scholarly journals Gas trapping of hot dust around main-sequence stars

2020 ◽  
Vol 498 (2) ◽  
pp. 2798-2813 ◽  
Author(s):  
Tim D Pearce ◽  
Alexander V Krivov ◽  
Mark Booth
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Main Sequence Stars ◽  
System Architectures ◽  
Mid Infrared ◽  
Gas Trapping ◽  
Order Of Magnitude ◽  
Nir Emission ◽  
Small Grains ◽  
Specialized System

ABSTRACT In 2006, Vega was discovered to display excess near-infrared (NIR) emission. Surveys now detect this phenomenon for one fifth of main-sequence stars, across various spectral types and ages. The excesses are interpreted as populations of small, hot dust grains very close to their stars, which must originate from comets or asteroids. However, the presence of such grains in copious amounts is mysterious, since they should rapidly sublimate or be blown out of the system. Here, we investigate a potential mechanism to generate excesses: dust migrating inwards under radiation forces sublimates near the star, releasing modest quantities of gas that then traps subsequent grains. This mechanism requires neither specialized system architectures nor high dust supply rates, and could operate across diverse stellar types and ages. The model naturally reproduces many features of inferred dust populations, in particular their location, preference for small grains, steep size distribution, and dust location scaling with stellar luminosity. For Sun-like stars, the mechanism can produce ${2.2 \; \mu {\rm m}}$ excesses that are an order of magnitude larger than those at ${8.5 \; \mu {\rm m}}$, as required by observations. However, for A-type stars the simulated NIR excesses were only twice those in the mid-infrared; grains would have to be 5–10 times smaller than those trapped in our model to be able to explain observed NIR excesses around A stars. Further progress with any hot dust explanation for A stars requires a means for grains to become very hot without either rapidly sublimating or being blown out of the system.

scholarly journals IPHAS A-type Stars with Mid-IR Excesses in Spitzer Surveys

2009 ◽  
Vol 5 (H15) ◽  
pp. 815-815
Author(s):  
Antonio S. Hales ◽  
Michael J. Barlow ◽  
Janet E. Drew ◽  
Yvonne C. Unruh ◽  
Robert Greimel ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Main Sequence ◽  
Terrestrial Planet ◽  
Circumstellar Disks ◽  
Main Sequence Stars ◽  
Intermediate Mass ◽  
Mid Infrared ◽  
Isaac Newton ◽  
Intermediate Mass Stars ◽  
Dust Disks

AbstractThe Isaac Newton Photometric H-Alpha Survey (IPHAS) provides (r′-Hα)-(r′-i′) colors, which can be used to select AV0-5 Main Sequence star candidates (age~20-200 Myr). By combining a sample of 23050 IPHAS-selected A-type stars with 2MASS, GLIMPSE and MIPSGAL photometry we searched for mid-infrared excesses attributable to dusty circumstellar disks. Positional cross-correlation yielded a sample of 2692 A-type stars, of which 0.6% were found to have 8-μm excesses above the expected photospheric values. The low fraction of main sequence stars with mid-IR excesses found in this work indicates that dust disks in the terrestrial planet zone of Main Sequence intermediate mass stars are rare. Dissipation mechanisms such as photo-evaporation, grain growth, collisional grinding or planet formation could possibly explain the depletion of dust detected in the inner regions of these disks.

scholarly journals Dust spreading in debris discs: do small grains cling on to their birth environment?

2019 ◽  
Vol 487 (4) ◽  
pp. 5874-5888 ◽  
Author(s):  
Nicole Pawellek ◽  
Attila Moór ◽  
Ilaria Pascucci ◽  
Alexander V Krivov
Keyword(s):  
Main Sequence ◽  
Angular Resolution ◽  
Spatial Location ◽  
Stellar Winds ◽  
Main Sequence Stars ◽  
Gravitational Forces ◽  
James Webb Space Telescope ◽  
Ring Location ◽  
Small Grains ◽  
Birth Environment

