Accretion in $\mathsf{\rho}$ Ophiuchus brown dwarfs:  infrared hydrogen line ratios

Brown dwarfs with masses below 0.075 solar masses are thought to form like low-mass stars (e.g., the Sun).However, it is still unclear how the physical formation processes occurin brown dwarfs at the ealiest stages (i.e., proto-brown dwarfs) of their formation.Up to date, only a few proto-brown dwarfs have been detected.The detection of proto-brown dwarfs offers us excellent benchmarks to studythe formation process of brown dwarfs, and thus understand their formation mechanism.In this paper, we present our identification of a proto-brown dwarf candidate in the star-forming regionrho Ophiuchus.The candidate shows a small-scale bipolar molecular outlfow that is similar to the outflows observed inother young brown dwarfs. The detection of this candidateprovides us with additional important implications for the formation mechanism of brown dwarfs.

Download Full-text

Very Low-Mass Stars and Brown Dwarfs

10.1017/cbo9780511564758 ◽

2000 ◽

Cited By ~ 2

Keyword(s):

Brown Dwarfs ◽

Low Mass Stars ◽

Low Mass

Download Full-text

Hydrogen line profiles at low densities

Annales de Physique ◽

10.1051/anphys:0198400904069700 ◽

1984 ◽

Vol 9 (4) ◽

pp. 697-704 ◽

Cited By ~ 8

Author(s):

C. Stehlé ◽

N. Feautrier

Keyword(s):

Line Profiles ◽

Hydrogen Line

Download Full-text

Translocations In Space-Time and Simultaneous States of the Universe: Convergent Quantifications and Alternative Solutions from the Principles of Physics for the Challenges of â€œTime Travelâ€ and â€œParallel Universesâ€

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v11i8.195 ◽

2016 ◽

pp. 4058-4069

Author(s):

Michael A Persinger

Keyword(s):

Single Photon ◽

Rest Mass ◽

Space Time ◽

Hydrogen Line ◽

Magnetic Forces ◽

Universal Space ◽

Potential Applications ◽

Order Of Magnitude ◽

Alternative Solutions ◽

The Universe

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Translation of four dimensional axes anywhere within the spatial and temporal boundaries of the universe would require quantitative values from convergence between parameters that reflect these limits. The presence of entanglement and volumetric velocities indicates that the initiating energy for displacement and transposition of axes would be within the upper limit of the rest mass of a single photon which is the same order of magnitude as a macroscopic Hamiltonian of the modified SchrÃ¶dinger wave function. The representative metaphor is that any local 4-D geometry, rather than displaying restricted movement through Minkowskian space, would instead expand to the total universal space-time volume before re-converging into another location where it would be subject to cause-effect. Within this transient context the contributions from the anisotropic features of entropy and the laws of thermodynamics would be minimal.Â The central operation of a fundamental unit of 10-20 J, the hydrogen line frequency, and the Bohr orbital time for ground state electrons would be required for the relocalized manifestation. Similar quantified convergence occurs for the ~1012 parallel states within space per Planckâ€™s time which solve for phase-shift increments where Casimir and magnetic forces intersect. Â Experimental support for these interpretations and potential applications is considered. The multiple, convergent solutions of basic universal quantities suggest that translations of spatial axes into adjacent spatial states and the transposition of four dimensional configurations any where and any time within the universe may be accessed but would require alternative perspectives and technologies.

Download Full-text

Variability of L Dwarfs in the Near Infrared

Symposium - International Astronomical Union ◽

10.1017/s0074180900211121 ◽

2003 ◽

Vol 211 ◽

pp. 455-456 ◽

Cited By ~ 2

Author(s):

José A. Caballero ◽

Víctor J. S. Béjar ◽

Rafael Rebolo

Keyword(s):

Time Scales ◽

Near Infrared ◽

Brown Dwarfs ◽

L Dwarfs ◽

Atmospheric Changes ◽

Changes Over Time ◽

Over Time

We have obtained series of images in the near infrared J and Ks bands for seven L-type dwarfs with a duration of 3 to 6 hours. We present results on: 1) the amplitude of variability associated with atmospheric changes over time scales from minutes to several hours; 2) the search for cool companions in wide orbits; 3) the search for transits of brown dwarfs and planetary companions in very close orbits.

