DOCSLIB.ORG

Brown Dwarfs in the Pleiades Cluster Confirmed by the Lithium Test

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Brown Dwarfs in the Pleiades Cluster Confirmed by the Lithium Test To app ear in ApJ Letters Brown Dwarfs in the Pleiades Cluster Conrmed by the Lithium Test R Reb olo E L Martn Instituto de Astrofsicade Canarias E La Laguna Tenerife Spain G Basri G W Marcy Department of Astronomy University of California Berkeley Berkeley CA USA and M R Zapatero Osorio Instituto de Astrofsicade Canarias E La Laguna Tenerife Spain email addresses rrliaces egeiaces basrisoleilb erkeleyedu gmarcyetoileb erkeleyedu mosorioiaces ABSTRACT We present m Keck sp ectra of the two Pleiades brown dwarfs Teide and Calar showing a clear detection of the nm Li resonance line In Teide we have also obtained evidence for the presence of the sub ordinate line at nm A high Li abundance log N Li consistent with little if any depletion is inferred from the observed lines Since Pleiades brown dwarfs are unable to burn Li the signicant preservation of this fragile element conrms the substellar nature of our two ob jects Regardless of their age their low luminosities and Li content place Teide and Calar comfortably in the astro-ph/9607002 1 Jul 1996 genuine brown dwarf realm Given the probable age of the Pleiades cluster their masses are estimated at Jupiter masses Subject headings op en clusters and asso ciations individual Pleiades stars abundances stars lowmass brown dwarfs stars evolution stars fundamental parameters Based on observations obtained at the WM Keck Observatory which is op erated jointly by the University of California and the Californian Institute of Technology Introduction In stellar interiors Li nuclei are destroyed via proton collisions at relatively low temp eratures K This element has long b een used as a tracer see eg Reb olo Michaud Charb onneau of internal structure in stars of dierent types The strong convection of very lowmass stars M M causes an extremely ecient mixing of Li and indeed signicant depletion has b een observed in these stars even in the very young ones Zapatero Osorio et al a Garca Lopez Reb olo Martn Martn Reb olo Magazz u Ob jects with masses M M M Jupiter mass J units are well b elow the minimum mass for hydrogen burning and cannot reach the Li burning temp erature so unlike very low mass stars they must preserve a signicant amount of their initial Li content during their lifetime This can b e detected sp ectroscopically and therefore can provide a diagnostic of substellar nature for brown dwarf candidates Reb olo Martn Magazz u Magazz u Martn Reb olo At the age of the Pleiades cluster even the most massive brown dwarfs M J should have preserved a large amount of their initial Li but searches Martn et al Marcy Basri Graham of the faintest prop er motion members failed to detect it An obvious conclusion was that brown dwarfs had not b een discovered yet in the cluster This prompted the search for new fainter and co oler candidates that led to the discovery of Teide and Calar Reb olo Zapatero Osorio Martn Zapatero Osorio Reb olo Martnb These are two very latetype dwarfs near the center of the cluster with radial velocities photometric and sp ectroscopic prop erties and a prop er motion measurement in the case of Teide consistent with Pleiades membership Reb olo et al Zapatero Osorio et al b Martn Reb olo Zapatero Osorio Their luminosities and eective temp eratures qualify them according to all the available evolutionary mo dels as brown dwarfs However a denitive conrmation of their substellar nature can only b e obtained via the Li test Such conrmation is a key step to consolidate our understanding of brown dwarf interiors Very recently Li has b een discovered Basri Marcy Graham in PPl a photometric