.
Our data suggests that GDD placement can provide glaucoma control in a high percentage (71%) of eyes with PK even at 5 years. Furthermore, the success of PK in eyes with GDD remains reasonable (54%) at 5 years. IOP control and graft survival rates are comparable with earlier published studies with shorter follow-up or tube placement in the vitreous cavity.
To review studies of fungal keratitis related to contact lenses and determine whether the recent insurgence is a new phenomenon or an exacerbation of an ongoing trend.
A review of the recent ...literature on contact lens-related fungal ulcers and a comparison to older studies.
The incidence of fungal keratitis associated with contact lenses increased from 5% in the 1980s to between 10% and 25% in the 1990s and was noted to be 44% in Florida at the turn of the century. The most recent study from Florida showed that the incidence had increased from 29% in the late 1990s to 52% in the early 2000s, even before the Fusarium keratitis epidemic in 2004 and 2005. This increase mainly represented an increase in the number related to nontherapeutic contact lenses.
Contact lens-related fungal keratitis was relatively rare 20 years ago. However, the incidence has progressively increased since then. Contact lens-related fungal ulcers had become more common even before the recent Fusarium keratitis epidemic. This change may be related to changing contact lens care habits and younger patients being fitted with contact lenses.
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