CRIRES-POP Spectra of Cool Stars

The discovery and precise characterisation of exoplanets hinges on good understanding of their host stars. There is growing focus on searching for Earth-mass exoplanets in the habitable zones of M dwarf stars, as their low masses and luminosities will allow easier detection of such Earth analogues. These stars are best studied at near infrared wavelengths, but no high quality empirical M dwarf atlas exists in this region of the spectrum. An important part of the search for habitable planets around M dwarfs is therefore a detailed characterisation of their near infrared spectra. This project will satisfy this requirement. Our primary aim is to explore the near infrared spectrum of M dwarfs to identify and evaluate regions where planetary markers can be found. We will reduce and analyse high resolution, high signal-to-noise near infrared spectra of the M dwarf Barnards Star, observed as part of the CRIRES-POP project, which will provide a public database of high quality near infrared spectra of stars of different spectral types. There is significant overlap of atomic and molecular lines in cool dwarf and cool giant spectra, and in parallel with our M dwarf analysis we will investigate the near infrared spectra of several CRIRES-POP evolved giants. Our analysis will include making comprehensive line identifications, measuring abundances and isotope ratios, and deriving stellar parameters, resulting in a complete description of each cool star. Our line identification will focus on improving identification of weak lines and resolvable blends, providing feedback to revise incomplete atomic and molecular linelists, which will in turn help improve cool star model atmospheres. We will derive abundances of elements with important lines in the near infrared by fitting synthetic spectra to our observed spectra, the broad wavelength coverage of which will be advantageous to high precision abundance measurements. Combining the spectral information with other available data like optical spectra, colour, and variability information, we will derive properties such as luminosity, radius, and temperature for each star. These full characterisations of cool stars, and their high quality spectra, will be important references for future research. As the main focus of this project, the M dwarf spectrum will be most rigorously analysed. In particular we will identify and evaluate those regions of the M dwarf spectrum where planetary markers can be found. As well as contributing to a public library of stellar spectral atlases, this project will provide an accurate description of the near infrared spectrum of an M dwarf at a time when there is growing demand in the exoplanet community for such a reference.

The project CRIRES-POP Spectra of Cool Stars was part of a larger project (CRIRES-POP) whose aim is to produce a high resolution, high signal-to-noise, near-infrared spectral library of stars of several different types. The aim of CRIRES-POP Spectra of Cool Stars was to begin the data reduction and spectrum production of the CRIRES-POP project, focusing on producing the spectra of the cool stars in the library. Particular aims were the description of the near-infrared spectrum of M dwarfs, to aid the ongoing planet searches around these stars; a parallel investigation of the near-infrared spectrum of cool giants; and to contribute to the CRIRES-POP spectral library, a publicly available dataset that will allow the study of a wide range of astrophysical phenomena.The major results of this project are:A fully reduced CRIRES-POP spectrum of the K1 III giant 10 LeoThe journal paper on 10 Leo and the fully reduced spectrum published to online open access archivesA fully developed methodology for the reduction and preparation of all future CRIRES-POP spectra Reduction codes developed for the preparation of all future CRIRES-POP spectra.This project produced the first spectrum from the CRIRES-POP project, using a new and better technique to correct for the influence of Earths atmosphere, a specially developed reduction methodology including several purpose-built codes, and a new method for combining individual observed spectra into a single data product. Reference spectra at 1 - 5 microns are rare, especially at high resolution, and the CRIRES-POP spectrum of 10 Leo will be important for the study of many types of cool stars, including dwarfs. This spectrum is therefore a valuable, state-of-the-art resource for the near-infrared astronomical community. Possible applications include a better understanding of the understudied near-infrared region and the telluric contribution in that wavelength range, a better characterisation of cool stars in their most relevant wavelength range, important feedback to atomic and molecular linelists, and improvement to stellar model atmospheres.Due to time constraints and the necessity of altering the order of the original work plan, only the second and third original project aims were met. For practical reasons the analysis had to start with the cool giants instead of the M dwarf, and there were obstacles and necessary extra work that were not foreseen, meaning the time spent on each task was underestimated. However, the results of this project will be crucial to the execution of the larger CRIRES-POP project, and should speed the production of subsequent spectra.