Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Perseus |
Right ascension | 02h 35m 17.127s [1] |
Declination | +56° 08′ 44.72″ [1] |
Apparent magnitude (V) | 10.5 - 16.0 [2] |
Characteristics | |
Spectral type | C5,4pJ: [3] C-R4+ C25.5 [4] |
B−V color index | 1.79 [5] |
V−R color index | 1.12 [5] |
J−H color index | 0.185 [6] |
J−K color index | 1.963 [6] |
Variable type | DY Per [7] |
Astrometry | |
Radial velocity (Rv) | −38 [8] km/s |
Proper motion (μ) | RA: +2.264 [1] mas/yr Dec.: −0.675 [1] mas/yr |
Parallax (π) | 0.6718 ± 0.0251 mas [1] |
Distance | 1,500 [9] pc |
Absolute magnitude (MV) | −2.5 (max) [7] |
Details | |
Radius | 87 [10] R☉ |
Luminosity | 522 [11] L☉ |
Surface gravity (log g) | 0.0 [12] cgs |
Temperature | 2,900-3,100 [12] K |
Metallicity [Fe/H] | −2.0 to −0.5 [12] dex |
Other designations | |
Database references | |
SIMBAD | data |
DY Persei is a variable star and carbon star in the Perseus constellation. At maximum it is 11th magnitude and at its faintest it drops to 16th magnitude. DY Persei is the prototype of the very rare DY Persei class of variables that pulsate like red variables but also fade from sight like R Coronae Borealis variables.
DY Persei is located on the outskirts of the Trumpler 2 open cluster, near the famous Double Cluster. At 1,500 pc, DY Persei is thought to be much further away than Trumpler 2 and not a member.
DY Persei was reported to be variable in 1947. [13] It was initially classified as a semiregular variable star with a brightness range of magnitude 10.6 to 13.2 and an approximate period of 900 days. [14] Further study revealed that it showed deep declines every few years as well as continuous variations with a rough period of 792 days. The deep declines were considered to be related to the declines seen in R CrB stars, but DY Persei was a unique example, being a cool carbon star and showing large amplitude semiregular variations when not in decline. [15]
DY Persei is now classed as a member of the very rare class of DY Persei variables, with only four known in the Milky Way and 13 more in the Magellanic Clouds. [16] It has shown declines as deep as visual magnitude 16.0. [9]
The deep declines of DY Persei occur much more regularly than those of most R CrB stars, and they are generally symmetrical with slower decline and recovery rates than other R CrB stars. It is unclear whether it is really a member of the class or a pulsating asymptotic giant branch star with unrelated veiling ejections, [7] or just the cooler version of R CrB stars. [17]
There is a 14th magnitude star 2.5" from DY Persei, but it appears to be a chance alignment. It was not generally recognised until 2005, and would have strongly affected observations when DY Per was below maximum light. The companion is likely to be a G5 main sequence star much further away than DY Per. [9] It had been reported that the colour of DY Persei became more blue during a deep decline, highly unexpected for a star of this type, but this has been explained as the relatively increased contribution to the light from the companion as DY Persei itself becomes fainter. [7]
DY Persei is a carbon star, with an excess of carbon relative to oxygen in its atmosphere. This causes dramatic changes in the atmospheric chemistry that are visible in the spectrum.
The spectral type under the original M-K carbon star system is C5,4pJ: (C54pJ:). This means that the spectrum overall is comparable to a late K or early M class, with strong C2 Swan bands. The "p" indicates that there are peculiarities and the "J" that there are isotopic bands from 13C. In the revised M-K system, the spectral type is C-R4+ C25.5. This describes essentially the same spectral features, although the C-R type indicates that the isotopic bands are strong but not sufficiently so to merit a "J". The exact 13C/12C ratio for DY Persei is disputed. S-process metal spectral lines are weak compared to other carbon stars, suggesting that DY Persei is not a thermally-pulsing asymptotic giant branch star. Overall, hydrogen spectral features are weak and metal lines typical, showing that DY Persei is hydrogen-deficient but not metal-poor. [9]
During deep minima, the carbon-related spectral bands become less prominent, and some emission lines are seen. In typical R CrB variables, the spectra at minimum show many strong emission lines of metals, but in DY Persei only a few are detected. A broad emission line of neutral sodium is seen, together with possible emission from neutral calcium and carbon. [9]
DY Persei has a temperature around 3,000 K, but at a deep minimum its spectrum has been best modelled as the sum of two black body objects, one of 1,700 K typical of dusty circumstellar material and one of 2,400 K typical of the coolest giant stars. [7]
The size and luminosity of DY Persei, and other DY Persei and R Coronae Borealis stars, are very poorly known. [9] The absolute magnitude is thought to be around −2.5, about 855 times brighter than the sun. [7]
The metallicity of DY Persei has been reported to be much lower than solar, but other studies consider it to be near-solar. [12] [7]
R Coronae Borealis is a low-mass yellow supergiant star in the constellation of Corona Borealis. It is the prototype of the R Cor Bor class of variable stars, which fade by several magnitudes at irregular intervals. R Coronae Borealis itself normally shines at approximately magnitude 6, just about visible to the naked eye, but at intervals of several months to many years fades to as faint as 15th magnitude. Over successive months it then gradually returns to its normal brightness, giving it the nickname "reverse nova", after the more common type of star which rapidly increases in brightness before fading.
T Coronae Borealis, is a recurring nova in the constellation Corona Borealis. It was first discovered in outburst in 1866 by John Birmingham, although it had been observed earlier as a 10th magnitude star.
UU Aurigae is a carbon star in the constellation Auriga. It is approximately 341 parsecs from Earth.
