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Abstract Recurrent novae undergo thermonuclear-powered eruptions separated by less than 100 yr, enabled by subgiant or red giant donors transferring hydrogen-rich matter at very high rates onto their massive white dwarf companions. The most rapidly moving parts of envelopes ejected in successive recurrent nova events are predicted to overtake and collide with the slowest ejecta of the previous eruption, leading to the buildup of vast (∼10–100 pc) superremnants surrounding all recurrent novae, but only three examples are currently known. We report deep narrowband imaging and spectroscopy, which have revealed a ∼70 pc diameter shell surrounding the frequently recurring nova RS Ophiuchi. We estimate the superremnant mass to be ∼20–200M⊙, expanding at a few tens of km/s, with an age of order 50–100 kyr. Its extremely low surface brightness and large angular size help explain the hitherto surprising absence of nova superremnants. Our results support the prediction that all recurrent novae are surrounded by similar extended structures.
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Introducing the Condor Array Telescope – III. The expansion and age of the shell of the dwarf nova Z Camelopardalis, and detection of a second, larger shell
ABSTRACT The existence of a vast nova shell surrounding the prototypical dwarf nova Z Camelopardalis (Z Cam) proves that some old novae undergo metamorphosis to appear as dwarf novae thousands of years after a nova eruption. The expansion rates of ancient nova shells offer a way to constrain both the time between nova eruptions and the time for post-nova mass transfer rates to decrease significantly, simultaneously testing nova thermonuclear runaway models and hibernation theory. Previous limits on the expansion rate of part of the Z Cam shell constrain the inter-eruption time between Z Cam nova events to be >1300 yr. Deeper narrow-band imaging of the ejecta of Z Cam with the Condor Array Telescope now reveals very low surface brightness areas of the remainder of the shell. A second, even fainter shell is also detected, concentric with and nearly three times the size of the ‘inner’ shell. This is the first observational support of the prediction that concentric shells must surround the frequently erupting novae of relatively massive white dwarfs. The Condor images extend our Z Cam imaging baseline to 15 yr, yielding the inner shell’s expansion rate as v = 83 ± 37 km s−1 at 23 deg south of west, in excellent agreement with our 2012 prediction. This velocity corresponds to an approximate age of $$t = 2672^{-817}_{+2102}$$ yr. While consistent with the suggestion that the most recent nova eruption of Z Cam was the transient recorded by Chinese imperial astrologers in the year 77 bce, the age uncertainty is still too large to support or disprove a connection with Z Cam.
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- PAR ID:
- 10493871
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 529
- Issue:
- 1
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 212-223
- Size(s):
- p. 212-223
- Sponsoring Org:
- National Science Foundation
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