A Demarcation Criterion for Hydrogen Burning of Millinovae
Millinovae are a new class of transient supersoft X-ray sources with no clear signature of mass ejection. They show similar triangle shapes of V / I band light curves with 1000 times fainter peaks than typical classical novae. Maccarone et al. regarded the prototype millinova, ASASSN-16oh, as a dwar...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/adc107 |
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| Summary: | Millinovae are a new class of transient supersoft X-ray sources with no clear signature of mass ejection. They show similar triangle shapes of V / I band light curves with 1000 times fainter peaks than typical classical novae. Maccarone et al. regarded the prototype millinova, ASASSN-16oh, as a dwarf nova and interpreted the supersoft X-rays to originate from an accretion belt on a white dwarf (WD). Kato et al. proposed a nova model induced by high-rate mass accretion during a dwarf nova outburst; the X-rays originate from the photosphere of a hydrogen-burning hot WD, whereas the V / I band photons are from the irradiated accretion disk. Because each peak brightness differs largely from millinova to millinova, we suspect that not all millinova candidates host a hydrogen-burning WD. Based on the light-curve analysis of the classical nova KT Eri that has a bright disk, we find that the disk is more than 2 magnitudes brighter when the disk is irradiated by the hydrogen-burning WD than when not irradiated. We present the demarcation criterion for hydrogen burning to be ${I}_{{\rm{q}}}-{I}_{{\rm{\max }}}\gt 2.2$ , where I _q and ${I}_{{\rm{\max }}}$ are the I magnitudes in quiescence and at maximum light, respectively. Among many candidates, this requirement is satisfied with the two millinovae in which soft X-rays were detected. |
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| ISSN: | 1538-4357 |