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.

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

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 Anomalous Spectral Types and Intrinsic Colors of Young Stars

2015 ◽  
Vol 10 (S314) ◽  
pp. 85-90 ◽  
Author(s):  
Mark J. Pecaut
Keyword(s):  
Infrared Spectra ◽  
Spectral Type ◽  
Main Sequence ◽  
Near Infrared ◽  
Systematic Errors ◽  
Optical Spectra ◽  
Young Stars ◽  
Main Sequence Stars ◽  
Near Infrared Spectra ◽  
Dynamical Masses

AbstractWe highlight differences in spectral types and intrinsic colors observed in pre-main sequence (pre-MS) stars. Spectral types of pre-MS stars are wavelength-dependent, with near-infrared spectra being 3-5 spectral sub-classes later than the spectral types determined from optical spectra. In addition, the intrinsic colors of young stars differ from that of main-sequence stars at a given spectral type. We caution observers to adopt optical spectral types over near-infrared types, since Hertzsprung-Russell (H-R) diagram positions derived from optical spectral types provide consistency between dynamical masses and theoretical evolutionary tracks. We also urge observers to deredden pre-MS stars with tabulations of intrinsic colors specifically constructed for young stars, since their unreddened colors differ from that of main sequence dwarfs. Otherwise, V-band extinctions as much as ~0.6 mag erroneously higher than the true extinction may result, which would introduce systematic errors in the H-R diagram positions and thus bias the inferred ages.

scholarly journals VISION – Vienna survey in Orion

2019 ◽  
Vol 622 ◽  
pp. A149 ◽  
Author(s):  
Josefa Elisabeth Großschedl ◽  
João Alves ◽  
Paula S. Teixeira ◽  
Hervé Bouy ◽  
Jan Forbrich ◽  
...  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Far Infrared ◽  
Circumstellar Disks ◽  
Mass Star ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Spatial Coverage ◽  
Significant Difference ◽  
Infrared Data

We have extended and refined the existing young stellar object (YSO) catalogs for the Orion A molecular cloud, the closest massive star-forming region to Earth. This updated catalog is driven by the large spatial coverage (18.3 deg2, ∼950 pc2), seeing limited resolution (∼0.7″), and sensitivity (Ks < 19 mag) of the ESO-VISTA near-infrared survey of the Orion A cloud (VISION). Combined with archival mid- to far-infrared data, the VISTA data allow for a refined and more robust source selection. We estimate that among previously known protostars and pre-main-sequence stars with disks, source contamination levels (false positives) are at least ∼6.4% and ∼2.3%, respectively, mostly due to background galaxies and nebulosities. We identify 274 new YSO candidates using VISTA/Spitzer based selections within previously analyzed regions, and VISTA/WISE based selections to add sources in the surroundings, beyond previously analyzed regions. The WISE selection method recovers about 59% of the known YSOs in Orion A’s low-mass star-forming part L1641, which shows what can be achieved by the all-sky WISE survey in combination with deep near-infrared data in regions without the influence of massive stars. The new catalog contains 2980 YSOs, which were classified based on the de-reddened mid-infrared spectral index into 188 protostars, 185 flat-spectrum sources, and 2607 pre-main-sequence stars with circumstellar disks. We find a statistically significant difference in the spatial distribution of the three evolutionary classes with respect to regions of high dust column-density, confirming that flat-spectrum sources are at a younger evolutionary phase compared to Class IIs, and are not a sub-sample seen at particular viewing angles.

scholarly journals The VMC survey – XXXIV. Morphology of stellar populations in the Magellanic Clouds

2019 ◽  
Vol 490 (1) ◽  
pp. 1076-1093 ◽  
Author(s):  
Dalal El Youssoufi ◽  
Maria-Rosa L Cioni ◽  
Cameron P M Bell ◽  
Stefano Rubele ◽  
Kenji Bekki ◽  
...  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Stellar Populations ◽  
Magellanic Clouds ◽  
Main Sequence Stars ◽  
Spiral Arms ◽  
Star Forming ◽  
Star Forming Regions ◽  
Tidal Interactions ◽  
Using Data

ABSTRACT The Magellanic Clouds are nearby dwarf irregular galaxies whose morphologies show different properties when traced by different stellar populations, making them an important laboratory for studying galaxy morphologies. We study the morphology of the Magellanic Clouds using data from the Visible and Infrared Survey Telescope for Astronomy survey of the Magellanic Clouds system. We used about 10 and 2.5 million sources across an area of ∼105 and ∼42 deg2 towards the Large and Small Magellanic Cloud (LMC and SMC), respectively. We estimated median ages of stellar populations occupying different regions of the near-infrared (J − Ks, Ks) colour–magnitude diagram. Morphological maps were produced and detailed features in the central regions were characterized for the first time with bins corresponding to a spatial resolution of 0.13 kpc (LMC) and 0.16 kpc (SMC). In the LMC, we find that main-sequence stars show coherent structures that grow with age and trace the multiple spiral arms of the galaxy, star-forming regions become dimmer as we progress in age, while supergiant stars are centrally concentrated. Intermediate-age stars, despite tracing a regular and symmetrical morphology, show central clumps and hints of spiral arms. In the SMC, young main-sequence stars depict a broken bar. Intermediate-age populations show signatures of elongation towards the Magellanic Bridge that can be attributed to the LMC–SMC interaction ∼200 Myr ago. They also show irregular central features suggesting that the inner SMC has also been influenced by tidal interactions.

scholarly journals A Near-Infrared Imaging Survey of the Lupus 3 Dark Cloud: A Modest Cluster of Low-Mass, Pre–Main-Sequence Stars

2000 ◽  
Vol 119 (2) ◽  
pp. 873-881 ◽  
Author(s):  
Yasushi Nakajima ◽  
Motohide Tamura ◽  
Yumiko Oasa ◽  
Tadashi Nakajima
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Main Sequence Stars ◽  
Near Infrared Imaging ◽  
Dark Cloud ◽  
Low Mass

scholarly journals A Comparative Anatomy of Dusty Disks Imaged by NICMOS

2004 ◽  
Vol 202 ◽  
pp. 308-315
Author(s):  
Glenn Schneider ◽  
Dean C. Hines ◽  
Murray Silverstone ◽  
Alycia J. Weinberger ◽  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Comparative Anatomy ◽  
Scattered Light ◽  
Infrared Camera ◽  
Main Sequence Stars ◽  
Spatially Resolved ◽  
T Tauri ◽  
Dusty Disks

Using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope we have conducted a coronagraphic imaging survey of 18 main sequence stars with large infrared excesses, searching for circumstellar dust (debris) in scattered light. Dusty disks with radial and hemispheric brightness anisotropies and complex morphologies, both possibly indicative of dynamical interactions with unseen planetary mass companions, were spatially resolved and imaged around three young (≲ 10Myr old) stars. From these observations we describe the debris systems around: a) HR 4796A (A0V), a 70 AU radius ring less than 14 AU wide with unequal ansal flux densities; b) HD 141569A (Herbig Ae/Be), a 400 AU radius disk with a 40 AU wide gap; and c) TW Hya (K7 T-Tauri), a pole-on circularly symmetric disk with a radial break in its surface density of scattering particles. Additionally, our non-detection of scattered light and high precision photometry of a fourth system of similar age, HD 98800 A/B, coupled with mid and thermal IR measurements, greatly constrain a likely model for the debris about the B component.

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