scholarly journals Exploring the planetary-mass population in the Upper Scorpius association*

2021 ◽  
Author(s):  
N Lodieu ◽  
N C Hambly ◽  
N J G Cross
Keyword(s):  
Infrared Spectroscopy ◽  
Mass Spectrum ◽  
Central Region ◽  
Luminosity Function ◽  
Spectral Features ◽  
The Sun ◽  
Planetary Mass ◽  
Substellar Objects ◽  
Low Mass ◽  
Current Sequence

Abstract We aim at identifying very low-mass isolated planetary-mass member candidates in the nearest OB association to the Sun, Upper Scorpius (145 pc; 5–10 Myr), to constrain the form and shape of the luminosity function and mass spectrum in this regime. We conducted a deep multi-band (Y = 21.2, J = 20.5, Z = 22.0 mag) photometric survey of six square degrees in the central region of Upper Scorpius. We extend the current sequence of astrometric and spectroscopic members by about two magnitudes in Y and one magnitude in J, reaching potentially T-type free-floating members in the association with predicted masses below 5 Jupiter masses, well into the planetary-mass regime. We extracted a sample of 57 candidates in this area and present infrared spectroscopy confirming two of them as young L-type members with characteristic spectral features of 10 Myr-old brown dwarfs. Among the 57 candidates, we highlight 10 new candidates fainter than the coolest members previously confirmed spectroscopically. We do not see any obvious sign of decrease in the mass spectrum of the association, suggesting that star processes can form substellar objects with masses down to 4–5 Jupiter masses.

scholarly journals Disks in Brown Dwarf Systems

2003 ◽  
Vol 211 ◽  
pp. 127-132
Author(s):  
Leonardo Testi ◽  
Antonella Natta ◽  
Fernando Comerón ◽  
Ernesto Oliva ◽  
Francesca D'Antona
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Circumstellar Disks ◽  
Brown Dwarf ◽  
Infrared Excess ◽  
Mid Infrared ◽  
Star Forming ◽  
Planetary Mass ◽  
Substellar Objects

We discuss evidence for and properties of disks associated with brown dwarfs in the star-forming region ρ Oph. We derived photospheric parameters from low resolution near infrared spectroscopy and modeled the mid-infrared excess of nine substellar object candidates in the ρ OphISOCAM survey of Bontemps et al. (2001). In all cases, the mid-infrared excess is consistent with the SED expected from irradiated disks. These results suggest that circumstellar disks are commonly associated to young brown dwarfs and planetary-mass objects. Finally, we discuss the possibility of using these data to discriminate between various formation scenarios for substellar objects.

scholarly journals The Stellar Luminosity Function and Binary Stars

1992 ◽  
Vol 135 ◽  
pp. 234-237
Author(s):  
Pavel Kroupa ◽  
Christopher A. Tout ◽  
Gerard Gilmore
Keyword(s):  
Binary Stars ◽  
Luminosity Function ◽  
Binary Systems ◽  
Small Volume ◽  
Mass Function ◽  
Stellar Mass ◽  
The Sun ◽  
Single Star ◽  
Luminosity Functions ◽  
Low Mass

AbstractIf all stars within a small volume surrounding the sun are counted we obtain an approximation of the low-mass single-star luminosity function. Alternatively, deep photographic surveys cannot resolve most of the binary systems, and consequently we obtain an approximation to the system luminosity function. Comparing the single-star and system luminosity functions we derive the stellar mass function and constrain the properties of binary systems.

scholarly journals Exploring Flaring Behaviour on Low Mass Stars, Solar-type Stars and the Sun

2019 ◽  
Vol 15 (S354) ◽  
pp. 384-391
Author(s):  
L. Doyle ◽  
G. Ramsay ◽  
J. G. Doyle ◽  
P. F. Wyper ◽  
E. Scullion ◽  
...  
Keyword(s):  
High Energy ◽  
The Sun ◽  
Low Mass Stars ◽  
Highly Active ◽  
Rotation Phase ◽  
Solar Type ◽  
Low Mass ◽  
Insight Into ◽  
Reconnection Model ◽  
High Cadence