Download Full-text

Very Low-Luminosity Objects in Star-Forming Regions

Highlights of Astronomy ◽

10.1017/s1539299600021626 ◽

1998 ◽

Vol 11 (1) ◽

pp. 423-424

Author(s):

Motohide Tamura ◽

Yoichi Itoh ◽

Yumiko Oasa ◽

Alan Tokunaga ◽

Koji Sugitani

Keyword(s):

Brown Dwarfs ◽

Mass Function ◽

T Tauri Stars ◽

Initial Mass Function ◽

Formation Mechanisms ◽

Star Forming ◽

Star Forming Regions ◽

T Tauri ◽

Low Mass ◽

Stellar Sources

Abstract In order to tackle the problems of low-mass end of the initial mass function (IMF) in star-forming regions and the formation mechanisms of brown dwarfs, we have conducted deep infrared surveys of nearby molecular clouds. We have found a significant population of very low-luminosity sources with IR excesses in the Taurus cloud and the Chamaeleon cloud core regions whose extinction corrected J magnitudes are 3 to 8 mag fainter than those of typical T Tauri stars in the same cloud. Some of them are associated with even fainter companions. Follow-up IR spectroscopy has confirmed for the selected sources that their photospheric temperature is around 2000 to 3000 K. Thus, these very low-luminosity young stellar sources are most likely very low-mass T Tauri stars, and some of them might even be young brown dwarfs.

Download Full-text

A Deep Large area Search for Low Luminosity Stars

Highlights of Astronomy ◽

10.1017/s1539299600021675 ◽

1998 ◽

Vol 11 (1) ◽

pp. 435-435

Author(s):

Hugh R.A. Jones ◽

Mike R.S. Hawkins

Keyword(s):

Spectral Type ◽

Low Temperatures ◽

Current Model ◽

Brown Dwarfs ◽

Evolutionary Models ◽

Spectral Indices ◽

Late Type ◽

Brown Dwarf ◽

Large Area ◽

M Dwarfs

In a recent survey for faint red stars from a digital stack of Schmidt plates a number of candidate objects were identified. Parallax’s for three of these objects have been reported showing them to have luminosities which interpreted within the available evolutionary models indicate them to be good brown dwarf candidates. Here we examine spectra of these objects and others from the plate stack. Using standard spectral indices we find that for a given spectral type their spectra are more consistent with the Pleiades brown dwarfs (PPL 15, Teide 1 and Calar 3) than with standard late-type M dwarfs. Our interpretation is that this is due to their selection by RF IN colours which at values > 3 preferentially selects objects with relatively low gravities. For late-type M dwarfs and brown dwarfs low gravities are expected to be a reliable indication of youth. We also notice that the stack objects generally have strong FeH absorption for their spectral type. Current model atmospheres suggest that FeH strongly increases in strength toward lower metallicities and lower temperatures. We believe that this is not consistent with the available observational evidence from late-type M dwarfs. It is possible that solid Fe is forming inthe low temperature atmospheres relatively depleting FeH strengths toward lower temperatures. We find some evidence that for dwarfs at low temperatures dust formation is less prevalent in lower gravity objects suggesting that dwarfs at low temperatures stronger FeH may be an indication of youth. In addition to the spectral evidence the three stack objects whose parallax’s have been measured show small tangential velocities which is a further indication of youth.

Download Full-text

Spectra of M Dwarfs - Dimmed by Dust

Highlights of Astronomy ◽

10.1017/s1539299600021717 ◽

1998 ◽

Vol 11 (1) ◽

pp. 439-440

Author(s):

T. Tsuji ◽

K. Ohnaka ◽

W. Aoki ◽

H.R.A. Jones

Keyword(s):

Chemical Composition ◽

Brown Dwarfs ◽

Surface Chemical ◽

Basic Information ◽

M Dwarfs ◽

Surface Chemical Composition ◽

Molecular Lines ◽

Low Mass

Spectra of M dwarfs are rich in atomic and molecular lines. These spectra provide such basic information as Teff (or radius), log g (or mass), surface chemical composition, and something more (e.g. activity) if properly interpreted. It is recognized, however, that spectra of M dwarfs are already dimmed by the dust formed in their photospheres (Tsuji et al. 1996a) and this effect, which has been overlooked until recently, should be taken into account in any interpretation and analysis of the spectra of very low mass objects (VLMOs) including late M dwarfs and brown dwarfs.

Download Full-text