A spectroscopic analysis of the eclipsing nova-like EC 21178−5417 – discovery of spiral density structures

ABSTRACT We present phase-resolved optical spectroscopy of the eclipsing nova-like cataclysmic variable EC 21178−5417 obtained between 2002 and 2013. The average spectrum of EC 21178−5417 shows broad double-peaked emission lines from He ii 4686 Å (strongest feature) and the Balmer series. The high-excitation feature, C iii/N iii at 4640–4650 Å, is also present and appears broad in emission. A number of other lines, mostly He i, are clearly present in absorption and/or emission. The average spectrum of EC 21178−5417 taken at different months and years shows variability in spectral features, especially in the Balmer lines beyond Hγ, from pure line emission, mixed line absorption, and emission to pure absorption lines. Doppler maps of the He ii 4686 Å emission reveal the presence of a highly inclined asymmetric accretion disc and a two spiral arm-like structure, whereas that of the Balmer lines (Hα and Hβ) reveal a more circular accretion disc. There is no evidence of a bright-spot in the Doppler maps of EC 21178−5417 and no emission from the secondary star is seen in the tomograms of the He ii 4686 Å and Balmer lines. Generally, the emission in EC 21178−5417 is dominated by emission from the accretion disc. We conclude that EC 21178−5417 is a member of the RW Tri or UX UMa subtype of nova-like variables based on these results and because it shows different spectral characteristics at different dates. This spectral behaviour suggests that EC 21178−5417 undergoes distinct variations in mass transfer rate on the observed time-scales of months and years.

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Optical spectra of FO Aquarii during low and high accretion rates

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1415 ◽

2020 ◽

Vol 495 (4) ◽

pp. 4445-4462

Author(s):

M R Kennedy ◽

P M Garnavich ◽

C Littlefield ◽

T R Marsh ◽

P Callanan ◽

...

Keyword(s):

Transfer Rate ◽

Mass Transfer Rate ◽

Cataclysmic Variables ◽

Accretion Disc ◽

High State ◽

Secondary Star ◽

Accretion Rates ◽

Magnetic Poles ◽

The Impact ◽

Impact Region

ABSTRACT Between 2016 May and 2018 September, the intermediate polar (IP) FO Aquarii exhibited two distinct low states and one failed low state. We present optical spectroscopy of FO Aquarii throughout this period, making this the first detailed study of an accretion disc during a low state in any IP. Analysis of these data confirm that the low states are the result of a drop in the mass transfer rate between the secondary star and the magnetic white dwarf primary, and are characterized by a decrease in the system’s brightness coupled with a change of the system’s accretion structures from an accretion disc-fed geometry to a combination of disc-fed and ballistic stream-fed accretion, and that effects from accretion on to both magnetic poles become detectable. The failed low state only displays a decrease in brightness, with the accretion geometry remaining primarily disc-fed. We also find that the WD appears to be exclusively accretion disc-fed during the high state. There is evidence for an outflow close to the impact region between the ballistic stream and the disc which is detectable in all of the states. Finally, there is marginal evidence for narrow high-velocity features in the H α emission line during the low states which may arise due to an outflow from the WD. These features may be evidence of a collimated jet, a long predicted yet elusive feature of cataclysmic variables.

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Mapping the Line Emission Distribution of Cataclismic Variable Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100104671 ◽

1987 ◽

Vol 93 ◽

pp. 85-89

Author(s):

T.R. Marsh ◽

K. Horne

Keyword(s):

Formation Process ◽

Variable Star ◽

Line Emission ◽

Variable Stars ◽

Accretion Disc ◽

Bright Spot ◽

Cataclysmic Variable ◽

Two Dimensional ◽

Line Formation ◽

Line Profiles

AbstractWe describe a method for imaging the accretion disc of a Cataclysmic Variable star. We use the two-dimensional information contained in the line profiles as they vary with phase to invert the line formation process. Asymmetries in the disc, as are caused by the bright-spot, for example, are accounted for naturally.

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Long-Term Variability and Outburst Activity of FS Aurigae: Further Evidence for a Third Body in the System

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311026986 ◽

2011 ◽

Vol 7 (S282) ◽

pp. 79-80

Author(s):

V. Neustroev ◽

G. Sjoberg ◽

G. Tovmassian ◽

S. Zharikov ◽

T. Arranz Heras ◽

...

