35 research outputs found
Dwarf nova EZ Lyncis second visit to instability strip
© 2014 © The Author 2014. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved. The analysis of 14 periodograms of EZLyn for data spaced over 565d in 2012-2014 (2-3.5yr after the 2010 outburst) yielded the existence of a stable signal around 100cycles/day (c/d) and three signals around 310c/d, 338c/d, and 368c/d (the corresponding periods are 864s, 279s, 256s, and 235s). We interpret them as independent nonradial pulsations of the white dwarf in EZLyn, but the possibility that a linear combination of a frequency of 100c/d and a harmonic of the orbital period might produce a frequency of 368c/d also cannot be excluded. The signal at 100c/d was detected as a transient during the first stay in the instability strip. The period at 338c/d has been a known nonradial pulsation since EZLyn entered the instability strip after the 2010 outburst. We detected the signals around 310c/d and 368c/d for the first time. We applied the two-dimensional least absolute shrinkage and selection operator (Lasso) analysis for the first time to explore the behavior of these signals on a time scale of hours in nightly runs of observations having a duration of 6-12hr. The Lasso analysis revealed the simultaneous existence of all three frequencies (310c/d, 338c/d, and 368c/d) on a majority of nights of observations, but with variable amplitudes and variable drifts of frequencies by 2%-6% on a time scale of ∼5-7hr. The largest drift we detected corresponded to 17.5s in period in ∼5hr
Superhump evolution of WZ Sge-type dwarf nova ASASSN-14cv at rebrightening stage
© 2016, Pleiades Publishing, Ltd.We report the results of observations of a WZ Sge-type dwarf nova ASASSN-14cv, acquired in 2014 and covering the end of a superoutburst and a rebrightening stage. We detected 8 rebrightenings of this star. Based on the light curve profiles of the rebrightenings, we conclude on the existence of both the “inside-out” and “outside-in” outbursts. During the entire course of the rebrightening stage, a brightness variability with the mean period of P = 0.d06042(8) was detected, which was identified as a superhump period during the stage B of the superoutburst. The character of the registered superhump evolution can be either described by a parabolic approximation with the negative Pdot = −1.1 × 10−5, or by an approximation with 2 linear areas with the corresponding periods of 0.d06074(3) and 0.d06046(9)
SRGeJ045359.9+622444: A 55-min Period Eclipsing AM CVn Discovered from a Joint SRG/eROSITA + ZTF Search
AM CVn systems are ultra-compact binaries where a white dwarf accretes from a
helium-rich degenerate or semi-degenerate donor. Some AM CVn systems will be
among the loudest sources of gravitational waves for the upcoming Laser
Interferometer Space Antenna (LISA), yet the formation channel of AM CVns
remains uncertain. We report the study and characterisation of a new eclipsing
AM CVn, SRGeJ045359.9+622444 (hereafter SRGeJ0453), discovered from a joint
SRG/eROSITA and ZTF program to identify cataclysmic variables (CVs). We
obtained optical photometry to confirm the eclipse of SRGeJ0453 and determine
the orbital period to be min. We
constrain the binary parameters by modeling the high-speed photometry and
radial velocity curves and find
and . The X-ray spectrum is
approximated by a power-law model with an unusually flat photon index of
previously seen in magnetic CVs with SRG/eROSITA, but verifying
the magnetic nature of SRGeJ0453 requires further investigation. Optical
spectroscopy suggests that the donor star of SRGeJ0453 could have initially
been a He star or a He white dwarf. SRGeJ0453 is the ninth eclipsing AM CVn
system published to date, and its lack of optical outbursts have made it
elusive in previous surveys. The discovery of SRGeJ0453 using joint X-ray and
optical surveys highlights the potential for discovering similar systems in the
near future.Comment: Submitted to Ap
First Detection of Two Superoutbursts during Rebrightening Phase of a WZ Sge-type Dwarf Nova: TCP J21040470+4631129
We report photometric and spectroscopic observations and analysis of the 2019
superoutburst of TCP J21040470+4631129. This object showed a 9-mag
superoutburst with early superhumps and ordinary superhumps, which are the
features of WZ Sge-type dwarf novae. Five rebrightenings were observed after
the main superoutburst. The spectra during the post-superoutburst stage showed
the Balmer, He I and possible sodium doublet features. The mass ratio is
derived as 0.0880(9) from the period of the superhump. During the third and
fifth rebrightenings, growing superhumps and superoutbursts were observed,
which have never been detected during a rebrightening phase among WZ Sge-type
dwarf novae with multiple rebrightenings. To induce a superoutburst during the
brightening phase, the accretion disk was needed to expand beyond the 3:1
resonance radius of the system again after the main superoutburst. These
peculiar phenomena can be explained by the enhanced viscosity and large radius
of the disk suggested by the higher luminosity and the presence of late-stage
superhumps during the post-superoutburst stage, plus by more mass supply from
the cool mass reservoir and/or from the secondary because of the enhanced mass
transfer than those of other WZ Sge-type dwarf novae.Comment: 13 pages, 10 figures, accepted for publication in PAS
First detection of two superoutbursts during rebrightening phase of a WZ Sge-type Dwarf Nova : TCP J21040470+4631129
We report on photometric and spectroscopic observations and analysis of the 2019 superoutburst of TCP J21040470+4631129. This object showed a 9 mag superoutburst with early superhumps and ordinary superhumps, which are the features of WZ Sge-type dwarf novae. Five rebrightenings were observed after the main superoutburst. The spectra during the post-superoutburst stage showed Balmer, He I, and possible sodium doublet features. The mass ratio is derived as 0.0880(9) from the period of the superhump. During the third and fifth rebrightenings, growing superhumps and superoutbursts were observed, which have never been detected during a rebrightening phase among WZ Sge-type dwarf novae with multiple rebrightenings. To induce a superoutburst during the brightening phase, the accretion disk needs to have expanded beyond the 3 : 1 resonance radius of the system again after the main superoutburst. These peculiar phenomena can be explained by the enhanced viscosity and large radius of the accretion disk suggested by the higher luminosity and the presence of late-stage superhumps during the post-superoutburst stage, plus by more mass supply from the cool mass reservoir and/or from the secondary because of the enhanced mass transfer than those of other WZ Sge-type dwarf novae.peer-reviewe