scholarly journals Using Source Proper Motion to Validate Terrestrial Parallax: OGLE-2019-BLG-1058

2021 ◽  
Vol 162 (6) ◽  
pp. 267
Author(s):  
In-Gu Shin ◽  
Jennifer C. Yee ◽  
Kyu-Ha Hwang ◽  
Andrzej Udalski ◽  
Andrew Gould ◽  
...  
Keyword(s):  
Direct Measurement ◽  
Proper Motion ◽  
Precise Measurement ◽  
Mass Star ◽  
Supporting Evidence ◽  
Single Source ◽  
Single Lens ◽  
Low Mass ◽  
The Mean

Abstract We show that because the conditions for producing terrestrial microlens parallax (TPRX; i.e., a nearby disk lens) will also tend to produce a large lens-source relative proper motion (μ rel), source proper motion ( μ S) measurements in general provide a strong test of TPRX signals, which Gould & Yee (2013) showed were an important probe of free-floating planet (FFP) candidates. As a case study, we report a single-lens/single-source microlensing event designated as OGLE-2019-BLG-1058. For this event, the short timescale (∼2.5 days) and very fast μ rel (∼17.6 mas yr−1) suggest that this isolated lens is an FFP candidate located in the disk of our Galaxy. For this event, we find a TPRX signal consistent with a disk FFP, but at low significance. A direct measurement of the μ S shows that the large μ rel is due to an extreme μ S, and thus, the lens is consistent with being a very-low-mass star in the bulge and the TPRX measurement is likely spurious. By contrast, we show how a precise measurement of μ S with the mean properties of the bulge proper motion distribution would have given the opposite result; i.e., provided supporting evidence for an FFP in the disk and the TPRX measurement.

scholarly journals Discovery of a Tight Brown Dwarf Companion to the Low Mass Star LHS 2397a

2003 ◽  
Vol 211 ◽  
pp. 261-264 ◽  
Author(s):  
Melanie Freed ◽  
Laird M. Close ◽  
Nick Siegler
Keyword(s):  
Adaptive Optics ◽  
Spectral Type ◽  
Proper Motion ◽  
Near Infrared ◽  
Mass Star ◽  
Infrared Photometry ◽  
Brown Dwarf ◽  
Dynamical Mass ◽  
Low Mass ◽  
Adaptive Optics System

Using the adaptive optics system, Hōkūpa'a, at Gemini-North, we have directly imaged a companion around the UKIRT faint standard M8 star, LHS 2397a (FS 129) at a separation of 2.96 AU. Near-Infrared photometry obtained on the companion has shown it to be an L7.5 brown dwarf and confirmed the spectral type of the primary to be an M8. We also derive a substellar mass of the companion of 0.068M⊙, although masses in the range (0.061 – 0.069) are possible, and the primary mass as 0.090M⊙ (0.089 – 0.094). Reanalysis of archival imaging from HST has confirmed the secondary as a common proper motion object. This binary represents the first clear example of a brown dwarf companion within 4 AU of a low mass star, and should be the first L7.5 to have a dynamical mass. As part of a larger survey of M8-M9 stars, this object may indicate that there is no “brown dwarf desert” around low mass primaries.

scholarly journals Evolutionary Models of RR Lyrae Stars

1993 ◽  
Vol 139 ◽  
pp. 294-303
Author(s):  
Young-Wook Lee
Keyword(s):  
Variable Stars ◽  
Mass Star ◽  
Supporting Evidence ◽  
Evolutionary Models ◽  
Rr Lyrae Stars ◽  
Cosmological Distance Scale ◽  
Rr Lyrae ◽  
Low Mass ◽  
Lyrae Stars ◽  
Distance Indicators

As tracers of old stellar populations and as primary Population II standard candles, RR Lyrae stars have played an important role in the development of modern astronomy. Our knowledge of stellar evolution has identified these variable stars in a core helium burning phase of low-mass star evolution, the hoiizontal-branch (HB) phase. Consequently, not only to understand fully the nature of RR Lyrae stars, but also to apply them correctly as population probes and distance indicators, we must understand the underlying evolutionary effect of HB stars.In this paper, I briefly review the most important properties of RR Lyrae stars predicted from the HB evolutionary models, and present many pieces of supporting evidence for these models. For the implications of these models on the chronology of the Galactic formation and on the cosmological distance scale, the reader is referred to several recent publications by Lee (1992a,b,c,d).

scholarly journals A low-mass triple system with a wide L/T transition brown dwarf component: NLTT 51469AB/SDSS 2131−0119