member Stauer Hamilton Probst of the Pleiades ab out one magnitude brighter than Teide and Calar which strongly encouraged us to extend the search for Li in these new ob jects PPl app ears to dene the Li reapp earance b oundary in the Pleiades and sits on the frontier b etween stars and brown dwarfs Observations and results We rep ort sp ectroscopic observations of Teide and Calar that provide clear evidence for the presence of Li in b oth The observations were carried out at the m Keck telescop e Mauna Kea Hawaii on November and and February using the Low Resolution Imaging Sp ectrograph LRIS The gmm grating provided a disp ersion of Apixel on the TEK pix detector in the region of the nm Li i resonance doublet and Apixel in the region of the sub ordinate nm Li i line The arcsec slit width nally gave an eective resolution of A The total integration time for Teide in the sp ectral regions of the nm and nm Li i lines was and hr resp ectively individual exp osures ranged from to min Only one min sp ectrum could b e obtained for Calar on February at the wavelength of the resonance line due to bad weather The individual images have b een indep endently pro cessed using standard pro cedures within the IRAF package which included debias at eld optimal extraction and wavelength calibration using arc lamps The sp ectra in the region of the Li resonance line were ux calibrated using the standard star GBB Massey et al The nal sp ectra of Teide and Calar centered at nm are shown in Fig H is seen in emission equivalent widths of A and A resp ectively and lines of K i at nm as well as TiO and VO bandheads are clearly detected The new more accurate radial velocities of Teide and Calar are and km s fully consistent with Pleiades membership and previous measurements Reb olo et al Martnet al They were determined by crosscorrelating with the sp ectrum of vB v kms Goldb erg obtained with the same instrumental conguration The r nm VO absorption index Kirkpatrick Henry Simons previously employed for sp ectral classication Reb olo et al was also measured in the new sp ectra resulting in values of and in Teide and Calar resp ectively in very go o d agreement with measurements for other very latetype dwarfs The Li i line at nm is clearly present in the sp ectra of Teide and Calar with remarkable strength as compared with the nearby TiO bands as can b e seen in Fig a An accurate measurement of the equivalent width of the Li i nm line cannot b e p erformed at our sp ectral resolution b ecause of the strong blending with the nearby TiO lines In order to determine approximate equivalent widths we subtracted the sp ectrum of other very latetype dwarfs vB LHS observed with the same conguration for which much higher resolution sp ectra do not show any evidence of Li absorption and then measured the equivalent width of the feature at the p osition of the resonance doublet We found these pseudoequivalent widths to b e A and A in Teide and Calar resp ectively They are useful as a reference for future searches although they should IRAF is distributed by National Optical Astronomy Observatories which is op erated by the Asso ciation of Universities for Research in Astronomy Inc under contract with the National Science Foundation b e used with caution to derive an abundance from the available theoretical curves of growth Pavlenko et al since these curves were computed considering pure Li absorption The same pro cedure was applied to the nal sp ectrum of Teide in the region of the Li i at nm After subtraction of the sp ectrum of a typical M dwarf obtained averaging the sp ectra of LP and vB an absorption is apparent see Fig b at this precise wavelength with a pseudoequivalent width of mA which we interpret as additional evidence for the presence of Li in the atmosphere