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 Optical light curves of FUor and FUor-like objects

2016 ◽  
Vol 12 (S325) ◽  
pp. 266-269
Author(s):  
Evgeni Semkov ◽  
Stoyanka Peneva ◽  
Sunay Ibryamov
Keyword(s):  
Light Curve ◽  
Photographic Plate ◽  
Light Curves ◽  
Curve Shape ◽  
Photometric Study ◽  
Maximum Light ◽  
Photometric Observations ◽  
Rate Of Increase ◽  
Photometric Monitoring

AbstractUsing recent data from photometric monitoring and data from the photographic plate archives we aim to study, the long-term photometric behavior of FUors. 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. Our CCD photometric observations were performed with the telescopes of the Rozhen (Bulgaria) and Skinakas (Crete, Greece) observatories. Most suitable for long-term photometric study are the plate archives of the big Schmidt telescopes, as the telescopes at Kiso Observatory, Asiago Observatory, Palomar Observatory and others. In comparing our results with light curves of the well-studied FUors, we conclude that every new FUor 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 Long-term optical photometric monitoring of the FUor star V900 Mon

2021 ◽  
pp. 31-38
Author(s):  
E.H. Semkov ◽  
S.P. Peneva ◽  
S.I. Ibryamov
Keyword(s):  
Stellar Evolution ◽  
Stellar Magnitude ◽  
Photometric Data ◽  
Light Curves ◽  
Pass Band ◽  
Archival Data ◽  
Space Telescopes ◽  
History Of ◽  
Photometric Monitoring

We present results from photometric monitoring of V900 Mon, one of the newly discovered and still under-studied object from the FU Orionis type. The FUor phenomenon is very rarely observed, but it is essential for stellar evolution. Since we only know about twenty stars of this type, the study of each new object is very important for our knowledge. Our data were obtained in optical spectral region with the BVRI Johnson-Cousins set of filters during the period from September 2011 to April 2021. In order to follow the photometric history of the object, we measured its stellar magnitudes on available plates from the Mikulski Archive for Space Telescopes. The collected archival data suggest that the rise in brightness of V900 Mon began after January 1989 and the outburst goes on so far. In November 2009, when the outburst was registered, the star had already reached the level of brightness close to the current one. Our observations indicate that during the period 2011-2017 the stellar magnitude increased gradually in each pass band. The observed amplitude of the outburst is about 4 magnitudes (R). During the last three years, the increase in brightness has stopped and there has even been a slight decline. The comparison of light curves of the known FUor objects shows that they are very diverse and are rarely repeated. However, the photometric data we have so far show that V900 Mon's light curve is somewhat similar to those of V1515 Cyg and V733 Cep.

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 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 Long rotation period main-sequence stars from Kepler SAP light curves

2019 ◽  
Vol 489 (4) ◽  
pp. 5513-5529 ◽  
Author(s):  
Kaiming Cui ◽  
Jifeng Liu ◽  
Shuhong Yang ◽  
Qing Gao ◽  
Huiqin Yang ◽  
...  
Keyword(s):  
Light Curve ◽  
Main Sequence ◽  
Rotation Period ◽  
Light Curves ◽  
Stellar Rotation ◽  
Main Sequence Stars ◽  
Found Objects ◽  
Period Detection ◽  
Search Data

ABSTRACT Stellar rotation plays a key role in stellar activity. The rotation period could be detected through light curve variations caused by star-spots. Kepler provides two types of light curves: one is the Pre-search Data Conditioning (PDC) light curves, and the other is the Simple Aperture Photometer (SAP) light curves. Compared with the PDC light curves, the SAP light curves keep the long-term trend, relatively suitable for searches of long-period signals. However, SAP data are inflicted by some artefacts such as quarterly rolls and instrumental errors, making it difficult to find the physical periods in the SAP light curves. We explore a systematic approach based on the light curve pre-processing, period detection, and candidate selection. We also develop a simulated light curve test to estimate our detection limits for the SAP-like LCs. After applying our method to the raw SAP light curves, we found more than 1000 main-sequence stars with periods longer than 30 d; 165 are newly discovered. Considering the potential flaw of the SAP, we also inspect the newly found objects with photometry methods, and most of our periodical signals are confirmed.

scholarly journals Properties of CVSO 30 from TESS measurements: probably a binary T Tauri star with complex light curves and no obvious planets

2020 ◽  
Vol 494 (3) ◽  
pp. 4349-4356
Author(s):  
C Koen
Keyword(s):  
Light Curve ◽  
Small Group ◽  
T Tauri Stars ◽  
Light Curves ◽  
Tauri Star ◽  
Curve Shape ◽  
T Tauri

ABSTRACT ‘Transiting Exoplanet Survey Satellite’ (TESS) photometry of CVSO 30 spanned 21.8 d, with a single large gap of 1.1 d. This allows alias-free determination of the two periodicities in the data. It is confirmed that both of these are non-sinusoidal: the dominant P1 = 0.4990 d has two detectable harmonics and P2 = 0.4486 d has seven. The large number of harmonics in the second periodicity characterizes a very complex light curve shape. One of the features in the light curve is a sharp dip of duration ∼2 h: this is probably the source of the previously claimed planetary transit signature. The star is a member of a small group of T Tauri stars with complex light curves, which have recently been exhaustively studied using Kepler and TESS observations. The two non-commensurate periods are most simply interpreted as being from two stars, i.e. CVSO 30 is probably a binary.