2019 ◽  
Vol 487 (1) ◽  
pp. 1149-1159 ◽  
Author(s):  
B Gauza ◽  
V J S Béjar ◽  
A Pérez-Garrido ◽  
N Lodieu ◽  
R Rebolo ◽  
...  
Keyword(s):  
Spectral Type ◽  
Proper Motion ◽  
Near Infrared ◽  
Close Binary ◽  
Mass Star ◽  
X Rays ◽  
Brown Dwarf ◽  
Uv Excess ◽  
Low Mass ◽  
Gaia Dr2

Abstract We demonstrate that the previously identified L/T transition brown dwarf SDSS J213154.43−011939.3 (SDSS 2131−0119) is a widely separated (82${^{\prime\prime}_{.}}$3, ∼3830 au) common proper motion companion to the low-mass star NLTT 51469, which we reveal to be a close binary itself, separated by 0${^{\prime\prime}_{.}}$64 ± 0${^{\prime\prime}_{.}}$01 (∼30 au). We find the proper motion of SDSS 2131−0119 of μαcos δ = −100 ± 20 mas yr−1 and μδ = −230 ± 20 mas yr−1 consistent with the proper motion of the primary provided by Gaia DR2: μαcos δ = −95.49 ± 0.96 mas yr−1 and μδ = −239.38 ± 0.96 mas yr−1. Based on optical and near-infrared spectroscopy, we classify the primary NLTT 51469A as an M3 ± 1 dwarf, estimate photometrically the spectral type of its close companion NLTT 51469B at ∼M6, and confirm the spectral type of the brown dwarf to be L9 ± 1. Using radial velocity, proper motion, and parallax, we derived the UVW Galactic space velocities of NLTT 51469A, showing that the system does not belong to any known young stellar moving group. The high V, W velocities, lack of a 670.8 nm Li i absorption line, and absence of H α emission, detected X-rays, or UV excess, indicate that the system is likely a member of the thin disc population and is older than 1 Gyr. For the parallactic distance of 46.6 ± 1.6 pc from Gaia DR2, we determined luminosities of $-1.50^{+0.02}_{-0.04}$ and −4.4 ± 0.1 dex of the M3 and L9, respectively. Considering the spectrophotometric estimation, which yields a slightly lower distance of $34^{+10}_{-13}$ pc, the obtained luminosities are $-1.78^{+0.02}_{-0.04}$ and $-4.7^{+0.3}_{-0.5}$ dex. We also estimated their effective temperatures and masses, and obtained 3410$^{+140}_{-210}$ K and 0.42 ± 0.02 M⊙ for the primary, and 1400–1650 K and 0.05–0.07 M⊙ for the wide companion. For the ∼M6 component, we estimated Teff = 2850 ± 200 K and m = 0.10$^{+0.06}_{-0.01}$ M⊙.

scholarly journals A Case Study of Low‐Mass Star Formation

2008 ◽  
Vol 174 (1) ◽  
pp. 202-222 ◽  
Author(s):  
Jonathan J. Swift ◽  
William J. Welch
Keyword(s):  
Star Formation ◽  
Mass Star ◽  
Low Mass

scholarly journals Preliminary proper motion analysis of the Carina dwarf spheroidal

2007 ◽  
Vol 3 (S248) ◽  
pp. 492-493
Author(s):  
J. L. Carlin ◽  
S. R. Majewski ◽  
D.I. Casetti-Dinescu ◽  
T. M. Girard
Keyword(s):  
Motion Analysis ◽  
Proper Motion ◽  
Precise Measurement ◽  
Proper Motions ◽  
Preliminary Results ◽  
Motion Study ◽  
The Mean ◽  
Absolute Frame

AbstractWe present preliminary results from a proper motion study of the Carina dwarf spheroidal galaxy. Our proper motions show a scatter of ~1.1 mas yr−1 per Carina member star, and we determinate the mean ensemble motion to an accuracy of ~7 mas century−1. While this is a precise measurement of the relative proper motions of Carina members, our correction to an absolute frame is limited by the small number of measured QSOs in the field.

