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 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 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 Long-term Photometric Monitoring of Cool Hydrogen-deficient Carbon Stars

1995 ◽  
Vol 155 ◽  
pp. 431-432
Author(s):  
P.L. Cottrell ◽  
A.C. Gilmore ◽  
P.M. Kilmartin ◽  
W.A. Lawson
Keyword(s):  
Large Amplitude ◽  
Stellar Atmospheres ◽  
Light Curves ◽  
Maximum Light ◽  
Stellar Nucleosynthesis ◽  
Grain Formation ◽  
The Galaxy ◽  
Photometric Monitoring ◽  
Low Amplitude

Interest in the hydrogen-deficient carbon (HdC) stars, and the R Coronae Borealis (RCB) stars in particular, has been rekindled by the realisation that these stars provide the potential for testing models in a number of areas. These include: pulsation theory; grain formation; grain evolution; stellar nucleosynthesis and extended stellar atmospheres.Observational work on these objects has increased dramatically over the last 10 years. This has included both spectroscopic and photometric projects, see Lambert & Rao (1994) and Lawson et al. (1990).We have continued to observe a number of the cool HdC stars in the Galaxy and the LMC and now have light curves exceeding 2000 days in duration for many of these objects. In particular, we are observing the RCB stars to investigate both the low amplitude, pulsation-related variations present at maximum light and the photometric behaviour during the large amplitude declines.

scholarly journals A Spectroscopic and Photometric Study of the Shell Star EW Lac

2000 ◽  
Vol 175 ◽  
pp. 554-557
Author(s):  
Huilai Cao ◽  
Zhongwei Li ◽  
Lin Huang ◽  
Yulian Guo
Keyword(s):  
Active Phase ◽  
Anomalous Behavior ◽  
Absorption Lines ◽  
Photometric Study ◽  
Short Term ◽  
Photometric Observations ◽  
Shell Star

AbstractWe report on combined spectroscopic and photometric observations of EW Lac during its outburst of 1983. At this time the star’s Hα and Hβ lines showed strong doubled-peaked emission profiles which were variable with time. UBV photometry exhibited a long-term and frequent erratic short-term variations. The amplitude of U, B and V variations reached about 0.3 magnitude on October 15, 1983. Both Hβ emission and the structure of the shell absorption lines of the star also displayed anomalous behavior in 1983. It is evident that this star was in a strong active phase at that time.

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.

scholarly journals Photometric Monitoring Of The Lensed QSO 0957+561

1996 ◽  
Vol 173 ◽  
pp. 53-54
Author(s):  
D. Sinachopoulos ◽  
M. Burger ◽  
E. van Dessel ◽  
M. Geffert ◽  
M. Thibor ◽  
...  
Keyword(s):  
Time Delay ◽  
Gravitational Lens ◽  
Large Field ◽  
Photometric Study ◽  
First Results ◽  
Photometric Monitoring

We present our first results of a photometric monitoring project of the twin quasar 0957+561. This project aims mainly at the improvement of the determination of the time delay ΔT(A,B) for this gravitational lens, since the “time delay controversy on QSO 0957+561 (is) not yet decided” (Pelt et al. 1994). In addition, the quite large field of the CCD used allows also a long-term astrometric and photometric study of stars and galaxies in the field within a radius of about 10 arcminutes around the lens.

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 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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