T Coronae Borealis (T CrB), nicknamed the Blaze star, is a recurrent nova in the constellation Corona Borealis.[11] It was first discovered in outburst in 1866 by John Birmingham,[12] although it had been observed earlier as a 10th magnitude star.[13] It may have been observed in 1217 and in 1787 as well.[14][15] It is expected to undergo an outburst again in 2024.
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Corona Borealis |
Right ascension | 15h 59m 30.1622s[1] |
Declination | 25° 55′ 12.613″[1] |
Apparent magnitude (V) | 2.0–10.8[2] |
Characteristics | |
Evolutionary stage | Red giant + white dwarf |
Spectral type | M3III+p[3] |
Variable type | recurrent nova[2] |
Astrometry | |
Radial velocity (Rv) | −27.79[4] km/s |
Proper motion (μ) | RA: −4.220[5] mas/yr Dec.: 12.364[5] mas/yr |
Parallax (π) | 1.2127 ± 0.0488 mas[5] |
Distance | 806+34 −30[6] pc |
Orbit | |
Period (P) | 227.8 d[7] |
Semi-major axis (a) | 0.54 AU[6] |
Eccentricity (e) | 0.0[7] |
Inclination (i) | 67[8]° |
Details | |
Red giant | |
Mass | 1.12[6] M☉ |
Radius | 75[8] R☉ |
Luminosity | 655[9] L☉ |
Surface gravity (log g) | 2.0[10] cgs |
Temperature | 3,600[10] K |
White dwarf | |
Mass | 1.37[6] M☉ |
Luminosity | ~100[8] L☉ |
Other designations | |
Database references | |
SIMBAD | data |
T CrB normally has a magnitude of about 10, which is near the limit of typical binoculars. Outbursts have been seen twice, reaching magnitude 2.0 on May 12, 1866 and magnitude 3.0 on February 9, 1946,[16] although a more recent paper shows the 1866 outburst with a possible peak range of magnitude 2.5 ± 0.5.[17] Even when at peak magnitude of 2.5, this recurrent nova is dimmer than about 120 stars in the night sky.[18] It is sometimes nicknamed the Blaze Star.[19]
T CrB is a binary system containing a large cool component and a smaller hot component. The cool component is a red giant which is transferring material to the hot component. The hot component is a white dwarf surrounded by an accretion disc, all hidden inside a dense cloud of material from the red giant. When the system is quiescent, the red giant dominates the visible light output and the system appears as an M3 giant. The hot component contributes some emission and dominates the ultraviolet output. During outbursts, the transfer of material to the hot component increases greatly, the hot component expands, and the luminosity of the system increases.[6][8][20][21]
The two components of the system orbit each other every 228 days. The orbit is almost circular and is inclined at an angle of 67°. The stars are separated by 0.54 AU.[6]
On 20 April 2016, the Sky & Telescope website reported a sustained brightening since February 2015 from magnitude 10.5 to about 9.2. A similar event was reported in 1938, followed by another outburst in 1946.[22] By June 2018, the star had dimmed slightly but still remained at an unusually high level of activity. In March or April 2023, it dimmed to magnitude 12.3.[23] A similar dimming occurred in the year before the 1946 outburst, indicating that it will likely erupt between April and September 2024.[24]