A Multiwavelength Light-curve Analysis of the Classical Nova YZ Ret: An Extension of the Universal Decline Law to the Nebular Phase

Hachisu, Izumi; Kato, Mariko

doi:10.3847/1538-4357/acdfd3

Cited by 4 publications

(9 citation statements)

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“…Such a large variety in wavelengths (or energies) of emissions indicates that various emissions originate from different places or times of the nova ejecta. Hachisu & Kato (2022) and Hachisu & Kato (2023) proposed nova ejecta evolution models based on the fully selfconsistent nova outburst model of Kato et al (2022a). The authors found that a strong shock naturally arises in nova ejecta far outside the WD photosphere without ad hoc or arbitrary settings on the nova ejecta, and elucidated the origin of nova absorption/emission line systems raised by McLaughlin (1942).…”

Section: Shock Formationmentioning

confidence: 99%

“…In the later phase, the shocked shell far outside the photosphere begins to contribute to the V-band flux. Hachisu & Kato (2023) estimated the luminosity of free-free emission from the shocked shell as…”

Section: Emission From the Shocked Shellmentioning

confidence: 99%

“…Note that this expression roughly includes the fluxes of bound-free and bound-bound emission by replacing B ff with B bf or B bb , where B bf and B bb are the coefficients of bound-free and bound-bound emissions, respectively. The other details and derivation of Equation ( 9) are described in Appendix B of Hachisu & Kato (2023).…”

Section: Emission From the Shocked Shellmentioning

confidence: 99%

“…for the total flux instead of a simple summation of the two, because the shocked shell may absorb a part of L V,ff,wind + L V,ph and re-emit it as a part of L V,shell . We show the shell emission calculated from Equation (9) in Figure 8(a); (thick red line labeled shell), which is taken from Hachisu & Kato (2023). The shocked shell emission gradually increases after the shock arises and reaches a plateau peak on day 16, followed by a slow decay of approximately L V ∝ t −1.75 (thick cyan line labeled t −1.75 ).…”

Section: Emission From the Shocked Shellmentioning

confidence: 99%

“…Also, high-energy emissions, such as hard X-rays and gamma-rays are expected from the shock (e.g., Friedjung 1987;Mukai & Ishida 2001;Martin et al 2018). Hachisu & Kato (2023) explained how and where McLaughlin's optical multiple emission/absorption line systems arise in classical novae.…”

Section: Introductionmentioning

confidence: 99%

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A Multiwavelength Light-curve Model of the Classical Nova V339 Del: A Mechanism for the Coexistence of Dust Dip and Supersoft X-Rays

Hachisu,

Kato,

Matsumoto

2024

ApJ

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The classical nova V339 Del 2013 is characterized by a 1.5 mag dip of the V light curve owing to a dust shell formation, with which soft X-ray emissions coexist. We present a Strömgren y-band light curve, which represents continuum emission, not influenced by strong [O iii] emission lines. The y light curve monotonically decreases in marked contrast to the V light curve that shows a 1.5 mag dip. We propose a multiwavelength light-curve model that reproduces the y and V light curves as well as the gamma-ray and X-ray light curves. In our model, a strong shock arises far outside the photosphere after optical maximum, because later ejected matter collides with earlier ejected gas. Our shocked shell model explains optical emission lines, Hα, hard X-ray, and gamma-ray fluxes. A dust shell forms behind the shock that suppresses [O iii]. This low flux of [O iii] shapes a 1.5 mag drop in the V light curve. Then, the V flux recovers with an increasing contribution from [O iii] lines, while the y flux does not. However, the optical depth of the dust shell is too small to absorb the photospheric (X-ray) emission of the white dwarf. This is the reason that a dust shell and soft X-ray radiation coexist. We determined the white dwarf mass to be M WD = 1.25 ± 0.05 M ☉ and the distance modulus in the V band to be (m − M) V = 12.2 ± 0.2; the distance is d = 2.1 ± 0.2 kpc for the reddening of E(B − V) = 0.18.

