Recurrent Nova Eruptions Research Articles

A Search for recurrent novae among Far Eastern guest stars

According to recent theoretical studies, classical novae are expected to erupt every ∼105 years, while the recurrence time scale of modern recurrent novae (Nr) stars ranges from 10 to ∼100 years. To bridge this huge gap in our knowledge (three orders of magnitude in time scales), it appears attractive to consider historical data: In Far Eastern sources, we searched for brightening events at different epochs but similar positions that possibly refer to recurrent nova eruptions. Probing a sample of ∼185 Asian observations from ∼500 BCE to 1700 CE, we present a method to systematically filter possible events. The result are a few search fields with between 2 and 5 flare ups and typical cadences between 102 and 103 years. For most of our recurrence candidates, we found possible counterparts among known cataclysmic variables in the corresponding search areas. This work is based on an interdisciplinary approach, combining methods from digital humanities and computational astrophysics when applying our previously developed methods in searches for classical novae among Far Eastern guest stars. A first and rather preliminary comparison of (possible) historical and (well known) modern recurrent novae reveals first tentative hints on some of their properties, stimulating further studies in this direction.

Isotopic ratios in the red giant component of the recurrent nova T Coronae Borealis

ABSTRACT We report the determination of abundances and isotopic ratios for C, O, and Si in the photosphere of the red giant (RG) component of the recurrent nova (RN) T Coronae Borealis from new 2.284–2.402 μm and 3.985–4.155 μm spectroscopy. Abundances and isotopic ratios in the photosphere may be affected by (i) processes in the RG interior which are brought to the surface during dredge-up and (ii) contamination of the RG, either during the common envelope phase of the binary evolution or by material synthesized in RN eruptions, or a combination of the two. We find that the abundances of C, O, and Si are reasonably consistent with the expected composition of an RG after first dredge-up, as is the 16O/17O ratio. The 28Si/29Si ratio is found to be 8.6 ± 3.0, and that for 28Si/30Si is 21.5 ± 3.0. The 12C/13C ratio (10 ± 2) is somewhat lower than expected for first dredge-up. The 16O/18O ratio (41 ± 3) is highly inconsistent with that expected either from RG evolution (∼550) or from contamination of the RG by the products of a nova thermonuclear runaway. In particular, the C and O isotopic ratios taken in combination are a puzzle. We urge confirmation of our results using spectroscopy at high resolution. We also encourage a thorough theoretical study of the effects on the secondary star in an RN system of contamination by ejecta having anomalous abundances and isotopic ratios.

A search for the modern counterparts of the Far Eastern guest stars 369 CE, 386 CE and 393 CE

ABSTRACT In this study, we apply our previously developed method to investigate ancient transient sightings in order to derive consequences for modern astrophysical problems. We present case studies of three observations of so-called guest stars in the fourth century CE, which lasted several months each. These three observations had been discussed and suggested as possible supernovae, but slow novae are also viable alternatives. Our careful re-interpretation of the historical texts and the currently known objects in the given fields shed new light on this topic. In particular, for the two events in 386 and 393 CE we suggest possible supernova identifications, while in all three cases there are interesting candidates for past classical or recurrent nova eruptions among known cataclysmic variables (CVs) and/or symbiotic stars. We suggest that the transient of 369 can be explained as a classical and possibly recurrent nova instead of a supernova. The most plausible candidates are BZ Cam, a CV with a possible nova shell, or CQ Dra, a naked-eye multiple system perhaps able to permit an overwhelmingly bright nova with day-time visibility.

OGLE ATLAS OF CLASSICAL NOVAE. II. MAGELLANIC CLOUDS

ABSTRACT The population of classical novae in the Magellanic Clouds was poorly known because of a lack of systematic studies. There were some suggestions that nova rates per unit mass in the Magellanic Clouds were higher than in any other galaxy. Here, we present an analysis of data collected over 16 years by the OGLE survey with the aim of characterizing the nova population in the Clouds. We found 20 eruptions of novae, half of which are new discoveries. We robustly measure nova rates of 2.4 ± 0.8 yr−1 (LMC) and 0.9 ± 0.4 yr−1 (SMC) and confirm that the K-band luminosity-specific nova rates in both Clouds are 2–3 times higher than in other galaxies. This can be explained by the star formation history in the Magellanic Clouds, specifically the re-ignition of the star formation rate a few Gyr ago. We also present the discovery of the intriguing system OGLE-MBR133.25.1160, which mimics recurrent nova eruptions.

