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| V Sagittae | |
|---|---|
| Name | V Sagittae |
| Constellation | Sagitta |
| Epoch | J2000 |
| Ra | 19h 55m 15.7s |
| Dec | +20° 46′ 30″ |
| Apparent magnitude | 8.7–13.5 (variable) |
| Spectral type | peculiar/variable |
| Radial velocity | ~ -40 km/s |
| Distance | ~8,000–11,000 ly |
| Other names | BD+20° 4346, GSC 01640-00999 |
V Sagittae is a luminous, eclipsing and eruptive binary star system in the constellation Sagitta that has been identified as a candidate for a dramatic, nova-like brightening in the 21st century. The system is notable for its short orbital period, unusual emission-line spectrum, and evolving accretion dynamics that have attracted attention from observers at Harvard College Observatory, Palomar Observatory, and amateur networks such as the American Association of Variable Star Observers. V Sagittae links studies across observational programs at institutions including NASA, European Space Agency, Mount Wilson Observatory, Keck Observatory, and Very Large Telescope facilities.
V Sagittae is an interacting binary that exhibits photometric and spectroscopic behavior associable with high-accretion cataclysmic variables and with the rare class of objects undergoing thermal-timescale mass transfer. The system has been observed in campaigns coordinated by organizations like International Astronomical Union, AAVSO, Royal Astronomical Society, and projects using instruments on Hubble Space Telescope, Chandra X-ray Observatory, and XMM-Newton. Research teams from universities such as Harvard University, Yale University, University of Cambridge, University of California, Berkeley, and Caltech have published analyses alongside surveys like Gaia, Pan-STARRS, and Sloan Digital Sky Survey.
The binary comprises a compact accretor identified as a white dwarf candidate and a mass-donating companion evolving off the main sequence, with an orbital period near 0.514 days. Detailed modeling by groups at Max Planck Institute for Astronomy, Institute of Astronomy, Cambridge, University of Tokyo, University of Oxford, and Princeton University invokes Roche-lobe overflow, a bright accretion disk, and intense wind-driven outflows. Parameters constrained by spectroscopy and photometry draw on calibrations from Hipparcos, Gaia DR2, and empirical relations from studies at Mount Stromlo Observatory and McDonald Observatory. The system displays strong helium and nitrogen lines, consistent with processed material transferred from an evolved donor, a scenario explored in theoretical work at Institute for Advanced Study and Kavli Institute for Theoretical Physics.
Discovered in the early 20th century and cataloged in surveys like Bonner Durchmusterung and later in the General Catalogue of Variable Stars, V Sagittae has been monitored by observatories including Lick Observatory, Cerro Tololo Inter-American Observatory, and Kitt Peak National Observatory. Photographic plate archives at Harvard College Observatory and spectroscopic archives at Palomar Observatory provided historical baselines used by teams from University of Toronto and University of Edinburgh. Modern time-domain programs such as ASAS-SN, Zwicky Transient Facility, and OGLE augmented follow-up by amateur networks coordinated through AAVSO and collaborations with NOAO.
The light curve exhibits deep eclipses, quasi-periodic variability, and a secular brightening trend interpreted as increasing mass transfer. Time-series photometry has been obtained with facilities like Kepler (K2 campaigns), TESS, and ground-based arrays linked to Las Cumbres Observatory, yielding data analyzed using methods from Astropy, ISIS, and techniques developed at Institut d'Astrophysique de Paris. Period analyses employed algorithms from Rice University and Massachusetts Institute of Technology groups, while long-term trends were compared against archival datasets from WISE and IRAS to assess infrared changes.
High-resolution spectra from instruments on Keck Observatory, Very Large Telescope, Subaru Telescope, and Gemini Observatory show strong emission lines of helium, nitrogen, and hydrogen with P Cygni profiles indicative of fast winds. Ultraviolet observations by International Ultraviolet Explorer and Hubble Space Telescope COS/STIS detected high-excitation lines also seen in symbiotic novae and supersoft X-ray sources studied at Los Alamos National Laboratory and Lawrence Berkeley National Laboratory. X-ray behavior recorded by Chandra and XMM-Newton suggests variable soft X-ray emission comparable to objects analyzed by researchers at Columbia University and University of Chicago.
Models developed at University of Southampton, Monash University, University of Washington, and Durham University predict that thermal-timescale mass transfer will culminate in a luminous eruption within decades, potentially rivaling historical classical novae studied in contexts like Nova Persei 1901 and Nova Cygni 1975. Population-synthesis codes from Space Telescope Science Institute and theoretical frameworks at Max Planck Institute for Astrophysics and CEA Saclay show pathways including accretion-induced outbursts, common-envelope episodes, or a luminous red nova-like transient examined in studies by European Southern Observatory teams. These scenarios inform observing campaigns planned by consortia including LSST Science Collaboration and ZTF follow-up groups.
Imaging with narrowband filters and interferometry at Mount Palomar Observatory, Alma and instruments associated with National Radio Astronomy Observatory reveal faint nebulosity and possible bipolar outflows, analogous to structures seen around objects observed by Hubble Space Telescope and mapped in molecular lines by IRAM and JCMT. Studies connecting the circumstellar medium to mass-loss episodes invoke comparisons with nebulae around systems analyzed by European VLTI, CHARA Array, and imaging projects at Space Telescope Science Institute and Smithsonian Astrophysical Observatory.
Category:Binary stars Category:Variable stars Category:Sagitta