We present a detailed study of the 2019 outburst of the cataclysmic variable V1047 Cen, which hosted a classical nova eruption in 2005. The peculiar outburst occurred 14 years after the classical nova event, lasted for more than 400 days, and reached
an amplitude of around 6 magnitudes in the optical. Early spectral follow-up revealed what could be a dwarf nova (accretion disk instability) outburst in a classical nova system. However, the outburst duration, high velocity ($>$2000 km s$^{-1}$) features in the optical line profiles, luminous optical emission, and the presence of prominent long-lasting radio emission, together suggest a phenomenon more exotic and energetic than a dwarf nova outburst. There are striking similarities between this V1047 Cen outburst and those of combination novae in classical symbiotic stars. We suggest that the outburst may have started as a dwarf nova that led to the accretion of a massive disk, which in turn triggered enhanced nuclear shell burning on the white dwarf and eventually led to generation of a wind/outflow. From optical photometry we find a bf{possible} orbital period of 8.36 days, which supports the combination nova scenario and makes the system an intermediate case between typical cataclysmic variables and classical symbiotic binaries. If true, such a phenomenon would be the first of its kind to occur in a system that has undergone a classical nova eruption and is intermediate between cataclysmic variables and symbiotic binaries.
The nano-particle systems under theoretically and experimentally investigation because of the potential applications in the nano-technology such as drug delivery, ferrofluids mechanics, magnetic data storage, sensors, magnetic resonance imaging, and
cancer therapy. Recently, it is reported that interacting nano-particles behave as spin-glasses and experimentally show that the relaxation of these systems obeys stretched exponential i.e., KWW relaxation. Therefore, in this study, considering the interacting nano-particle systems we model the relaxation and investigate frequency and temperature behaviour depends on slow relaxation by using a simple operator formalism. We show that relaxation deviates from Debye and obeys to KWW in the presence of the memory effects in the system. Furthermore, we obtain the frequency and temperature behaviour depend on KWW relaxation. We conclude that the obtained results are consistent with experimental results and the simple model, presented here, is very useful and pedagogical to discuss the slow relaxation of the interacting nano-particles.
In this study, we analytically formulated the path integral representation of the conditional probabilities for non-Markovian kinetic processes in terms of the free energy of the thermodynamic system. We carry out analytically the time-fractional kin
etic equations for these processes. Thus, in a simple way, we generalize path integral solutions of the Markovian to the non-Markovian cases. We conclude that these pedagogical results can be applied to some physical problems such as the deformed ion channels, internet networks and non-equilibrium phase transition problems.
The physical mechanism driving mass ejection during a nova eruption is still poorly understood. Possibilities include ejection in a single ballistic event, a common envelope interaction, a continuous wind, or some combination of these processes. Here
we present a study of 12 Galactic novae, for which we have pre-maximum high-resolution spectroscopy. All 12 novae show the same spectral evolution. Before optical peak, they show a slow P Cygni component. After peak a fast component quickly arises, while the slow absorption remains superimposed on top of it, implying the presence of at least two physically distinct flows. For novae with high-cadence monitoring, a third, intermediate-velocity component is also observed. These observations are consistent with a scenario where the slow component is associated with the initial ejection of the accreted material and the fast component with a radiation-driven wind from the white dwarf. When these flows interact, the slow flow is swept up by the fast flow, producing the intermediate component. These colliding flows may produce the gamma-ray emission observed in some novae. Our spectra also show that the transient heavy element absorption lines seen in some novae have the same velocity structure and evolution as the other lines in the spectrum, implying an association with the nova ejecta rather than a pre-existing circumbinary reservoir of gas or material ablated from the secondary. While this basic scenario appears to qualitatively reproduce multi-wavelength observations of classical novae, substantial theoretical and observational work is still needed to untangle the rich diversity of nova properties.
