- ID:
- ivo://CDS.VizieR/J/AJ/127/1181
- Title:
- Binary speckle measurements at Calar Alto
- Short Name:
- J/AJ/127/1181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of our second observational run of binary star interferometric measurements with an ICCD speckle camera attached to the 1.52m telescope of the Observatorio Astronomico Nacional at Calar Alto (Almeria, Spain) in 2000 June-July are presented. The measured angular separations range from 0.096" to 6.558". With the use of the new speckle data, the orbits of the visual binaries WDS 14369+4813 and WDS 21597+4908 are improved.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/366/868
- Title:
- Binary speckle measurements at Calar Alto. I.
- Short Name:
- J/A+A/366/868
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of our speckle interferometric measurements of binary stars made with the ICCD speckle camera using the 1.52-m telescope of the Observatorio Astronomico Nacional at Calar Alto (Spain) in September, 1999. The data contain 123 observations of 83 systems. The measured angular separations range from 0.153" to 6.727". We have used there new speckle measurements to improve the orbital elements for the binaries COU 247 and BU 524 AB.
- ID:
- ivo://CDS.VizieR/J/A+AS/105/503
- Title:
- Binary star speckle measurements
- Short Name:
- J/A+AS/105/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have continued to survey visual and interferometric binary stars with significant orbital motion by means of speckle method at the telescopes of the Special Astrophysical Observatory (SAO) in Zelenchuk. Here we present the lists of 267 speckle observations made with the 6 m and the 1 m telescopes in the period May 1989 - November 1993.
- ID:
- ivo://CDS.VizieR/J/A+AS/140/287
- Title:
- 1992-1997 binary star speckle measurements
- Short Name:
- J/A+AS/140/287
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of speckle interferometric measurements of binary stars made with the television photon-counting camera at the 6-m Big Azimuthal Telescope (BTA) and 1-m telescope of the Special Astrophysical Observatory (SAO) between August 1992 and May 1997. The data contain 89 observations of 62 star systems on the large telescope and 21 on the smaller one. For the 6-m aperture 18 systems remained unresolved. The measured angular separation ranged from 39 mas, two times above the BTA diffraction limit, to 1593 mas.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A34
- Title:
- Bright AGN VLBI imaging study at 2 and 8GHz
- Short Name:
- J/A+A/544/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate statistical and individual astrophysical properties of active galactic nuclei (AGNs), such as parsec-scale flux density, core dominance, angular and linear sizes, maximum observed brightness temperatures of VLBI core components, spectral index distributions for core and jet components, and evolution of brightness temperature along the jets. Furthermore, we statistically compare core flux densities and brightness temperature as well as jet spectral indices of {gamma}-ray bright and weak sources. We used 19 very long baseline interferometry (VLBI) observing sessions carried out simultaneously at 2.3GHz and 8.6GHz with the participation of 10 Very Long Baseline Array (VLBA) stations and up to 10 additional geodetic telescopes. The observations span the period 1998-2003. We present here single-epoch results from high-resolution radio observations of 370 AGNs. Our VLBI images at 2.3GHz and 8.6GHz as well as Gaussian models are presented and analyzed. At least one-fourth of the cores are completely unresolved on the longest baselines of the global VLBI observations. The VLBI core components are partially opaque with the median value of spectral index of alpha_core_~0.3, while the jet features are usually optically thin alpha_jet_~-0.7. The spectral index typically decreases along the jet ridge line owing to the spectral aging, with a median value of -0.05mas^-1^. Brightness temperatures are found to be affected by Doppler boosting and reach up to ~10^13^K with a median of ~2.5x10^11^K at both frequencies. The brightness temperature gradients along the jets typically follow a power law T_b_~r^-2.2^ at both frequencies. We find that 147 sources (40%) positionally associated with gamma-ray detections from the Fermi LAT Second Source Catalog have higher core flux densities and brightness temperatures, and are characterized by the less steep radio spectrum of the optically thin jet emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/744/138
- Title:
- Calibrated visibilities of {epsilon} Eri
- Short Name:
- J/ApJ/744/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measured the angular diameter of the exoplanet host star {epsilon} Eridani using the Navy Optical Interferometer. We determined its physical radius, effective temperature, and mass by combining our measurement with the star's parallax, photometry from the literature, and the Yonsei-Yale isochrones, respectively. We used the resulting stellar mass of 0.82+/-0.05M_{sun}_ plus the mass function from Benedict et al. to calculate the planet's mass, which is 1.53+/-0.22M_Jupiter_. Using our new effective temperature, we also estimated the extent of the habitable zone for the system.