ABSTRACT Debris discs are dusty belts of planetesimals around main-sequence stars, similar to the asteroid and Kuiper belts in our Solar system. The planetesimals cannot be observed directly, yet they produce detectable dust in mutual collisions. Observing the dust, we can try to infer properties of invisible planetesimals. Here, we address the question of what is the best way to measure the location of outer planetesimal belts that encompass extrasolar planetary systems. A standard method is using resolved images at millimetre wavelengths, which reveal dust grains with sizes comparable to the observational wavelength. Smaller grains seen in the infrared (IR) are subject to several non-gravitational forces that drag them away from their birth rings, and so may not closely trace the parent bodies. In this study, we examine whether imaging of debris discs at shorter wavelengths might enable determining the spatial location of the exo-Kuiper belts with sufficient accuracy. We find that around M-type stars the dust best visible in the mid-IR is efficiently displaced inwards from their birth location by stellar winds, causing the discs to look more compact in mid-IR images than they actually are. However, around earlier-type stars where the majority of debris discs is found, discs are still the brightest at the birth ring location in the mid-IR regime. Thus, sensitive IR facilities with good angular resolution, such as MIRI on James Webb Space Telescope, will enable tracing exo-Kuiper belts in nearby debris disc systems.

Further mid-infrared study of the rho Ophiuchi cloud young stellar population: Luminosities and masses of pre-main-sequence stars

1994 ◽  
Vol 434 ◽  
pp. 614 ◽  
Author(s):  
Thomas P. Greene ◽  
Bruce A. Wilking ◽  
Philippe Andre ◽  
Erick T. Young ◽  
Charles J. Lada
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Infrared Study ◽  
Mid Infrared ◽  
Rho Ophiuchi

EXPANDING THE CHARA/FLUOR HOT DISKS SURVEY

2013 ◽  
Vol 02 (02) ◽  
pp. 1340010 ◽  
Author(s):  
B. MENNESSON ◽  
N. SCOTT ◽  
T. TEN BRUMMELAAR ◽  
G. BRYDEN ◽  
N. TURNER ◽  
...  
Keyword(s):  
Solar System ◽  
Main Sequence ◽  
Near Infrared ◽  
Dust Cloud ◽  
Main Sequence Stars ◽  
Second Development ◽  
Zodiacal Dust ◽  
Dust Component ◽  
Initial Survey ◽  
Better Than

Little is presently known about the hot (>300 K) dust component of debris disks surrounding main sequence stars, similar to the zodiacal dust cloud found in the inner solar system. While extensive surveys have been carried out from space, the majority of detections have surprisingly come from the ground, where near infrared interferometric observations have recently revealed small (~1%) resolved excesses around a dozen nearby main sequence stars. Most of these results have come from the CHARA array "FLUOR" instrument (Mt. Wilson, CA), which has demonstrated the best sensitivity worldwide so far for this type of studies, and has carried out an initial survey of ~40 stars. In order to further understand the origin of this "hot dust phenomenon", we will extend this initial survey to a larger number of stars and lower excess detection limits, i.e. higher visibility accuracy providing higher contrast measurements. To this end, two major instrumental developments are underway at CHARA. The first one aims at improving FLUOR's sensitivity to a median K-band magnitude limit of 5 (making 200 targets available). The second development is based on a method that we recently developed for accurate (better than 0.1%) null depth measurements of stars, and that can be extended to regular interferometric visibility measurements.

scholarly journals Medium-Resolution Near-Infrared (2.15-2.35 micron) Spectroscopy of Late-Type Main-Sequence Stars

1995 ◽  
Vol 110 ◽  
pp. 2415 ◽  
Author(s):  
B. Ali ◽  
John S. Carr ◽  
D. L. Depoy ◽  
Jay A. Frogel ◽  
K. Sellgren
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Late Type ◽  
Main Sequence Stars ◽  
Medium Resolution

scholarly journals On the simultaneous optical and near-infrared variability of pre-main sequence stars

2002 ◽  
Vol 384 (3) ◽  
pp. 1038-1049 ◽  
Author(s):  
C. Eiroa ◽  
R. D. Oudmaijer ◽  
J. K. Davies ◽  
D. de Winter ◽  
F. Garzón ◽  
...  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Main Sequence Stars

scholarly journals From birth associations to field stars: mapping the small-scale orbit distribution in the Galactic disc

2020 ◽  
Vol 495 (4) ◽  
pp. 4098-4112 ◽  
Author(s):  
Johanna Coronado ◽  
Hans-Walter Rix ◽  
Wilma H Trick ◽  
Kareem El-Badry ◽  
Jan Rybizki ◽  
...  
Keyword(s):  
Main Sequence ◽  
Milky Way ◽  
Space Distribution ◽  
Small Scale ◽  
Galactic Disc ◽  
Main Sequence Stars ◽  
Orbital Phase ◽  
Angle Space ◽  
Order Of Magnitude ◽  
Gaia Dr2

