Spectroscopic diagnostics of dust formation and evolution in classical nova ejecta

Shore, Steven N.; Kuin, N. P. M.; Mason, E.; Aquino, I. De Gennaro

doi:10.1051/0004-6361/201833204

Cited by 21 publications

(28 citation statements)

References 44 publications

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“…The D light curve type is defined by presenting a significant isolated minimum in the post-eruption light curve. This feature is caused by dust absorption and has been found to also affect line emission (Shore et al 2018). In our data, this is especially evident in the [Oiii] data of DQ Her (top right panel of Fig.…”

Section: Luminosity Evolutionsupporting

confidence: 57%

The luminosity evolution of nova shells

Tappert

Vogt

Ederoclite

et al. 2020

A&A

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Over the last decade, nova shells have been discovered around a small number of cataclysmic variables that had not been known to be post-novae, while other searches around much larger samples have been mostly unsuccessful. This raises the question about how long such shells are detectable after the eruption and whether this time limit depends on the characteristics of the nova. So far, there has been only one comprehensive study of the luminosity evolution of nova shells, undertaken almost two decades ago. Here, we present a re-analysis of the Hα and [O III] flux data from that study, determining the luminosities while also taking into account newly available distances and extinction values, and including additional luminosity data of “ancient” nova shells. We compare the long-term behaviour with respect to nova speed class and light curve type. We find that, in general, the luminosity as a function of time can be described as consisting of three phases: an initial shallow logarithmic decline or constant behaviour, followed by a logarithmic main decline phase, with a possible return to a shallow decline or constancy at very late stages. The luminosity evolution in the first two phases is likely to be dominated by the expansion of the shell and the corresponding changes in volume and density, while for the older nova shells, the interaction with the interstellar medium comes into play. The slope of the main decline is very similar for almost all groups for a given emission line, but it is significantly steeper for [O III], compared to Hα, which we attribute to the more efficient cooling provided by the forbidden lines. The recurrent novae are among the notable exceptions, along with the plateau light curve type novae and the nova V838 Her. We speculate that this is due to the presence of denser material, possibly in the form of remnants from previous nova eruptions, or of planetary nebulae, which might also explain some of the brighter ancient nova shells. While there is no significant difference in the formal quality of the fits to the decline when grouped according to light curve type or to speed class, the former presents less systematic scatter. It is also found to be advantageous in identifying points that would otherwise distort the general behaviour. As a by-product of our study, we revised the identification of all novae included in our investigation with sources in the Gaia Data Release 2 catalogue.

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Section: Luminosity Evolutionsupporting

confidence: 57%

The luminosity evolution of nova shells

Tappert

Vogt

Ederoclite

et al. 2020

A&A

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“…A steeper power-law would indicate a non-spherical outflow: for example, the ballistic ejection of bipolar blobs which then undergo additional expansion due to their own internal pressure. This has been used to explain some observations of classical novae (Shore et al 2018), but to our knowledge this geometry of mass ejection is not predicted by TDE simulations.…”

Section: The Constant-velocity Phasementioning

confidence: 99%

An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz

Nicholl

Wevers

Oates

et al. 2020

Monthly Notices of the Royal Astronomical Society

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At 66 Mpc, AT2019qiz is the closest optical tidal disruption event (TDE) to date, with a luminosity intermediate between the bulk of the population and the faint-and-fast event iPTF16fnl. Its proximity allowed a very early detection and triggering of multiwavelength and spectroscopic follow-up well before maximum light. The velocity dispersion of the host galaxy and fits to the TDE light curve indicate a black hole mass ≈106 M⊙, disrupting a star of ≈1 M⊙. By analysing our comprehensive UV, optical, and X-ray data, we show that the early optical emission is dominated by an outflow, with a luminosity evolution L ∝ t2, consistent with a photosphere expanding at constant velocity (≳2000 km s−1), and a line-forming region producing initially blueshifted H and He ii profiles with v = 3000–10 000 km s−1. The fastest optical ejecta approach the velocity inferred from radio detections (modelled in a forthcoming companion paper from K. D. Alexander et al.), thus the same outflow may be responsible for both the fast optical rise and the radio emission – the first time this connection has been observed in a TDE. The light-curve rise begins 29 ± 2 d before maximum light, peaking when the photosphere reaches the radius where optical photons can escape. The photosphere then undergoes a sudden transition, first cooling at constant radius then contracting at constant temperature. At the same time, the blueshifts disappear from the spectrum and Bowen fluorescence lines (N iii) become prominent, implying a source of far-UV photons, while the X-ray light curve peaks at ≈1041 erg s−1. Assuming that these X-rays are from prompt accretion, the size and mass of the outflow are consistent with the reprocessing layer needed to explain the large optical to X-ray ratio in this and other optical TDEs, possibly favouring accretion-powered over collision-powered outflow models.

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“…the UVOT grism images need careful analysis (see Shore et al 2018, for details). The grism images were compared to the star field and contaminating zeroth orders were flagged.…”

Section: Swift Uv Spectroscopymentioning

confidence: 99%

“…Morpho-kinematical emission line profile modelling with SHAPE 2 (Ribeiro et al 2013a,b) shows bipolar geometries. Recent Monte-Carlo based radiative transfer models of ejecta far enough after the eruption to ensure low densities and frozen-in state provide good fits to cone-shape geometries (Shore et al 2013a(Shore et al ,b, 2016 and can include embedded dust (Shore et al 2018).…”

Section: Introductionmentioning

confidence: 99%

The 2016 January eruption of recurrent Nova LMC 1968

Kuin

Page

Mróz

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present a comprehensive review of all observations of the eclipsing recurrent Nova LMC 1968 in the Large Magellanic Cloud which was previously observed in eruption in 1968, 1990, 2002, 2010, and most recently in 2016. We derive a probable recurrence time of 6.2 ± 1.2 years and provide the ephemerides of the eclipse. In the ultraviolet-optical-IR photometry the light curve shows high variability right from the first observation around two days after eruption. Therefore no colour changes can be substantiated. Outburst spectra from 2016 and 1990 are very similar and are dominated by H and He lines longward of 2000Å. Interstellar reddening is found to be E(B-V) = 0.07 ± 0.01. The super soft X-ray luminosity is lower than the Eddington luminosity and the X-ray spectra suggest the mass of the WD is larger than 1.3 M . Eclipses in the light curve suggest that the system is at high orbital inclination. On day four after the eruption a recombination wave was observed in Fe II ultraviolet absorption lines. Narrow line components are seen after day 6 and explained as being due to reionisation of ejecta from a previous eruption. The UV spectrum varies with orbital phase, in particular a component of the He II 1640Å emission line, which leads us to propose that early-on the inner WD Roche lobe might be filled with a bound opaque medium prior to the re-formation of an accretion disk. Both this medium and the ejecta can cause the delay in the appearance of the soft X-ray source.

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Spectroscopic diagnostics of dust formation and evolution in classical nova ejecta

Cited by 21 publications

References 44 publications

The luminosity evolution of nova shells

The luminosity evolution of nova shells

An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz

The 2016 January eruption of recurrent Nova LMC 1968

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