The multi-wavelength view of shocks in the fastest nova V1674 Her
K. V. Sokolovsky, T. J. Johnson, S. Buson, P. Jean, C. C. Cheung, K. Mukai, L. Chomiuk, E. Aydi, B. Molina, A. Kawash, J. D. Linford, A. J. Mioduszewski, M. P. … 展开作者
K. V. Sokolovsky, T. J. Johnson, S. Buson, P. Jean, C. C. Cheung, K. Mukai, L. Chomiuk, E. Aydi, B. Molina, A. Kawash, J. D. Linford, A. J. Mioduszewski, M. P. Rupen, J. L. Sokoloski, M. N. Williams, E. Steinberg, I. Vurm, B. D. Metzger, K. L. Page, M. Orio, R. M. Quimby, A. W. Shafter, H. Corbett, S. Bolzoni, J. DeYoung, K. Menzies, F. D. Romanov, M. Richmond, J. Ulowetz, T. Vanmunster, G. Williamson, D. J. Lane, M. Bartnik, M. Bellaver, E. Bruinsma, E. Dugan, J. Fedewa, C. Gerhard, S. Painter, D. -M. Peterson, J. E. Rodriguez, C. Smith, H. Sullivan, S. Watson
Classical novae are shock-powered multi-wavelength transients triggered by a thermonuclear runaway on an accreting white dwarf. V1674 Her is the fastest nova ever recorded (time to declined by two magnitudes is t_2=1.1 d) that challenges our understanding of shock formation in novae. We investigate the physical mechanisms behind nova emission from GeV gamma-rays to cm-band radio using coordinated Fermi-LAT, NuSTAR, Swift and VLA observations supported by optical photometry. Fermi-LAT detected short-lived (18 h) 0.1-100 GeV emission from V1674 Her that appeared 6 h after the eruption began; this was at a level of (1.6 +/- 0.4)x10^-6 photons cm^-2 s^-1. Eleven days later, simultaneous NuSTAR and Swift X-ray observations revealed optically thin thermal plasma shock-heated to kT_shock = 4 keV. The lack of a detectable 6.7 keV Fe K_alpha emission suggests super-solar CNO abundances. The radio emission from V1674 Her was consistent with thermal emission at early times and synchrotron at late times. The radio spectrum steeply rising with frequency may be a result of either free-free absorption of synchrotron and thermal emission by unshocked outer regions of the nova shell or the Razin-Tsytovich effect attenuating synchrotron emission in dense plasma. The development of the shock inside the ejecta is unaffected by the extraordinarily rapid evolution and the intermediate polar host of this nova.
We present long-slit intermediate-dispersion spectroscopic observations and narrow-band direct imaging of four classical nova shells, namely TAur, HRDel, DQHer and QUVul, and the nova-like source CKVul. These are used to construct models of their nebular remnants using the morpho-kinematic modelling tool Shape to reveal their 3D shape. All these nova remnants but CKVul can be described by prolate ellipsoidal shells with different eccentricity degree, from the spherical QUVul to the highly elongated shell with an equatorial component HRDel. On the other hand, CKVul shows a more complex structur…
We report a detection of a 0.153 days period in the classical nova V1674 Her using the NICER observations taken within a month since the outburst (i.e., about MJD 59405). The X-ray period is consistent with the orbital period previously found in the optical band, strongly suggesting the NICER signal as the X-ray orbital periodicity of the system. A seemingly double-humped profile was obtained by folding the detrended X-ray light curve with the period after removing the rotational X-ray pulsations of the nova. The profile may be caused by occultation by the companion or the accretion disk, poss…
A remarkable recurrent nova in M 31: The predicted 2014 outburst in X-rays with Swift
