Spectroscopic and photometric observations of dwarf nova superoutbursts by the 3.8 m telescope Seimei and the Variable Star Network

Tampo, Yusuke; Isogai, Keisuke; Kojiguchi, Naoto; Maehara, Hiroyuki; Taguchi, Kenta; Katô, Takeo; Kimura, M.; Wakamatsu, Yasuyuki; Shibata, Masaaki; Nogami, Daisaku; Kawabata, Miho; Maeda, Keiichi; Namekata, Kosuke; Okamoto, Soshi; Otsuka, Masaaki; Burgaz, U.; Nagoshi, Shumpei; Itoh, Hiroshi; Vanmunster, Tonny; Tordai, Tamás; Stone, Geoffrey; Matsumoto, Katsura; Fujii, Daiti; Matsumura, R.; Nakagawa, Momoka; Takeuchi, Nodoka; Zenkou, Yuki; Павленко, Е. П.; Antonyuk, K. A.; Pit, Nikolaj V.; Antonyuk, Oksana I.; Babina, Julia V.; Baklanov, A. V.; Sosnovskij, Aleksei A.; Shugarov, S. Yu.; Katysheva, N.; Chochol, D.; Dvorak, Shawn; Dubovský, Pavol A.; Medulka, Tomas; Kudzej, Igor; Kiyota, S.; Zubareva, A. M.; Belinski, A. A.; Иконникова, Н. П.; Бурлак, М. А.; Sano, Y.; Mizutani, Manabu; Ruiz, Javier; Pickard, R.; Hambsch, Franz-Josef; Dufoer, Sjoerd; Brincat, Stephen M.; Galdies, Charles; Menzies, Kenneth; Moriyama, M.; Hiraga, Mitsutaka; Maeda, Yutaka; Hirosawa, Kenji; Funada, Masao; Yamamoto, Masaaki

doi:10.1093/pasj/psab036

Cited by 5 publications

(1 citation statement)

References 72 publications

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“…For WZ-type stars, early superhumps are observed in the initial days following an outburst and typically exhibit a double-wave modulation with a small amplitude (up to a few hundredths of a magnitude). The period during this stage remains constant and equals the orbital period (Kato 2015;Tampo et al 2021Tampo et al , 2022. However, some systems have been found to exhibit exceptionally large amplitudes of early superhumps.…”

Section: Introductionmentioning

confidence: 99%

Investigation of WZ Sge-type Dwarf Nova ASASSN-19oc: Optical Spectroscopy and Multicolor Light Curve Analysis

Krushevska,

Shugarov,

Ochner

et al. 2024

Res. Astron. Astrophys.

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In this study, we present an investigation of the newly discovered dwarf nova ASASSN-19oc during its superoutburst on June 2, 2019. We carried out detailed UBVRcIc - photometric observations and also obtained a spectrum on day 7 of the outburst, which shows the presence of hydrogen absorption lines commonly found in dwarf novae outbursts. Analysis of photometric data reveals the occurrence of early superhumps in the initial days of observations, followed by ordinary and late superhumps. We have accurately calculated the period of the ordinary superhumps as Pord = 0.05681(10) days and determined the periods at different stages, as well as the rate of change of the superhumps period (Pdot = dP/P = 8.1 × 10-5). Additionally, we have derived the mass ratio of the components (q = 0.09), estimated the color temperature during the outburst as ~11000 K, the distance to the system (d = 560 pc) and absolute magnitude of the system in outburst (Mv = 5.3). We have shown that outbursts of this star are very rare: based on brightness measurements on 600 archival photographic plates, we found only one outburst that occurred in 1984. This fact, as well as the properties listed above, convincingly show that the variable ASASSN-19oc is a dwarf nova of WZ Sge type.

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Section: Introductionmentioning

confidence: 99%

Investigation of WZ Sge-type Dwarf Nova ASASSN-19oc: Optical Spectroscopy and Multicolor Light Curve Analysis

Krushevska,

Shugarov,

Ochner

et al. 2024

Res. Astron. Astrophys.