We present a detailed study of the 2017 eruption of the classical nova ASASSN-17pf (LMCN 2017-11a), which is located in the Large Magellanic Cloud, including data from AAVSO, ASAS-SN, SALT, SMARTS, SOAR, and the Neil Gehrels textit{Swift} Observatory
. The optical light-curve is characterized by multiple maxima (flares) on top of a slowly evolving light-curve (with a decline time, $t_2>$ 100 d). The maxima correlate with the appearance of new absorption line systems in the optical spectra characterized by increasing radial velocities. We suggest that this is evidence of multiple episodes of mass-ejection with increasing expansion velocities. The line profiles in the optical spectra indicate very low expansion velocities (FWHM $sim$ 190 km s$^{-1}$), making this nova one of the slowest expanding ever observed, consistent with the slowly evolving light-curve. The evolution of the colors and spectral energy distribution show evidence of decreasing temperatures and increasing effective radii for the pseudo-photosphere during each maximum. The optical and infrared light-curves are consistent with dust formation 125 days post-discovery. We speculate that novae showing several optical maxima have multiple mass-ejection episodes leading to shocks that may drive $gamma$-ray emission and dust formation.
We present a detailed study of the 2016 eruption of nova V407 Lupi (ASASSN-16kt), including optical, near-infrared, X-ray, and ultraviolet data from SALT, SMARTS, SOAR, Chandra, Swift, and XMM-Newton. Timing analysis of the multiwavelength light-curv
es shows that, from 168 days post-eruption and for the duration of the X-ray supersoft source phase, two periods at 565 s and 3.57 h are detected. We suggest that these are the rotational period of the white dwarf and the orbital period of the binary, respectively, and that the system is likely to be an intermediate polar. The optical light-curve decline was very fast ($t_2 leq$ 2.9 d), suggesting that the white dwarf is likely massive ($gtrsim 1.25$ M$_{odot}$). The optical spectra obtained during the X-ray supersoft source phase exhibit narrow, complex, and moving emission lines of He II, also characteristics of magnetic cataclysmic variables. The optical and X-ray data show evidence for accretion resumption while the X-ray supersoft source is still on, possibly extending its duration.
We report on multiwavelength observations of nova SMCN 2016-10a. The present observational set is one of the most comprehensive for any nova in the Small Magellanic Cloud, including: low, medium, and high resolution optical spectroscopy and spectropo
larimetry from SALT, FLOYDS, and SOAR; long-term OGLE $V$- and $I$- bands photometry dating back to six years before eruption; SMARTS optical and near-IR photometry from $sim$ 11 days until over 280 days post-eruption; $Swift$ satellite X-ray and ultraviolet observations from $sim$ 6 days until 319 days post-eruption. The progenitor system contains a bright disk and a main sequence or a sub-giant secondary. The nova is very fast with $t_2 simeq$ 4.0 $pm$ 1.0 d and $t_3 simeq$ 7.8 $pm$ 2.0 d in the $V$-band. If the nova is in the SMC, at a distance of $sim$ 61 $pm$ 10 kpc, we derive $M_{V,mathrm{max}} simeq - 10.5$ $pm$ 0.5, making it the brightest nova ever discovered in the SMC and one of the brightest on record. At day 5 post-eruption the spectral lines show a He/N spectroscopic class and a FWHM of $sim$ 3500 kms$^{-1}$ indicating moderately high ejection velocities. The nova entered the nebular phase $sim$ 20 days post-eruption, predicting the imminent super-soft source turn-on in the X-rays, which started $sim$ 28 days post-eruption. The super-soft source properties indicate a white dwarf mass between 1.2 M$_{odot}$ and 1.3 M$_{odot}$ in good agreement with the optical conclusions.
We report spectroscopic and photometric follow-up of the peculiar nova V5852~Sgr (discovered as OGLE-2015-NOVA-01), which exhibits a combination of features from different nova classes. The photometry shows a flat-topped light curve with quasi-period
ic oscillations, then a smooth decline followed by two fainter recoveries in brightness. Spectroscopy with the Southern African Large Telescope shows first a classical nova with an Fe II or Fe IIb spectral type. In the later spectrum, broad emissions from helium, nitrogen and oxygen are prominent and the iron has faded which could be an indication to the start of the nebular phase. The line widths suggest ejection velocities around $1000,{rm km,s^{-1}}$. The nova is in the direction of the Galactic bulge and is heavily reddened by an uncertain amount. The $V$ magnitude 16 days after maximum enables a distance to be estimated and this suggests that the nova may be in the extreme trailing stream of the Sagittarius dwarf spheroidal galaxy. If so it is the first nova to be detected from that, or from any dwarf spheroidal galaxy. Given the uncertainty of the method and the unusual light curve we cannot rule out the possibility that it is in the bulge or even the Galactic disk behind the bulge.
