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.

Can complex T Tauri star light curves be modelled with star-spots?

2020 ◽  
Vol 500 (1) ◽  
pp. 1366-1379
Author(s):  
C Koen
Keyword(s):  
Ridge Regression ◽  
Young Stars ◽  
Light Curves ◽  
Stellar Surface ◽  
Tauri Star ◽  
T Tauri ◽  
Almost All

ABSTRACT ‘Transiting Exoplanet Survey Satellite’ photometry of 10 young stars with very complex periodic light curves is considered. Previous findings that these cannot be due to dark surface spots are re-evaluated by allowing arbitrarily shaped areas on the stellar surface to have sub-photospheric fluxes. This is done by approximating flux integrals by sums over surface elements. The unknown ratios of spot to photospheric fluxes are determined by lasso or ridge regression procedures. It is found that almost all light curves can be modelled very accurately in this way. The usual, if rarely stated, caveat applies – star-spot models presented in the paper are not unique.

scholarly journals New Data on the Eclipsing Binary V1848 Ori and Improved Orbital and Light Curve Solutions

2020 ◽  
Vol 29 (1) ◽  
pp. 72-80 ◽  
Author(s):  
Fatemeh Davoudi ◽  
Atila Poro ◽  
Fahri Alicavus ◽  
Afshin Halavati ◽  
Saeed Doostmohammadi ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Mass Function ◽  
Light Curves ◽  
Complete Analysis ◽  
Physical Parameters ◽  
Mass Ratio ◽  
Third Body ◽  
Eclipsing Binary

AbstractNew observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system’s orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f (m3) = 0.0058 M⊙ in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O’Connell effect was not seen in the light curve and there is no need to add spot.

scholarly journals Variability of young stars: Determination of rotational periods of weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region

2009 ◽  
Vol 330 (5) ◽  
pp. 482-492
Author(s):  
A. Koeltzsch ◽  
M. Mugrauer ◽  
St. Raetz ◽  
T.O.B. Schmidt ◽  
T. Roell ◽  
...  
Keyword(s):  
T Tauri Stars ◽  
Young Stars ◽  
Weak Line ◽  
Star Forming ◽  
T Tauri

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 A polarization outburst in the T Tauri star UY Aurigae

1987 ◽  
Vol 122 ◽  
pp. 133-134 ◽  
Author(s):  
F. Ménard ◽  
P. Bastien
Keyword(s):  
Linear Polarization ◽  
T Tauri Stars ◽  
Tauri Star ◽  
Monitoring Programme ◽  
Strong Polarization ◽  
Visual Binary ◽  
T Tauri ◽  
First Time

During the course of a monitoring programme of the linear polarization of various T Tauri stars, UY Aur was observed to undergo a strong polarization burst between 1984 October and 1985 January. The linear polarization rised from about 1.5% early in 1984 to a maximum of 7.6% in 1984 October and declined back to the earlier value after 3 to 4 months. It is the first time that such a large increase in linear polarization is reported in a T Tauri star. However the interpretation is complicated by the fact that UY Aur is a visual binary with a separation of 0.8 and both components were included in the measurements.

scholarly journals Optical photometric variable stars towards Cygnus OB7

2019 ◽  
Vol 487 (2) ◽  
pp. 1765-1776 ◽  
Author(s):  
Somnath Dutta ◽  
Soumen Mondal ◽  
Santosh Joshi ◽  
Ramkrishna Das
Keyword(s):  
Variable Stars ◽  
T Tauri Stars ◽  
Light Curves ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Rotation Rates ◽  
T Tauri ◽  
Photometric Observations ◽  
Sky Survey ◽  
Magnitude Diagram

ABSTRACT We present optical I-band light curves of the stars towards a star-forming region Cygnus OB7 from 17-night photometric observations. The light curves are generated from a total of 381 image frames with very good photometric precision. From the light curves of 1900 stars and their periodogram analyses, we detect 31 candidate variables including five previously identified. 14 out of 31 objects are periodic and exhibit the rotation rates in the range of 0.15–11.60 d. We characterize those candidate variables using optical/infrared colour–colour diagram and colour–magnitude diagram (CMD). From spectral indices of the candidate variables, it turns out that four are probably Classical T-Tauri stars (CTTSs), rest remain unclassified from present data, they are possibly field stars or discless pre-main-sequence stars towards the region. Based on their location on the various CMDs, the ages of two T Tauri Stars were estimated to be ∼5 Myr. The light curves indicate at least five of the periodic variables are eclipsing systems. The spatial distribution of young variable candidates on Planck 857 GHz (350 $\mu$m) and 2MASS (Two Micron All Sky Survey) Ks images suggest that at least two of the CTTSs are part of the active star-forming cloud Lynds 1003.

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 LIGHT CURVE TYPES OF CLASSIC T TAURI STARS

2015 ◽  
Vol 28 (2) ◽  
pp. 227-230
Author(s):  
N. Z. Ismailov ◽  
H. N. Adygezalzade
Keyword(s):  
Light Curve ◽  
T Tauri Stars ◽  
T Tauri
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