scholarly journals 2MASS J15491331-3539118: a new low-mass wide companion of the GQ Lup system

2020 ◽  
Vol 635 ◽  
pp. L1 ◽  
Author(s):  
J. M. Alcalá ◽  
F. Z. Majidi ◽  
S. Desidera ◽  
A. Frasca ◽  
C. F. Manara ◽  
...  
Keyword(s):  
Special Interest ◽  
Triple System ◽  
Brown Dwarfs ◽  
Position Angle ◽  
Stellar Object ◽  
Young Stellar Object ◽  
System A ◽  
Low Mass ◽  
Substellar Companions

Substellar companions at wide separation around stars hosting planets or brown dwarfs (BDs) yet close enough for their formation in the circumstellar disc are of special interest. In this Letter we report the discovery of a wide (projected separation ∼16″​​.0, or 2400 AU, and position angle 114.61°) companion of the GQ Lup A-B system, most likely gravitationally bound to it. A VLT/X-shooter spectrum shows that this star, 2MASS J15491331-3539118, is a bonafide low-mass (∼0.15 M⊙) young stellar object (YSO) with stellar and accretion/ejection properties typical of Lupus YSOs of similar mass, and with kinematics consistent with that of the GQ Lup A-B system. A possible scenario for the formation of the triple system is that GQ Lup A and 2MASS J15491331-3539118 formed by fragmentation of a turbulent core in the Lup I filament, while GQ Lup B, the BD companion of GQ Lup A at 0″​​.7, formed in situ by the fragmentation of the circumprimary disc. The recent discoveries that stars form along cloud filaments would favour the scenario of turbulent fragmentation for the formation of GQ Lup A and 2MASS J15491331-3539118.

scholarly journals The MUCHFUSS photometric campaign

2018 ◽  
Vol 614 ◽  
pp. A77 ◽  
Author(s):  
V. Schaffenroth ◽  
S. Geier ◽  
U. Heber ◽  
R. Gerber ◽  
D. Schneider ◽  
...  
Keyword(s):  
Brown Dwarfs ◽  
Close Binary ◽  
Red Giants ◽  
Reflection Effect ◽  
Common Envelope ◽  
Sdb Stars ◽  
Solar Type ◽  
Low Mass ◽  
Substellar Companions ◽  
Almost All

Hot subdwarfs (sdO/Bs) are the helium-burning cores of red giants, which have lost almost all of their hydrogen envelope. This mass loss is often triggered by common envelope interactions with close stellar or even substellar companions. Cool companions like late-type stars or brown dwarfs are detectable via characteristic light-curve variations like reflection effects and often also eclipses. To search for such objects, we obtained multi-band light curves of 26 close sdO/B binary candidates from the MUCHFUSS project with the BUSCA instrument. We discovered a new eclipsing reflection effect system (P = 0.168938 d) with a low-mass M dwarf companion (0.116 M⊙). Three more reflection effect binaries found in the course of the campaign have already been published; two of them are eclipsing systems, and in one system only showing the reflection effect but no eclipses, the sdB primary is found to be pulsating. Amongst the targets without reflection effect a new long-period sdB pulsator was discovered and irregular light variations were found in two sdO stars. The found light variations allowed us to constrain the fraction of reflection effect binaries and the substellar companion fraction around sdB stars. The minimum fraction of reflection effect systems amongst the close sdB binaries might be greater than 15% and the fraction of close substellar companions in sdB binaries may be as high as 8.0%. This would result in a close substellar companion fraction to sdB stars of about 3%. This fraction is much higher than the fraction of brown dwarfs around possible progenitor systems, which are solar-type stars with substellar companions around 1 AU, as well as close binary white dwarfs with brown dwarf companions. This might suggest that common envelope interactions with substellar objects are preferentially followed by a hot subdwarf phase.

scholarly journals The B-Star Exoplanet Abundance Study: a co-moving 16–25 MJup companion to the young binary system HIP 79098

2019 ◽  
Vol 626 ◽  
pp. A99 ◽  
Author(s):  
Markus Janson ◽  
Ruben Asensio-Torres ◽  
Damien André ◽  
Mickaël Bonnefoy ◽  
Philippe Delorme ◽  
...  
Keyword(s):  
Proper Motion ◽  
Massive Stars ◽  
Brown Dwarfs ◽  
Mass Ratio ◽  
Low Mass Stars ◽  
Spectroscopic Binary ◽  
Bona Fide ◽  
Low Mass ◽  
Substellar Companions ◽  
Dependent Mass

Wide low-mass substellar companions are known to be very rare among low-mass stars, but appear to become increasingly common with increasing stellar mass. However, B-type stars, which are the most massive stars within ~150 pc of the Sun, have not yet been examined to the same extent as AFGKM-type stars in that regard. In order to address this issue, we launched the ongoing B-star Exoplanet Abundance Study (BEAST) to examine the frequency and properties of planets, brown dwarfs, and disks around B-type stars in the Scorpius-Centaurus (Sco-Cen) association; we also analyzed archival data of B-type stars in Sco-Cen. During this process, we identified a candidate substellar companion to the B9-type spectroscopic binary HIP 79098 AB, which we refer to as HIP 79098 (AB)b. The candidate had been previously reported in the literature, but was classified as a background contaminant on the basis of its peculiar colors. Here we demonstrate that the colors of HIP 79098 (AB)b are consistent with several recently discovered young and low-mass brown dwarfs, including other companions to stars in Sco-Cen. Furthermore, we show unambiguous common proper motion over a 15-yr baseline, robustly identifying HIP 79098 (AB)b as a bona fide substellar circumbinary companion at a 345 ± 6 AU projected separation to the B9-type stellar pair. With a model-dependent mass of 16–25 MJup yielding a mass ratio of <1%, HIP 79098 (AB)b joins a growing number of substellar companions with planet-like mass ratios around massive stars. Our observations underline the importance of common proper motion analysis in the identification of physical companionship, and imply that additional companions could potentially remain hidden in the archives of purely photometric surveys.

scholarly journals Short-Lived Nuclei in the Early Solar System: A Low Mass Stellar Source?