- ID:
- ivo://CDS.VizieR/J/AJ/153/16
- Title:
- Calibrator stars catalog for interferometers
- Short Name:
- J/AJ/153/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Benchmark stars with known angular diameters are key to calibrating interferometric observations. With the advent of optical interferometry, there is a need for suitably bright, well-vetted calibrator stars over a large portion of the sky. We present a catalog of uniformly computed angular diameters for 1510 stars in the northern hemisphere, brighter than V=6 and with declinations -15{deg}<delta<82{deg}. The median angular stellar diameter is 0.529 mas. The list has been carefully cleansed of all known binary and multiple stellar systems. We derive the angular diameters for each of the stars by fitting spectral templates to the observed spectral energy distributions (SEDs) from literature fluxes. We compare these derived angular diameters against those measured by optical interferometry for 75 of the stars, as well as to 176 diameter estimates from previous calibrator catalogs, finding in general excellent agreement. The final catalog includes our goodness-of-fit metrics as well as an online atlas of our SED fits. The catalog presented here permits selection of the best calibrator stars for current and future visible-light interferometric observations.
- ID:
- ivo://CDS.VizieR/J/A+A/433/1155
- Title:
- Calibrator stars for 200m baseline interferometry
- Short Name:
- J/A+A/433/1155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of reference stars suitable for calibrating infrared interferometric observations. In the K band, visibilities can be calibrated with a precision of 1% on baselines up to 200 meters for the whole sky, and up to 300 meters for some part of the sky. This work, extending to longer baselines a previous catalog compiled by Borde et al. (2002, Cat. <J/A+A/393/183>), is particularly well adapted to hectometric-class interferometers. We use the absolute spectro-photometric calibration method introduced by Cohen et al. (1999AJ....117.1864C) to derive the angular diameters of our new set of stars.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A150
- Title:
- CasA, CygA, TauA, VirA 30MHz & 77MHz models
- Short Name:
- J/A+A/635/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (<100MHz) can reach several thousands of janskys, and they often contaminate observations of the low-frequency sky by interfering with image processing. Furthermore, these sources are foreground objects for all-sky observations hampering the study of faint signals, such as the cosmological 21cm line from the epoch of reionisation. We aim to produce robust models for the surface brightness emission as a function of frequency for the A-team sources at ultra-low frequencies. These models are needed for the calibration and imaging of wide-area surveys of the sky with low-frequency interferometers. This requires obtaining images at an angular resolution better than 1500 with a high dynamic range and good image fidelity. We observed the A-team with the Low Frequency Array (LOFAR) at frequencies between 30MHz and 77MHz using the Low Band Antenna (LBA) system. We reduced the datasets and obtained an image for each A-team source. The paper presents the best models to date for the sources Cassiopeia A, Cygnus A, Taurus A, and Virgo A between 30MHz and 77MHz. We were able to obtain the aimed resolution and dynamic range in all cases. Owing to its compactness and complexity, observations with the long baselines of the International LOFAR Telescope will be required to improve the source model for Cygnus A further.
- ID:
- ivo://CDS.VizieR/J/A+A/386/492
- Title:
- Catalog of High Angular Resolution Measurements
- Short Name:
- J/A+A/386/492
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Catalog of High Angular Resolution Measurements (CHARM) includes most of the measurements obtained by the techniques of lunar occultations and long-baseline interferometry at visual and infrared wavelengths, which have appeared in the literature or have otherwise been made public until mid-2001. A total of 2432 measurements of 1625 sources are included, along with extensive auxiliary information. In particular, visual and infrared photometry is included for almost all the sources. This has been partly extracted from currently available catalogs, and partly obtained specifically for CHARM. The main aim is to provide a compilation of sources which could be used as calibrators or for science verification purposes by the new generation of large ground-based facilities such as the ESO Very Large Interferometer and the Keck Interferometer.