Period-Luminosity-Shape of Light Curve Relation for Cepheids in LMC and SMC

2005 ◽  
Vol 201 ◽  
pp. 480-481
Author(s):  
P. Ligeza ◽  
P. Moskalik ◽  
A. Schwarzenberg-Czerny
Keyword(s):  
Light Curve ◽  
Principal Components Analysis ◽  
Principal Components ◽  
Fundamental Mode ◽  
Light Curves ◽  
Analysis Of Covariance ◽  
Curve Shape ◽  
Long Period ◽  
Classical Cepheids ◽  
Components Analysis

In this paper we report our analysis of the period-luminosity-shape of light curve (P-L-S) relation. The data we used came from LMC and SMC Cepheid light curves produced by OGLE-II microlensing survey. We used Principal Components Analysis of covariance matrix of the sets for Cepheids in LMC and SMC separately. Our calibrating set was bounded to long period classical Cepheids pulsating in fundamental mode. The results are used to derive a method for estimation of distances from light curve shape.

scholarly journals Supersoft X-ray phases of recurrent novae as an indicator of their white dwarf masses

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Mariko Kato ◽  
Izumi Hachisu
Keyword(s):  
Light Curve ◽  
White Dwarf ◽  
Total Duration ◽  
Simple Relation ◽  
Light Curves ◽  
Curve Shape ◽  
Plateau Phase ◽  
Hydrogen Burning ◽  
X Ray ◽  
Recurrent Nova

Abstract We have examined the optical/X-ray light curves of seven well-observed recurrent novae, V745 Sco, M31N 2008-12a, LMC N 1968, U Sco, RS Oph, LMC N 2009a, T Pyx, and one recurrent nova candidate LMC N 2012a. Six novae out of the eight show a simple relation that the duration of supersoft X-ray source (SSS) phase is 0.70 times the total duration of the outburst (= X-ray turnoff time), i.e., tSSS = 0.70 toff, the total duration of which ranges from 10 to 260 d. These six recurrent novae show a broad rectangular X-ray light curve shape, the first half-period of which is highly variable in the X-ray count rate. The SSS phase also corresponds to an optical plateau phase that indicates a large accretion disk irradiated by a hydrogen-burning white dwarf (WD). The two other recurrent novae, T Pyx and V745 Sco, show a narrow triangular-shaped X-ray light curve without an optical plateau phase. Their relations between tSSS and toff are rather different from the above six recurrent novae. We also present theoretical SSS durations for recurrent novae with various WD masses and stellar metallicities (Z = 0.004, 0.01, 0.02, and 0.05) and compare them with the observed durations of these recurrent novae. We show that SSS duration is a good indicator of WD mass in recurrent novae with a broad rectangular X-ray light curve shape.

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 Structure of the Gaseous Disk in RX Cas

1980 ◽  
Vol 88 ◽  
pp. 269-270
Author(s):  
S. Kříž
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
Bright Spot ◽  
Period Increase ◽  
Long Period ◽  
Short Period ◽  
Observational Errors ◽  
The Times ◽  
Image Position

RX Cas appers to be a long-period Algol-like binary with very fast mass exchange (Struve 1944). In the period 1975-1977, this star was observed photometrically by Arsenijevič, Grygar, Harmanec, Horn, Koubský, Kříž and Pavlovski at Hvar Observatory (Yugoslavia) and by Zverko at Skalnaté Pleso Observatory (Czechoslovakia). The resulting UBV light curves seem to be rather peculiar, for the following reasons:1) Combining our observations with the older ones, we obtain the following formula for the times of minima: The period increase is surprisingly high.2) The scatter of observed points is considerable (about 0.2 mag.) and cannot be caused by observational errors. It corresponds to short period light variations on the time scale of several days.3) After J.D. 24422660, the brightness of the whole system decreased in all colours. This decrease is about 0.2 mag. in V colour and 0.5 mag. in U colour. Only after J.D. 2442900 the brightness increased again. Such a behaviour confirms the reality of old observations by Gaposchkin (1944) and Martynov (1950) who found a long-term light variation with a period of approximately 500 days.4) The part of the light curve around the phase 0.75 is definitely much lower than the corresponding part around the phase 0.25. This effect is most pronounced in the ultraviolet; the depression around the phase 0.75 is much deeper than the secondary minimum. This behaviour is opposite to the behaviour of dwarf novae. Instead of a bright shoulder connected with a bright spot, we observe some darkening.

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