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Search for New Bright Nearby M Dwarfs with Virtual Observatory Tools M´asterUniversitario en Astrof´ısica Universidad Complutense de Madrid Trabajo de Fin de M´aster Search for new bright nearby M dwarfs with Virtual Observatory tools Alumno: Rub´en Fedriani Lopez´ I Directores: Enrique Solano II (CAB), Jos´eAntonio Caballero III (CAB) Tutores: David Montes IV (UCM), Rosario Lorente V (ESAC) Septiembre 2015 [email protected] [email protected] [email protected] [email protected] [email protected] Resumen: Contexto: Existen numerosas estrellas enanas M en el vecindario solar sin identificar. Estos objetos son muy impor- tantes para los siguientes surveys de velocidad radial en la b´usqueda de exoplanetas de baja masa en el infrarrojo cercano. La identificaci´onde estos exoplanetas es m´assencilla en enanas M, en comparaci´oncon otras estrellas, tales como G o K, debido a su favorable contraste en el cociente de radios planeta/estrella. Objetivos: En este Trabajo Fin de M´aster,buscamos estas nuevas estrellas enanas M. Preparamos una lista a partir de una muestra suficientemente testeada de candidatos a estrellas M. Adem´as,estimamos temperaturas efectivas, gravedades superficiales, distancias y tipos espectrales. M´etodos: Cruzando los cat´alogosde CMC15 y 2MASS elaboramos una tabla de objetos. Aplicamos numerosos filtros de movimiento propio, colores y magnitudes con herramientas de Observatorio Virtual con el objetivo de catalogar nuevas estrellas enanas M. Inspeccionamos visualmente cada estrella usando el programa Aladin sky atlas y estimamos par´ametrosastrof´ısicoscon VOSA. Usamos los lenguajes de programaci´onPython y R para estimar distancias y tipos espectrales usando datos fotom´etricosde trabajos previos. Por otro lado, tuvimos la oportunidad de ir al Centro Astron´omicoHispano Alem´an,gracias al M´asteren Astrof´ısica con la asignatura de T´ecnicasExperimentales en Astrof´ısica.All´ı,observamos espectroscopicamente con CAFOS en el telescopio de 2.2m seis de nuestros objetos. Resultados: Hemos elaborado un cat´alogode 1929 estrellas, de las cuales 849 son completamente nuevas y est´an presentes por primera vez en este trabajo, y hemos estimado sus temperaturas efectivas, gravedades superficiales, distancias y tipos espectrales. Casi 100 de nuestras estrellas pueden estar a menos de 25 pc, y otras cinco tienen tipos espectrales M6.0 V o m´astard´ıo. Adem´as,derivamos tipos espectrales de las seis estrellas observadas con CAFOS, que est´anentre M4.5−5.0 V, identificando bandas moleculares t´ıpicasy caracter´ısticasespectrales de enanas M. Los resultados obtenidos en la identificaci´onvisual se corresponden con los resultados estimados en nuestro estudio fotom´etrico,validando nuestro trabajo. Conclusiones: Este nuevo cat´alogode 849 candidatas a estrellas enanas M ayudar´aa estudios relacionados con la b´usquedade exoplanetas, estudios de estrellas fr´ıasen el vecindario solar y para surveys espectrosc´opicosen la identificaci´onde estrellas cercanas. Palabras clave: Herramientas de Observatorio Virtual | estrellas: actividad | estrellas: tipo tard´ıo| estrellas: baja masa | estrellas: enanas | estrellas: par´ametros fundamentales | Galaxia: vecindad | t´ecnicas:espectrocop´ıa Abstract: Context: There are several unidentified M-dwarf stars in the Solar neighbourhood. These objects are very important for next radial-velocity surveys of low-mass exoplanets in the near infrared. Their identification is easier than other kind of stars, such us G or K, because of their favourable planet/star contrast ratio radius. Aims: In this MSc thesis, we search for such new M-dwarf stars. We prepare a list from a well tested sample of M-dwarf candidates. In addition, we estimate effective temperatures, surface gravities, distances and spectral types. Methods: By cross-matching CMC15 and 2MASS catalogues, we prepared a list of M-dwarf candidates. We applied several proper-motion, colours and magnitude filters with Virtual Observatory tools in order to catalogue new M- dwarf stars. We visually inspected each target using the Aladin sky atlas and estimated astrophysical parameters with VOSA. We developed both Python and R scripts to estimate distances and spectral types using photometric data. On the other hand, we had the chance to go to the Centro Astron´omicoHispano Alem´an,within the Astrophysics Master degree framework of the subject T´ecnicasExperimentales en Astrof´ısica. There, we observed spectroscopically with CAFOS at the 2.2 m telescope five of our previously unknown objects plus a known object. Results: We computed a catalogue of 1929 stars, of which 849 are presented for the first time in this MSc thesis, and estimated their effective temperatures, surface gravities, distances and spectral types. Almost 100 of our stars could be at least than 25 pc, and another five have spectral types M6.0 V or later. Besides, we derived M4.5−5.0 V spectral types for the six stars