Roche tomography of cataclysmic variables – VIII. The irradiated and spotted dwarf nova, SS Cygni

Hill, C. A.; Smith, Robert C.; Hebb, Leslie; Szkody, Paula

doi:10.1093/mnras/stx2260

Cited by 21 publications

(13 citation statements)

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“…Tmax, α, and the normalization in the CEVMKL model, and the line width (σ) and the normalization in the GAUSSIAN model are free to vary. The inclination angle of the reflector is set to be that of the binary system, 45 deg (Hill et al 2017). Here we use 114.25 pc as the distance to SS Cyg, which is obtained by the Gaia parallax (Bailer-Jones et al 2018).…”

Section: Results Of Spectral Modelingmentioning

confidence: 99%

“…This may imply that the inner disk edge extends toward the WD as the accretion rate of the disk increases. The WD radius is ∼5×10 8 cm for the WD mass of 0.94M⊙ (Nauenberg 1972;Provencal et al 1998;Hill et al 2017). By contrast, the innermost disk radius appears to stay at a smaller value during Event B (see the squares in the same figure).…”

Section: X-ray Stochastic Variabilitymentioning

confidence: 90%

“…For the data before the pre-stage, we extract the light curve fainter than 11 mag during BJD 2453868-2458700. We fold the RC-band light curve with the orbital period of 0.27512973 d derived by Hessman (1986) and determine the orbital phase using the epoch BJD 2456190.62771 reported by Hill et al (2017), which corresponds to the inferior conjunction of the secondary star. Before folding light curves, we subtract the long-term trend of light curves from the observational data by locally weighted polynomial regression (LOWESS; Cleveland 1979).…”

Section: Optical Orbital Light Curvesmentioning

confidence: 99%

“…The ellipsoidal modulation is generated by the change in the projection area of the distorted secondary star to the observer and peaks at the orbital phases of 0.25 and 0.75 (see e.g., Allan et al 1996). Since the inclination angle of SS Cyg is measured to be 45 deg (Hill et al 2017), these two effects are observable and the disk and the WD are not eclipsed.…”

Section: Optical Orbital Light Curvesmentioning

confidence: 99%

See 3 more Smart Citations

On the nature of the anomalous event in 2021 in the dwarf nova SS Cygni and its multi-wavelength transition

Kimura,

Yamada,

Nakaniwa

et al. 2021

Preprint

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SS Cyg has long been recognized as the prototype of a group of dwarf novae that show only outbursts. However, this object has entered a quite anomalous event in 2021, which at first appeared to be standstill, i.e., an almost constant luminosity state, observed in Z Cam-type dwarf novae. This unexpected event gives us a great opportunity to reconsider the nature of standstill in cataclysmic variables. We have observed this anomalous event and its forerunner, a gradual and simultaneous increase in the optical and X-ray flux during quiescence, through many optical telescopes and the X-ray telescopes NICER and NuSTAR. We have not found any amplification of the orbital hump during quiescence before the anomalous event, which suggests that the mass transfer rate did not significantly fluctuate on average. The estimated X-ray flux was not enough to explain the increment of the optical flux during quiescence via X-ray irradiation of the disk and the secondary star. It would be natural to consider that viscosity in the quiescent disk was enhanced before the anomalous event, which increased mass accretion rates in the disk and raised not only the optical flux but also the X-ray flux. We suggest that enhanced viscosity also triggered the standstill-like phenomenon in SS Cyg, which is considered to be a series of small outbursts. The inner part of the disk would always stay in the outburst state and only its outer part would be unstable against the thermal-viscous instability during this phenomenon, which is consistent with the observed optical color variations. This scenario is in line with our X-ray spectral analyses which imply that the X-ray emitting inner accretion flow became hotter than usual and vertically expanded and that it became denser and was cooled down after the onset of the standstill-like state.