It would b e desirable in principle to conrm this feature with higher sp ectral resolution and SN ratio Lithium abundances and brown dwarf status To estimate the Li abundance in our ob jects we have used sp ectral synthesis computations based on Allard Hauschildt AH mo del atmospheres for very co ol dwarfs The eective temp eratures of Teide and Calar were estimated from a new sp ectral type classication using pseudocontinuum indices Martn et al and the T calibration given in Kirkpatrick et al which was revised Kirkpatrick e according to the new AH mo dels For M dwarfs this calibration yields an eective temp erature of K The M dwarf PPl would have a T ab out K hotter e The Li abundance was determined by comparison with the available sp ectral synthesis Pavlenko et al and with new computations kindly provided by Ya Pavlenko using various molecular line lists Kurucz A set of sp ectra with several Li abundances were generated for the AH mo dels with eective temp eratures of and K While these mo dels describ e reasonably well the TiO bands in the vicinity of the Li resonance line co oler AH mo dels pro duce to o broad and deep TiO absorption bands which do not t the observed sp ectrum and app ear to indicate that the eective temp erature of our two ob jects is indeed higher than K Unfortunately the limitations in the available molecular line lists and the uncertainties in the eective temp erature prevent a very precise determination of the Li abundance We should note that there are other eective temp erature calibrations in the literature Brett Tsuji Ohnaka Aoki which give lower values by K for very latetype dwarfs Several computations have b een conducted to determine the sensitivity of the Li resonance doublet to uncertainties in the eective temp erature It can b e safely concluded that Teide and Calar have a rather high Li abundance in the range log N Li where the usual scale is log N H At present we cannot claim any dierence in the Li content b etween Calar and Teide Our preliminary
Load more

Recommended publications
  • Exoplanet.Eu Catalog Page 1 # Name Mass Star Name
    exoplanet.eu_catalog # name mass star_name star_distance star_mass OGLE-2016-BLG-1469L b 13.6 OGLE-2016-BLG-1469L 4500.0 0.048 11 Com b 19.4 11 Com 110.6 2.7 11 Oph b 21 11 Oph 145.0 0.0162 11 UMi b 10.5 11 UMi 119.5 1.8 14 And b 5.33 14 And 76.4 2.2 14 Her b 4.64 14 Her 18.1 0.9 16 Cyg B b 1.68 16 Cyg B 21.4 1.01 18 Del b 10.3 18 Del 73.1 2.3 1RXS 1609 b 14 1RXS1609 145.0 0.73 1SWASP J1407 b 20 1SWASP J1407 133.0 0.9 24 Sex b 1.99 24 Sex 74.8 1.54 24 Sex c 0.86 24 Sex 74.8 1.54 2M 0103-55 (AB) b 13 2M 0103-55 (AB) 47.2 0.4 2M 0122-24 b 20 2M 0122-24 36.0 0.4 2M 0219-39 b 13.9 2M 0219-39 39.4 0.11 2M 0441+23 b 7.5 2M 0441+23 140.0 0.02 2M 0746+20 b 30 2M 0746+20 12.2 0.12 2M 1207-39 24 2M 1207-39 52.4 0.025 2M 1207-39 b 4 2M 1207-39 52.4 0.025 2M 1938+46 b 1.9 2M 1938+46 0.6 2M 2140+16 b 20 2M 2140+16 25.0 0.08 2M 2206-20 b 30 2M 2206-20 26.7 0.13 2M 2236+4751 b 12.5 2M 2236+4751 63.0 0.6 2M J2126-81 b 13.3 TYC 9486-927-1 24.8 0.4 2MASS J11193254 AB 3.7 2MASS J11193254 AB 2MASS J1450-7841 A 40 2MASS J1450-7841 A 75.0 0.04 2MASS J1450-7841 B 40 2MASS J1450-7841 B 75.0 0.04 2MASS J2250+2325 b 30 2MASS J2250+2325 41.5 30 Ari B b 9.88 30 Ari B 39.4 1.22 38 Vir b 4.51 38 Vir 1.18 4 Uma b 7.1 4 Uma 78.5 1.234 42 Dra b 3.88 42 Dra 97.3 0.98 47 Uma b 2.53 47 Uma 14.0 1.03 47 Uma c 0.54 47 Uma 14.0 1.03 47 Uma d 1.64 47 Uma 14.0 1.03 51 Eri b 9.1 51 Eri 29.4 1.75 51 Peg b 0.47 51 Peg 14.7 1.11 55 Cnc b 0.84 55 Cnc 12.3 0.905 55 Cnc c 0.1784 55 Cnc 12.3 0.905 55 Cnc d 3.86 55 Cnc 12.3 0.905 55 Cnc e 0.02547 55 Cnc 12.3 0.905 55 Cnc f 0.1479 55
    [Show full text]
  • A Review on Substellar Objects Below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs Or What?
