Absolute Dimensions and Evolutionary Status of the Semi-detached Algol W Ursae Minoris

In order to check the evolutionary status and theoretical models of eclipsing binaries of Algol type, a reliable determination of their absolute dimensions is needed. In this communication, we compare the most commonly used methods to derive absolute parametors in single-lined aclipsing binaries. Let us first assume that the mass function, f(m), is known from the analysis of the radial velocity curve while the relative radii and orbital inclination are derived from the light curve. The determination of absolute parameters is then equivalent to the obtention of the mass ratio, q = m2/m1. The following methods are available to estimate q from observed parameters — over-all errors being estimated for observational uncertainties of the order of 5 % in relative radii and temperatures and 15 % in f(m) —:1.qs: It is assumed that the primary component follows the mass-luminosity relation for main-sequence stars. This procedure provides qs with an uncertainty of about 10 %.2.qsD: It is assumed that the secondary component fills its Roche lobe. Errors of at least 15 to 20 % are expected from this procedure mainly due to its high sensitivity to small variations in the observed value of r2, particularly if r2 > 0.2.Both methods can be used together when f(m) is doubtful, or completely unknown, but errors can not be expected to be better than in case 2.3.qn: It is assumed that the primary component rotates synchronously in a circular orbit. This assumption is difficult to adopt due to the expected transfer of angular momentum through mass transfer and the value of qn is estimated with about 20 to 30 % error.4.qED: It is assumed that the primary component, is well reproduced by standard evolutionary models within the main sequence. Adopting a grid of models for a given chemical composition, an iterative procedure in the log Ti,.–log g plane permits the determination of m1 and thus q. This method is equivalent to (1) but avoids errors due to evolution from the ZAMS to the TAMS, not taken into account in the previous method, and allows to reach a higher accuracy, around 5 %, except for those primary stars located around the TAMS, where the determination of mi is not unique.

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Gaia DR2 data and the evolutionary status of eight high-velocity hot post-AGB candidates

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psaa097 ◽

2020 ◽

Vol 72 (6) ◽

Author(s):

Mudumba Parthasarathy ◽

Tadafumi Matsuno ◽

Wako Aoki

Keyword(s):

Effective Temperature ◽

High Velocity ◽

Circumstellar Dust ◽

Evolutionary Status ◽

Agb Stars ◽

Horizontal Branch ◽

Dust Shells ◽

The Past ◽

Gaia Dr2 ◽

Branch Star

Abstract From Gaia DR2 data of eight high-velocity hot post-AGB candidates, LS 3593, LSE 148, LS 5107, HD 172324, HD 214539, LS IV −12 111, LS III +52 24, and LS 3099, we found that six of them have accurate parallaxes which made it possible to derive their distances, absolute visual magnitudes (MV) and luminosity (log L/L⊙). All the stars except LS 5107 have an accurate effective temperature (Teff) in the literature. Some of these stars are metal poor, and some of them do not have circumstellar dust shells. In the past, the distances of some stars were estimated to be 6 kpc, which we find to be incorrect. The accurate Gaia DR2 parallaxes show that they are relatively nearby, post-AGB stars. When compared with post-AGB evolutionary tracks we find their initial masses to be in the range 1 M⊙ to 2 M⊙. We find the luminosity of LSE 148 to be significantly lower than that of post-AGB stars, suggesting that this is a post-horizontal-branch star or post-early-AGB star. LS 3593 and LS 5107 are new high-velocity hot post-AGB stars from Gaia DR2.

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Twin stars as tracers of binary evolution in the Kepler era

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab343 ◽

2021 ◽

Author(s):

Sara Bulut ◽

Baris Hoyman ◽

Ahmet Dervisoglu ◽

Orkun Özdarcan ◽

Ömür Cakilrli

Keyword(s):

High Resolution ◽

Internal Structure ◽

Spectroscopic Analysis ◽

Independent Method ◽

Eclipsing Binaries ◽

Physical Parameters ◽

Evolutionary Status ◽

Mass Ratio ◽

Orbital Parameters ◽

Binary Evolution

Abstract We present results of the combined photometric and spectroscopic analysis of four systems, which are eclipsing binaries with a twin–component (mass ratio q ≃ 1). These are exceptional tools to provide information for probing the internal structure of stars. None of the systems were previously recognized as twin binaries. We used a number of high–resolution optical spectra to calculate the radial velocities and later combined them with photometry to derive orbital parameters. Temperatures and metallicities of systems were estimated from high-resolution spectra. For each binary, we obtained a full set of orbital and physical parameters, reaching precision below 3 per cent in masses and radii for whole pairs. By comparing our results with PARSEC and MIST isochrones, we assess the distance, age and evolutionary status of the researched objects. The primary and/or secondary stars of EPIC 216075815 and EPIC 202843107 are one of the cases where asteroseismic parameters of δ Sct and γ Dor pulsators were confirmed by an independent method and rare examples of the twin–eclipsing binaries, therefore the following analyses and results concern the pulsating nature of the components.