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A disc wind origin for the optical spectra of dwarf novae in outburst

Tampo,

Knigge,

Long

et al. 2024

Monthly Notices of the Royal Astronomical Society

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Many high-state cataclysmic variables (CVs) exhibit blue-shifted absorption features in their ultraviolet (UV) spectra – a smoking-gun signature of outflows. However, the impact of these outflows on optical spectra remains much more uncertain. During its recent outburst, the eclipsing dwarf nova V455 And displayed strong optical emission lines whose cores were narrower than expected from a Keplerian disc. Here, we explore whether disc + wind models developed for matching UV observations of CVs can also account for these optical spectra. Importantly, V455 And was extremely bright at outburst maximum: the accretion rate implied by fitting the optical continuum with a standard disc model is $\dot{M}_{\rm acc} \simeq 10^{-7}~{\rm M}_\odot ~{\rm yr^{-1}}$. Allowing for continuum reprocessing in the outflow helps to relax this constraint. A disc wind can also broadly reproduce the optical emission lines, but only if the wind is (i) highly mass-loaded, with a mass-loss rate reaching $\dot{M}_{\rm wind} \simeq 0.4 \dot{M}_{\rm acc}$, and/or (ii) clumpy, with a volume filling factor $f_V \simeq 0.1$. The same models can describe the spectral evolution across the outburst, simply by lowering $\dot{M}_{\rm acc}$ and $\dot{M}_{\rm wind}$. Extending these models to lower inclinations and into the UV produces spectra consistent with those observed in face-on high-state CVs. We also find, for the first time in simulations of this type, P-Cygni-like absorption features in the Balmer series, as have been observed in both CVs and X-ray binaries. Overall, dense disc winds provide a promising framework for explaining multiple observational signatures seen in high-state CVs, but theoretical challenges persist.

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Spectroscopic observations of V455 Andromedae superoutburst in 2007: The most exotic spectral features in dwarf nova outbursts

Tampo

Nogami

Katô

et al. 2022

Publications of the Astronomical Society of Japan

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We present our spectroscopic observations of V455 Andromedae during the 2007 superoutburst. Our observations cover this superoutburst from around the optical peak of the outburst to the post-superoutburst stage. During the early superhump phase, the emission lines of the Balmer series, He i, He ii, Bowen blend, and C iv/N iv blend were detected. The He ii 4686 line exhibited a double-peaked emission profile, where Balmer emission lines were single-peaked, which is unexpected from its high inclination. In the ordinary superhump phase, the Balmer series transitioned to double-peaked emission profiles, and high-ionization lines were significantly weakened. These transitions of the line profiles should be related to the structural transformation of the accretion disk, as expected between the early and ordinary superhump transition in the thermal–tidal instability model. The Doppler map of Hα during the early superhump phase exhibits a compact blob centered at the primary white dwarf. In analogy to SW Sex-type cataclysmic variables, this feature could emerge from the disk wind and/or the mass accretion column on to the magnetized white dwarf. The Doppler map of He ii 4686 Å is dominated by the ring-like structure and imposed two flaring regions with the velocity of ∼300 km s−1, which is too slow for a Keplerian accretion disk. The phase of the flaring regions was coincident with the inner spiral arm structure identified during the early superhump phase. Our disk wind model with the enhanced emission from the wind component launched from the inner arm structure successfully reproduced the observed properties of He ii 4686 Å. Therefore, V455 And is the first case in dwarf nova outbursts where the presence of the disk wind is inferred from an optical spectrum.

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Spectroscopic and photometric observations of dwarf nova superoutbursts by the 3.8 m telescope Seimei and the Variable Star Network

Cited by 5 publications

References 72 publications

Investigation of WZ Sge-type Dwarf Nova ASASSN-19oc: Optical Spectroscopy and Multicolor Light Curve Analysis

Investigation of WZ Sge-type Dwarf Nova ASASSN-19oc: Optical Spectroscopy and Multicolor Light Curve Analysis

A disc wind origin for the optical spectra of dwarf novae in outburst

Spectroscopic observations of V455 Andromedae superoutburst in 2007: The most exotic spectral features in dwarf nova outbursts

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