- ID:
- ivo://CDS.VizieR/J/A+A/606/L3
- Title:
- Barnard 1b CO, NH_2_D and SO images
- Short Name:
- J/A+A/606/L3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extremely young Class 0 object B1b-S and the first hydrostatic core (FSHC) candidate, B1b-N, provide a unique opportunity to study the chemical changes produced in the elusive transition from the prestellar core to the protostellar phase. We present 40"x70" images of Barnard 1b in the ^13^CO 1-0, C^18^O 1-0, NH_2_D 1(1,1)a-1(0,1)s, and SO 3(2)-2(1) lines obtained with the NOEMA interferometer. The observed chemical segregation allows us to unveil the physical structure of this young protostellar system down to scales of ~500au. The two protostellar objects are embedded in an elongated condensation, with a velocity gradient of ~0.2-0.4m/s/au in the east-west direction, reminiscent of an axial collapse. The NH_2_D data reveal cold and dense pseudo-disks (R~500-1000au) around each protostar. Moreover, we observe evidence of pseudo-disk rotation around B1b-S. We do not see any signature of the bipolar outflows associated with B1b-N and B1b-S, which were previously detected in H_2_CO and CH_3_OH, in any of the imaged species.The non-detection of SO constrains the SO/CH_3_OH abundance ratio in the high-velocity gas.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/4160
- Title:
- BETA pilot multi-epoch continuum survey
- Short Name:
- J/MNRAS/457/4160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Boolardy Engineering Test Array is a 6x12m dish interferometer and the prototype of the Australian Square Kilometre Array Pathfinder (ASKAP), equipped with the first generation of ASKAP's phased array feed (PAF) receivers. These facilitate rapid wide-area imaging via the deployment of simultaneous multiple beams within an ~30deg^2^ field of view. By cycling the array through 12 interleaved pointing positions and using nine digitally formed beams, we effectively mimic a traditional 1hx108 pointing survey, covering ~150deg^2^ over 711-1015MHz in 12h of observing time. Three such observations were executed over the course of a week. We verify the full bandwidth continuum imaging performance and stability of the system via self-consistency checks and comparisons to existing radio data. The combined three epoch image has arcminute resolution and a 1{sigma} thermal noise level of 375{mu}Jy/beam, although the effective noise is a factor of ~3 higher due to residual sidelobe confusion. From this we derive a catalogue of 3722 discrete radio components, using the 35 per cent fractional bandwidth to measure in-band spectral indices for 1037 of them. A search for transient events reveals one significantly variable source within the survey area. The survey covers approximately two-thirds of the Spitzer South Pole Telescope Deep Field. This pilot project demonstrates the viability and potential of using PAFs to rapidly and accurately survey the sky at radio wavelengths.
- 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.
- 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+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/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/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.
- ID:
- ivo://CDS.VizieR/J/A+A/393/183
- Title:
- Catalogue of calibrator stars for LBSI
- Short Name:
- J/A+A/393/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long baseline stellar interferometry shares with other techniques the need for calibrator stars in order to correct for instrumental and atmospheric effects. We present a catalogue of 374 stars carefully selected to be used for that purpose in the near infrared. Owing to several convergent criteria with the work of Cohen et al. (1999AJ....117.1864C), this catalogue is in essence a subset of their self-consistent all-sky network of spectro-photometric calibrator stars. For every star, we provide the angular limb-darkened diameter, uniform disc angular diameters in the J, H and K bands, the Johnson photometry and other useful parameters. Most stars are type III giants with spectral types K or M0, magnitudes V=3-7 and K=0-3. Their angular limb-darkened diameters range from 1 to 3 mas with a median uncertainty as low as 1.2%. The median distance from a given point on the sky to the closest reference is 5.2{deg}, whereas this distance never exceeds 16.4{deg} for any celestial location.
