A Link Between the Semimajor Axis of Extrasolar Gas Giant Planets and Stellar Metallicity
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Disertaciones Astronómicas Boletín Número 69 De Efemérides Astronómicas 17 De Marzo De 2021
Disertaciones astronómicas Boletín Número 69 de efemérides astronómicas 17 de marzo de 2021 Realiza Luis Fernando Ocampo O. ([email protected]). Noticias de la semana. La Luz Zodiacal y su origen. Imagen 1: Imagen de la Luz Zodiacal hacia el este, junto antes del amanecer. Crédito: spacew.com/gallery/DominicCantin>. La luz zodiacal (también llamada falso amanecer cuando se ve antes del amanecer) es un resplandor blanco tenue, difuso y aproximadamente triangular que es visible en el cielo nocturno y parece extenderse desde la dirección del Sol y a lo largo del zodíaco, en el sentido de la eclíptica. La luz solar dispersada por el polvo interplanetario provoca este fenómeno. Sin embargo, el brillo es tan tenue que la luz de la luna y / o la contaminación lumínica lo eclipsan, haciéndolo invisible. El polvo interplanetario en el Sistema Solar forma colectivamente una nube gruesa con forma de panqueque llamada nube zodiacal, que se extiende a ambos lados del plano de la eclíptica. Los tamaños de partículas oscilan entre 10 y 300 micrómetros, lo que implica masas desde un nanogramo hasta decenas de microgramos. Las observaciones de la nave espacial Pioneer 10 en la década de 1970 vincularon la luz zodiacal con la nube de polvo interplanetaria en el Sistema Solar. En las latitudes medias, la luz zodiacal se observa mejor en el cielo occidental en la primavera después de que el crepúsculo vespertino ha desaparecido por completo, o en el cielo oriental en otoño, justo antes de que aparezca el crepúsculo matutino. La luz zodiacal aparece como una columna, más brillante en el horizonte, inclinada en el ángulo de la eclíptica. -
Lurking in the Shadows: Wide-Separation Gas Giants As Tracers of Planet Formation
Lurking in the Shadows: Wide-Separation Gas Giants as Tracers of Planet Formation Thesis by Marta Levesque Bryan In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2018 Defended May 1, 2018 ii © 2018 Marta Levesque Bryan ORCID: [0000-0002-6076-5967] All rights reserved iii ACKNOWLEDGEMENTS First and foremost I would like to thank Heather Knutson, who I had the great privilege of working with as my thesis advisor. Her encouragement, guidance, and perspective helped me navigate many a challenging problem, and my conversations with her were a consistent source of positivity and learning throughout my time at Caltech. I leave graduate school a better scientist and person for having her as a role model. Heather fostered a wonderfully positive and supportive environment for her students, giving us the space to explore and grow - I could not have asked for a better advisor or research experience. I would also like to thank Konstantin Batygin for enthusiastic and illuminating discussions that always left me more excited to explore the result at hand. Thank you as well to Dimitri Mawet for providing both expertise and contagious optimism for some of my latest direct imaging endeavors. Thank you to the rest of my thesis committee, namely Geoff Blake, Evan Kirby, and Chuck Steidel for their support, helpful conversations, and insightful questions. I am grateful to have had the opportunity to collaborate with Brendan Bowler. His talk at Caltech my second year of graduate school introduced me to an unexpected population of massive wide-separation planetary-mass companions, and lead to a long-running collaboration from which several of my thesis projects were born. -
Nitrogen Abundances in Planet-Harbouring Stars
A&A 418, 703–715 (2004) Astronomy DOI: 10.1051/0004-6361:20035717 & c ESO 2004 Astrophysics Nitrogen abundances in planet-harbouring stars A. Ecuvillon1, G. Israelian1,N.C.Santos2,3, M. Mayor3,R.J.Garc´ıa L´opez1,4, and S. Randich5 1 Instituto de Astrof´ısica de Canarias, 38200 La Laguna, Tenerife, Spain 2 Centro de Astronomia e Astrofisica de Universidade de Lisboa, Observatorio Astronomico de Lisboa, Tapada de Ajuda, 1349-018 Lisboa, Portugal 3 Observatoire de Gen`eve, 51 ch. des Maillettes, 1290 Sauverny, Switzerland 4 Departamento de Astrof´ısica, Universidad de La Laguna, Av. Astrof´ısico Francisco S´anchez s/n, 38206 La Laguna, Tenerife, Spain 5 INAF/Osservatorio Astrofisico di Arcetri, Largo Fermi 5, 50125 Firenze, Italy Received 20 November 2003 / Accepted 4 February 2004 Abstract. We present a detailed spectroscopic analysis of nitrogen abundances in 91 solar-type stars, 66 with and 25 without known planetary mass companions. All comparison sample stars and 28 planet hosts were analysed by spectral synthesis of the near-UV NH band at 3360 Å observed at high resolution with the VLT/UVES, while the near-IR N 7468 Å was measured in 31 objects. These two abundance indicators are in good agreement. We found that nitrogen abundance scales with that of iron in the metallicity range −0.6 < [Fe/H] < +0.4 with the slope 1.08 ± 0.05. Our results show that the bulk of nitrogen production at high metallicities was coupled with iron. We found that the nitrogen abundance distribution in stars with exoplanets is the high [Fe/H] extension of the curve traced by the comparison sample of stars with no known planets. -
Appendix 1 Some Astrophysical Reminders
Appendix 1 Some Astrophysical Reminders Marc Ollivier 1.1 A Physics and Astrophysics Overview 1.1.1 Star or Planet? Roughly speaking, we can say that the physics of stars and planets is mainly governed by their mass and thus by two effects: 1. Gravitation that tends to compress the object, thus releasing gravitational energy 2. Nuclear processes that start as the core temperature of the object increases The mass is thus a good parameter for classifying the different astrophysical objects, the adapted mass unit being the solar mass (written Ma). As the mass decreases, three categories of objects can be distinguished: ∼ 1. if M>0.08 Ma ( 80MJ where MJ is the Jupiter mass) the mass is sufficient and, as a consequence, the gravitational contraction in the core of the object is strong enough to start hydrogen fusion reactions. The object is then called a “star” and its radius is proportional to its mass. 2. If 0.013 Ma <M<0.08 Ma (13 MJ <M<80 MJ), the core temperature is not high enough for hydrogen fusion reactions, but does allow deuterium fu- sion reactions. The object is called a “brown dwarf” and its radius is inversely proportional to the cube root of its mass. 3. If M<0.013 Ma (M<13 MJ) the temperature a the center of the object does not permit any nuclear fusion reactions. The object is called a “planet”. In this category one distinguishes giant gaseous and telluric planets. This latter is not massive enough to accrete gas. The mass limit between giant and telluric planets is about 10 terrestrial masses. -