We present near-infrared (1 - 2.5 micron) spectroscopic and photometric results of Nova V2615 Ophiuchi which was discovered in outburst in 2007 March. Our observations span a period of ~ 80 days starting from 2007 March 28 when the nova was at its maximum light. The evolution of the spectra are shown from the initial P-Cygni phase to an emission-line phase and finally to a dust formation stage. The characteristics of the JHK spectra are very similar to those observed in a nova outburst occurring on a carbon-oxygen white dwarf. We analyse an observed line at 2.088 micron and suggest it could be due to FeII excited by Lyman alpha fluorescence. The highlight of the observations is the detection of the first overtone bands of carbon monoxide (CO) in the 2.29 - 2.40 micron region. The CO bands are modeled to estimate the temperature and mass of the emitting CO gas and also to place limits on the 12C/13C ratio. The CO bands are recorded over several epochs thereby allowing a rare opportunity to study its evolution from a phase of constant strength through a stage when the CO is destroyed fairly rapidly. We compare the observed timescales involved in the evolution of the CO emission and find a good agreement with model predictions that investigate the chemistry in a nova outflow during the early stages.
A novel method is presented which can pin down the time the accretion disk re-established itself in the RS Oph system after it experienced a nova disruption. The method is based on the re-ionisation of the ejecta by photoionisation from the radiation released in the boundary layer from accretion.
Optical spectroscopy of the recurrent nova RS Ophiuchi - from the outburst of 2006 to quiescence
这里展示了2006年蛇夫座RS爆发后一天开始到爆发后一年多的光谱。光谱的演变被发现是类似的，在以前的爆发。早期阶段的光谱主要由氢和氦（I和II）线。后期出现日冕和星云线。发射线的宽度随着时间的推移而变窄，这被解释为一个冲击波扩展到红巨星风。使用光电离代码云，光谱在9个时代跨越14个月后的爆发峰值，从而涵盖了广泛的电离和激发水平的喷出物，建模。最佳拟合的模型参数表明存在一个热的白矮星源，其光度大致恒定为1.26 x 10^{37} erg/s。在前三个月，发现的He，N，O，Ne，Ar，Fe，Ca，S和Ni的丰度（按数量计）高于太阳丰度，这些元素的丰度在后期下降。还提供了在静止期间获得的光谱。静态光谱的光电离模型表明存在低光度的吸积盘吸积盘。在静止期氦的丰度在太阳之下。
The first hours and days of the 2021 explosion of the recurrent symbiotic nova RS Ophiuchii
Astronomical Institute, Slovak Academy of Sciences（斯洛伐克科学院天文研究所）；Private observatory Liptovská Štiavnica（利普托夫斯卡什佳夫尼察私人天文台）；ARAS Eruptive Stars Group（ARAS爆发恒星小组）；Fujii Kurosaki Observatory（藤井黑崎天文台）；Astronomical Institute, Czech Academy of Sciences（捷克科学院天文研究所）；Astronomical Institute of Charles University（查理大学天文研究所）
Multiwavelength modelling the SED of supersoft X-ray sources. II. RS Ophiuchi: From the explosion to the SSS phase
RS Oph是一颗周期性的共生新星，在20年的时间尺度上经历了类似新星的爆发。它的最后两次喷发（1985年和2006年）是从X射线到无线电的密集多波长观测活动的主题。这一贡献的目的是确定物理参数和电离结构的新星从爆炸到第一次出现的超软X射线（第26天）通过使用的方法多波长建模的SED。从爆发的一开始，SED模型就揭示了光谱中存在强烈的恒星和星云辐射成分。在最初的4天里，这颗新星显示出一个双锥电离结构。$\sim 8200$ K温暖和160 - 200 R $_{\odot}$扩展的伪光球围绕白矮星（WD）的赤道到纬度$>40^{\circ}$。WD两极周围的剩余空间被电离，通过WD的快风产生了一个发射测量值为$EM \sim 2.3 \times 10^{62}$ cm $^{-3}$的强星云连续体。燃烧WD的光度是高度超爱丁顿的整个调查期间。风的质量损失率为$10^{-4} - 10^{-5}$ M $_{\odot}$ yr $^{-1}$和喷流的存在表明整个盘以高速率吸积，这有助于维持吸积体的超爱丁顿光度很长一段时间。
The Expanding Nebular Remnant of the Recurrent Nova RS Ophiuchi (2006): II. Modeling of Combined Hubble Space Telescope Imaging and Ground-based Spectroscopy
We present the evolution of the optical spectra of the 2021 outburst of RS Ophiuchi (RS Oph) over about a month after the outburst. The spectral evolution is similar to the previous outbursts. Early spectra show prominent P Cygni profiles of hydrogen Balmer, \ion{Fe}{ii}, and \ion{He}{i} lines. The emission lines were very broad during the initial days, which later became narrower and sharper as the nova evolved. This is interpreted as the expanding shocked material into the winds of the red giant companion. We find that the nova ejecta expanded freely for $\sim 4$ days, and afterward, the sho…
A MeerKAT survey of nearby dwarf novae: I. New detections
Radboud University（拉德堡德大学）；University of Cape Town（开普敦大学）；South African Astronomical Observatory（南非天文台）；Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester（曼彻斯特大学物理与天文学学院乔德雷尔银行天体物理学中心）；University of Oxford（牛津大学）；Rhodes University（罗德岛大学）；South African Radio Astronomy Observatory（南非射电天文台）；University of Warwick（华威大学）；University of Southampton（南安普顿大学）
We present an analysis of archival Spitzer InfraRed Spectrograph (IRS) observations of the recurrent nova RS Ophiuchi obtained on several occasions, beginning about 7 months after the outburst in 2006. These data show atomic emission lines, absorption bands due to photospheric SiO, and the well known silicate dust features at $9.7\,μ$m and $18\,μ$m. The dust emission, arising in the wind of the secondary star, is fitted by Dusty models for mass-loss rates in the range $1.0-1.7\times10^{-7}$M$_{\odot}$yr$^{-1}$. The silicate features are similar in profile to those seen in circumstellar environ…
Smooth X-ray variability from $ρ$ Ophiuchi A+B. A strongly magnetized primary B2 star?