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Section: Results Of Spectral Modelingmentioning

confidence: 99%

Section: X-ray Stochastic Variabilitymentioning

confidence: 90%

Section: Optical Orbital Light Curvesmentioning

confidence: 99%

Section: Optical Orbital Light Curvesmentioning

confidence: 99%

See 2 more Smart Citations

On the nature of the anomalous event in 2021 in the dwarf nova SS Cygni and its multi-wavelength transition

Kimura,

Yamada,

Nakaniwa

et al. 2021

Preprint

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show abstract

“…A recent paper by Hill et al (2017) suggests to me to tell the history of the determination of the parameters of SS Cygni, and more, especially for the benefit of younger colleagues. Indeed, Fig.…”

Section: Pos(golden2019)001mentioning

confidence: 99%

The Golden Age of Cataclysmic Variables and Related Objects (some critical comments)

Giovannelli¹

2021

Proceedings of the Golden Age of Cataclysmic Variables and Related Objects v — PoS(GOLDEN2019)

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In the last few years we assisted to a substantial improvement on the number of cataclysmic variables (CVs) discovered, but only few exciting results have been obtained such as the discovery of a white dwarf pulsar in AR Sco. In this paper I will comment, from a personal point of view, some news about the route to be followed in the investigations on CVs and Related Objects. The paper will be developed as follows:

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Ejection processes in the young open cluster NGC 2264

McGinnis

Dougados

Alencar

et al. 2018

A&A

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Context. Statistical studies of the spectral signatures of jets and winds in young stars are crucial to characterize outflows and understand their impact on disk and stellar evolution. The young, open cluster NGC 2264 contains hundreds of well-characterized classical T Tauri stars (CTTS), being thus an ideal site for these statistical studies. Its slightly older age than star forming regions studied in previous works, such as Taurus, allows us to investigate outflows in a different phase of CTTS evolution. Aims. We search for correlations between the [OI]λ6300 line, a well-known tracer of jets and winds in young stars, and stellar, disk and accretion properties in NGC 2264, aiming to characterize the outflow phenomena that occur within the circumstellar environment of young stars. Methods. We analyzed FLAMES spectra of 184 stars, detecting the [OI]λ6300 line in 108 CTTSs and two Herbig AeBe stars. We identified the main features of this line: a high-velocity component (HVC), and a broad and narrow low-velocity components (BLVC and NLVC). We calculated luminosities and kinematic properties of these components, then compared them with known stellar and accretion parameters.Results. The luminosity of the [OI]λ6300 line and its components correlate positively with the stellar and accretion luminosity. The HVC is only detected among systems with optically thick inner disks; the BLVC is most common among thick disk systems and rarer among systems with anemic disks and transition disks; and the NLVC is detected among systems with all types of disks, including transition disks. Our BLVCs present blueshifts of up to 50 km s −1 and widths consistent with disk winds originating between ∼0.05 au and ∼0.5 au from the central object, while the NLVCs in our sample have widths compatible with an origin between ∼0.5 au and ∼5 au, in agreement with previous studies in Taurus. A comparison of [OI]λ6300 profiles with CoRoT light curves shows that the HVC is found most often among sources with irregular, aperiodic photometric variability, usually associated with CTTSs accreting in an unstable regime. No stellar properties (T e f f , mass, rotation) appear to significantly influence any property of protosellar jets. We find jet velocities on average similar to those found in Taurus. Conclusions. We confirm earlier findings in Taurus which favor an inner MHD disk wind as the origin of the BLVC, while there is no conclusive evidence that the NLVC traces photoevaporative disk winds. The [OI]λ6300 line profile shows signs of evolving as the disk disperses, with the HVC and BLVC disappearing as the inner disk becomes optically thin, in support of the scenario of inside-out gas dissipation in the inner disk.

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Roche tomography of cataclysmic variables – VIII. The irradiated and spotted dwarf nova, SS Cygni

Cited by 21 publications

References 50 publications

On the nature of the anomalous event in 2021 in the dwarf nova SS Cygni and its multi-wavelength transition

On the nature of the anomalous event in 2021 in the dwarf nova SS Cygni and its multi-wavelength transition

The Golden Age of Cataclysmic Variables and Related Objects (some critical comments)

Ejection processes in the young open cluster NGC 2264

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