Photometry of WD 1145+017 in Early 2017

2017 ◽  
Vol 34 ◽  
Author(s):  
Diana P. Kjurkchieva ◽  
Dinko P. Dimitrov ◽  
Nikola I. Petrov
Keyword(s):  
White Dwarf ◽  
Photometric Observations ◽  
Inhomogeneous Disk

AbstractWe present photometric observations of WD 1145+017 during six nights in early 2017. They exhibited asymmetric transits with durations of 10–50 mins and depths up to 50% in flux. We managed to track two deep features that drift in phase during 2.5-month season. This effect may be explained by period decreasing of the transiting formations due to their slow spiralling to the white dwarf. One of them seems to fragment in several smaller parts within a month. The structures causing the two deep transits have elongated shape whose sizes perpendicular and along the orbit are of the order of 1 R⊕ and 100 R⊕. They are parts of geometrically thin inhomogeneous disk (ring) around the white dwarf that is well within its Roche radius. This explains the observed dip activity of WD 1145+017 during the year 2017.

scholarly journals Searching for optical companions to four binary millisecond pulsars with the Gran Telescopio Canarias

2020 ◽  
Vol 492 (2) ◽  
pp. 3032-3040 ◽  
Author(s):  
A Yu Kirichenko ◽  
A V Karpova ◽  
D A Zyuzin ◽  
S V Zharikov ◽  
E A López ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Optical Data ◽  
Pure Hydrogen ◽  
Millisecond Pulsars ◽  
Upper Limit ◽  
Photometric Observations ◽  
Low Mass

ABSTRACT We report on multiband photometric observations of four binary millisecond pulsars with the Gran Telescopio Canarias. The observations led to detection of binary companions to PSRs J1630+3734, J1741+1351, and J2042+0246 in the Sloan g′, r′, and i′ bands. Their magnitudes in the r′ band are ≈24.4, 24.4, and 24.0, respectively. We also set a 3σ upper limit on the brightness of the PSR J0557+1550 companion in the r′ band of ≈25.6 mag. Combining the optical data with the radio timing measurements and white dwarf cooling models, we show that the detected companions are cool low-mass white dwarfs with temperatures and ages in the respective ranges of (4–7) × 103 K and 2–5 Gyr. All the detected white dwarfs are found to likely have either pure hydrogen or mixed helium–hydrogen atmospheres.

Study of Pulsations in the Nova-like Variable KR Aur and the Intermediate Polar BG CMi

1991 ◽  
Vol 9 (2) ◽  
pp. 279-280
Author(s):  
J. Singh ◽  
P. C. Agrawal ◽  
M. V. K. Apparao ◽  
R. K. Manchanda ◽  
P. Vivekananda Rao ◽  
...  
Keyword(s):  
Neutron Star ◽  
White Dwarf ◽  
Accretion Disc ◽  
Light Curves ◽  
Pulsation Period ◽  
Variable Amplitude ◽  
X Ray ◽  
Photometric Observations ◽  
The Times ◽  
Made In

AbstractFast photometric observations of a nova-like variable KR Aurigae and the intermediate polar BG CMi (3A0729+103) were made in the B and U bands during 1984–89 to study pulsations in them. The light curves of KR Aur show large amplitude quasi-periodic pulsations with periods in the range 500–800s which can be ascribed to inhomogeneities in the accretion disc. The light curves of the X-ray emitting intermediate polar BG CMi show variable amplitude pulsations with 913s period. From the times of maxima of the pulsations obtained from observations over the period 1984–1989, the pulsation period is derived to be 0.010572966 ± 8 days and the spin-up rate to be (−5.7 ± 0.5) × 10−11 ss−1. The spin-up rate is consistent with the pulsating source being a white dwarf and not a neutron star.

scholarly journals Asteroseismology of the DOV star PG 1159−035

2019 ◽  
Vol 488 (2) ◽  
pp. 2253-2262
Author(s):  
Y H Chen
Keyword(s):  
Kinetic Energy ◽  
White Dwarf ◽  
Period Change ◽  
Photometric Data ◽  
Optimal Model ◽  
Frequency Splitting ◽  
The Core ◽  
Star Models ◽  
Photometric Observations ◽  
Atmospheric Constituent