来自大质量恒星的X射线无处不在，但尚未被清楚地理解。在一次专门观测蛇夫座$ρ$暗星云中第一个恒星形成点的XMM-牛顿观测中，我们探测到蛇夫座$ρ$的B2 IV + B2 V系统的平稳变化的X射线辐射。暂时我们将发射分配给主分量。pn照相机的光变曲线示出了低的、几乎稳定的速率的第一阶段，然后是持续时间为10 k s的上升阶段，接着是高速率阶段。主要在1.0-8.0 keV频带中观察到可变性，而在1 keV以下检测到很少的可变性。的三个阶段的光谱分析揭示了在3.0千电子伏的热分量的存在下，加起来两个相对冷的组件在0.9千电子伏和2.2千电子伏。我们解释了平滑的变化与出现的一个扩展的活跃区域的表面上的主要恒星，由于其快速旋转（v $sin~i \sim315$公里/秒）。我们估计该区域的直径在$0.5-0.6$ R $_*$范围内。硬X射线发射和它的变化暗示了一种磁起源，就像其他几颗晚O型$-$早B型恒星所暗示的那样。我们还讨论了另一种解释的基础上出现的年轻（5-10万年）的低质量伴星明亮和热的X射线掩星。
The recently discovered high energy emission from the recurrent nova RS Ophiuchi by Fermi-LAT ($>$ 100 MeV), H.E.S.S. and MAGIC ($>$ 100 GeV), hints towards a possible hadronic origin of this radiation component. From the observed high energy photon flux we derive the expected number of neutrino events that could be detected by present and future neutrino telescopes in the different energy ranges. We find that both hadronic and leptonic processes remain valid interpretations for this $ \ gamma $ emission. Preliminary estimates indicate that with the "next-generation" instrument IceCube-Gen2, t…
Peaking at 3.7 mag on 2020 July 11, YZ Ret was the second-brightest nova of the decade. The nova's moderate proximity (2.7 kpc from Gaia) provided an opportunity to explore its multi-wavelength properties in great detail. Here we report on YZ Ret as part of a long-term project to identify the physical mechanisms responsible for high-energy emission in classical novae. We use simultaneous Fermi/LAT and NuSTAR observations complemented by XMM-Newton X-ray grating spectroscopy to probe the physical parameters of the shocked ejecta and the nova-hosting white dwarf. The XMM-Newton observations reve…
We propose a theoretical explanation of absorption/emission line systems in classical novae based on a fully self-consistent nova explosion model. We found that a reverse shock is formed far outside the photosphere ($\gtrsim 10^{13}$ cm) because later-ejected mass with a faster velocity collides with earlier-ejected matter. Optically thick winds blow continuously at a rate of $\sim 10^{-4} ~M_\odot$ yr$^{-1}$ near the optical maximum, but its velocity decreases toward the optical maximum and increases afterward, so that the shock arises only after the optical maximum. The nova ejecta is divide…
There are indications that the third known eruption of the recurrent nova T CrB is imminent, and multi-wavelength observations prior to the eruption are important to characterise the system before it erupts. T CrB is known to display the SiO fundamental vibrational feature at 8$\,μ$m. When the anticipated eruption occurs, it is possible that the shock produced when the ejected material runs into the wind of the red giant in the system may be traced using SiO maser emission. We have used the 100m Effelsberg Radio Telescope to search for $^{28}$SiO emission in the $\upsilon=1$, $\upsilon=2$, $J=…