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Colloquial features in Word Englishes

International Journal of Corpus Linguistics ◽

10.1075/ijcl.18.4.02col ◽

2013 ◽

Vol 18 (4) ◽

pp. 479-505 ◽

Cited By ~ 12

Author(s):

Peter Collins ◽

Xinyue Yao

Keyword(s):

Twentieth Century ◽

American English ◽

World Englishes ◽

Evolutionary Status ◽

First Person ◽

Functional Interpretation ◽

Person Plural ◽

World English ◽

First Person Plural ◽

Grammatical Change

A powerful discourse-pragmatic agent of grammatical change in English since the mid-twentieth century has been the increasing acceptance of colloquialism. Little is known, however, about its influence on grammatical developments in regional varieties of World English other than the two inner circle ‘supervarieties’, British and American English. This paper reports findings from a corpus-based study of three grammatical categories known to be undergoing a colloquialism-related rise in contemporary English, across a range of registers in ten World Englishes: quasi-modals (have to, have got to, be going to, want to), get-passives, and first person plural inclusive let’s. In each case comparisons are drawn with non-colloquial variants: modals (must, should, will, shall), be-passives, and let us. Subsequent functional interpretation of the data is used to explore the effect upon the quantitative patterns identified of the phenomenon of colloquialism and of further factors with which it interacts (including Americanism, prescriptivism, and evolutionary status).

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Ultralong-period Cepheids: a possible primary distance indicator?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312021552 ◽

2012 ◽

Vol 8 (S289) ◽

pp. 282-286 ◽

Cited By ~ 2

Author(s):

G. Fiorentino ◽

F. Annibali ◽

G. Clementini ◽

R. Contreras Ramos ◽

M. Marconi ◽

...

Keyword(s):

Spiral Galaxies ◽

Hubble Space Telescope ◽

Hubble Constant ◽

Variable Stars ◽

Evolutionary Status ◽

Stellar Systems ◽

Classical Cepheids ◽

Type Ia ◽

Distance Indicator ◽

Crucial Test

AbstractWe present a project that aims to provide a complete theoretical and observational framework for an as yet unexplored class of variable stars, the ultralong-period Cepheids (P longer than 80–100 days). Given their very high luminosities (MV up to −7 mag), with the Hubble Space Telescope we will be able to observe them easily in stellar systems located at large distances (~ 100 Mpc). This limit will be further increased, out to the Hubble flow (~ 350 Mpc), using future ground-based facilities such as the European Extremely Large Telescope. The nature of their pulsation is as yet unclear, as is their evolutionary status, which seems different from the central helium-burning phase generally associated with classical Cepheids. These objects have been found to cover a very large metallicity range, from [Fe/H] ~ −2 dex to solar values, and they are located in heterogeneous stellar systems, from dwarf to spiral galaxies. Once completely characterized, they could provide a crucial test, since they have been found in all Type Ia supernova host spiral galaxies that have been monitored for variability over long periods and that currently offer sound constraints on the estimated value of the Hubble constant.

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Cytogenetic evaluation of two species of Cynanchum L. (Apocynaceae) from South India: A possible clue to evolution

Phytotaxa ◽

10.11646/phytotaxa.357.3.4 ◽

2018 ◽

Vol 357 (3) ◽

pp. 198 ◽

Cited By ~ 1

Author(s):

NEETHU KANNAN B. ◽

JOHN E. THOPPIL

Keyword(s):

Image Analysis ◽

South India ◽

Preparation Method ◽

Chromosome Count ◽

Evolutionary Status ◽

Image Analysis System ◽

Squash Preparation ◽

Karyotypic Formula ◽

Karyotype Formula ◽

Analysis System

The present study evaluates the chromosome count as well as the karyomorphological analysis of two species of Cynanchum L. (Apocynaceae) viz., C. viminale and C. sarcomedium. In order to investigate cytogenetic variation in Cynanchum species, mitotic squash preparation method was employed. Image analysis system and micro-measure software (AutoCad) were used to provide cytogenetic parameter measurements of karyotypes. The two plant species possess the same diploid (2n = 22) and haploid (n = 11) chromosome numbers and they are differentiated by their karyotype formula and quantitative parameters of the karyotypes. The karyotypic formula of C. viminale and C. sarcomedium are 22 nm and 16 nm + 6 nsm (-) respectively. Various karyomorphometric parameters or indices revealed the evolutionary status of the two species as primitive.

