Ultra Low-Dispersion Spectroscopy with Gaia and Photographic Objective Prism Surveys

R Hudec ,L Hudec,Miloš Klíma

doi:10.14311/1318

Abstract

This paper discusses the ultra low-dispersion spectroscopy to be applied in the ESA Gaia space observatory and the ground-based objective-prism plate surveys. Although the dispersion in plate surveys is usually larger than in the Gaia BP/RP spectrometers, the spectral resolutions differ by a factor of 2–3 only, since the resolution in ground-based spectra is seeing-limited. We argue that some of the algorithms developed for digitized objective-prism plates can also be applied for the Gaia spectra. At the same time, the plate results confirm the feasibility of observing strong emission lines with Gaia RP/BP.

Highlights

The ESA Gaia satellite payload consists of a single integrated instrument, the design of which is characterised by a dual telescope concept with a common structure and a common focal plane
The archival spectral plates taken with the objective prism offer the possibility to simulate the Gaia low dispersion spectra and related procedures such as searches for spectral variability and variability analyses based on spectro-photometry
3.2 Comparison of Gaia low dispersion spectra and spectral plates. The motivation for these studies is as follows: (1) Comparison of the simulated Gaia BP/RP images with those obtained from digitized Schmidt spectral plates for 8 selected test fields, and (2) Feasibility study for application for the algorithms developed for the plates for Gaia

Summary

Introduction

The ESA Gaia satellite payload consists of a single integrated instrument, the design of which is characterised by a dual telescope concept with a common structure and a common focal plane (http://sci.esa.int/gaia/). Both telescopes are based on a three-mirror anastigmat (TMA) design. We note that certain types of variable stars (VS) such as Miras, Cepheids, and a few cases of other stars, mostly peculiar variables, exhibit large variations in their spectral types This field is, little exploited, as these studies used to be very laborious (plates were mostly visually inspected) and limited, and no review on the spectral variability among VS exists. The plates show numerous examples of objects with very prominent emission lines, which he found in a very extended time-consuming and laborious project (Figure 4)

Ultra low dispersion spectral plate databases

Algorithms

Comparison of Gaia low dispersion spectra and spectral plates

Conclusion