The orbital period of the recurrent nova U Sco has been observed to decrease during the 1999 outburst. In an outburst mass is ejected from the surface of the white dwarf. The separation of the binary system widens and the orbital period increases. We find that magnetic braking between outbursts, mass transfer to the companion, and frictional angular momentum losses during outbursts are all too small to account for this unexpected change. We find, however, that if the secondary has a sufficiently strong magnetic field, B=8x10^3 G, then the ejected material can couple to it and corrotate with the system. The ejected material gains angular momentum while the binary system loses it and the period decreases. If such a strong magnetic field is indeed present, then we predict that a period decrease should be observed also during the current 2010 outburst. If, however, the presence of such a field can be ruled out observationally, then the cause for the period decrease (if confirmed) remains unknown.
One very important object for understanding the nature of red novae is V1309 Sco. Its pre-outburst observations showed that, before its red-nova eruption in 2008, it was a contact binary quickly evolving to the merger of the components. It thus provided us with a direct evidence that the red novae result from stellar mergers. We analyse the spectral energy distribution (SED) of the object and its evolution with time. From various optical and infrared surveys and observing programmes carried out with OGLE, HST, VVV, Gemini South, WISE, Spitzer, and Herschel we constructed observed SED in 2010 a…
Thomson Scattering and Collisional Ionization in the X-rays Grating Spectra of the Recurrent Nova U Scorpii
我们提出了一个钱德拉观察经常性的新星天蝎座U，在2010年观察到的视觉最大值后的第18天用HRC-S探测器和LETG光栅完成，并将其与XMM-牛顿观测在最大值后的第23天和第35天进行比较。总吸收通量在2.2-2.6 x 10^（-11）erg cm^（-2）s^（-1）范围内，对应于未吸收光度7-8.5 x 10^（36）x（d/12 kpc）^2，N（H）=2- 2.7 x 10 ^（21）cm^（-2）。在第18天，70%的软X托盘通量是在一个典型的非常热的白矮星（WD）大气，这占了约80%的通量在第23和35天的连续。此外，所有的光谱显示非常宽的发射线，由于较高的电离阶段在稍后的时间。与钱德拉，我们观察到明显的P天鹅座配置文件。我们发现，这些奇特的配置文件是不是由于蓝移吸收和红移发射光电离喷出物，像光学P Cyg的新星，但他们是一个叠加的WD大气吸收功能所反映的已经发现的汤姆逊散射日冕，和发射线由于碰撞电离凝聚在喷出物。在第23天和第35天，吸收组分不再可测量，已经失去了最初的大的蓝移，该蓝移使它们从宽发射线的核心移位。我们将其解释为表明质量损失在第18天和第23天之间停止。在第35天，发射线光谱变得非常复杂，具有几个不同的组分。模型大气表明，WD大气温度在第18天约为730，000 K，在第35天达到900，000 K-一百万K。该峰值温度与至少1.3 M（溶胶）的WD质…
U Sco is a recurrent nova with eleven observed eruptions, most recently in 2010.1 and 2022.4. I report on my program (running since 1989) of measuring eclipse times and brightnesses of U Sco in quiescence, from 2010 to 2022. The orbital period suddenly increased by +22.4 +- 1.0 parts-per-million across the 2010.1 eruption. This period change is greater than the near-zero period change (+3.9 +- 6.1 parts-per-million) across the 1999.2 eruption. This period change cannot come from any of the usual mechanisms, whereas the one remaining possibility is that the period changes are dominated by the l…
We perform photoionization modeling of the dusty nova V1280 Scorpii (V1280 Sco) with an aim to study the changes in the physical and chemical parameters. We model pre and post dust phase, optical and near-Infrared (NIR), spectra using the photoionization code \textsc{cloudy}, v.17.02, considering a two-component (low density and high density region) model. From the best-fit model, we find that the temperature and luminosity of the central ionizing source in the pre-dust phase are in the range 1.32 - 1.50 $\times 10^4$ K and 2.95 - 3.16 $\times 10^{36}$ ergs$^{-1}$, respectively, which increase…
Morphology of nova ejecta is essential for fully understanding the physical processes involved in nova eruptions. We studied the 3D morphology of the expanding ejecta of the extremely slow nova V1280 Sco with a unique light curve. Synthetic line profile spectra were compared to the observed [O III] 4959, 5007 and [N II] 5755 emission line profiles in order to find the best-fit morphology, inclination angle, and maximum expansion velocity of the ejected shell. We derive the best fitting expansion velocity, inclination, and squeeze as $V_{\rm exp} = 2100^{+100}_{-100}$ \,km\,s$^{-1}$, $i = 80^{+…