2003 ◽  
Vol 20 (4) ◽  
pp. 356-370 ◽  
Author(s):  
M. Busso ◽  
R. Gallino ◽  
G. J. Wasserburg
Keyword(s):  
Solar System ◽  
Asymptotic Giant Branch ◽  
Early Solar System ◽  
Uncertainty Range ◽  
System A ◽  
Free Decay ◽  
Low Mass ◽  
Stellar Source ◽  
Review Current

AbstractWe discuss possible stellar origins of short-lived radioactive nuclei with meanlife τ ≤ 100 Myr, which were shown to be alive in the Early Solar System (ESS). We first review current ideas on the production of nuclides having 10 ≤ τ ≤ 100 Myr, which presumably derive from the continuous interplay of galactic astration, nucleosynthesis from massive supernovae and free decay in the interstellar medium. The abundance of the shorter lived 53Mn might be explained by this same scenario. Then we consider the nuclei 107Pd, 26Al, 41Ca and 60Fe, whose early solar system abundances are too high to have originated in this way. Present evidence favours a stellar origin, particularly for 107Pd, 26Al and 60Fe, rather than an in situ production by energetic solar particles. The idea of an encounter (rather close in time and space) between the forming Sun and a dying star is therefore discussed: this star may or may not have also triggered the solar formation. Recent nucleosynthesis calculations for the yields of the relevant short-lived isotopes and of their stable reference nuclei are discussed. Massive stars evolving to type II supernovae (either leaving a neutron star or a black hole as a remnant) seem incapable of explaining the four most critical ESS radioactivities in their observed abundance ratios. An asymptotic giant branch (AGB) star seems to be a viable source, especially if of relatively low initial mass (M ≤ 3 M⊙) and with low neutron exposure: this model can provide a solution for 26Al, 41Ca and 107Pd, with important contributions to 60Fe, which are inside the present uncertainty range of the 60Fe early solar system abundance. Such a model requires that 26Al is produced substantially on the AGB by cool bottom processing. The remaining inventory of short-lived species in the solar nebula would then be attributed to the continuous galactic processing, with the exception of 10Be, which must reflect production by later proton bombardment at a low level during early solar history.

scholarly journals Atlas of low-mass young stellar object disks from mid-infrared interferometry

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
J. Varga ◽  
P. Ábrahám ◽  
Th. Ratzka ◽  
J. Menu ◽  
K. Gabányi ◽  
...  
Keyword(s):  
Circumstellar Disks ◽  
Stellar Object ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Mid Infrared ◽  
Young Stellar Object ◽  
Low Mass ◽  
Infrared Interferometry

AbstractWe present our approach of visibility modeling of disks around low-mass (< 2 M⊙) young stellar objects (YSOs). We compiled an atlas based on mid-infrared interferometric observations from the MIDI instrument at the VLTI. We use three different models to fit the data. These models allow us to determine overall sizes (and the extent of the inner gaps) of the modeled circumstellar disks.

scholarly journals Formation of compact systems of super-Earths via dynamical instabilities and giant impacts

2019 ◽  
Vol 491 (4) ◽  
pp. 5595-5620 ◽  
Author(s):  
Sanson T S Poon ◽  
Richard P Nelson ◽  
Seth A Jacobson ◽  
Alessandro Morbidelli
Keyword(s):  
Initial Conditions ◽  
Post Processing ◽  
Significant Modification ◽  
Kepler Mission ◽  
Giant Impacts ◽  
Low Mass ◽  
In Situ Formation ◽  
Dynamical Instabilities ◽  
Gaseous Envelopes

ABSTRACT The NASA’s Kepler mission discovered ∼700 planets in multiplanet systems containing three or more transiting bodies, many of which are super-Earths and mini-Neptunes in compact configurations. Using N-body simulations, we examine the in situ, final stage assembly of multiplanet systems via the collisional accretion of protoplanets. Our initial conditions are constructed using a subset of the Kepler five-planet systems as templates. Two different prescriptions for treating planetary collisions are adopted. The simulations address numerous questions: Do the results depend on the accretion prescription?; do the resulting systems resemble the Kepler systems, and do they reproduce the observed distribution of planetary multiplicities when synthetically observed?; do collisions lead to significant modification of protoplanet compositions, or to stripping of gaseous envelopes?; do the eccentricity distributions agree with those inferred for the Kepler planets? We find that the accretion prescription is unimportant in determining the outcomes. The final planetary systems look broadly similar to the Kepler templates adopted, but the observed distributions of planetary multiplicities or eccentricities are not reproduced, because scattering does not excite the systems sufficiently. In addition, we find that ∼1 per cent of our final systems contain a co-orbital planet pair in horseshoe or tadpole orbits. Post-processing the collision outcomes suggests that they would not significantly change the ice fractions of initially ice-rich protoplanets, but significant stripping of gaseous envelopes appears likely. Hence, it may be difficult to reconcile the observation that many low-mass Kepler planets have H/He envelopes with an in situ formation scenario that involves giant impacts after dispersal of the gas disc.

scholarly journals Very Low-Luminosity Objects in Star-Forming Regions

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.

scholarly journals Spectra of M Dwarfs - Dimmed by Dust

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.

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