Found 5 talks width keyword subdwarfs

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Tuesday November 5, 2013
Dr. ZengHua Zhang
IAC

Abstract

 

Studying the Halo via Its NEarby low-mass Dwarfs (SHINED) is an ongoing project aiming to understand the Galactic halo with metal-deficient low-mass stars (LMS) and brown dwarfs (BD). At the first stage of the project we are focusing on the discovery and characterisation of halo LMS and BD. I give an overview of the SHINED project then brief discuss the proprieties of halo LMS and BD. I introduce the main results of our work on red subdwarf binaries (Zhang et al. MNRAS, 434, 1005). I talk more about our work on the search of L subdwarfs from SDSS and UKIDSS. I discuss the spectral types of L subdwarfs, and spectral signature of halo BD. I also discuss the location of the Substellar Subdwarf Gap predicted by low-mass evolutionary models.

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Tuesday October 9, 2012
Mr. Bartek Gauza
IAC

Abstract

We report on the discovery of a fourth component in the HD 221356 star system, previously known to be formed by an F8V, slightly metal-poor primary ([Fe/H]= -0.26), and a distant M8V+L3V pair. In our ongoing common proper motion search based on VISTA Hemisphere Survey (VHS) and 2MASS catalogues, we have detected a faint (J = 13.76 ± 0.04 mag) co-moving companion of the F8 star located at a projected distance of ~312 AU. Near-infrared spectroscopy of the new companion indicates an L1±1 spectral type. Using evolutionary models the mass of the new companion is estimated at ~0.08 solar masses, which places the object close to the stellar-substellar borderline. This multiple system provides an interesting example of objects with masses slightly above and below the hydrogen burning mass limit.


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Tuesday June 21, 2011
Miss Karla Yulién Peña Ramírez
Instituto de Astrofísica de Canarias

Abstract

The proper characterization of the least massive population of the young Sigma Orionis star cluster is required to understand the form of the cluster mass function and its impact on our comprehension of the substellar formation processes. SOri70 (T5.5±1) and SOri73, two T-type cluster member candidates, would have likely masses between 3 and 7 MJup if their age is 3 Myr. SOri73 awaits confirmation of its methane atmosphere. Here I present the results of a search of T-type objects in an area of ~120 arcmin^2 in the Sigma Orionis cluster, the confirmation of the presence of methane absorption in SOri73 and the study of SOri70 and 73 cluster membership via photometric colors and accurate proper motion analysis. This results would have a dramatic impact in the cluster mass function, in one of the scenarios explored, they suggest a decrease in cluster members with planetary masses in the interval 3.5-6 Mjup.


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Thursday January 28, 2010
Dr. Nicolas Lodieu
Instituto de Astrofísica de Canarias, Spain

Abstract

In this Breaking News seminar, I will describe our project dedicated to the search for ultracool low-metallicity dwarfs (or subdwarfs) in the large-scale databases. The highlight of the seminar is the discovery of a mid-L subdwarf, the fifth known to date, and the first one identified in the UKIRT Infrared Deep Sky Survey (UKIDSS). The spectroscopic nature of this subdwarf was confirmed with data obtained with GTC/OSIRIS in April 2009.

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Thursday October 30, 2008
Prof. Edward Guinan
Villanova University, USA

Abstract

Red Dwarf (dM) stars are the most numerous stars in our Galaxy. These faint, cool, long-lived, and low mass stars make up > 80% of all stars in the Universe. Determining the number of red dwarfs with planets and assessing planetary habitability (a planet’s potential to develop and sustain life) are critically important because such studies would indicate how common life is in the universe. Our program - "Living with a Red Dwarf" addresses these questions by investigating the long-term nuclear evolution and magnetic-dynamo coronal and chromospheric X-ray to Ultraviolet properties of red dwarf stars with widely different ages. The major focus of the program is to study the magnetic-dynamo generated X-ray-Ultraviolet emissions and flare properties of red dwarf stars from youth to old age. Emphasized are how the stellar X-UV emissions, flares & winds affect hosted planets and impact their habitability. We have developed age-rotation-activity relations and also are constructing irradiance tables (X-UV fluxes) that can be used to model the effects of X-UV radiation on planetary atmospheres and on possible life on nearby hosted planets. Despite the earlier pessimistic view that red dwarfs stars are not suitable for habitable planets - mainly because their low luminosities require a hosted planet to orbit quite close (r <0.3 AU) to be sufficiently warm to support life. Our initial results indicate that red dwarf stars (in particular the warmer dM stars) can indeed be suitable hosts for habitable planets capable of sustaining life for hundreds of billion years. Some examples of red dwarf stars currently known to host planets are discussed.

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  • TBD
    Donaji Esparza Arredondo
    Tuesday September 17, 2019 - 12:30  (Aula)
  • COLLOQUIA: TBD
    Prof. Michael Kramer
    Thursday October 3, 2019 - 10:30  (Aula)

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