<i>Chandra</i> observations of nova KT Eridani in outburst

Pei, Songpeng; Orio, Marina; Ness, Jan-Uwe; Ospina, N.

doi:10.1093/mnras/stab2298

Cited by 3 publications

(1 citation statement)

References 38 publications

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“…This nova appears to show absorption in a continuous wind that accelerates outward from the stellar photosphere. Pei et al (2021) therefore compare the measured spectrum to a set of model spectra for a stellar atmosphere with a wind of prescribed kinematics (van Rossum 2012). This is in contrast to the case for Nova Del 2013, in which we found the outflow to have the properties of a discrete shell, with little or no evidence for absorption or emission from slowly moving, accelerating gas near the stellar surface.…”

Section: Discussionmentioning

confidence: 99%

The High-resolution Soft X-Ray Spectrum of Nova Delphini 2013

Milla

Paerels

2023

ApJ

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We present the high-resolution soft X-ray spectrum of Nova Delphini 2013. Two spectra were taken with the Low Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory, on 2013 November 9 and 2013 December 6, 87 and 114 days after the nova eruption, respectively. The spectra are of very high statistical quality, and reveal clear spectral evolution between the two observations. The source is bright enough on the two occasions that the third spectral order, with resolving power up to ∼3000, can easily be seen. We observe the photospheric emission spectrum of the hot white dwarf, which exhibits a rich absorption line spectrum from an atmosphere of effective temperature likely near T eff ∼ 640,000 K, and complex chemical abundances. Superimposed on this photospheric spectrum, we detect the absorption spectrum of a shell of highly ionized gas, comprising absorption by the K-shell ions of C and N, blueshifted (outflowing) by ∼1400 km s−1, and with a velocity width of ∼1000 km s−1. The abundance ratio C/N is clearly very nonsolar, and indicative of thermonuclear fusion by the CNO cycle. We discuss the physical properties (kinematics, ionization balance, radiative transfer, mechanical energy balance, chemical abundances) of this hot shell, in the context of the physics of nova eruptions.

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Section: Discussionmentioning

confidence: 99%

The High-resolution Soft X-Ray Spectrum of Nova Delphini 2013

Milla

Paerels

2023

ApJ

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The nova KT Eri Is a recurrent nova with a recurrence time-scale of 40–50 yr

Schaefer

Walter

Hounsell

et al. 2022

Monthly Notices of the Royal Astronomical Society

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KT Eridani was a very fast nova in 2009 peaking at V = 5.42 mag. We marshal large data sets of photometry to finally work out the nature of KT Eri. From the TESS light curve, as confirmed with our radial velocity curve, we find an orbital period of 2.61595 days. With our 272 spectral energy distributions from simultaneous BVRIJHK measures, the companion star has a temperature of 6200±500 K. Our century-long average in quiescence has V = 14.5. With the Gaia distance (5110$^{+920}_{-430}$ parsecs), the absolute magnitude is $M_{V_q}$ = +0.7 ±0.3. We converted this absolute magnitude (corrected to the disc light alone) to accretion rates, $\dot{M}$, with a full integration of the α-disc model. This $\dot{M}$ is very high at 3.5× 10−7 M⊙ yr−1. Our search and analysis of archival photographs shows that no eruption occurred from 1928–1954 or after 1969. With our analysis of the optical light curve, the X-ray light curve, and the radial velocity curve, we derive a white dwarf mass of 1.25±0.03 M⊙. With the high white dwarf mass and very-high $\dot{M}$, KT Eri must require a short time to accumulate the required mass to trigger the next nova event. Our detailed calculations give a recurrence time-scale of 12 years with a total range of 5–50 years. When combined with the archival constraints, we conclude that the recurrence time-scale must be between 40–50 years. So, KT Eri is certainly a recurrent nova, with the prior eruption remaining undiscovered in a solar gap of coverage from 1959 to 1969.

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NICER Monitoring of Supersoft X-Ray Sources

Orio

Gendreau

Giese³

et al. 2022

ApJ

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We monitored four supersoft sources—two persistent ones, CAL 83 and MR Vel, and the recent novae YZ Ret (Nova Ret 2020), and V1674 Her (Nova Her 2021)—with NICER. The two persistent supersoft X-ray sources (SSS) were observed with unvaried X-ray flux level and spectrum, respectively, 13 and 20 yr after the last observations. Short-period modulations of the SSS appear where the spectrum of the luminous central source was fully visible (in CAL 83 and V1674 Her) and were absent in YZ Ret and MR Vel, in which the flux originated in photoionized or shocked plasma, while the white dwarf (WD) was not observable. We thus suggest that the pulsations occur on, or very close to, the WD surface. The pulsations of CAL 83 were almost unvaried after 15 yr, including an irregular drift of the ≃67 s period by 2.1 s. Simulations, including previous XMM-Newton data, indicate actual variations in period length within hours, rather than an artifact of the variable amplitude of the pulsations. Large amplitude pulsations with a period of 501.53 ± 0.30 s were always detected in V1674 Her, as long as the SSS was observable. This period seems to be due to rotation of a highly magnetized WD. We cannot confirm the maximum effective temperature of (≃145,000 K) previously inferred for this nova, and discuss the difficulty in interpreting its spectrum. The WD appears to present two surface zones, one of which does not emit SSS flux.

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Chandra observations of nova KT Eridani in outburst

Cited by 3 publications

References 38 publications

The High-resolution Soft X-Ray Spectrum of Nova Delphini 2013

The High-resolution Soft X-Ray Spectrum of Nova Delphini 2013

The nova KT Eri Is a recurrent nova with a recurrence time-scale of 40–50 yr

NICER Monitoring of Supersoft X-Ray Sources

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