Rod Stubbings has discovered a new southern Z Cam hiding in the weeds, disguised as an ordinary dwarf nova no one has paid attention to in years.
Congratulations to Rod. His story is a testament to the value of patience, persistence and visual observations.
Abstract: Long term optical monitoring of the dwarf nova OQ Car has been conducted to study the previously unknown behaviour of this star system. The observations have shown OQ Car to have frequent dwarf nova outbursts and revealed the first recorded standstill of this star system. Based on this, we conclude that OQ Car is a new member of the Z Cam type dwarf novae.
We studied the background dwarf nova of KIC 11412044 in the Kepler public data and identified it with GALEX J194419.33+491257.0. This object turned out to be a very active SU UMa-type dwarf nova having a mean supercycle of about 150 d and frequent normal outbursts having intervals of 4-10 d. The object showed strong persistent signal of the orbital variation with a period of 0.0528164(4) d (76.06 min) and superhumps with a typical period of 0.0548 d during superoutbursts. Most of the superoutbursts were accompanied by a precursor outburst. All these features are unusual for this very short orbital period. We succeeded in detecting the evolving stage of superhumps (stage A superhumps) and obtained a mass ratio of 0.141(2), which is unusually high for this orbital period. We suggest that the unusual outburst properties are a result of this high mass ratio. We suspect that this object is a member of the recently recognized class of cataclysmic variables (CVs) with a stripped core evolved secondary which are evolving toward AM CVn-type CVs. The present determination of the mass ratio using stage A superhumps makes the first case in such systems.
Authors: Taichi Kato (Kyoto U.), Yoji Osaki (U. of Tokyo)
The Nearby Supernova Factory based at Berkeley Lab shows that Type Ia supernovae have a surprisingly large range of masses
Until recently, scientists thought they knew why Type Ia supernovae are all so much alike. But their favorite scenario was wrong.
The assumption was that carbon-oxygen white dwarf stars, the progenitors of the supernovae, capture additional mass by stripping it from a companion star or by merging with another white dwarf; when they approach the Chandrasekhar limit (40 percent more massive than our sun) they experience thermonuclear runaway. Type Ia brightnesses were so similar, scientists thought, because the amounts of fuel and the explosion mechanisms were always the same.
Greg Aldering summarizes the most basic result of the new analysis: “The white dwarfs exploding as Type Ia supernovae have a range of masses, and the resulting light-curve width is directly proportional to the total mass involved in the explosion.”
When University of California, Berkeley, astronomer Alex Filippenko’s research team looked for the supernova in data collected by the Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory near San Jose, Calif., they discovered that the robotic telescope had actually taken a photo of it 37 hours after it appeared, unnoticed, on Jan. 14.
Combining this observation with another chance observation by a Japanese amateur astronomer, Filippenko’s team was able to calculate that SN 2014J had unusual characteristics – it brightened faster than expected for a Type Ia supernova and, even more intriguing, it exhibited the same unexpected, rapid brightening as another supernova that KAIT discovered and imaged last year – SN 2013dy.
“Now, two of the three most recent and best-observed Type Ia supernovae are weird, giving us new clues to how stars explode,” said Filippenko, referring to a third, though apparently ‘normal,’ Type Ia supernova, SN 2011fe, discovered three years ago. “This may be teaching us something general about Type Ia supernovae that theorists need to understand. Maybe what we think of as ‘normal’ behavior for these supernovae is actually unusual, and this weird behavior is the new normal.”