scholarly journals Evolutionary Changes in LUMINOUS STARS

1998 ◽  
Vol 11 (1) ◽  
pp. 346-346
Author(s):  
E. Zsldos
Keyword(s):  
Light Curve ◽  
19Th Century ◽  
Stellar Evolution ◽  
Colour Change ◽  
Light Curves ◽  
Appreciable Change ◽  
Luminous Blue Variables ◽  
Secular Changes ◽  
Evolutionary Changes ◽  
The 19Th Century

The light curves of luminous stars often show spectacular secular changes which can be connected to stellar evolution. Such events are, e.g. the outbursts of P Cygni in the 17th century and 77 Carinae in the last century. Both stars belong to the Luminous Blue Variables, but these changes are not restricted to blue stars. The light curve of HR 8752 (V509 Cassiopeiae) shows a certain similarity to that of the former two stars. When it was first catalogued in the middle of the 19th century, it had been a 6m star. During 100 years the star showed a secular brightening of lm. A similar yellow hypergiant, p Cassiopeiae produced at least two outbursts this century, though both have smaller amplitudes than it is in the case of the LBVs. Moreover, these yellow variables also have an apparently secular colour change: the B − V colour of HR 8752 is decreasing while that of ρ Cassiopeiae is increasing. In both cases evolutionary changes are possible but one cannot exclude other causes. Besides these well studied stars there are several other yellow hypergiants with promising light curves. One of the most interesting cases seems to be R Puppis, which was discovered to be variable in the last century, but then did not show any appreciable change in the following 70-80 years. In the late 1970s, however, it began to vary once more.

scholarly journals Long-term Photometric Monitoring of FUor and FUor-like Objects

2018 ◽  
pp. 240-248
Author(s):  
E. Semkov ◽  
S. Ibryamov ◽  
S. Peneva ◽  
A. Mutafov
Keyword(s):  
Light Curve ◽  
Significant Role ◽  
Stellar Evolution ◽  
Photographic Plate ◽  
Light Curves ◽  
Curve Shape ◽  
Rate Of Increase ◽  
Fu Ori ◽  
Photometric Monitoring

A phenomenon with a significant role in stellar evolution is the FU Orionis (FUor) type of outburst. The first three (classical) FUors (FU Ori, V1515 Cyg and V1057 Cyg) are well-studied and their light curves are published in the literature. But recently, over a dozen new objects of this type were discovered, whose photometric history we do not know well. Using recent data from photometric monitoring and data from the photographic plate archives we aim to study, the long-term photometric behavior of FUor and FUor-like objects. The construction of the historical light curves of FUors could be very important for determining the beginning of the outburst, the time to reach the maximum light, the rate of increase and decrease in brightness, the pre-outburst variability of the star. So far we have published our results for the light curves of V2493 Cyg, V582 Aur, Parsamian 21 and V1647 Ori. In this paper we present new data that describe more accurate the photometric behavior of these objects. In comparing our results with light curves of the well-studied FUors (FU Ori, V1515 Cyg and V1057 Cyg), we conclude that every object shows different photometric behavior. Each known FUor has a different rate of increase and decrease in brightness and a different light curve shape.

scholarly journals The effect of stellar evolution on the light curves’ shapes of RR Lyrae stars in M3

2004 ◽  
Vol 193 ◽  
pp. 171-175
Author(s):  
Johanna Jurcsik
Keyword(s):  
Light Curve ◽  
Stellar Evolution ◽  
Light Curves ◽  
Horizontal Branch ◽  
Homogeneous Sample ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

AbstractThe light curve characteristics of a homogeneous sample of variables in M3 are studied in detail. Accurate light curves and mean magnitudes of about 100 RRab and 50 RRc stars which do not show any type of modulation are analyzed. According to their mean magnitudes and Fourier parameters the variables can be sorted into four groups, representing different stages of the horizontal branch stellar evolution.

scholarly journals TU Muscae and the Early-type Overcontact Binaries

2002 ◽  
Vol 187 ◽  
pp. 319-323
Author(s):  
Dirk Terrell
Keyword(s):  
Light Curve ◽  
Stellar Evolution ◽  
Spectroscopic Analysis ◽  
Light Curves ◽  
Early Type ◽  
Mass Ratio ◽  
Reflection Effect ◽  
Detailed Treatment

