scholarly journals Simultaneous Photometric and Spectroscopic Observations of the unusual Variable F-type stars HD 224638 and HD 224945.

1995 ◽  
Vol 155 ◽  
pp. 339-340 ◽  
Author(s):  
L. Mantegazza ◽  
E. Poretti ◽  
M. Bossi ◽  
F.M. Zerbi
Keyword(s):  
Time Scales ◽  
Spectral Type ◽  
Characteristic Frequency ◽  
Small Amplitude ◽  
Characteristic Time ◽  
Light Curves ◽  
Wave Shape ◽  
Spectroscopic Observations ◽  
New Class ◽  
Photometric And Spectroscopic Observations

The stars HD 224638 and HD 224945 belong to the new class of F0 V spectral type stars which show an unusual kind of variability for that region of the HR diagram (Mantegazza et al. 1993).The variability of these two stars has been discovered and studied by Mantegazza, Poretti & Zerbi (1994). They show small amplitude light variations with characteristic time scales of the order of one day. The light curves are not periodic and it is difficult to satisfactorily fit them even with several periodic terms.In order to explain our 1991 B colour observations we tentatively suggested that in both stars two close periodic terms were present with a characteristic frequency of about 0.8 c/d, and that these terms had a double wave shape for HD 224638 and a triple wave one for HD 224945.

scholarly journals TESS photometry of extreme helium stars PV Tel and V821 Cen

2020 ◽  
Vol 495 (1) ◽  
pp. L135-L138 ◽  
Author(s):  
C Simon Jeffery ◽  
Geert Barentsen ◽  
Gerald Handler
Keyword(s):  
Light Curve ◽  
Time Scales ◽  
Characteristic Time ◽  
Satellite Observations ◽  
Light Curves ◽  
Single Site ◽  
Helium Stars ◽  
First Time

ABSTRACT PV Tel variables are extreme helium (EHe) stars known to be intrinsic light and velocity variable on characteristic time-scales of 0.1–25 d. With two exceptions, they are best described as irregular. Light curves have invariably been obtained from single-site terrestrial observatories. We present Transiting Exoplanet Survey Satellite observations of two bright EHe stars, Popper’s star (V821 Cen) and Thackeray’s star (PV Tel). PV Tel is variable on time-scales previously reported. V821 Cen is proven to be variable for the first time. Neither light curve shows any evidence of underlying regularity. Implications are considered.

scholarly journals Photometric and H-Alpha Variability in Some Be Stars

1987 ◽  
Vol 92 ◽  
pp. 101-103
Author(s):  
S. Catalano ◽  
G. Umana
Keyword(s):  
Magnetic Fields ◽  
Time Scales ◽  
Time Scale ◽  
Small Amplitude ◽  
Rotation Period ◽  
Light Curves ◽  
Radial Pulsation ◽  
Be Stars ◽  
Relative Movement ◽  
Short Term

Short-term variations, typically with small amplitude (Δm < 0.1 mag.), time-scales of hours or near one day and in many cases correlated with the rotation period have been found to be commonplace among Be stars (see Harmanec and Pavlovski 1983 for review and papers). Radial and non-radial pulsation modes have been proposed to explain this variability. However, the light curves are often double-peaked, at first suggesting the stars may have large organized dipole magnetic fields and spots not unlike those in the Ap or Bp stars (Harmanec 1983). These rotationally modulated variations are not stable, and seem to vary in both amplitude and period in the sense that intervals with well defined light curves alternate with intervals when variations are absent. This phenomenon is very reminiscent of formation and apparent relative movement in longitude of spots (groups) in some RS CVn binaries (Catalano 1983, Rodono 1986), but on a much more rapid time scale.

scholarly journals Photometric and Spectroscopic Observations of the Cataclysmic Variable AC Cancri

1983 ◽  
Vol 72 ◽  
pp. 17-20
Author(s):  
M. Kitamura ◽  
A. Okazaki ◽  
A. Yamasaki
Keyword(s):  
Astronomical Observatory ◽  
Light Curves ◽  
Cataclysmic Variable ◽  
Image Tube ◽  
Spectroscopic Observations ◽  
Photometric And Spectroscopic Observations

ABSTRACTThe eclipsing variable AC Cancri, recently identified as a cataclysmic variable by Shugarov (1981) and Okazaki, Kitamura and Yamasaki (1982), was further studied in detail on the bases of UBVcolours, multi-channel photoelectric light curves and image-tube spectrograms which were newly obtained at Tokyo Astronomical Observatory. The result of analysis of these materials for the nature of the cataclysmic variable is presented.