HSTIMAGES FLASH IONIZATION OF OLD EJECTA BY THE 2011 ERUPTION OF RECURRENT NOVA T PYXIDIS

T Pyxidis is the only recurrent nova known to be surrounded by knots of material ejected in previous outbursts. Following the eruption that began on 2011 April 14.29, we obtained seven epochs (from 4 to 383 days after eruption) of Hubble Space Telescope narrowband Hα images of T Pyx. The ionizing flash of radiation from the nova event had no discernible effect on the surrounding ejecta until at least 55 days after the eruption began. Photoionization of hydrogen located north and south of the central star was seen 132 days after the beginning of the eruption. That photoionized hydrogen recombined in the following 51 days, allowing us to determine a hydrogen atom density of at least —at least an order of magnitude denser than the previously detected, unresolved [N ii] knots surrounding T Pyx. Material to the northwest and southeast was photoionized, and became bright between 132 and 183 days after the eruption began. Ninety-nine days later that northwest and southeast hydrogen had recombined. Both then (282 days after outburst) and 101 days later, we detected almost no trace of hydrogen emission around T Pyx. We determine that there is a large reservoir of previously unseen, cold diffuse hydrogen overlapping the previously detected, [N ii]-emitting knots of T Pyx ejecta. The mass of this newly detected hydrogen is model-dependent, but is is probably an order of magnitude larger than that of the [N ii] knots. We also determine that there is no significant reservoir of undetected hydrogen-rich ejecta, with density comparable to the flash-ionized ejecta we have detected, from the outer boundaries of the previously detected ejecta out to about twice that distance. The lack of distant ejecta is consistent with the Schaefer et al. scenario for T Pyx, in which the star underwent its first eruption within five years of 1866 after many millennia of quiescence, followed by the six observed recurrent nova eruptions since 1890. The lack of distant ejecta, demonstrated by our observations, is not consistent with scenarios in which T Pyx has been erupting continuously as a recurrent nova for many centuries or millennia.

Recurrent Novae — A Review

In recent years, recurrent nova eruptions are often observed very intensely in wide range of wavelengths from radio to optical to X-rays. Here I present selected highlights from recent multi-wavelength observations. The enigma of T Pyx is at the heart of this paper. While our current understanding of CV and symbiotic star evolution can explain why certain subset of recurrent novae have high accretion rate, that of T Pyx must be greatly elevated compared to the evolutionary mean. At the same time, we have extensive data to be able to estimate how the nova envelope was ejected in T Pyx, and it turns to be a rather complex tale. One suspects that envelope ejection in recurrent and classical novae in general is more complicated than the textbook descriptions. At the end of the review, I will speculate that these two may be connected.

NO X-RAYS FROM THE VERY NEARBY TYPE Ia SN 2014J: CONSTRAINTS ON ITS ENVIRONMENT

Deep X-ray observations of the post-explosion environment around the very nearby Type Ia SN\,2014J (Dl=3.5 Mpc) reveal no X-ray emission down to a luminosity L<7x10^{36} erg/s (0.3-10 keV) at t~20 days after the explosion. We interpret this limit in the context of Inverse Compton emission from upscattered optical photons by the supernova shock and constrain the pre-explosion mass-loss rate of the stellar progenitor system to be <10^{-9} M_sun yr-1 (for wind velocity v_w=100 km/s). Alternatively, the SN shock might be expanding into a uniform medium with density $n_CSM<3 cm-3. These results rule out single-degenerate (SD) systems with steady mass-loss until the terminal explosion and constrain the fraction of transferred material lost at the outer Lagrangian point to be <1%. The allowed progenitors are (i) WD-WD progenitors, (ii) SD systems with unstable hydrogen burning experiencing recurrent nova eruptions with recurrence time t<300 yrs and (iii) stars where the mass loss ceases before the explosion.

