| 1. |
- de Jong, R. S., et al.
(författare)
-
4MOST : Project overview and information for the First Call for Proposals
- 2019
-
Ingår i: The Messenger. - : European Southern Observatory. - 0722-6691. ; 175, s. 3-11
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (R = λ/Δλ ~ 6500), and 812 fibres transferring light to the high-resolution spectrograph (R ~ 20 000). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations.
|
|
| 2. |
- Karovicova, I., et al.
(författare)
-
Accurate effective temperatures of the metal-poor benchmark stars HD140283, HD122563, and HD103095 from CHARA interferometry
- 2018
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966 .- 1745-3925 .- 1745-3933. ; 475:1, s. L81-L85
-
Tidskriftsartikel (refereegranskat)abstract
- Large stellar surveys of the MilkyWay require validation with reference to a set of 'benchmark' stars whose fundamental properties are well determined. For metal-poor benchmark stars, disagreement between spectroscopic and interferometric effective temperatures has called the reliability of the temperature scale into question. We present new interferometric measurements of three metal-poor benchmark stars, HD140283, HD122563, and HD103095, from which we determine their effective temperatures. The angular sizes of all the stars were determined from observations with the PAVO beam combiner at visible wavelengths at the CHARA array, with additional observations of HD103095 made with the VEGA instrument, also at the CHARA array. Together with photometrically derived bolometric fluxes, the angular diameters give a direct measurement of the effective temperature. For HD140283, we find theta(LD) = 0.324 +/- 0.005 mas, T-eff = 5787 +/- 48 K; for HD122563,theta(LD) = 0.926 +/- 0.011 mas, T-eff = 4636 +/- 37 K; and for HD103095,theta(LD) = 0.595 +/- 0.007 mas, T-eff = 5140 +/- 49 K. Our temperatures for HD140283 and HD103095 are hotter than the previous interferometric measurements by 253 and 322 K, respectively. We find good agreement between our temperatures and recent spectroscopic and photometric estimates. We conclude some previous interferometric measurements have been affected by systematic uncertainties larger than their quoted errors.
|
|
| 3. |
- Wittkowski, M., et al.
(författare)
-
Near-infrared spectro-interferometry of Mira variables and comparisons to 1D dynamic model atmospheres and 3D convection simulations
- 2016
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 587
-
Tidskriftsartikel (refereegranskat)abstract
- Aims:We aim at comparing spectro-interferometric observations of Mira variable asymptotic giant branch (AGB) stars with the latest 1D dynamic model atmospheres based on self-excited pulsation models (CODEX models) and with 3D dynamic model atmospheres including pulsation and convection (CO5BOLD models) to better understand the processes that extend the molecular atmosphere to radii where dust can form.Methods: We obtained a total of 20 near-infrared K-band spectro-interferometric snapshot observations of the Mira variables o Cet, R Leo, R Aqr, X Hya, W Vel, and R Cnc with a spectral resolution of about 1500. We compared observed flux and visibility spectra with predictions by CODEX 1D dynamic model atmospheres and with azimuthally averaged intensities based on CO5BOLD 3D dynamic model atmospheres.Results: Our visibility data confirm the presence of spatially extended molecular atmospheres located above the continuum radii with large-scale inhomogeneities or clumps that contribute a few percent of the total flux. The detailed structure of the inhomogeneities or clumps show a variability on time scales of 3 months and above. Both modeling attempts provided satisfactory fits to our data. In particular, they are both consistent with the observed decrease in the visibility function at molecular bands of water vapor and CO, indicating a spatially extended molecular atmosphere. Observational variability phases are mostly consistent with those of the best-fit CODEX models, except for near-maximum phases, where data are better described by near-minimum models. Rosseland angular diameters derived from the model fits are broadly consistent between those based on the 1D and the 3D models and with earlier observations. We derived fundamental parameters including absolute radii, effective temperatures, and luminosities for our sources.Conclusions: Our results provide a first observational support for theoretical results that shocks induced by convection and pulsation in the 3D CO5BOLD models of AGB stars are roughly spherically expanding and of similar nature to those of self-excited pulsations in 1D CODEX models. Unlike for red supergiants, the pulsation- and shock-induced dynamics can levitate the molecular atmospheres of Mira variables to extensions that are consistent with observations.
|
|