DY Persei variables are a subclass of R Coronae Borealis variables. They are carbon-rich asymptotic giant branch (AGB) stars that exhibit pulsational variability of AGB stars and irregular fades similar to R CrB stars.
An R Coronae Borealis variable is an eruptive variable star that varies in luminosity in two modes, one low amplitude pulsation, and one irregular, unpredictably-sudden fading by 1 to 9 magnitudes. The prototype star R Coronae Borealis was discovered by the English amateur astronomer Edward Pigott in 1795, who first observed the enigmatic fadings of the star. Only about 150 RCB stars are currently known in our Galaxy while up to 1000 were expected, making this class a very rare kind of star.
WZ Cassiopeiae is a deep red hued star in the northern constellation of Cassiopeia. It is a variable star with a magnitude that ranges from 6.3 down to 8.8, placing it near the limit of naked eye visibility at peak magnitude. The estimated distance to this star, as determined from its annual parallax shift of 2.1 mas, is about 1,540 light years. It is moving closer to the Earth with a heliocentric radial velocity of −34 km/s.
Theta Coronae Borealis, Latinized from θ Coronae Borealis, is a binary star system in the constellation Corona Borealis. It shines with a combined apparent visual magnitude of 4.13. There are two components: Theta Coronae Borealis A with an apparent magnitude of about 4.2, while Theta Coronae Borealis B lies around 1 arcsecond distant and has an apparent magnitude of 6.29. The system is located around 375 light-years from Earth, as estimated from its parallax of 8.69 milliarcseconds. It is estimated to be 85 million years old, with the primary star expected to remain on the main sequence burning its core hydrogen for another 75 million years and the secondary around 500 million years. Both stars will cool and expand once their core hydrogen is exhausted, becoming red giants.
Epsilon Coronae Borealis, Latinized from ε Coronae Borealis, is a multiple star system in the constellation Corona Borealis located around 230 light-years from the Solar System. It shines with a combined apparent magnitude of 4.13, meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations. It is an orange giant around 1.7 times as massive as the Sun of spectral type K2III, which has exhausted its core fuel supply of hydrogen and swollen to 21 times the Sun's diameter and 151 times its luminosity. That is, Epsilon Coronae Borealis's diameter is about one-quarter of Mercury's orbit. Its surface temperature has been calculated to be 4365 ± 9 K, or 4406 ± 15 K. It is thought to be around 1.74 billion years old.
Delta Coronae Borealis, Latinized from δ Coronae Borealis, is a variable star in the constellation Corona Borealis. Its apparent magnitude varies regularly between apparent magnitude 4.57 and 4.69, and it is around 170 light-years distant.
Lambda Coronae Borealis, its name Latinised from λ Coronae Borealis, is a single star in the northern constellation of Corona Borealis. In publications it is also identified as HR 5936 and HD 142908. It has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.43. The star is located at a distance of 136 light years based on parallax, but is drifting closer with a radial velocity of −12 km/s.
RY Sagittarii is a yellow supergiant and an R Coronae Borealis type variable star in the constellation Sagittarius. Although it ostensibly has the spectrum of a G-type star, it differs markedly from most in that it has almost no hydrogen and much carbon.
9 Persei is a single variable star in the northern constellation Perseus, located around 4,300 light years away from the Sun. It has the Bayer designation i Persei; 9 Persei is the Flamsteed designation. This body is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of about 5.2. It is moving closer to the Sun with a heliocentric radial velocity of −15.2 km/s. The star is a member of the Perseus OB1 association of co-moving stars.
Z Ursae Minoris is a carbon star and R Coronae Borealis variable in the constellation Ursa Minor.
RS Telescopii, abbreviated RS Tel, is a variable star in the southern constellation of Telescopium. It is a dim star with an apparent visual magnitude of 10.67, which is much too faint to be visible without a telescope. The variability of this star was discovered by Evelyn F. Leland and announced by Edward C. Pickering in 1910. It was first studied by Cecilia H. Payne in 1928 at the Harvard College Observatory.
V Coronae Australis is a R Coronae Borealis variable (RCB) star in the constellation Corona Australis. These are extremely hydrogen-deficient supergiants thought to have arisen as the result of the merger of two white dwarfs; fewer than 100 have been discovered as of 2012. V Coronae Australis dimmed in brightness from 1994 to 1998.
WX Coronae Australis is an R Coronae Borealis star in the constellation Corona Australis, one of the brightest examples of this extremely rare class of variable star. Despite the rarity, Corona Australis hosts another R CrB star, V Coronae Australis.
Sigma Coronae Borealis is a star system in the constellation of Corona Borealis. It is a quintuple star system containing three sunlike main-sequence stars and two other low-mass stars. The combined visual magnitude is 5.3 and the system lies 74 light years from Earth. σ CrB A is the variable star TZ Coronae Borealis.
W Coronae Borealis is a Mira-type long period variable star in the constellation Corona Borealis. Its apparent magnitude varies between 7.8 and 14.3 over a period of 238 days.
Upsilon Coronae Borealis, Latinized from υ Coronae Borealis, is a solitary star in the northern constellation of Corona Borealis. It is a white-hued star that is dimly visible to the naked eye with an apparent visual magnitude of 5.78. The distance to this object is approximately 630 light-years based on parallax.
S Apodis, also known as HD 133444 is a variable star located in the southern circumpolar constellation Apus. It has an apparent magnitude ranging from 9.6 to 17, which is below the limit for naked eye visibility. The object is located relatively far at a distance of approximately 15,000 light years based on Gaia DR3 parallax measurements, but it is drifting closer with a heliocentric radial velocity of −75 km/s.