Keyword(s):

Transfer Rate ◽

Mass Transfer Rate ◽

Cataclysmic Variables ◽

Close Binary ◽

Third Body ◽

Secondary Star ◽

Long Term Monitoring ◽

Binary Orbit ◽

Term Monitoring

AbstractFS Aurigae is famous for a variety of uncommon and puzzling periodic photometric and spectroscopic variabilities which do not fit well into any of the established sub-classes of cataclysmic variables. Here we present preliminary results of long-term monitoring of the system, conducted during the 2010-2011 observational season. We show that the long-term variability of FS Aur and the character of its outburst activity may be caused by variations in the mass transfer rate from the secondary star as the result of eccentricity modulation of a close binary orbit induced by the presence of a third body on a circumbinary orbit.

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The Deuterium Balmer Series

Highlights of Astronomy ◽

10.1017/s1539299600017202 ◽

2005 ◽

Vol 13 ◽

pp. 811-812

Author(s):

Guillaume Hébrard

Keyword(s):

Spectral Resolution ◽

Magellanic Clouds ◽

High Spectral Resolution ◽

Excitation Mechanism ◽

Balmer Series ◽

Detection And Identification ◽

Balmer Lines ◽

Low Metallicity ◽

Resolution Data ◽

Narrow Emission

AbstractThe first detection and identification of deuterium Balmer lines were recently reported in H ii regions, using high spectral resolution data secured at CFHT and VLT. The Di lines appear as faint, narrow emission features in the blue wings of the H i Balmer lines and can be distinguished from high-velocity Hi emission. The identification as deuterium and the excitation mechanism as fluorescence are both established beyond doubt. The deuterium Balmer series might lead to a new, optical method of deuterium abundance measurement in the interstellar medium. This may be the only way to observe atomic deuterium in objects like the Magellanic Clouds or low metallicity blue compact galaxies.

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Long photometric cycle and disk evolution in the β Lyrae-type binary OGLE-BLG-ECL-157529

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038110 ◽

2020 ◽

Vol 641 ◽

pp. A91

Author(s):

R. E. Mennickent ◽

J. Garcés ◽

G. Djurašević ◽

P. Iwanek ◽

D. Schleicher ◽

...

Keyword(s):

Mass Transfer ◽

Light Curve ◽

Hot Spot ◽

Mass Transfer Rate ◽

Variable Mass ◽

Bright Spot ◽

Relative Depth ◽

Disk Radius ◽

Long Cycle ◽

Stellar Component

Context. The subtype of hot algol semidetached binaries dubbed double periodic variables (DPVs) are characterized by a photometric cycle longer than the orbital one, whose nature has been related to a magnetic dynamo in the donor component controlling the mass transfer rate. Aims. We aim to understand the morphologic changes observed in the light curve of OGLE-BLG-ECL-157529 that are linked to the long cycle. In particular, we want to explain the changes in the relative depth of primary and secondary eclipses. Methods. We analyzed I and V-band OGLE photometric times series spanning 18.5 years and modeled the orbital light curve. Results. We find that OGLE-BLG-ECL-157529 is a new eclipsing Galactic DPV of orbital period 24d.8, and that its long cycle length decreases in amplitude and length during the time baseline. We show that the changes in the orbital light curve can be reproduced considering an accretion disk of variable thickness and radius that surrounds the hottest stellar component. Our models indicate changes in the temperatures of the hot spot and the bright spot during the long cycle, and also in the position of the bright spot. This, along with the changes in disk radius, might indicate a variable mass transfer in this system.

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The disappearance and reformation of the accretion disc during a low state of FO Aquarii

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731226 ◽

2017 ◽

Vol 606 ◽

pp. A7 ◽

Cited By ~ 6

Author(s):

J.-M. Hameury ◽

J.-P. Lasota

Keyword(s):