AbstractWe report on our project to study the activity in both the Sun and low mass stars. Utilising high cadence, Hα observations of a filament eruption made using the CRISP spectropolarimeter mounted on the Swedish Solar Telescope has allowed us to determine 3D velocity maps of the event. To gain insight into the physical mechanism which drives the event we have qualitatively compared our observation to a 3D MHD reconnection model. Solar-type and low mass stars can be highly active producing flares with energies exceeding erg. Using K2 and TESS data we find no correlation between the number of flares and the rotation phase which is surprising. Our solar flare model can be used to aid our understanding of the origin of flares in other stars. By scaling up our solar model to replicate observed stellar flare energies, we investigate the conditions needed for such high energy flares.

scholarly journals Giant planets around AF and M stars

2013 ◽  
Vol 8 (S299) ◽  
pp. 64-65
Author(s):  
Julien Rameau ◽  
Gaël Chauvin ◽  
Anne-Marie Lagrange ◽  
Philippe Delorme ◽  
Justine Lannier
Keyword(s):  
Giant Planets ◽  
Early Type ◽  
Late Type ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Planetary Mass ◽  
Nearby Stars ◽  
Low Mass ◽  
M Stars ◽  
The One

AbstractWe present the results of two three-year surveys of young and nearby stars to search for wide orbit giant planets. On the one hand, we focus on early-type and massive, namely β Pictoris analogs. On the other hand, we observe late type and very low mass stars, i.e., M dwarfs. We report individual detections of new planetary mass objects. According to our deep detection performances, we derive the observed frequency of giant planets between these two classes of parent stars. We find frequency between 6 to 12% but we are not able to assess a/no correlation with the host-mass.

scholarly journals PLANETS AROUND LOW-MASS STARS (PALMS). VI. DISCOVERY OF A REMARKABLY RED PLANETARY-MASS COMPANION TO THE AB DOR MOVING GROUP CANDIDATE 2MASS J22362452+4751425

2016 ◽  
Vol 153 (1) ◽  
pp. 18 ◽  
Author(s):  
Brendan P. Bowler ◽  
Michael C. Liu ◽  
Dimitri Mawet ◽  
Henry Ngo ◽  
Lison Malo ◽  
...  
Keyword(s):  
Low Mass Stars ◽  
Planetary Mass ◽  
Low Mass

scholarly journals The Evolution of 3He, 4He and D in the Galaxy

2000 ◽  
Vol 198 ◽  
pp. 540-546 ◽  
Author(s):  
Cristina Chiappini ◽  
Francesca Matteucci
Keyword(s):  
Chemical Evolution ◽  
Present Model ◽  
Galactic Disk ◽  
The Sun ◽  
Mixing Process ◽  
Low Mass Stars ◽  
A Value ◽  
The Galaxy ◽  
Low Mass ◽  
Standing Problem

In this work we present the predictions of a modified version of the ‘two-infall model’ (Chiappini et al. 1997 - CMG) for the evolution of 3He, 4He and D in the solar vicinity, as well as their distributions along the Galactic disk. In particular, we show that when allowing for extra-mixing process in low mass stars (M < 2.5 M⊙), as predicted by Charbonnel and do Nascimento (1998), a long standing problem in chemical evolution is solved, namely: the overproduction of 3He by the chemical evolution models as compared to the observed values in the sun and in the interstellar medium. Moreover, we show that chemical evolution models can constrain the primordial value of the deuterium abundance and that a value of (D/H)p < 3 × 10—5 is suggested by the present model. Finally, adopting the primordial 4He abundance suggested by Viegas et al. (1999), we obtain a value for ΔY/ΔZ ≃ 2 and a better agreement with the solar 4He abundance.

scholarly journals The NIBLES bivariate luminosity–H I mass distribution function revised using Arecibo follow-up observations

2020 ◽  
Vol 642 ◽  
pp. A175
Author(s):  
Z. Butcher ◽  
W. van Driel ◽  
S. Schneider
Keyword(s):  
Mass Distribution ◽  
Radio Telescope ◽  
Luminosity Function ◽  
Mass Function ◽  
Bivariate Analysis ◽  
Dimensional Distribution ◽  
Low Mass ◽  
The One ◽  
Mass Distribution Function