ABSTRACT Grids of DOV star models are evolved by wdec with fixed atmospheric constituent to the spectral values of XC/XHe/XO = 50/33/17. The core compositions are from white dwarf models at highest Teff evolved by mesa. The eigenfrequencies are calculated and used to fit the observed modes. Based on 264.1 h of photometric observations on PG 1159−035, Winget et al. identified 125 individual frequencies. Costa et al. identified 198 pulsation modes for PG 1159−035 according to the WET photometric data from 1983, 1985, 1989, and 2002. Both of them derived frequency splitting values of δσl = 1 ∼ 4.2 $\mu$Hz and δσl = 2 ∼ 6.9 $\mu$Hz. According to the values of δσl = 1 and δσl = 2, 20 triplets and 9 quintuplets are selected and used to constrain the fitting models. Our optimal model has Teff = 129 000 K, M* = 0.63 M⊙, log g = 7.59, log(Menv/M*) = −5.0, and σRMS = 1.97 s. The values of Teff and log g are consistent with that values of Córsico et al. The calculated modes of minimum rate of period change correspond to modes with maximum kinetic energy distributed in the envelope. The observed rates of period change with positive and negative values can also be partially reproduced. In particular, there are negative rates of period change for the calculated modes from our optimal model, which is not found in previous work.

scholarly journals Nova Models and their Problems

1977 ◽  
Vol 42 ◽  
pp. 301-310
Author(s):  
H.-C. Thomas
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Main Sequence Star ◽  
Late Type ◽  
Hydrogen Bomb ◽  
Binary Model ◽  
Photometric Observations

Very detailed spectroscopic and photometric observations of Novae are available today. Unfortunately they do not directly tell us what suddenly makes a star a million times brighter, sometimes even transforming the familiar constellations on the sky. Twenty-five years after its publication, Mestel’s (1952) metaphor of a gigantic hydrogen bomb seems to be most widely accepted, although he at that time applied his model to a Supernova outburst. Later Giannone and Weigert (1967) as well as Rose (1968), Saslaw (1968) and others have computed hydrostatic models of such an event, using Kraft’s (1963) binary model of a late type main sequence star and a white dwarf. Detailed hydrodynamic computations were carried out by Starrfield and his collaborators (for references see Sparks, Starrfield, and Truran, 1977) and recently by Prialnik, Shara, and Shaviv (A & A 62, 339, 1978).

scholarly journals The Symbiotic Star UV Aurigae

1988 ◽  
Vol 103 ◽  
pp. 293-294
Author(s):  
Parag Seal
Keyword(s):  
White Dwarf ◽  
Near Infrared ◽  
Infrared Region ◽  
Symbiotic Star ◽  
Photometric Observations ◽  
Optical Region ◽  
Near Infrared Region

The symbiotic variable UV Aur was observed by Merrill (1941) and Sanford (1944, 1949). UV Aur is classified as C8 ep carbon variable (Kukarkin et al. 1969) with a hot white dwarf and surrounding nebula. Infrared photometric observations have been done by Allen (1982), Noguchi et al. (1981) and Kenyon and Gallagher (1983) in the near infrared region and by woolf (1973) at 2.2 micron to 20 micron region. UV Aur has also been observed by IRAS and IUE Satellite. Polarimetry of UV Aur has been studied by Khudyakova (1985) in the optical region.

scholarly journals New Photometric Observations of RS Oph

2011 ◽  
Vol 7 (S281) ◽  
pp. 201-202
Author(s):  
Irina Voloshina ◽  
Vladimir Metlov
Keyword(s):  
Binary System ◽  
White Dwarf ◽  
Astronomical Institute ◽  
Long Period ◽  
Photometric Observations ◽  
Sternberg Astronomical Institute ◽  
Recurrent Nova ◽  
Type Giant ◽  
Chandrasekhar Limit

AbstractThe recurrent nova RS Oph is a long period (~455 days) binary system consisting of a hot white dwarf with mass close to the Chandrasekhar limit and an M-type giant secondary. Here we present the results of photometric observations of this nova which were made during recent years with the telescopes of the Sternberg Astronomical Institute in Crimea.

scholarly journals Ground-based observation of ZZ Ceti stars and the discovery of four new variables

2019 ◽  
Vol 490 (2) ◽  
pp. 1803-1820 ◽  
Author(s):  
Alejandra D Romero ◽  
L Antunes Amaral ◽  
T Klippel ◽  
D Sanmartim ◽  
L Fraga ◽  
...  
Keyword(s):  
White Dwarf ◽  
Signal To Noise Ratio ◽  
Structural Parameters ◽  
Instability Strip ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
Photometric Observations ◽  
Best Fitting ◽  
New Variables