The recurrent symbiotic nova V745 Sco exploded on 2014 February 6 and was observed on February 22 and 23 by the Chandra X-ray Observatory Transmission Grating Spectrometers. By that time the supersoft source phase had already ended and Chandra spectra are consistent with emission from a hot, shock-heated circumstellar medium with temperatures exceeding 10^7K. X-ray line profiles are more sharply peaked than expected for a spherically-symmetric blast wave, with a full width at zero intensity of approximately 2400 km/s, a full width at half maximum of 1200 +/- 30 km/s and an average net blueshif…
Orbital Period Changes of Recurrent Nova U Scorpii Demonstrate that M$_{\rm ejecta}$=26$\times$M$_{\rm accreted}$ and Is Not a Type Ia Supernova Progenitor
We reviewed the light curves of 10 known recurrent novae (RNs) in the modified scales of the "logarithmic of time, amplitude of outburst". A unified rule was established to normalize the time scale. Confirmation of the known result: in a series of recurrent outbursts, the light curve of nova retains its shape, was realized by distinguishing three groups amongst these 10 novae. The CI Aql (+V2487 Oph) and T Pyx (+ IM Nor) groups contain by one additional member. The V745 Sco group includes V394 CrA and V3890 Sgr. Three RNs: T CrB, RS Oph and U Sco, have its own uniqueness. After comparing the l…
A spectrum of the quiescent counterpart of the Recurrent Nova candidate M31N 1966-08a (= M31N 1968-10c) obtained with LRS2 on the Hobby-Eberly Telescope reveals the object to be a foreground Galactic dMe flare star, and not a nova in M31.
M31 is an ideal laboratory for observing and studying recurrent novae. To date, there have been 18 recurrent nova discovered in M31, six of which have recurrence periods less than nine years. M31N 2017-12a (AT2017jdm) is a transient that was reported near the center of M31, with the time of outburst estimated to be 2017 December 24.141 +/- 0.42 based on constraints from previous data. Here we present the photometric observations of M31N 2017-12a, which we confirm as a recurrence of M31N 2007-10b.
The classical nova V2491 Cyg was once suggested to be a recurrent nova. We have broadly reproduced the light curve of V2491 Cyg by a nova outburst model on a cold $1.36~M_\odot$ white dwarf (WD), which strongly suggests that V2491 Cyg is a classical nova outbursting on a cold very massive WD rather than a recurrent nova outbursting on a warmer WD like the recurrent nova RS Oph. In a long-term evolution of a cataclysmic binary, an accreting WD has been settled down to a thermal equilibrium state with the balance of gravitational energy release and neutrino loss. The central temperature of the W…
Models have long predicted that the frequency-averaged masses of white dwarfs in Galactic classical novae are twice as large as those of field white dwarfs. Only a handful of dynamically well-determined nova white dwarf masses have been published, leaving the theoretical predictions poorly tested. The recurrence time distributions and mass accretion rate distributions of novae are even more poorly known. To address these deficiencies, we have combined our extensive simulations of nova eruptions with the Strope et al (2010) and Schaefer et al (2010) databases of outburst characteristics of Gala…
We report spectroscopic observations of the $Hα$ emission line of the recurrent nova RS~Oph obtained between 12 and 23 August 2021 during the recent outburst. On the basis of the sharp P~Cyg profile superimposed onto the strong H-alpha emission, we estimate that the outflowing velocity of the material surrounding RS Oph is in the range 32 km/s < V_{out} < 68 km/s. The new GAIA distance indicates that the red giant should be probably classified in between II and III luminosity class. The spectra are available upon request from the authors and on Zenodo.
