Dwarf-Nova Outbursts

Osaki, Yoji

doi:10.1086/133689

Cited by 473 publications

(471 citation statements)

References 54 publications

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“…Their super-cycles are stable both in length and outburst pattern (Osaki 1996;Patterson 1998;Downes et al 2001). V1159 Ori was discovered by Wolf & Wolf (1906), who gave it the name "Var.,Orionis 36.1906", and first investigated by Kippenhahn (1953) and Jablonski & Cieslinski (1992).…”

Section: V1159 Ori (No 01)mentioning

confidence: 99%

Finding the most variable stars in the Orion Belt with the All Sky Automated Survey

2010

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We look for high-amplitude variable young stars in the open clusters and associations of the Orion Belt. We use public data from the ASAS-3 Photometric V -band Catalogue of the All Sky Automated Survey, infrared photometry from the 2MASS and IRAS catalogues, proper motions, and the Aladin sky atlas to obtain a list of the most variable stars in a survey area of side 5 deg centred on the bright star Alnilam (ǫ Ori) in the centre of the Orion Belt. We identify 32 highly-variable stars, of which 16 had not been reported to vary before. They are mostly variable young stars and candidates (16) and background giants (8), but there are also field cataclysmic variables, contact binaries, and eclipsing binary candidates. Of the young stars, which typically are active Herbig Ae/Be and T Tauri stars with Hα emission and infrared flux excess, we discover four new variables and confirm the variability status of another two. Some of them belong to the well known σ Orionis cluster. Besides, six of the eight giants are new variables, and three are new periodic variables.

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Section: V1159 Ori (No 01)mentioning

confidence: 99%

Finding the most variable stars in the Orion Belt with the All Sky Automated Survey

2010

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“…The commonly accepted cause for dwarf nova outbursts is a thermal instability in the accretion disc (e.g. Cannizzo et al 1986;Osaki 1996). Within this theoretical framework, accretion discs undergo outbursts if the accretion rate is below a critical value,Ṁ crit .…”

Section: Introductionmentioning

confidence: 99%

“…Rappaport et al 1983;Spruit & Ritter 1983;King 1988). For such low mass transfer rates, the disc instability model predicts thermally unstable accretion discs that produce dwarf-nova outbursts (Cannizzo 1993;Osaki 1996). Because of the long evolution time scale of low-mass transfer CVs population models built upon the disrupted magnetic braking scenario predict that 99% of all CVs should have periods below 3 h (Kolb 1993;Howell et al 1997), which implies that the vast majority of all CVs is expected to be dwarf novae.…”

Section: Introductionmentioning

confidence: 99%

Dwarf novae in the Hamburg quasar survey: rarer than expected

Aungwerojwit¹,

Gänsicke²,

Rodríguez‐Gil

et al. 2006

A&A

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Aims. We report the discovery of five new dwarf novae that were spectroscopically identified in the Hamburg Quasar Survey (HQS), and discuss the properties of the sample of new dwarf novae from the HQS. Methods. Follow-up time-resolved spectroscopy and photometry have been obtained to characterise the new systems. Results. The orbital periods determined from analyses of the radial velocity variations and/or orbital photometric variability are P orb 105.1 min or P orb 109.9 min for HS 0417+7445, P orb = 114.3 ± 2.7 min for HS 1016+3412, P orb = 92.66 ± 0.17 min for HS 1340+1524, P orb = 272.317 ± 0.001 min for HS 1857+7127, and P orb = 258.02 ± 0.56 min for HS 2214+2845. HS 1857+7127 is found to be partially eclipsing. In HS 2214+2845 the secondary star of spectral type M3 ± 1 is clearly detected, and we estimate the distance to the system to be d = 390 ± 40 pc. We recorded one superoutburst of HS 0417+7445, identifying the system as a SU UMatype dwarf nova. HS 1016+3412 and HS 1340+1524 have rare outbursts, and their subtype is yet undetermined. HS 1857+7127 frequently varies in brightness and may be a Z Cam-type dwarf nova. HS 2214+2845 is a U Gem-type dwarf nova with a most likely cycle length of 71 d. Conclusions. To date, 14 new dwarf novae have been identified in the HQS. The ratio of short-period (<3 h) to long-period (>3 h) systems of this sample is 1.3, much smaller compared to the ratio of 2.7 found for all known dwarf novae. The HQS dwarf novae display typically infrequent or low-amplitude outburst activity, underlining the strength of spectroscopic selection in identifying new CVs independently of their variability. The spectroscopic properties of short-period CVs in the HQS, newly identified and previously known, suggest that most, or possibly all of them are still evolving towards the minimum period. Their total number agrees with the predictions of population models within an order of magnitude. However, the bulk of all CVs is predicted to have evolved past the minimum period, and those systems remain unidentified. This suggests that those post-bounce systems have markedly weaker Hβ emission lines compared to the average known short-period CVs, and undergo no or extremely rare outbursts.

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“…Some CVs show superhumps in their optical lightcurves during the normal brightness state. In most cases such CVs are bright nova-like variables and nova remnants (Osaki 1996;Retter & Naylor 2000). These superhumps are called permanent superhumps.…”

Section: Introductionmentioning

confidence: 99%

Detection of superhumps in the Z Camelopardalis-type dwarf nova AT Cnc at standstill

Kozhevnikov

2004

A&A

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Abstract. We present results of our photometry of the Z Camelopardalis-type dwarf nova AT Cnc. The observational data were obtained during 13 nights in February and March 2003 when AT Cnc was in its long standstill. Two sets of our data reveal brightness variations with quasi-periods of (4.65 ± 0.02) and of (4.74 ± 0.02) h. The semiamplitude of these variations was observed in the range 5-9 mmag, showing changes from night to night. This signal varies in period and in phase on a time-scale of weeks, as is typical of superhumps. A comparison with the orbital period obtained by Nogami et al. (1999) from the radial velocity measurements of AT Cnc, which equals (4.826 ± 0.014) h, shows that this signal can be a negative superhump since the average period of brightness variations is approximately 3% shorter than the orbital period. These results make AT Cnc a permanent superhump system with a rather large orbital period and a large mass ratio. This is also the first detection of superhumps in a Z Camelopardalis-type system. In addition, we have found signs of an unstable signal with a period of about 2.3 h, which may represent the second harmonic of the 4.7-h signal or the second orbital sideband of the wobble frequency of the tilted precessing accretion disc. The average power spectrum of AT Cnc reveals a broad hump at frequencies in the range 0.4-0.7 mHz, which is evidence of quasiperiodic oscillations. The hump crest corresponds to a period of 1700-1800 s, which is remarkably close to 10% of the orbital period. This may indicate that this system contains a magnetic white dwarf creating the tilted accretion disc.

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Dwarf-Nova Outbursts

Cited by 473 publications

References 54 publications

Finding the most variable stars in the Orion Belt with the All Sky Automated Survey

Finding the most variable stars in the Orion Belt with the All Sky Automated Survey

Dwarf novae in the Hamburg quasar survey: rarer than expected

Detection of superhumps in the Z Camelopardalis-type dwarf nova AT Cnc at standstill

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