最近发现的M31新星M31 N 2008- 12 a是一颗复发新星（RN），复发时间约为1年。这是迄今为止已知RNe中最快的递归时间尺度。我们的光学监测计划在10月初检测到了预测的2014年M31 N 2008- 12 a爆发。我们立即启动了X射线/紫外线监测活动与斯威夫特研究的多波长演变的爆发。我们在发现M31 N 2008- 12 a后的20天内每天都用Swift观测，覆盖了整个超软X射线源（SSS）阶段。我们在爆发后第六天左右检测到SSS发射。SSS状态持续约两周，直至约第19天。M31 N 2008- 12 a是一个具有高黑体温度的明亮X射线源。这次爆发的X射线特性与2013年的爆发非常相似。结合X射线光谱表明，快速上升和下降的有效黑体温度。短期X射线光曲线显示出强烈的非周期性变化，在约14天后显著降低。总的来说，M31 N 2008- 12 a的X射线特性与M31新星的平均人口特性一致。它的光学和X射线光变曲线可以统一地缩放，以显示与银河系RNe U Sco或RS Oph相似的时间尺度。SSS演化的时间尺度和有效温度与高质量WD一致。我们预测M31 N 2008- 12 a的下一次爆发将发生在2015年秋季。
Optical observations of the fast nova V1674 Herculis
Indian Institute of Astrophysics（印度天体物理研究所）；Pondicherry University（本地治里大学）；INAF–Osservatorio Astronomico di Cagliari（意大利国家天体物理研究所-卡利亚里天文台）；Department of Physical Sciences, Indian Institute of Science Education and Research Mohali（印度科学教育与研究学院穆扎法尔加尔物理科学系）
Nova Her 2021 (V1674 Her), which erupted on 2021 June 12, reached naked-eye brightness and has been detected from radio to $γ$-rays. An extremely fast optical decline of 2 magnitudes in 1.2 days and strong Ne lines imply a high-mass white dwarf. The optical pre-outburst detection of a 501.42s oscillation suggests a magnetic white dwarf. This is the first time that an oscillation of this magnitude has been detected in a classical nova prior to outburst. We report X-ray outburst observations from {\it Swift} and {\it Chandra} which uniquely show: (1) a very strong modulation of super-soft X-rays…
V906 Carinae was one of the best observed novae of recent times. It was a prolific dust producer and harboured shocks in the early evolving ejecta outflow. Here, we take a close look at the consequences of these early interactions through study of high-resolution UVES spectroscopy of the nebular stage and extrapolate backwards to investigate how the final structure may have formed. A study of ejecta geometry and shaping history of the structure of the shell is undertaken following a spectral line SHAPE model fit. A search for spectral tracers of shocks in the nova ejecta is undertaken and an a…
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 present the analysis of XMM-Newton European Photon Imaging Camera (EPIC) observations of the nova shell IPHASX J210204.7$+$471015. We detect X-ray emission from the progenitor binary star with properties that resemble those of underluminous intermediate polars such as DQ Her: an X-ray-emitting plasma with temperature of $T_\mathrm{X}=(6.4\pm3.1)\times10^{6}$ K, a non-thermal X-ray component, and an estimated X-ray luminosity of $L_\mathrm{X}=10^{30}$ erg s$^{-1}$. Time series analyses unveil the presence of two periods, the dominant with a period of $2.9\pm0.2$ hr, which might be attributed…
Accurate determination of the rates of nova eruptions in different kinds of galaxies give us strong constraints on those galaxies' underlying white dwarf and binary populations, and those stars' spatial distributions. Until 2016, limitations inherent in ground-based surveys of external galaxies - and dust extinction in the Milky Way - significantly hampered the determination of those rates and how much they differ between different types of galaxies. Infrared Galactic surveys and dense cadence Hubble Space Telescope (HST)-based surveys are overcoming these limitations, leading to sharply incre…
The nova rate in the Milky Way remains largely uncertain, despite its vital importance in constraining models of Galactic chemical evolution as well as understanding progenitor channels for Type Ia supernovae. The rate has been previously estimated in the range of $\approx10-300$ yr$^{-1}$, either based on extrapolations from a handful of very bright optical novae or the nova rates in nearby galaxies; both methods are subject to debatable assumptions. The total discovery rate of optical novae remains much smaller ($\approx5-10$ yr$^{-1}$) than these estimates, even with the advent of all-sky o…