    geosciences Review A Review on Substellar Objects below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs or What? José A. Caballero Centro de Astrobiología (CSIC-INTA), ESAC, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain; [email protected] Received: 23 August 2018; Accepted: 10 September 2018; Published: 28 September 2018 Abstract: “Free-floating, non-deuterium-burning, substellar objects” are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups, and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. In this paper, their nomenclature, history of discovery, sites of detection, formation mechanisms, and future directions of research are reviewed. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST. Keywords: planetary systems; stars: brown dwarfs; stars: low mass; galaxy: solar neighborhood; galaxy: open clusters and associations 1. Introduction I can’t answer why (I’m not a gangstar) But I can tell you how (I’m not a flam star) We were born upside-down (I’m a star’s star) Born the wrong way ’round (I’m not a white star) I’m a blackstar, I’m not a gangstar I’m a blackstar, I’m a blackstar I’m not a pornstar, I’m not a wandering star I’m a blackstar, I’m a blackstar Blackstar, F (2016), David Bowie The tenth star of George van Biesbroeck’s catalogue of high, common, proper motion companions, vB 10, was from the end of the Second World War to the early 1980s, and had an entry on the least massive star known [1–3].
    [Show full text]
  • Search for X-Ray Emission from Bona-Fide and Candidate Brown
    A&A manuscript no. (will be inserted by hand later) ASTRONOMY AND Your thesaurus codes are: ASTROPHYSICS 06(08.12.1; 08.12.2; 13.25.5) 11.9.2018 Search for X-ray emission from bona-fide and candidate brown dwarfs R. Neuh¨auser1, C. Brice˜no2, F. Comer´on3, T. Hearty1, E.L. Mart´ın4, J.H.M.M. Schmitt5, B. Stelzer1, R. Supper1, W. Voges1, and H. Zinnecker6 1 MPI f¨ur extraterrestrische Physik, Giessenbachstraße 1, D-85740 Garching, Germany 2 Yale University, Department of Physics, New Haven, CT 06520-8121, USA 3 European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching, Germany 4 Astronomy Department, University of California at Berkeley, Berkeley, CA 94720, USA 5 Universit¨at Hamburg, Sternwarte, Gojensbergweg 112, D-21029 Hamburg, Germany 6 Astrophysikalisches Institut, An der Sternwarte 16, D-14482 Potsdam, Germany Received 24 Sep 1998; accepted 10 Dec 1998 Abstract. Following the recent classification of the X- for a recent review. They continue to contract until elec- ray detected object V410 x-ray 3 with a young brown tron degeneracy halts further contraction. Depending on dwarf candidate (Brice˜no et al. 1998) and the identifica- metallicity and model assumptions made in for calculating tion of an X-ray source in Chamaeleon as young bona- theoretical evolutionary tracks, the limiting mass between fide brown dwarf (Neuh¨auser & Comer´on 1998), we inves- normal stars and brown dwarfs is ∼ 0.075 to 0.08 M⊙ tigate all ROSAT All-Sky Survey and archived ROSAT (Burrows et al. 1995, 1997, D’Antona & Mazzitelli 1994, PSPC and HRI pointed observations with bona-fide or 1997, Allard et al.
    [Show full text]
  • THE STAR FORMATION NEWSLETTER an Electronic Publication Dedicated to Early Stellar Evolution and Molecular Clouds
    THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar evolution and molecular clouds No. 44 — 15 May 1996 Editor: Bo Reipurth ([email protected]) Abstracts of recently accepted papers Lifetimes of Ultracompact HII Regions: High Resolution Methyl Cyanide Observations R.L. Akeson & J.E. Carlstrom Owens Valley Radio Observatory, California Institute of Technology, Pasadena, CA 91125, USA We observed the dense molecular cores associated with two ultracompact HII regions, G5.89 + 0.4 and G34.3 + 0.2, in the J=6–5 transitions of CH3CN to probe the temperature and density of the gas. Simultaneously, each region was observed in the J=1–0 transition of a CO isotope to probe the molecular column density. The molecular cores are found to have densities ∼ 106 cm−3 and kinetic temperatures of 90 K and 250 K, respectively. We also find possible evidence for infall of molecular gas toward the HII regions. The lifetime of the HII region ultracompact phase is critically dependent on the properties of the surrounding molecular gas. Based on the number of ultracompact HII regions versus the total number of O stars, it has been suggested that the lifetime of the ultracompact phase is inconsistent with spherical expansion confined only by the ambient medium. We show that for the molecular cloud parameters given above and including the effect of the shell of neutral material formed by the expansion, pressure confinement by the ambient medium may significantly increase the lifetime of the ultracompact phase of the HII regions. Accepted by Ap. J. Probing the initial conditions of star formation: The structure of the prestellar core L1689B P.