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Section: Shock Formationmentioning

confidence: 99%

Section: Emission From the Shocked Shellmentioning

confidence: 99%

Section: Emission From the Shocked Shellmentioning

confidence: 99%

Section: Emission From the Shocked Shellmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Multiwavelength Light-curve Model of the Classical Nova V339 Del: A Mechanism for the Coexistence of Dust Dip and Supersoft X-Rays

Hachisu,

Kato,

Matsumoto

2024

ApJ

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Physics of nova outbursts: Theoretical models of classical nova outbursts with optically thick winds on 1.2 M⊙ and 1.3 M⊙ white dwarfs

Kato,

Saio,

Hachisu

2024

Publications of the Astronomical Society of Japan

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We present time-dependent nova outburst models with optically thick winds for 1.2 and 1.35$\, M_{\odot }$ white dwarfs (WDs) with a mass-accretion rate of $5 \times 10^{-9}\, M_{\odot }$ yr−1 and for a 1.3$\, M_{\odot }$ WD with $2 \times 10^{-9}\, M_{\odot }$ yr−1. The X-ray flash occurs 11 d before the optical peak of the 1.2$\, M_{\odot }$ WD and 2.5 d before the peak of the 1.3$\, M_{\odot }$ WD. The wind mass-loss rate of the 1.2$\, M_{\odot }$ WD (1.3$\, M_{\odot }$ WD) reaches a peak of $6.4 \times 10^{-5}\, M_{\odot }$ yr−1 ($7.4 \times 10^{-5}\, M_{\odot }$ yr−1) at the epoch of the maximum photospheric expansion with the lowest photospheric temperature of log Tph (K) = 4.33 (4.35). The nuclear energy generated during the outburst is lost in the form of radiation (61% for the 1.2$\, M_{\odot }$ WD; 47% for the 1.3$\, M_{\odot }$ WD), gravitational energy of ejecta (39%; 52%), and kinetic energy of the wind (0.28%; 0.29%). We found an empirical relation for fast novae between the time to optical maximum from the outburst tpeak and the expansion timescale τexp. With this relation, we are able to predict the time to optical maximum tpeak from the ignition model (at t = 0) without following a time-consuming nova wind evolution.

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Mixing of Hot Shocked Plasma with Cold Gas in Nova YZ Ret 2020

Mitrani,

Behar,

Drake

et al. 2024

ApJ

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The origin of bright X-ray emission lines that appear late in a nova eruption remains largely a puzzle. We present two high-resolution X-ray grating spectra of the classical nova YZ Ret, observed 77 and 115 days post-eruption, using XMM-Newton and Chandra, respectively. Both spectra feature resolved emission lines blueshifted by v = –1500 km s−1 and broadened by σ v = 500 km s−1. The two spectra are well described by a collisionally ionized plasma of kT ∼ 70 eV that dimmed by a factor of ∼40 between the two exposures. The spectra also show narrow radiative recombination continua (RRCs) of C+4, C+5, and N+5, indicating the interaction of the hot ionized plasma with cold electrons of kT ∼ 2 eV. The high-n Rydberg series of C+4 is anomalously bright, allowing us to measure the electron density through continuum lowering, which is in agreement with the He-like N+5 density diagnostic of n e = (1.7 ± 0.4) × 1011 cm−3. The high population of these high-n levels constitutes the best evidence to date of charge exchange (CX) with neutral H in an astrophysical ionized plasma. The remarkable fact that the velocity and plasma temperature are the same after 38 days, despite the high density and decreasing flux, is evidence for ongoing heating. We suggest the heating is due to a reverse shock in the nova ejecta, which forms a thin X-ray shell. The narrow RRCs and CX are attributed to direct mixing with cold gas, which overtakes the hot plasma either from the shock front or through the contact discontinuity.

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A Multiwavelength Light-curve Analysis of the Classical Nova YZ Ret: An Extension of the Universal Decline Law to the Nebular Phase

Cited by 4 publications

References 51 publications

A Multiwavelength Light-curve Model of the Classical Nova V339 Del: A Mechanism for the Coexistence of Dust Dip and Supersoft X-Rays

A Multiwavelength Light-curve Model of the Classical Nova V339 Del: A Mechanism for the Coexistence of Dust Dip and Supersoft X-Rays

Physics of nova outbursts: Theoretical models of classical nova outbursts with optically thick winds on 1.2 M⊙ and 1.3 M⊙ white dwarfs

Mixing of Hot Shocked Plasma with Cold Gas in Nova YZ Ret 2020

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