AbstractA simultaneous photometric and spectroscopic analysis of the purported early-type overcontact binary TU Muscae is presented. With a well-behaved light curve and a mass ratio far from unity, if TU Mus is indeed an overcontact system, it presents an interesting challenge for 3-D stellar evolution codes, like the Djehuty code, that will be applied to early-type overcontact binaries. The analysis shows TU Mus is slightly overcontact and that a detailed treatment of the reflection effect is important for modeling the light curves.

scholarly journals Light Curve and Orbital Period Analysis of the Eclipsing Binary AT Peg

2011 ◽  
Vol 7 (S282) ◽  
pp. 55-56
Author(s):  
Alexios Liakos ◽  
Panagiotis Niarchos ◽  
Edwin Budding
Keyword(s):  
Light Curve ◽  
Orbital Period ◽  
Time Effect ◽  
Light Curves ◽  
Period Analysis ◽  
Eclipsing Binary ◽  
Secular Changes ◽  
Photometric Observations ◽  
Photometric Elements

AbstractCCD photometric observations of the Algol-type eclipsing binary AT Peg have been obtained. The light curves are analyzed with modern techniques and new geometric and photometric elements are derived. A new orbital period analysis of the system, based on the most reliable timings of minima found in the literature, is presented and apparent period modulations are discussed with respect to the Light-Time effect (LITE) and secular changes in the system. The results of these analyses are compared and interpreted in order to obtain a coherent view of the system's behaviour.

scholarly journals Pleione as a Variable Star

1976 ◽  
Vol 70 ◽  
pp. 105-106 ◽  
Author(s):  
A. S. Sharov ◽  
V. M. Lyuty
Keyword(s):  
Light Curve ◽  
19Th Century ◽  
Variable Star ◽  
Shell Star ◽  
Photoelectric Observations ◽  
The 19Th Century

The well-known shell star Pleione is also an interesting variable star, BU Tau. Its variability was first discovered by Calder (1937) from photoelectric observations in the 1930's. The light curve of this star from the end of the 19th century to 1954 was studied by Binnendijk (1949, 1955). Botsula and Sharov (1959) and Sharov (1961) added some old and new observations and continued the light curve up to 1959.

scholarly journals Supernova lightCURVE POPulation Synthesis II: Validation against supernovae with an observed progenitor

2019 ◽  
Vol 36 ◽  
Author(s):  
J. J. Eldridge ◽  
N. -Y. Guo ◽  
N. Rodrigues ◽  
E. R. Stanway ◽  
L. Xiao
Keyword(s):  
Light Curve ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Stellar Mass ◽  
Light Curves ◽  
Explosion Energy ◽  
Initial Mass ◽  
Multiple Models ◽  
Population Synthesis ◽  
Single Star

Abstract We use the results of a supernova light-curve population synthesis to predict the range of possible supernova light curves arising from a population of single-star progenitors that lead to type IIP supernovae. We calculate multiple models varying the initial mass, explosion energy, nickel mass and nickel mixing and then compare these to type IIP supernovae with detailed light curve data and pre-explosion imaging progenitor constraints. Where a good fit is obtained to observations, we are able to achieve initial progenitor and nickel mass estimates from the supernova lightcurve that are comparable in precision to those obtained from progenitor imaging. For 2 of the 11 IIP supernovae considered our fits are poor, indicating that more progenitor models should be included in our synthesis or that our assumptions, regarding factors such as stellar mass loss rates or the rapid final stages of stellar evolution, may need to be revisited in certain cases. Using the results of our analysis we are able to show that most of the type IIP supernovae have an explosion energy of the order of log(Eexp/ergs) = 50.52 ± 0.10 and that both the amount of nickel in the supernovae and the amount of mixing may have a dependence on initial progenitor mass.

scholarly journals ANALYSIS OF A SHORT PERIODIC PULSATOR: SX PHOENICIS STAR XX CYG

2020 ◽  
Vol 56 (2) ◽  
pp. 287-294
Author(s):  
Mohamed Abdel-Sabour ◽  
Ahmed Shokry ◽  
Ahmed Ibrahim
Keyword(s):  
Light Curve ◽  
Stellar Evolution ◽  
Light Curves ◽  
Instability Strip ◽  
Maximum Light ◽  
Photometric Observations ◽  
Ccd Observations