    [Show full text]
  • Exoplanet.Eu Catalog Page 1 Star Distance Star Name Star Mass
    exoplanet.eu_catalog star_distance star_name star_mass Planet name mass 1.3 Proxima Centauri 0.120 Proxima Cen b 0.004 1.3 alpha Cen B 0.934 alf Cen B b 0.004 2.3 WISE 0855-0714 WISE 0855-0714 6.000 2.6 Lalande 21185 0.460 Lalande 21185 b 0.012 3.2 eps Eridani 0.830 eps Eridani b 3.090 3.4 Ross 128 0.168 Ross 128 b 0.004 3.6 GJ 15 A 0.375 GJ 15 A b 0.017 3.6 YZ Cet 0.130 YZ Cet d 0.004 3.6 YZ Cet 0.130 YZ Cet c 0.003 3.6 YZ Cet 0.130 YZ Cet b 0.002 3.6 eps Ind A 0.762 eps Ind A b 2.710 3.7 tau Cet 0.783 tau Cet e 0.012 3.7 tau Cet 0.783 tau Cet f 0.012 3.7 tau Cet 0.783 tau Cet h 0.006 3.7 tau Cet 0.783 tau Cet g 0.006 3.8 GJ 273 0.290 GJ 273 b 0.009 3.8 GJ 273 0.290 GJ 273 c 0.004 3.9 Kapteyn's 0.281 Kapteyn's c 0.022 3.9 Kapteyn's 0.281 Kapteyn's b 0.015 4.3 Wolf 1061 0.250 Wolf 1061 d 0.024 4.3 Wolf 1061 0.250 Wolf 1061 c 0.011 4.3 Wolf 1061 0.250 Wolf 1061 b 0.006 4.5 GJ 687 0.413 GJ 687 b 0.058 4.5 GJ 674 0.350 GJ 674 b 0.040 4.7 GJ 876 0.334 GJ 876 b 1.938 4.7 GJ 876 0.334 GJ 876 c 0.856 4.7 GJ 876 0.334 GJ 876 e 0.045 4.7 GJ 876 0.334 GJ 876 d 0.022 4.9 GJ 832 0.450 GJ 832 b 0.689 4.9 GJ 832 0.450 GJ 832 c 0.016 5.9 GJ 570 ABC 0.802 GJ 570 D 42.500 6.0 SIMP0136+0933 SIMP0136+0933 12.700 6.1 HD 20794 0.813 HD 20794 e 0.015 6.1 HD 20794 0.813 HD 20794 d 0.011 6.1 HD 20794 0.813 HD 20794 b 0.009 6.2 GJ 581 0.310 GJ 581 b 0.050 6.2 GJ 581 0.310 GJ 581 c 0.017 6.2 GJ 581 0.310 GJ 581 e 0.006 6.5 GJ 625 0.300 GJ 625 b 0.010 6.6 HD 219134 HD 219134 h 0.280 6.6 HD 219134 HD 219134 e 0.200 6.6 HD 219134 HD 219134 d 0.067 6.6 HD 219134 HD
    [Show full text]
  • Arxiv:1912.05202V2 [Gr-Qc]
    Stellar structure models in modified theories of gravity: lessons and challenges Gonzalo J. Olmo Depto. de F´ısica Te´orica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Burjassot-46100, Valencia, Spain. Departamento de F´ısica, Universidade Federal da Para´ıba, 58051-900 Jo˜ao Pessoa, Para´ıba, Brazil. Diego Rubiera-Garcia Departamento de F´ısica Te´orica and IPARCOS, Universidad Complutense de Madrid, E-28040 Madrid, Spain Aneta Wojnar N´ucleo Cosmo-ufes & PPGCosmo, Universidade Federal do Esp´ırito Santo, 29075-910, Vit´oria, ES, Brasil Laboratory of Theoretical Physics, Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu, Estonia Abstract The understanding of stellar structure represents the crossroads of our theories of the nuclear force and the gravita- tional interaction under the most extreme conditions observably accessible. It provides a powerful probe of the strong field regime of General Relativity, and opens fruitful avenues for the exploration of new gravitational physics. The latter can be captured via modified theories of gravity, which modify the Einstein-Hilbert action of General