ABSTRACT We perform ground-based photometric observations of 22 DA white dwarf stars, 10 already known ZZ Cetis and 12 candidates with atmospheric parameters inside the classical instability strip. We report on the discovery of four new variable DA white dwarf stars. Two objects are near the middle of the instability strip, SDSS J082804.63+094956.6 and SDSS J094929.09+101918.8, and two red edge pulsators, GD 195 and L495−82. In addition, we classified four objects as possible variables, since evidence of variability was detected in the light curve, but the signal-to-noise ratio was not sufficient to establish a definite detection. Follow-up observations were performed for 10 known ZZ Ceti stars to verify period stability and search for new periodicities. For each confirmed variable, we perform a detailed asteroseismological fit and compare the structural parameters obtained from the best-fitting models with those obtained from spectroscopy and photometry from Gaia. Finally we present a study of the asteroseismological properties of a sample of 91 ZZ Ceti stars.

scholarly journals Discovery of a pre-cataclysmic binary with unusual chromaticity of the eclipsed white dwarf by the GPX survey

2020 ◽  
Vol 493 (4) ◽  
pp. 5208-5217 ◽  
Author(s):  
Vadim Krushinsky ◽  
Paul Benni ◽  
Artem Burdanov ◽  
Igor Antokhin ◽  
Eleonora Antokhina ◽  
...  
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Accretion Rate ◽  
Binary Star ◽  
Mass Ratio ◽  
Orbital Inclination ◽  
Common Envelope ◽  
Secondary Star ◽  
Photometric Observations ◽  
Spot Activity

ABSTRACT We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf (WD) and a main-sequence K7 star with clear signs of chromospheric and spot activity. The light curve of this system shows ∼0.2 mag ellipsoidal variability with a period of 0.297549 d and a short total eclipse of the WD. Based on our analysis of the spectral and photometric data, we estimated the parameters of the system. The K7V star is tidally deformed but does not fill its Roche lobe (the filling factor is about 0.86). The orbital inclination is i = $73{_{.}^{\circ}}1 \pm 0{_{.}^{\circ}}2$, and the mass ratio is q = M2/M1 ≈ 0.88. The parameters of the K7V star are M2 ≈ 0.64 M⊙, R2 = 0.645 ± 0.012R⊙, and T2 ≈ 4070 K. The parameters of the WD are M1 ≈ 0.72 M⊙, R1 = 0.013 ± 0.003R⊙, and T1 = 8700 ± 1100 K. Photometric observations in different bands revealed that the maximum depth of the eclipse is in the SDSS r filter, which is unusual for a system of a WD and a late main-sequence star. We suspect that this system is a product of the evolution of a common-envelope binary star, and that the WD accretes the stellar wind from the secondary star (the so-called low-accretion-rate polar, hereafter LARP).

scholarly journals High-speed photometric observations of the pulsating DA white dwarf GD 165

1993 ◽  
Vol 106 ◽  
pp. 1987 ◽  
Author(s):  
P. Bergeron ◽  
G. Fontaine ◽  
P. Brassard ◽  
R. Lamontagne ◽  
F. Wesemael ◽  
...  
Keyword(s):  
White Dwarf ◽  
High Speed ◽  
Photometric Observations

scholarly journals Observational Structure of Disk-like Envelope in the System DQ Her

1980 ◽  
Vol 88 ◽  
pp. 473-473
Author(s):  
A. M. Cherepashchuk ◽  
E. S. Dmitrienko
Keyword(s):  
Effective Temperature ◽  
White Dwarf ◽  
Major Axis ◽  
Radiation Temperature ◽  
Average Value ◽  
Bolometric Luminosity ◽  
Photometric Observations ◽  
Photometric Elements ◽  
Orbit Inclination ◽  
The Masses

The analysis of the eclipses in the system DQ Her based on the photometric observations of different authors during 1954, 1956 and 1975 allows us to obtain the photometric elements of the system and the structure of disk-like envelope surrounding the white dwarf. The orbit inclination of the system is i = 80° ± 3°, the major axis of the secondary component is 0.40 ± 0.03, the orbit radius is (10 ± 2)1010cm, the masses of the components are: mwd = (0.65 ± 0.35)M⊙, m2 = (0.50 ± 0.15)M⊙. A decrease in the optical luminosity of ≃20% and a total decrease in size of the disk-like envelope of ≃10% is observed from 1954 to 1975. The brightness of the disk-like envelope increases towards its center. The radiation temperature increases toward the center according to the laws T ≃ r−0.20 and T ≃ r−0.35 for 1954 and 1975, respectively. The average value of the radiation temperature of the disk-like envelope is about 104K. The bolometric luminosity of the envelope is (1 to 2)L⊙. The bolometric luminosity of the central white dwarf is anomalously high: ≃(20 to 200 L⊙) and the effective temperature of its surface is ≃(1.0 to 1.7)105K. All these results indicate that the disk-like envelope in the system DQ Her is an accreting disk.

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