observed with CAFOS, after identifying typical molecular bands and spectral features of M dwarfs. These results go in the same direction of our photometric study. Conclusions: This new catalogue of 849 new M-dwarf candidates serves for studies related with exoplanets hunting, for studies of cool dwarfs in the solar neighbourhood and for spectroscopic surveys aiming at the identification of nearby mid-late type M dwarfs. Keywords: Virtual Observatory tools | stars: activity | stars: late-type | stars: low-mass | stars: dwarfs | stars: fundamental parameters | Galaxy: neighbourhood | techniques: spectroscopy Index 1 Introduction 1 1.1 A brief introduction to M dwarfs . .1 1.2 Search for M dwarfs using astrometric and photometric catalogues . .3 1.3 Why M dwarfs? . .5 1.4 Objectives . .6 2 Analysis 7 2.1 Visual inspection . .9 2.2 Diagrams . 10 2.2.1 Colour-colour diagrams . 10 2.2.2 Colour-magnitude diagram . 11 2.2.3 Colour-reduced proper motion diagram . 11 2.2.4 Coordinates . 13 2.2.5 Histograms . 13 2.3 Spectral type estimation through photometric data . 15 2.4 Distance estimation through spectral type and MJ relationship . 16 2.5 Effective temperature and surface gravity estimation using VOSA . 17 3 Results and discussion 18 3.1 Spectral types and distances . 18 3.2 Teff and log g .................................................. 19 3.3 Top 20 stars . 19 3.3.1 Reddest . 20 3.3.2 Fastest . 21 3.3.3 Nearest . 22 3.3.4 Brightest . 23 3.4 Completeness and limiting for the CARMENES input catalogue . 23 3.5 Spectroscopy . 24 4 Conclusions and future research 25 Appendix A: Tables 28 Appendix B: Application for Observing Time 69 1 Introduction 1.1 A brief introduction to M dwarfs M dwarfs are the most common stars in the Solar neighbourhood, around 66%. Besides, the nearest star to the Sun, Proxima Centauri, is a red dwarf (M5.5 V). Red dwarfs are by far the most common type of star in the Milky Way, but they are not visible to the naked eye because of their low luminosity. The Research Consortium on Nearby Stars( RECONS1) studies the nature of the Sun's nearest stellar neighbours and according with its, the most common spectral type in the solar neighbourhood is M. The RECONS 25 Parsec Database (Henry et al. 2006) together with the RECONS Movie2 (Adric Riedel and the RECONS Team) allow us to know the statistic concerning the spectral types in the Sun's 25 pc neighbourhood, which is: Table 1: Statistics of the Spectral Type of Sun's 25 pc neighbourhood. SpT O B A F G K M Number 0 1 29 141 244 550 1093 Spectral classification is based on morphology where we notice regularities in the appearance and disappearance of particular spectral features. The traditional method of defining a spectral classification system is to take observations of a set of stars, ideally with known absolute magnitude and luminosity class (Reid & Hawley 2005). Identifying spectral features, strong enough to recognise in an easy way, provide us a correct classification. Particularly, M dwarfs are main-sequence stars whose spectra display bands of TiO (L´epine& Gaidos 2011), so the TiO bands which dominate spectra of M stars are a really good feature to be studied as a primary indicator of spectral type. The first Morgan & Keenan (MK) system was limited in M dwarfs classification because initially it was defined for stars with earlier type than M2 due to most photographic observations around 1940s were dominated to the blue region where the spectral features were saturated with low temperatures (intermediate and late type M). With the advent of larger telescopes and modern spectrographs and detectors, it became necessary to extend the classification to later types than M2, i.e., cooler stars. There were problems between different systems, such us Yerkes and Mount Wilson, because to the same stars they were classified as a different type. One of the problem in classifying M dwarfs using spectra located in the blue part of the electromagnetic spectrum is that those wavelengths lie far from the peak of the energy distribution. For this reason Boeshaar (1976) and Kirkpatrick et al. (1991), among others, extended the MK system by adding spectral features to redder wavelengths, designated KHM system which looked for features in the range 6300-9000 A.˚ There were several different systems to classify the luminosity class based on TiO or VO bands but the more widely used is the KHM system. Nowadays the best classification is given in Alonso-Floriano et al. (2015) and in a near future will be adopted a standardization for M. Figure 1 shows optical spectra of late-type K and M dwarfs covering the range 3800-9500 A.˚ In addition, it shows the principal spectral features. TiO is present, but weak, at K7, and grows in strength until type M6, where more bandheads saturate. Bands due to several metal hydrides, such us MgH, FeH and CaH, also become detectable among K7 stars and grow in prominence with later spectral type.
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