Mass Transfer ◽

Transfer Rate ◽

Hot Spot ◽

Mass Transfer Rate ◽

Accretion Disc ◽

Numerical Code ◽

Light Sources ◽

Instability Strip ◽

Dwarf Nova ◽

Nova Outbursts

Context. FO Aquarii, an asynchronous magnetic cataclysmic variable (intermediate polar) went into a low state in 2016, from which it slowly and steadily recovered without showing dwarf nova outbursts. This requires explanation since in a low state, the mass-transfer rate is in principle too low for the disc to be fully ionised and the disc should be subject to the standard thermal and viscous instability observed in dwarf novae. Aims. We investigate the conditions under which an accretion disc in an intermediate polar could exhibit a luminosity drop of two magnitudes in the optical band without showing outbursts. Methods. We use our numerical code for the time evolution of accretion discs, including other light sources from the system (primary, secondary, hot spot). Results. We show that although it is marginally possible for the accretion disc in the low state to stay on the hot stable branch, the required mass-transfer rate in the normal state would then have to be extremely high, of the order of 1019 g s-1 or even larger. This would make the system so intrinsically bright that its distance should be much larger than allowed by all estimates. We show that observations of FO Aqr are well accounted for by the same mechanism that we have suggested as explaining the absence of outbursts during low states of VY Scl stars: during the decay, the magnetospheric radius exceeds the circularisation radius, so that the disc disappears before it enters the instability strip for dwarf nova outbursts. Conclusions. Our results are unaffected, and even reinforced, if accretion proceeds both via the accretion disc and directly via the stream during some intermediate stages; the detailed process through which the disc disappears still requires investigation.

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FS Aur as a Permanent Superhump System

International Astronomical Union Colloquium ◽

10.1017/s0252921100152340 ◽

2004 ◽

Vol 194 ◽

pp. 169-171

Author(s):

Gaghik H. Tovmassian ◽

Sergei V. Zharikov

Keyword(s):

Mass Transfer ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Variable Mass ◽

Accretion Disc ◽

Light Curves ◽

Cataclysmic Variable ◽

Short Period ◽

Photometric Period ◽

Low Amplitude

AbstractWe discovered that the short period cataclysmic variable FS Aur at some epochs shows a photometric period close to the orbital. It exceeds the orbital period by ∽2%, which is a sign of the presence of a permanent superhump in the system. Superhumps tend to appear near short, low amplitude outbursts. We assume that FS Aur possesses a large thermally stable accretion disc and that the outburst may be due to the variable mass transfer rate. This, however, does not alter our previous explanation of yet another, 2.4 times longer than orbital, photometric period of FS Aur, found earlier, and persistently observed in its light curves.

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A Beat Phenomenon in Dwarf Nova Eruptions

International Astronomical Union Colloquium ◽

10.1017/s0252921100069396 ◽

1977 ◽

Vol 42 ◽

pp. 227-233

Author(s):

N. Vogt

Keyword(s):

Mass Transfer ◽

Orbital Period ◽

Transfer Rate ◽

Convection Zone ◽

Mass Transfer Rate ◽

Accretion Disc ◽

Light Curves ◽

Dwarf Nova ◽

Beat Phenomenon ◽

Photoelectric Observations

Photoelectric observations of the dwarf nova VW Hyi, obtained at the end of the December 1975 supermaximum, are presented. After decline from the outburst, the superhump period (0ḍ07622) combines with the orbital period (0ḍ07427) to a beat phenomenon: the O-C’s and the light curves of the orbital hump vary systematically with the phase of the beat period for at least one week after recovery from the supermaximum. It is suggested that the red secondary component, which rotates non-synchroneously with the superhump period, expands slightly at the beginning of a supermaximum and is heated up asymmetrically, probably due to instabilities in its convection zone. In addition, the increased mass transfer rate may trigger the long eruption in the accretion disc while short eruptions originate in the disc without participation of the secondary.

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Subionization and decelerated-flow in the vicinity of a B-shell star

International Astronomical Union Colloquium ◽

10.1017/s0252921100095269 ◽

1981 ◽

Vol 59 ◽

pp. 539-541

Author(s):

J. Zorec

Keyword(s):

Absorption Spectrum ◽

Main Sequence ◽

Type B ◽

Balmer Series ◽

B Stars ◽

Normal Absorption ◽

Balmer Lines ◽

Fixed Order ◽

Shell Star ◽

Normal Spectrum

Three types of spectra have been extensively observed among mainsequence B stars. B-normal is the classical absorption spectrum which defines a normal main-sequence B star. Be is a B-normal spectrum except : (i) some absorption lines, notably the first hydrogen Balmer series members, are replaced by emission lines; (ii) some lines from some singlyionized metals, not normally present in B stars, sometimes appear, either in emission or absorption. Be-shell is a Be spectrum with narrow and deep absorption cores in the Balmer and singly-ionized metal lines. A fourth type, B-shell, has been identified as a B-normal, absorption, spectrum except for the presence of FeII lines, and narrow, deep absorption cores in these and the hydrogen Balmer lines. Once thought to each represent a different kind of star, these spectra are now realized to simply represent different temporal phases, which one and the same star can traverse, apparently in no (as yet) fixed order. Some of the brightest stars --- eg γ Cas, 59 Cyg, Pleione --- have been observed in all of the 3 prominant phases; some stars, in only some of them; 70 % of the B stars have been observed only in the B-normal phase.

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