V1315 Aquilae
First nova-like variable star found with a nova shell.
V1315 Aquilae is a cataclysmic variable star located in the northern part of the equatorial constellation Aquila. It is classified as a nova-like variable, specifically a SW Sextantis star—a binary system consisting of a white dwarf and a donor star. In these systems, the white dwarf is non-magnetic and does not produce the bright eruptions seen in dwarf novae, though some evidence suggests a degree of magnetism may be present. Because the mass transfer rate is high, the accretion disk is in a steady state, keeping the system in constant outburst. Most of its visible light comes from this disk, and the star’s eclipse depth is 1.8 magnitudes. The donor star itself is not described.
The star was discovered in 1961 by L. P. Metik. Unusually, the discovery paper did not give celestial coordinates; instead, it included a map showing the star’s position relative to nearby stars. It received its variable star designation, V1315 Aquilae, in 1977.
A roughly spherical shell of material surrounds V1315 Aquilae, with a mass of at most 1×10⁻⁵ solar masses. This is too small to be a starburst nebula or a supernova remnant. The shell is consistent with a nova-scale eruption that occurred between 500 and 1,200 years ago (not accounting for light travel time). V1315 Aquilae is the first nova-like system found to possess such a nova shell.
- Constellation
- Aquila
- Variable star type
- nova-like (NL), SW Sextantis star
- Eclipse depth
- 1.8 mag
- Nova shell mass
- 1×10−5 solar masses
- Nova shell age estimate
- 500 to 1200 years old
- Discovery year
- 1961
- Discoverer
- L. P. Metik
- Variable star designation year
- 1977
Lore & Background
L. P. Metik discovered V1315 Aquilae in 1961. The discovery paper did not give celestial coordinates but instead presented a map showing the star's location relative to nearby stars. The star received its variable star designation, V1315 Aquilae, in 1977. As a SW Sextantis star, it has a non-magnetic white dwarf (though there is countering evidence for some magnetism) and does not undergo dwarf-nova eruptions. It has a high rate of mass transfer, resulting in steady-state accretion and a constant state of outburst. Most of its light is emitted in the visible range, originating from the accretion disk. The eclipse depth is 1.8 magnitudes. No description of the donor star is made in the source article.
Reader's Guide
V1315 Aquilae is significant as the first nova-like system discovered to possess a nova shell. This shell is roughly spherical, with a maximal mass of 1×10−5 solar masses, too small to be a starburst nebula or supernova remnant. It is consistent with models of a remnant from a nova-scale eruption estimated to be 500 to 1200 years old (plus light-travel time). The discovery of this shell provides observational evidence linking nova-like variables to past nova eruptions, challenging the traditional view that such systems are non-eruptive. The star's constant outburst state and high mass transfer rate, typical of SW Sextantis stars, further contextualize its behavior within cataclysmic variable evolution. The countering evidence for some magnetism adds nuance to its classification as a non-magnetic system.
Did You Know?
- Its nova shell has a mass of 1×10−5 solar masses and is estimated to be 500 to 1200 years old.
- The discovery paper from 1961 did not give coordinates but used a map to show the star's location.
Frequently Asked Questions
What is V1315 Aquilae?
V1315 Aquilae is a cataclysmic variable star in the constellation Aquila, classified as a nova-like object of the SW Sextantis subclass. It is a binary pair in which a white dwarf continuously accretes material from a companion, sustaining a perpetually active disk that supplies most of the system's visible light.
What makes V1315 Aquilae unique among variable stars?
It was the first nova-like variable ever found to be surrounded by a nova shell, the expanding remnant of an ancient nova explosion. That discovery linked a steady-state accretion system to a past eruptive event and opened a new line of inquiry into the evolutionary history of SW Sextantis-type stars.
How does V1315 Aquilae stay in constant outburst?
The donor star feeds the white dwarf at such a high rate that the accretion disk never fully drains, so the system never returns to a quiescent state. The white dwarf is largely non-magnetic, allowing the disk to persist without being channeled into discrete bursts, though faint signatures of magnetism have been detected.
What do we know about the nova shell around V1315 Aquilae?
Estimates place the shell's mass at roughly one ten-thousandth of a solar mass and its age between five hundred and one thousand two hundred years. In other words, the progenitor nova detonated centuries before modern telescopes, leaving only this faint, slowly expanding veil as a fossil record of the event.
When was V1315 Aquilae discovered and what eclipses does it show?
The star was first catalogued as a variable in 1961. It undergoes eclipses of about 1.8 magnitudes in depth, which occur when the donor star transits the bright accretion disk and temporarily blocks a significant portion of the system's light.
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