CIRCUMSTELLAR SHELL FORMATION IN SYMBIOTIC RECURRENT NOVAE

We present models of spherically symmetric recurrent nova shells interacting with circumstellar material in a symbiotic system composed of a red giant expelling a wind, and a white dwarf accreting from this material. Recurrent nova eruptions periodically eject material at high velocities ($\gtrsim 10^3$ km/s) into the red giant wind profile, creating a decelerating shock wave as circumstellar material is swept up. High circumstellar material densities cause the shocked wind and ejecta to have very short cooling times of days to weeks. Thus, the late time evolution of the shell is determined by momentum conservation instead of energy conservation. We compute and show evolutionary tracks of shell deceleration, as well as post-shock structure. After sweeping up all the red giant wind, the shell coasts at a velocity $\sim 100$ km/s, depending on system parameters. These velocities are similar to those measured in blue-shifted circumstellar material from the symbiotic nova RS Oph, as well as a few Type Ia supernovae that show evidence of circumstellar material, such as 2006X, 2007le, and PTF 11kx. Supernovae occurring in such systems may not show circumstellar material interaction until the inner nova shell gets hit by the supernova ejecta, days to months after the explosion.

THE NOVA SHELL AND EVOLUTION OF THE RECURRENT NOVA T PYXIDIS

T Pyxidis (T Pyx) is the prototypical recurrent nova (RN), with five eruptions from 1890 to 1967 and a mysterious nova shell. We report new observations of the nova shell with the Hubble Space Telescope (HST) in the year 2007, which provides a long time baseline to compare with HST images from 1994 and 1995. We find that the knots in the nova shell are expanding with velocities ranging from roughly 500 km s–1 to 715 km s–1, assuming a distance of 3500 pc. The fractional expansion of the knots is constant, which implies no significant deceleration of the knots, which must have been ejected by an eruption close to the year 1866. We see knots that have turned on after 1995; this shows that the knots are powered by shocks from the collision of the 1866 ejecta with fast ejecta from later RN eruptions. We derive that the 1866 ejecta has a total mass of ~10–4.5 M ☉, which with the low ejection velocity shows that the 1866 event was an ordinary nova eruption, not an RN eruption. This also implies that the accretion rate before the ordinary nova event must have been low (around the 4 × 10–11 M ☉ yr–1 expected for gravitational radiation alone), and that the matter accumulated on the surface of the white dwarf for ~750,000 years. The current accretion rate (>10–8 M ☉ yr–1) is ~1000× higher than expected for a system below the period gap, with the plausible reason being that the 1866 event started a continuing supersoft source that drives the accretion. The accretion rate has been declining since before the 1890 eruption, with the current rate being only 3% of its earlier value. The decline in the observed accretion rate shows that the supersoft source is not self-sustaining; we calculate that the accretion in T Pyx will effectively stop in upcoming decades. With this, T Pyx will enter a state of hibernation lasting for an estimated 2,600,000 years before gravitational radiation brings the system into contact again. Thus, T Pyx has an evolutionary cycle going from an ordinary CV state (lasting 750,000 years), to its current RN state (lasting little longer than a century), to a future hibernation state (lasting 2,600,000 years), and then repeating this cycle.

The Hot Component of RS Ophiuchi

view Abstract Citations (35) References (90) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Hot Component of RS Ophiuchi Dobrzycka, Danuta ; Kenyon, Scott J. ; Proga, Daniel ; Mikolajewska, Joanna ; Wade, Richard A. Abstract We analyze optical and ultraviolet spectrophotometry of the quiescent recurrent nova RS Ophiuchi. Our preferred model for this binary consists of an M-type giant and a B-type shell star with a luminosity of Lh∼100-600 Lsun. The ejecta from the recent outburst are slightly enhanced in helium relative to the solar abundance, which agrees with previous estimates from model fits to the optical and ultraviolet light curve. These results indicate that the hot component has a mass close to the Chandrasekhar limit. Although the hot component luminosity is consistent with the high accretion rate needed for recurrent nova eruptions in this system, our effective temperature estimate is not consistent with predicted cooling curves for massive white dwarfs. Publication: The Astronomical Journal Pub Date: May 1996 DOI: 10.1086/117945 Bibcode: 1996AJ....111.2090D Keywords: STARS: INDIVIDUAL: RS OPHIUCHI; STARS: FUNDAMENTAL PARAMETERS; STARS: CATACLYSMIC VARIABLES full text sources ADS | data products SIMBAD (5)