Relativity and/or some of its principles. These theories typically change the Tolman-Oppenheimer-Volkoff equations of stellar’s hydrostatic equilibrium, thus having a large impact on the astrophysical properties of the corresponding stars and opening a new window to constrain these theories with present and future observations of different types of stars. For relativistic stars, such as neutron stars, the uncertainty on the equation of state of matter at supranuclear densities intertwines with the new parameters coming from the modified gravity side, providing a whole new phenomenology for the typical predictions of stellar structure models, such as mass-radius relations, maximum masses, or moment of inertia.
    [Show full text]
  • Examination Paper for FY2450 Astrophysics
    1 Department of Physics Examination paper for FY2450 Astrophysics Academic contact during examination: Rob Hibbins Phone: 94820834 Examination date: 31-05-2014 Examination time: 09:00 – 13:00 Permitted examination support material: Calculator, translation dictionary, printed or hand-written notes covering a maximum of one side of A5 paper. Other information: The exam is in three parts and part 1 is multiple choice. Answer all questions in all three parts. The percentage of marks awarded for each question is shown. An Appendix of useful information is provided at the end of the question sheet. Language: English Number of pages: 7 (including cover) Number of pages enclosed: 0 Checked by: ____________________________ Date Signature 2 Part 1. (total 30%) Part 1 is multiple choice. 3 marks will be awarded for each correct answer. No marks will be awarded for an incorrect or missing answer. On your answer sheet draw a table that looks something like, Question 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 Answer and insert your answer in the boxes. Only the answers will be marked. A B C D E The diagram above shows a colour (B-V) versus absolute visual magnitude (MV) plot for solar neighbourhood stars compiled from observations from the Hipparcos satellite. Five regions labelled A, B, C, D and E are highlighted. Which region on the HR diagram contains: (1.1) the stars with the smallest diameter (3%) (1.2) the stars that emit the greatest energy per second per unit surface area (3%) 3 (1.3) the stars with the largest diameter (3%) (1.4) the stars with the lowest mass (3%) (1.5) the main sequence stars with the smallest mass to luminosity ratio (3%) observations Star Spectral apparent observed parallax visual type magnitude colour distance half angle extinction mV (B-V)obs d p Av (mag) (mag) (pc) (arcsecs) (mag) A B0V +0.50 300 B A0V +7.6 +0.32 C F0V +10.8 0.0 D G0V +1.27 0.0250 E K0V 50 0.3 The table above lists some observed properties of five different main sequence stars labelled A, B, C, D and E.