We present a modified optical luminosity–H I mass bivariate luminosity function based on H I line observations from the Nançay Interstellar Baryons Legacy Extragalactic Survey (NIBLES), including data from our new, four times more sensitive follow-up H I line observations obtained with the Arecibo radio telescope. The follow-up observations were designed to probe the underlying H I mass distribution of the NIBLES galaxies that were undetected or marginally detected in H I at the Nançay Radio Telescope. Our total follow-up sample consists of 234 galaxies, and it spans the entire luminosity and color range of the parent NIBLES sample of 2600 nearby (900 <  cz <  12 000 km s−1) SDSS galaxies. We incorporated the follow-up data into the bivariate analysis by scaling the NIBLES undetected fraction by an Arecibo-only distribution. We find the resulting increase in low H I mass-to-light ratio densities to be about 10% for the bins −1.0 ≤ log(MHI/M⊙/Lr/L⊙) ≤ −0.5, which produces an increased H I mass function (HIMF) low mass slope of α = −1.14 ± 0.07, being slightly shallower than the values of −1.35 ± 0.05 obtained by recent blind H I surveys. Applying the same correction to the optically corrected bivariate luminosity function from our previous paper produces a larger density increase of about 0.5 to 1 dex in the lowest H I mass-to-light ratio bins for a given luminosity while having a minimal effect on the resulting HIMF low mass slope, which still agrees with blind survey HIMFs. This indicates that while low H I-mass-to-light ratio galaxies do not contribute much to the one-dimensional HIMF, their inclusion has a significant impact on the densities in the two-dimensional distribution.

scholarly journals Correlations between H α equivalent width and galaxy properties at z = 0.47: Physical or selection-driven?

2021 ◽  
Vol 503 (4) ◽  
pp. 5115-5133
Author(s):  
A A Khostovan ◽  
S Malhotra ◽  
J E Rhoads ◽  
S Harish ◽  
C Jiang ◽  
...  
Keyword(s):  
Star Formation ◽  
Equivalent Width ◽  
Luminosity Function ◽  
Mass Function ◽  
Stellar Mass ◽  
High Mass ◽  
Selection Effects ◽  
Star Formation Activity ◽  
Low Mass ◽  
Stellar Masses

ABSTRACT The H α equivalent width (EW) is an observational proxy for specific star formation rate (sSFR) and a tracer of episodic, bursty star-formation activity. Previous assessments show that the H α EW strongly anticorrelates with stellar mass as M−0.25 similar to the sSFR – stellar mass relation. However, such a correlation could be driven or even formed by selection effects. In this study, we investigate how H α EW distributions correlate with physical properties of galaxies and how selection biases could alter such correlations using a z = 0.47 narrow-band-selected sample of 1572 H α emitters from the Ly α Galaxies in the Epoch of Reionization (LAGER) survey as our observational case study. The sample covers a 3 deg2 area of COSMOS with a survey comoving volume of 1.1 × 105 Mpc3. We assume an intrinsic EW distribution to form mock samples of H α emitters and propagate the selection criteria to match observations, giving us control on how selection biases can affect the underlying results. We find that H α EW intrinsically correlates with stellar mass as W0∝M−0.16 ± 0.03 and decreases by a factor of ∼3 from 107 M⊙ to 1010 M⊙, while not correcting for selection effects steepens the correlation as M−0.25 ± 0.04. We find low-mass H α emitters to be ∼320 times more likely to have rest-frame EW&gt;200 Å compared to high-mass H α emitters. Combining the intrinsic W0–stellar mass correlation with an observed stellar mass function correctly reproduces the observed H α luminosity function, while not correcting for selection effects underestimates the number of bright emitters. This suggests that the W0–stellar mass correlation when corrected for selection effects is physically significant and reproduces three statistical distributions of galaxy populations (line luminosity function, stellar mass function, EW distribution). At lower stellar masses, we find there are more high-EW outliers compared to high stellar masses, even after we take into account selection effects. Our results suggest that high sSFR outliers indicative of bursty star formation activity are intrinsically more prevalent in low-mass H α emitters and not a byproduct of selection effects.

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