HR Delphini, also known as Nova Delphini 1967, was a nova which appeared in the constellation

Delphinus Delphinus (Pronounced or ) is a small constellation in the Northern Celestial Hemisphere, close to the celestial equator. Its name is the Latin version for the Greek word for dolphin (). It is one of the 48 constellations listed by the 2nd c ...

in 1967. It was discovered by George Alcock at 22:35 UT on 8 July 1967, after searching the sky for over 800 hours with binoculars. At the time of discovery it had an apparent magnitude of 5.0. It reached a peak brightness of magnitude 3.5 on 13 December 1967, making it easily visible to the naked eye around that time. Pre-outburst photographs taken with the

Samuel Oschin telescope The Samuel Oschin telescope, also called the Oschin Schmidt, is a Schmidt camera at the Palomar Observatory in northern San Diego County, California. It consists of a 49.75-inch Schmidt corrector plate and a 72-inch (f/2.5) mirror. The instrument ...

showed it as a ~12th magnitude star which might have been variable. HR Delphini was discovered 158 days before it reached peak brightness, and its light curve around the peak was very well observed. It had a very slow rise to maximum brightness, when compared to other classical novae. It took 230 days for HR Delphini to fade from its peak by 3 magnitudes, which makes it a "slow" nova. Its decline from peak brightness showed several brief outbursts, leading to its light curve being classified as type "J" (for "jitters"). In June 1970, HR Delphini was detected in 3.7 cm and 11.1 cm radio wavelengths with the Green Bank Interferometer, and at 1.95 cm with the

Green Bank A green bank (sometimes referred to as green investment bank, clean energy finance authority, or clean energy finance corporation) is a financial institution, typically public or quasi-public, that uses innovative financing techniques and market ...

140 foot telescope. All novae are binary stars, with a "donor" star orbiting a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...

. The two stars are so close to each other that material is transferred from the donor to the white dwarf. In the case of HR Delphini, the orbital period of the binary pair is 5.14 hours. The mass of the white dwarf is estimated to be between 0.6 and 0.75 and the donor star is believed to be a main sequence star with a mass between 0.52 and 0.58 with a

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

in the range of K5V to M1V. HR Delphini is surrounded by a bipolar

nova remnant A nova remnant is made up of the material either left behind by a sudden explosive fusion eruption by classical novae, or from multiple ejections by recurrent novae. Over their short lifetimes, nova shells show expansion velocities of around 1000& ...

emission nebula An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emissio ...

, visible in Hα, Hβ as well as

forbidden lines In spectroscopy, a forbidden mechanism (forbidden transition or forbidden line) is a spectral line associated with absorption or emission of photons by atomic nuclei, atoms, or molecules which undergo a transition that is not allowed by a particul ...

of oxygen and nitrogen. It is roughly ellipsoidal, with a central ring around the equatorial region. It had a size of 3.7 × 2.5 arc seconds when it was discovered in 1981, and had expanded to roughly 8.5 × 6.1 arc seconds when it was observed with the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

in 1997.

References

{{DEFAULTSORT:HR Delphini Novae Delphinus (constellation) 1967 in science Delphini, HR 102190