ABSTRACT Stars born at the same time in the same place should have formed from gas of the same element composition. But most stars subsequently disperse from their birth siblings, in orbit and orbital phase, becoming ‘field stars’. Here, we explore and provide direct observational evidence for this process in the Milky Way disc, by quantifying the probability that orbit-similarity among stars implies indistinguishable metallicity. We define the orbit similarity among stars through their distance in action-angle space, Δ(J, θ), and their abundance similarity simply by Δ[Fe/H]. Analysing a sample of main-sequence stars from Gaia DR2 and LAMOST, we find an excess of pairs with the same metallicity (Δ[Fe/H] < 0.1) that extends to remarkably large separations in Δ(J, θ) that correspond to nearly 1 kpc distances. We assess the significance of this effect through a mock sample, drawn from a smooth and phase-mixed orbit distribution. Through grouping such star pairs into associations with a friend-of-friends algorithm linked by Δ(J,θ), we find 100s of mono-abundance groups with ≥3 (to ≳20) members; these groups – some clusters, some spread across the sky – are over an order-of-magnitude more abundant than expected for a smooth phase-space distribution, suggesting that we are witnessing the ‘dissolution’ of stellar birth associations into the field.

Temperatures and radii of O stars

1979 ◽  
Vol 83 ◽  
pp. 103-108
Author(s):  
A. B. Underhill ◽  
L. Divan ◽  
V. Doazan ◽  
M.L. Prévot-Burnichon
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Stellar Atmosphere ◽  
Class Iii ◽  
Main Sequence Stars ◽  
Class V ◽  
Intermediate Band ◽  
B Stars ◽  
Luminosity Class ◽  
Effective Temperatures

Angular diameters have been estimated for 18 O and 142 B stars using absolute intermediate-band photometry in the near infrared and they have been combined with integrated fluxes to yield effective temperatures. The effective temperatures of the O stars lie in the range 30000 K to about 47000 K. For a given subtype, the luminosity class I stars have lower effective temperatures than the main-sequence stars by about 1000 K. The absorption-line spectral types of the supergiants of types O and B reflect electron temperatures which are higher than can be maintained by the integrated flux which flows through the stellar atmosphere. Distances have been estimated for all the stars and linear diameters found. The average radius for an 08 to 09.5 supergiant is about 23.3 R⊙; the radii for luminosity class III and Class V O stars lie in the range 6.8 to 10.7⊙ R.

scholarly journals CP-Stars in the Near Infrared: Normal!

1986 ◽  
Vol 90 ◽  
pp. 191-194
Author(s):  
R. Kroll ◽  
H. Schneider ◽  
H.H. Voigt ◽  
F.A. Catalano
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Main Sequence Stars ◽  
Ir Filter

Abstract17 CP-stars have been measured in the IR filter bands J,H,K,L and M. No significant differences between CP- and normal main sequence stars can be found. Flux exzesses at 4.8 microns are not confirmed.

scholarly journals The Rotation of Low-Mass Pre-Main-Sequence Stars

2004 ◽  
Vol 215 ◽  
pp. 113-122 ◽  
Author(s):  
Robert D. Mathieu
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Rotation Period ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Rotation Periods ◽  
Order Of Magnitude ◽  
Critical Velocities

Major photometric monitoring campaigns of star-forming regions in the past decade have provided rich rotation period distributions of pre-main-sequence stars. The rotation periods span more than an order of magnitude in period, with most falling between 1 and 10 days. Thus the broad rotation period distributions found in 100 Myr clusters are already established by an age of 1 Myr. The most rapidly rotating stars are within a factor of 2-3 of their critical velocities; if angular momentum is conserved as they evolve to the ZAMS, these stars may come to exceed their critical velocities. Extensive efforts have been made to find connections between stellar rotation and the presence of protostellar disks; at best only a weak correlation has been found in the largest samples. Magnetic disk-locking is a theoretically attractive mechanism for angular momentum evolution of young stars, but the links between theoretical predictions and observational evidence remain ambiguous. Detailed observational and theoretical studies of the magnetospheric environments will provide better insight into the processes of pre-main-sequence stellar angular momentum evolution.

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