Photometric observations were made of the SX Phoenicis star XX Cyg between September and October 2019, using the 1.88-m Kottamia reflector telescope in Egypt. We used 340 CCD observations with blue-visible-red (BVR) filters to derive light curves. In addition, we obtained 9540 visual magnitudes for XX Cyg from the literature to prepare an observed-minus-calculated (O-C) diagram. 85 new times of maximum for XX Cyg are presented. We did not detect a bump in the descending portion of the light curve of maximum light for XX Cyg. However, we did detect a secular bump in the phased light curves, which changes with phase in some SuperWASP observations. We found the change in period of XX Cyg to be dP/dt = 15.5 × 10-5 s/yr, with its amplitude decreasing at a rate of 0.7 mmag/year. Stellar parameters of XX Cyg and its position in the instability strip of the Hertzsprung Russell stellar evolution diagram are presented.

scholarly journals Core-Collape Supernova Progenitors: Light-Curve and Stellar-Evolution Models

2016 ◽  
Vol 12 (S329) ◽  
pp. 25-31
Author(s):  
Melina C. Bersten
Keyword(s):  
Light Curve ◽  
Stellar Evolution ◽  
Light Curves ◽  
Current Understanding ◽  
Explosion Energy ◽  
Core Collapse ◽  
Powerful Method ◽  
Direct Identification ◽  
Normal Core ◽  
Hydrodynamical Modeling

AbstractA very active area of research in the field of core-collapse supernovae (SNe) is the study of their progenitors and the links with different subtypes. Direct identification using pre- and post-SN images is a powerful method but it can only be applied to the most nearby events. An alternative method is the hydrodynamical modeling of SN light curves and expansion velocities, which can serve to characterize the progenitor (e.g. mass and radius) and the explosion itself (e.g. explosion energy and radioactive yields). This latter methodology is particularly powerful when combined with stellar evolution calculations. We review our current understanding of the properties of normal core-collapse SNe based chiefly on these two methods.

The Eclipsing Binary WX Eridani

1979 ◽  
Vol 46 ◽  
pp. 385
Author(s):  
M.B.K. Sarma ◽  
K.D. Abhankar
Keyword(s):  
Light Curve ◽  
Spectral Type ◽  
Orbital Period ◽  
Primary Component ◽  
Light Curves ◽  
Absorption Feature ◽  
Primary Star ◽  
Eclipsing Binary ◽  
The Times ◽  
Phase Angles

AbstractThe Algol-type eclipsing binary WX Eridani was observed on 21 nights on the 48-inch telescope of the Japal-Rangapur Observatory during 1973-75 in B and V colours. An improved period of P = 0.82327038 days was obtained from the analysis of the times of five primary minima. An absorption feature between phase angles 50-80, 100-130, 230-260 and 280-310 was present in the light curves. The analysis of the light curves indicated the eclipses to be grazing with primary to be transit and secondary, an occultation. Elements derived from the solution of the light curve using Russel-Merrill method are given. From comparison of the fractional radii with Roche lobes, it is concluded that none of the components have filled their respective lobes but the primary star seems to be evolving. The spectral type of the primary component was estimated to be F3 and is found to be pulsating with two periods equal to one-fifth and one-sixth of the orbital period.

Grammatical Descriptions in Manchu Grammar Books from the Qing Dynasty

2019 ◽  
Vol 41 (1) ◽  
pp. 39-55
Author(s):  
Takashi Takekoshi
Keyword(s):  
19Th Century ◽  
Qing Dynasty ◽  
The Qing Dynasty ◽  
Chinese Scholars ◽  
High Degree ◽  
The 19Th Century

In this paper, we analyse features of the grammatical descriptions in Manchu grammar books from the Qing Dynasty. Manchu grammar books exemplify how Chinese scholars gave Chinese names to grammatical concepts in Manchu such as case, conjugation, and derivation which exist in agglutinating languages but not in isolating languages. A thorough examination reveals that Chinese scholarly understanding of Manchu grammar at the time had attained a high degree of sophistication. We conclude that the reason they did not apply modern grammatical concepts until the end of the 19th century was not a lack of ability but because the object of their grammatical descriptions was Chinese, a typical isolating language.

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