Early Spectroscopy of the 2010 Outburst of U Scorpii
我们在2010年爆发期间呈现了复发新星U~Sco的早期光谱。我们成功地获得了$t_{\rm d}=$ 0.37- 0.44 ~d的时间序列谱，其中$t_{\rm d}$表示从发现本次爆发的时间。这是U Sco爆发的第一个晚上的第一个时间分辨光谱。在$t_{\rm d}\sim 0.4$ ~d处，H $α$谱线由蓝移（$-5000$ km s $^{-1}$）窄吸收分量和宽发射分量组成，该宽发射分量具有三个峰值，即蓝移（$\sim -3000$ km s $^{-1}$）、中心（$\sim 0$ km s $^{-1}$）和红移（$\sim +3000$ km s $^{-1}$）。在第一个晚上，蓝色和红色的山峰比中央的山峰发展得更快。这种快速的变化可能是由于在爆发的最早阶段产生的非球面风的增长造成的。在$t_{\rm d}=1.4$ ~d的H $α$线具有几乎平顶的轮廓，在$\sim \pm 3000$ km s $^{-1}$处具有弱的蓝色和红色峰。这个轮廓可以归因于一个近似球形的外壳，而在第一个晚上增长的非球面仍然存在。$t_{\rm d}=9$ d后，风场非球面性减弱。
Optical (BVRI) photometry of the first three weeks of the 2016 outburst of the recurrent Nova LMC 1968 is presented and discussed. The 2016 I-band light-curve is an exact replica, even in the most minute details, of that for the 2010 eruption. The maximum is inferred to have occurred on 2016 Jan 21.2 at I=11.5 mag, corresponding to an absolute magnitude M(I)=-7.15. A ~1 day plateau is present in all bands about six days past optical maximum, simultaneous with the emergence of super-soft X-ray emission in Swift observations, signalling the widespread ionization of the ejecta. The nova entered a…
We present an analysis of the red giant component of the recurrent nova V3890 Sgr, using data obtained before and after its 2019 eruption. Its effective temperature is $T_{\rm eff}=3050\pm$200 K for $\log{g}=0.7$, although there are modest changes in $T_{\rm eff}$. There is an overabundance of both carbon ($0.20\pm0.05$~dex) and sodium ($1.0\pm0.3$~dex) relative to their solar values, possibly the result of ejecta from the 1990 nova eruption being entrained into the red giant photosphere. We find $^{12}$C/$^{13}$C $=25\pm2$, a value similar to that found in red giants in other recurrent novae.…
T CrB is a symbiotic recurrent nova known to exhibit active phases, characterised by apparent increases in the hot component temperature and the appearance of flickering, i.e. changes in the observed flux on the time-scale of minutes. Historical UV observations have ruled out orbital variability as an explanation for flickering and instead suggest flickering is caused by variable mass transfer. We have analysed optical and X-ray observations to investigate the nature of the flickering as well as the active phases in T CrB. The spectroscopic and photometric observations confirm that the active …
We report the determination of abundances and isotopic ratios for C, O and Si in the photosphere of the red giant component of the recurrent nova T Coronae Borealis from new 2.284--2.402 $μ$m and 3.985--4.155 $μ$m spectroscopy. Abundances and isotopic ratios in the photosphere may be affected by (i) processes in the red giant interior which are brought to the surface during dredge-up, (ii) contamination of the red giant, either during the common envelope phase of the binary evolution or by material synthesised in recurrent nova eruptions, or a combination of the two. We find that the abundance…
The spectroscopic evolution of the symbiotic-like recurrent nova V407 Cygni during its 2010 outburst. II. The circumstellar environment and the aftermath
We present and analyze optical photometry and high resolution SALT spectra of the symbiotic recurrent nova V3890 Sgr at quiescence. The orbital period, P=747.6 days has been derived from both photometric and spectroscopic data. Our double-line spectroscopic orbits indicate that the mass ratio is q=M_g/M_WD=0.78+/-0.05, and that the component masses are M_WD=1.35+/-0.13 Msun, and M_g=1.05+/-0.11 Msun. The orbit inclination is approximately 67-69 degr. The red giant is filling (or nearly filling) its Roche lobe, and the distance set by its Roche lobe radius, d=9 kpc, is consistent with that resu…