Models of Cataclysmic Variables from Photometric and Spectroscopic Data

1979 ◽  
Vol 46 ◽  
pp. 65-74 ◽  
Author(s):  
A.C. Fabian ◽  
J.E. Pringle ◽  
J.A.J. Whelan ◽  
J.A. Bailey
Keyword(s):  
Spectroscopic Data ◽  
Cataclysmic Variables ◽  
System Parameters ◽  
Dwarf Nova ◽  
Spectroscopic Observations ◽  
Photometric And Spectroscopic Observations

Abstract.Recent photometric and spectroscopic observations of the dwarf nova system Z Cha are discussed. Methods for constraining the system parameters are applied and the disc emissivity is deduced as a function of radius. Indications are found that the disc shrinks in size with increasing time after outburst.

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.

scholarly journals Light-curve properties of SN 2017fgc and HV SNe Ia

2021 ◽  
Vol 502 (3) ◽  
pp. 4112-4124
Author(s):  
Umut Burgaz ◽  
Keiichi Maeda ◽  
Belinda Kalomeni ◽  
Miho Kawabata ◽  
Masayuki Yamanaka ◽  
...  
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Light Curves ◽  
Normal Velocity ◽  
External Effects ◽  
Band Maximum ◽  
Bolometric Luminosity ◽  
V Band ◽  
Photometric And Spectroscopic Observations ◽  
Type Ia

ABSTRACT Photometric and spectroscopic observations of Type Ia supernova (SN) 2017fgc, which cover the period from −12 to + 137 d since the B-band maximum are presented. SN 2017fgc is a photometrically normal SN Ia with the luminosity decline rate, Δm15(B)true  = 1.10 ± 0.10 mag. Spectroscopically, it belongs to the high-velocity (HV) SNe Ia group, with the Si ii λ6355 velocity near the B-band maximum estimated to be 15 200 ± 480 km s−1. At the epochs around the near-infrared secondary peak, the R and I bands show an excess of ∼0.2-mag level compared to the light curves of the normal velocity (NV) SNe Ia. Further inspection of the samples of HV and NV SNe Ia indicates that the excess is a generic feature among HV SNe Ia, different from NV SNe Ia. There is also a hint that the excess is seen in the V band, both in SN 2017fgc and other HV SNe Ia, which behaves like a less prominent shoulder in the light curve. The excess is not obvious in the B band (and unknown in the U band), and the colour is consistent with the fiducial SN colour. This might indicate that the excess is attributed to the bolometric luminosity, not in the colour. This excess is less likely caused by external effects, like an echo or change in reddening but could be due to an ionization effect, which reflects an intrinsic, either distinct or continuous, difference in the ejecta properties between HV and NV SNe Ia.

scholarly journals An attempt of seismic modelling of β Cephei stars in NGC 6910

2014 ◽  
Vol 9 (S307) ◽  
pp. 222-223
Author(s):  
D. Moździerski ◽  
Z. Kołaczkowski ◽  
E. Zahajkiewicz
Keyword(s):  
Seismic Modeling ◽  
Preliminary Results ◽  
Spectroscopic Observations ◽  
Seismic Modelling ◽  
Photometric And Spectroscopic Observations

AbstractWe present preliminary results of seismic modeling of β Cephei-type stars in NGC 6910 based on simultaneous photometric and spectroscopic observations carried out in 2013 in Białków (photometry) and Apache Point (spectroscopy) observatories.

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

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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