    [Show full text]
  • Open Mroute-Dissertation.Pdf
    The Pennsylvania State University The Graduate School Department of Astronomy and Astrophysics RADIO OBSERVATIONS OF THE BROWN DWARF- EXOPLANET BOUNDARY A Dissertation in Astronomy and Astrophysics by Matthew Philip Route 2013 Matthew Philip Route Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2013 The dissertation of Matthew Philip Route was reviewed and approved* by the following: Alexander Wolszczan Evan Pugh Professor of Astronomy and Astrophysics Dissertation Advisor Chair of Committee Lyle Long Distinguished Professor of Aerospace Engineering, and Mathematics Director of the Computational Science Graduate Minor Program Kevin Luhman Associate Professor of Astronomy and Astrophysics John Mathews Professor of Electrical Engineering Steinn Sigurdsson Professor of Astronomy and Astrophysics Chair of the Graduate Program for the Department of Astronomy and Astrophysics Special Signatory Richard Wade Associate Professor of Astronomy and Astrophysics Donald Schneider Distinguished Professor of Astronomy and Astrophysics Head of the Department of Astronomy and Astrophysics *Signatures are on file in the Graduate School iii ABSTRACT Although exoplanets and brown dwarfs have been hypothesized to exist for many years, it was only in the last two decades that their existence has been directly verified. Since then, a large number of both types of substellar objects have been discovered; they have been studied, characterized, and classified. Yet knowledge of their magnetic properties remains difficult to obtain. Only radio emission provides a plausible means to study the magnetism of these cool objects. At the initiation of this research project, not a single exoplanet had been detected in the radio, and only a handful of radio emitting brown dwarfs were known.
    [Show full text]
  • Pleiades Low-Mass Brown Dwarfs: the Cluster L Dwarf Sequence
    A&A 458, 805–816 (2006) Astronomy DOI: 10.1051/0004-6361:20065124 & c ESO 2006 Astrophysics Pleiades low-mass brown dwarfs: the cluster L dwarf sequence G. Bihain1,2, R. Rebolo1,2,V.J.S.Béjar1,3, J. A. Caballero1,C.A.L.Bailer-Jones4, R. Mundt4, J. A. Acosta-Pulido1, and A. Manchado Torres1,2 1 Instituto de Astrofísica de Canarias, c/ Vía Láctea, s/n, 38205 La Laguna, Tenerife, Spain e-mail: [gbihain;rrl;zvezda;jap;amt]@ll.iac.es;[email protected] 2 Consejo Superior de Investigaciones Científicas, Spain 3 GTC Project, Instituto de Astrofísica de Canarias 4 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: [calj;mundt]@mpia-hd.mpg.de Received 1 March 2006 / Accepted 3 August 2006 ABSTRACT Aims. We present a search for low-mass brown dwarfs in the Pleiades open cluster. The identification of Pleiades members fainter and cooler than those currently known allows us to constrain evolutionary models for L dwarfs and to extend the study of the cluster mass function to lower masses. 2 Methods. We conducted a 1.8 deg near-infrared J-band survey at the 3.5 m Calar Alto Telescope, with completeness Jcpl ∼ 19.0. The detected sources were correlated with those of previously available optical I-band images (Icpl ∼ 22). Using a J versus I − J colour–magnitude diagram, we identified 18 faint red L-type candidates, with magnitudes 17.4 < J < 19.7 and colours I − J > 3.2. If Pleiades members, their masses would span ∼0.040−0.020 M.
    [Show full text]
  • 254 — 13 February 2014 Editor: Bo Reipurth ([email protected]) List of Contents
    THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar/planetary evolution and molecular clouds No. 254 — 13 February 2014 Editor: Bo Reipurth ([email protected]) List of Contents The Star Formation Newsletter Interview ...................................... 3 My Favorite Object ............................ 5 Editor: Bo Reipurth [email protected] Perspective ................................... 10 Technical Editor: Eli Bressert Abstracts of Newly Accepted Papers .......... 13 [email protected] Abstracts of Newly Accepted Major Reviews . 54 Technical Assistant: Hsi-Wei Yen Dissertation Abstracts ........................ 60 [email protected] New Jobs ..................................... 61 Editorial Board Meetings ..................................... 63 Summary of Upcoming Meetings ............. 66 Joao Alves Alan Boss Short Announcements ........................ 67 Jerome Bouvier New Books ................................... 68 Lee Hartmann Thomas Henning Paul Ho Jes Jorgensen Charles J. Lada Cover Picture Thijs Kouwenhoven Michael R. Meyer This image shows the blueshifted outflow cav- Ralph Pudritz ity from the embedded quadruple Class I source Luis Felipe Rodr´ıguez L1551 IRS5 based on Hα and [SII] images obtained Ewine van Dishoeck with the Subaru telescope images. Two short jets, Hans Zinnecker HH 154, are seen to emerge from the source region to the upper left. The outflow cavity has burst The Star Formation Newsletter is a vehicle for through the front of the cloud, exposing the rich fast distribution of information of interest for as- and complex Herbig-Haro shock structures within. tronomers working on star and planet formation A few faint knots from the HH 30 jet (outside the and molecular clouds. You can submit material field) are visible at the top of the image. The for the following sections: Abstracts of recently field is about 7×8 arcmin, corresponding to about accepted papers (only for papers sent to refereed 0.30×0.35 pc at the assumed distance of 150 pc.
