2007A&A...466.1025S -
Astronomy and Astrophysics, volume 466, 1025-1030 (2007/5-2)
The statistical significance of the superhump signal in U Geminorum.
SCHREIBER M.R.
Abstract (from CDS):
Although its well-determined mass ratio of q=Msec/Mwd=0.357±0.007 should avoid superoutbursts according to the thermal tidal instability model, in 1985 the prototypical dwarf nova UGem experienced an extraordinary long outburst very much resembling superoutbursts observed in SUUMa systems. Recently, the situation for the model became even worse as superhump detections have been reported for the 1985 outburst of UGem. The superhump signal is noisy and the evidence provided by simple periodograms seems to be weak. Therefore and because of the importance for our understanding of superoutbursts and superhumps, we determine the statistical significance of the recently published detection of superhumps in the AAVSO light curve of the famous long 1985 outburst of UGem. Using Lomb-Scargle periodograms, analysis of variance (AoV), and Monte-Carlo methods we analyse the 160 visual magnitudes obtained by the AAVSO during the outburst and relate our analysis to previous superhump detections. The 160 data points of the outburst alone do not contain a statistically significant period. However, using the characteristics of superhumps detected previously in other SUUMa systems additionally and searching only for signals that are consistent with these, we derive a 2σ significance for the superhump signal. The alleged appearance of an additional superhump at the end of the outbursts appears to be statistically insignificant. Although of weak statistical significance, the superhump signal of the long 1985 outburst of UGem can be interpreted as further indication of the SUUMa nature of this outburst. This further contradicts the tidal instability model as the explanation of the superhump phenomenon.
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Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
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(wavelength) : wavelength range of the measurement : Rad, mm, IR, Opt, UV, Xray, Gam or '∼'(unknown)
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References (1101 between 1850 and 2024) (Total 1101)
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