Nova multiwavelength light curves: predicting UV precursor flashes and pre-maximum halts

Hillman, Yael; Prialnik, Dina; Kovetz, A.; Shara, Michael M.; Neill, James D.

doi:10.1093/mnras/stt2027

Cited by 54 publications

(64 citation statements)

References 28 publications

(34 reference statements)

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“…Thus the two peaks are consistent with being such excursions from the general upwards trend, rather than being defined by dips that interrupt the rise. The combination of the change relative to the uncertainties and the deviation from what one would expect from backwards extrapolation of the rise, allows us to be confident that they can be reasonably described as PMHs as modelled by Hillman et al (2014).…”

Section: Pre-maximum Haltsmentioning

confidence: 93%

“…The cadence is around 40 min, making these the highest time-resolution observation of this phase to date. We discuss the rise phase, including the PMHs, in the context of the models of Hillman et al (2014). We also contrast the post-maximum behaviour with much slower Classical Novae (CNe) and suggest that the empirical split in this behaviour between slow and fast novae is in part a function of the typical one day sampling of the light-curves.…”

Section: Introductionmentioning

confidence: 92%

“…The PMH decline is to a level within 2 σ of the pre-rise magnitude. Modelling by Hillman et al (2014) suggests that PMHs are often short-lived excursions above the general upwards trend of the rise. We explore this by taking linear interpolations between the "before" and "after" points for both features.…”

Section: Pre-maximum Haltsmentioning

confidence: 99%

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Temporal resolution of a pre-maximum halt in a classical nova: V5589 Sgr observed with STEREO HI-1B

Eyres

Bewsher

Hillman

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Classical novae show a rapid rise in optical brightness over a few hours. Until recently the rise phase, particularly the phenomenon of a pre-maximum halt, was observed sporadically. Solar observation satellites observing Coronal Mass Ejections enable us to observe the pre-maximum phase in unprecedented temporal resolution. We present observations of V5589 Sgr with STEREO HI-1B at a cadence of 40 min, the highest to date. We temporally resolve a pre-maximum halt for the first time, with two examples each rising over 40 min then declining within 80 min. Comparison with a grid of outburst models suggests this double peak, and the overall rise timescale, are consistent with a white dwarf mass, central temperature and accretion rate close to 1.0 M ⊙ , 5 × 10 7 K and 10 −10 M ⊙ yr −1 respectively. The modelling formally predicts mass loss onset at JD 2456038.2391±0.0139, 12 hrs before optical maximum. The model assumes a main-sequence donor. Observational evidence is for a subgiant companion; meaning the accretion rate is under-estimated. Post-maximum we see erratic variations commonly associated with much slower novae. Estimating the decline rate difficult, but we place the time to decline two magnitudes as 2.1 < t 2 (days) < 3.9 making V5589 Sgr a "very fast" nova. The brightest point defines "day 0" as JD 2456038.8224±0.0139, although at this high cadence the meaning of the observed maximum becomes difficult to define. We suggest that such erratic variability normally goes undetected in faster novae due to the low cadence of typical observations; implying erratic behaviour is not necessarily related to the rate of decline.

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Section: Pre-maximum Haltsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 92%

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Temporal resolution of a pre-maximum halt in a classical nova: V5589 Sgr observed with STEREO HI-1B

Eyres

Bewsher

Hillman

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…This tendency agrees with our results. Hillman et al (2014) showed evolutionary change in the effective temperature of nova outbursts with the OPAL opacities. Their Figure 3 shows an X-ray flash duration (defined by log T eff (K) > 5.5) of a few hours for a 1.4 M ⊙ WD with a mass accretion rate of 10 −8 M ⊙ yr −1 .…”