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Singular agreement in there-existentials

English World-Wide ◽

10.1075/eww.33.1.03col ◽

2012 ◽

Vol 33 (1) ◽

pp. 53-68 ◽

Cited By ~ 13

Author(s):

Peter Collins

Keyword(s):

Indirect Evidence ◽

World Englishes ◽

Relative Influence ◽

Evolutionary Status ◽

The Subject ◽

Characteristic Style ◽

Selection Of

The phenomenon of “singular agreement” (“SA”) in there-existentials — the combination of a plural post-verbal notional subject and a singular verb — has been the subject of a number of studies which have confirmed its covariation with a range of social, stylistic and grammatical factors. Whereas the focus of most such studies has been on the relative influence of these factors, that of the present study is on the nature and frequency of SA across (a selection of eight) World Englishes. Beginning with the assumption, for which there is indirect evidence in the literature, that SA is on the rise in contemporary English, an attempt is made to relate the degree of advancement of the eight varieties to their evolutionary status and characteristic style orientations.

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V 3903 Sagitarii: A Main-Sequence (07V+09V) Detached Eclipsing Binary

International Astronomical Union Colloquium ◽

10.1017/s025292110001808x ◽

1993 ◽

Vol 137 ◽

pp. 371-373

Author(s):

L.P.R. Vaz ◽

N.C.S. Cunha ◽

E.F. Vieira ◽

M.L.M. Myrrha

Keyword(s):

Main Sequence ◽

Eclipsing Binary ◽

Spectroscopic Observations ◽

Photometric And Spectroscopic Observations ◽

Absolute Dimensions

AbstractPhotometric and spectroscopic observations of V3903 Sgr are analyzed, and absolute dimensions (masses and radii) are determined to a precision better then 3%.

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The evolutionary status of protostellar clumps hosting class II methanol masers

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa233 ◽

2020 ◽

Vol 493 (2) ◽

pp. 2015-2041 ◽

Cited By ~ 1

Author(s):

B M Jones ◽

G A Fuller ◽

S L Breen ◽

A Avison ◽

J A Green ◽

...

Keyword(s):

Galactic Plane ◽

Dust Emission ◽

Principal Component ◽

Far Infrared ◽

Class Ii ◽

Young Stellar Objects ◽

Galactic Centre ◽

Evolutionary Status ◽

Methanol Maser ◽

Methanol Masers

ABSTRACT The Methanol MultiBeam survey (MMB) provides the most complete sample of Galactic massive young stellar objects (MYSOs) hosting 6.7 GHz class II methanol masers. We characterize the properties of these maser sources using dust emission detected by the Herschel Infrared Galactic Plane Survey (Hi-GAL) to assess their evolutionary state. Associating 731 (73 per cent) of MMB sources with compact emission at four Hi-GAL wavelengths, we derive clump properties and define the requirements of an MYSO to host a 6.7 GHz maser. The median far-infrared (FIR) mass and luminosity are 630 M⊙ and 2500 L⊙ for sources on the near side of Galactic centre and 3200 M⊙ and 10000 L⊙ for more distant sources. The median luminosity-to-mass ratio is similar for both at ∼4.2 L⊙ M⊙−1. We identify an apparent minimum 70 μm luminosity required to sustain a methanol maser of a given luminosity (with $L_{70} \propto L_{6.7}\, ^{0.6}$). The maser host clumps have higher mass and higher FIR luminosities than the general Galactic population of protostellar MYSOs. Using principal component analysis, we find 896 protostellar clumps satisfy the requirements to host a methanol maser but lack a detection in the MMB. Finding a 70 μm flux density deficiency in these objects, we favour the scenario in which these objects are evolved beyond the age where a luminous 6.7 GHz maser can be sustained. Finally, segregation by association with secondary maser species identifies evolutionary differences within the population of 6.7GHz sources.

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