    [Show full text]
  • Stellar Structure Model in Hydrostatic Equilibrium in the Context of $ F
    Stellar structure model in hydrostatic equilibrium in the context of f(R)-gravity Ra´ıla Andr´e∗ and Gilberto M. Kremery Departamento de F´ısica, Universidade Federal do Paran´a, 81531-980 Curitiba, Brazil. (Dated: August 29, 2017) In this work we present a stellar structure model from f(R)-gravity point of view capable to de- scribe some classes of stars (White Dwarfs, Brown Dwarfs, Neutron stars, Red Giants and the Sun). 2 This model was based on f(R)-gravity field equations for f(R) = R+f2R , hydrostatic equilibrium equation and a polytropic equation of state. We compared the results obtained with those found by the Newtonian theory. It has been observed that in these systems, where high curvature regimes emerge, stellar structure equations undergo modifications. Despite the simplicity of this model, the results were satisfactory. The estimated values of pressure, density and temperature of the stars are within those determined by observations. This f(R)-gravity model has been proved to be necessary to describe stars with strong fields such as White Dwarfs, Neutron stars and Brown Dwarfs, while stars with weaker fields, such as Red Giants and the Sun, were best described by the Newtonian theory. I. INTRODUCTION developed. In [19], using the method of perturbative con- straints and corrections of the form Rn+1, they showed The f(R)-gravity is a class of theories that represent that the predicted mass-radius relation for neutron stars an approach to gravitational interaction. In this con- differs from that calculated in the General Relativity. text, General Relativity (GR) has to be extended in or- In [20], the mass-radius diagram for static neutron star der to solve several issues.
    [Show full text]
  • Neither Star Nor Planet
    Neither Star nor Planet They are often eclipsed by more attractive topics, like black holes or exoplanets. Even the name itself is less than sensational: brown dwarfs. But Viki Joergens and her colleagues from the Max Planck Institute for Astronomy in Heidelberg have gained fascinating insights in this research field. PHYSICS & ASTRONOMY_Brown Dwarfs TEXT THOMAS BÜHRKE he Milky Way probably has it. As Japanese theoreticians Chu-shiro Stars are formed when individual re- roughly as many brown dwarfs Hayashi and Takenori Nakano discov- gions in the interior of a large cloud of as it has planets. Astronomers ered back in 1963, this process requires gas and dust contract under the effects don’t know the precise num- a star to have at least 7 to 8 percent of of gravity. The core of such a cloud ro- ber, as these celestial bodies the solar mass, corresponding to 75 tates and forms a disk. The material in T are small and very dim, and thus diffi- times the mass of the planet Jupiter. the cloud center becomes more and cult to observe. They have, however, re- But bodies that are just below this more compressed until hydrogen fusion ally shaken our tried and tested defini- threshold should initially still be suffi- begins. The young star is then stable. tions of the terms “star” and “planet” ciently hot to fuse heavy hydrogen Dust particles collide with each oth- of which we have grown so fond. Spots (deuterium) to helium-3 and thus gen- er in the disk that still surrounds them, form on their surface like the spots on erate energy.
    [Show full text]