Section: Slow Evolution After X-ray Flashmentioning

confidence: 95%

X-RAY FLASHES IN RECURRENT NOVAE: M31N 2008-12a AND THE IMPLICATIONS OF THE SWIFT NONDETECTION

Kato

Saio

Henze

et al. 2016

ApJ

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Models of nova outbursts suggest that an X-ray flash should occur just after hydrogen ignition. However, this X-ray flash has never been observationally confirmed. We present four theoretical light curves of the X-ray flash for two very massive white dwarfs (WDs) of 1.380 and 1.385 M ⊙ and for two recurrence periods of 0.5 and 1 years. The duration of the X-ray flash is shorter for a more massive WD and for a longer recurrence period. The shortest duration of 14 hours (0.6 days) among the four cases is obtained for the 1.385 M ⊙ WD with one year recurrence period. In general, a nova explosion is relatively weak for a very short recurrence period, which results in a rather slow evolution toward the optical peak. This slow timescale and the predictability of very short recurrence period novae give us a chance to observe X-ray flashes of recurrent novae. In this context, we report the first attempt, using the Swift observatory, to detect an X-ray flash of the recurrent nova M31N 2008-12a (0.5 or 1 year recurrence period), which resulted in the non-detection of X-ray emission during the period of 8 days before the optical detection. We discuss the impact of these observations on nova outburst theory. The X-ray flash is one of the last frontiers of nova studies and its detection is essentially important to understand the pre-optical-maximum phase. We encourage further observations.

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“…Although in standard models novae are thought to be powered directly by the energy released from nuclear burning (e.g. Hillman et al 2014), growing evidence suggests that shock interaction plays an important role in powering nova emission across the electromagnetic spectrum. Evidence for shocks includes multiple velocity components in the optical spectra (e.g.…”

Section: Introductionmentioning

confidence: 99%

Novae as Tevatrons: prospects for CTA and IceCube

Metzger

Caprioli

Vurm

et al. 2016

Mon. Not. R. Astron. Soc.

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The discovery of novae as sources of ∼ 0.1 − 1 GeV gamma-rays highlights the key role of shocks and relativistic particle acceleration in these transient systems. Although there is evidence for a spectral cut-off above energies ∼ 1 − 100 GeV at particular epochs in some novae, the maximum particle energy achieved in these accelerators has remained an open question. The high densities of the nova ejecta (∼ 10 orders of magnitude larger than in supernova remnants) render the gas far upstream of the shock neutral and shielded from ionizing radiation. The amplification of the magnetic field needed for diffusive shock acceleration requires ionized gas, thus confining the acceleration process to a narrow photo-ionized layer immediately ahead of the shock. Based on the growth rate in this layer of the hybrid non-resonant cosmic ray current-driven instability (considering also ion-neutral damping), we quantify the maximum particle energy, E max , across the range of shock velocities and upstream densities of interest. We find values of E max ∼ 10 GeV -10 TeV, which are broadly consistent with the inferred spectral cut-offs, but which could also in principle lead to emission extending to higher energies ∼ > 100 GeV accessible to atmosphere Cherenkov telescopes, such as the planned Cherenkov Telescope Array (CTA). Detecting TeV neutrinos with IceCube in hadronic scenarios appears to be more challenging, although the prospects are improved for a particularly nearby event (distance ∼ < kpc) or if the shock power during the earliest, densest phases of the nova outburst is higher than is implied by the observed GeV light curves, due to downscattering of the gamma-rays by electrons within the ejecta. Novae provide ideal nearby laboratories to study magnetic field amplification and the onset of cosmic ray acceleration, because other time-dependent sources (e.g. radio supernovae) typically occur too distant to detect as gamma-ray sources.

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Nova multiwavelength light curves: predicting UV precursor flashes and pre-maximum halts

Cited by 54 publications

References 28 publications

Temporal resolution of a pre-maximum halt in a classical nova: V5589 Sgr observed with STEREO HI-1B

Temporal resolution of a pre-maximum halt in a classical nova: V5589 Sgr observed with STEREO HI-1B

X-RAY FLASHES IN RECURRENT NOVAE: M31N 2008-12a AND THE IMPLICATIONS OF THE SWIFT NONDETECTION

Novae as Tevatrons: prospects for CTA and IceCube

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