Status of “AGK4” Project

1978 ◽  
Vol 48 ◽  
pp. 527-533
Author(s):  
Chr. de Vegt
Keyword(s):  
Northern Hemisphere ◽  
Proper Motion ◽  
The Mean ◽  
Spectral Bandpass

The present accuracy limit for the majority of fainter stars on the northern hemisphere is set by the AGK2/3-catalogue, recently completely finished, but it should be noted that its epoch is much earlier (1960). Furtheron the AGK3-catalogue is a direct repetition of the AGK2, the plates have been taken with the same astrograph in a broad blue spectral bandpass and measured visually with the same equipment, therefore virtually an instrumental standard of 1930 is realized again. Figure 1 shows the mean errors of the AGK2/3 catalogue positions as a function of magnitude. The best accuracy for the AGK2/3 data is obtained for the stars of about ninth magnitude: 017 (AGK2) and 020 (AGK3) but decreases for the faint stars with mpg11 to 019 (AGK2) and Pg 027 (AGK3). Here the AGK3 data are even less accurate. With increasing distance to the catalogue epochs, the accuracy of positions decreases due to the proper motion errors. In the upper part of figure 2 the dependence of the AGK2/3 catalogue accuracy on time is shown for the faint stars separately and an averaged value.

Impacts of Sample Preparation Methodology on TEM Failure Analysis of Advanced Semiconductor Devices

2011 ◽  
Author(s):  
Yongkai Zhou ◽  
Jie Zhu ◽  
Han Wei Teo ◽  
ACT Quah ◽  
Lei Zhu ◽  
...  
Keyword(s):  
Sample Preparation ◽  
Failure Analysis ◽  
Case Studies ◽  
Thickness Measurement ◽  
Interface Roughness ◽  
Silicide Formation ◽  
Cross Sectional ◽  
Inspection Method ◽  
Low Mass

Abstract In this paper, two failure analysis case studies are presented to demonstrate the importance of sample preparation procedures to successful failure analyses. Case study 1 establishes that Palladium (Pd) cannot be used as pre-FIB coating for SiO2 thickness measurement due to the spontaneously Pd silicide formation at the SiO2/Si interface. Platinum (Pt) is thus recommended, in spite of the Pt/SiO2 interface roughness, as the pre-FIB coating in this application. In the second case study, the dual-directional TEM inspection method is applied to characterize the profile of the “invisible” tungsten residue defect. The tungsten residue appears invisible in the planeview specimen due to the low mass-thickness contrast. It is then revealed in the cross-sectional TEM inspection.

Low‐Mass Star Formation and the Initial Mass Function in IC 348

1998 ◽  
Vol 508 (1) ◽  
pp. 347-369 ◽  
Author(s):  
K. L. Luhman ◽  
G. H. Rieke ◽  
C. J. Lada ◽  
E. A. Lada
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Mass Star ◽  
Low Mass

scholarly journals Factors Influencing Smallholder Crop Diversification: A Case Study of Manicaland and Masvingo Provinces in Zimbabwe

2016 ◽  
Vol 3 (2) ◽  
pp. 1 ◽  
Author(s):  
Lighton Dube
Keyword(s):  
Smallholder Farmers ◽  
Diversity Index ◽  
Tobit Model ◽  
Crop Diversification ◽  
Factors Associated ◽  
Head Of Household ◽  
The Mean ◽  
Female Headed Households ◽  
Extension Support

<p>This study analyzes the degree of crop diversification and factors associated with crop diversification among 479 smallholder farmers in Manicaland and Masvingo provinces of Zimbabwe. The Herfindahl index used to estimate diversification, while the Tobit model evaluated factors associated with crop diversification.  The mean crop diversity index is 0.54. On average households in Nyanga and Bikita are the most diversified with indices of 0.48 and 0.49 respectively. The most specialized households are in Mutasa and Chiredzi with indices of 0.62. An analysis by gender shows that male headed households are slightly more diversified than female headed households. The Tobit model indicates that gender of head of household, education, number of livestock units, access to irrigation, membership to a farmers group, access to markets, farming experience, farms on flat terrain, farmer to farm extension, routine extension, agro-ecological zone and household income are significant contributors to increasing crop diversification. In turn, crop specialization is significantly associated with off-farm employment, soil fertility, farmers who are happy with extension contacts per year, farmers trained using the farmer field school approach and farmers who receive NGO extension support.</p>

scholarly journals MOTION VERIFIED RED STARS (MoVeRS): A CATALOG OF PROPER MOTION SELECTED LOW-MASS STARS FROMWISE, SDSS, AND 2MASS

2016 ◽  
Vol 151 (2) ◽  
pp. 41 ◽  
Author(s):  
Christopher A. Theissen ◽  
Andrew A. West ◽  
Saurav Dhital
Keyword(s):  
Proper Motion ◽  
Low Mass Stars ◽  
Low Mass
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