SX Arietis variable

SX Arietis variables are a class of variable stars. They are generally B-type main sequence stars of spectral types B0p to B9p— high-temperature analogues of Alpha2 Canum Venaticorum variables—and exhibit strong magnetic fields and intense He I and Si III spectral lines. They have brightness fluctuations of approximately 0.1 magnitudes with periods of about one day. The prototype of this class is 56 Arietis, which bears the variable star designation SX Arietis.


The following list contains selected SX Arietis variable that are of interest to amateur or professional astronomy. Unless otherwise noted, the given magnitudes are in the V-band.

(in days)
(in parsecs)
Alpha Sculptoris 4.27 B7IIIp 238
Sigma Lupi 4.42 B2III 3.02 176
HD 125823 4.42 B7IIIpv 8.82 140
HR 2949 4.43 B5IV 1.90 113
28 Cygni 4.93 B2.5Ve 0.70 317
36 Lyncis 5.29 B9 3.83 178
V913 Scorpii 5.43 B5V 0.98 170
V692 Coronae Australis 5.46 B2.5III 1.67 357
HD 21699 5.46 B8IIImnp 2.48 186
56 Arietis 5.76 B6IV-V 0.73 154
HD 133880 5.79 B8IVSi 0.88 111
HD 28843 5.81 B9III 1.37 146
3 Scorpii 5.87 B8III/IV 1.46 158
V957 Scorpii 5.90 B6V 258
V929 Scorpii 5.92 B8V 1.49 161
HR 7355 6.02 B2Vn 0.52 273
HD 145792 6.42 B6IV 1.70 144
HD 37017 6.56 B1.5V [n 1] 380
Sigma Orionis E 6.61 B2Vp 1.19 329
HD 37776 6.96 B2V 1.54 330
HD 37058 7.30 B3Vp 15.26
HD 184927 7.44 B2V 9.35 543
HD 191612 7.80 O8fpe 538 2041
HD 35298 7.91 B7IV 1.85 532
HD 36668 8.05 B8V 2.12 249
HD 34626 8.16 B1.5IVnp 0.50 483


  1. ^ also an eclipsing binary


Samus N.N., Durlevich O.V., et al. Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.)

12 Canis Majoris

12 Canis Majoris is a variable star located 184 light years away from the Sun in the southern constellation of Canis Major. It has the variable star designation HK Canis Majoris; 12 Canis Majoris is the Flamsteed designation. This body is just barely visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of +6.07. It is moving away from the Earth with a heliocentric radial velocity of +16 km/s. This is the brightest star in the vicinity of the open cluster NGC 2287, although it is probably not a member based on its proper motion.This star has a stellar classification of B7 II/III, matching a B-type giant/bright giant hybrid. (Cidale et al. (2007) show a class of B5 V, which would indicate it is instead a B-type main-sequence star.) It is a magnetic Bp star of the helium–weak variety (CP4), with the spectrum displaying evidence for vertical stratification of helium in the atmosphere. Samus et al. (2017) classify it as an SX Arietis variable with a brightness varies from magnitude +6.00 down to +6.05 over a period of 2.18045 days. It has 1.25 times the mass of the Sun and 2.73 times the Sun's radius. The star is radiating 498 times the Sun's luminosity from its photosphere at an effective temperature of 6,500 K.

28 Cygni

28 Cygni is a single star in the northern constellation of Cygnus. It is a faint blue-white hued star but visible to the naked eye with an apparent visual magnitude of 4.93. The distance to 28 Cyg, as estimated from its annual parallax shift of 5.3 mas, is around 620 light years. It has an absolute magnitude of −2.56, which means that if the star were just 10 parsecs (33 light-years) away it would be brighter than Sirius, the brightest star in the night sky.

This is a B-type main-sequence star with a stellar classification of B2.5 V, per Lesh (1968). Slettebak (1982) found a class of B2 IV(e), which would suggest this is a more evolved subgiant star. It is a Be star, which means the spectrum displays emission lines due a disk of ejected gas in a Keplerian orbit around the star. The star displays short-term variability with two or more periods, and is classified as an SX Arietis variable by Samus et al. (2017). It is spinning rapidly with a projected rotational velocity of 320 km/s; estimated at round 80% of the critical rotation rate. This is giving the star an oblate shape with an equatorial bulge out to 6.5 times the Sun's radius, compared to 5.7 at the poles.

36 Lyncis

36 Lyncis is a solitary variable star located around 570 light years away from the Sun in the northern constellation of Lynx. It has the variable star designation of EI Lyncis, while 36 Lyncis is the Flamsteed designation. This object is visible to the naked eye as a dim, blue-white hued star with an apparent visual magnitude of 5.30. It is moving further away from the Earth with a heliocentric radial velocity of 21 km/s.This is a magnetic, helium-weak Bp star with a stellar classification of B8 IIImnp. It is sometimes classified as a mercury-manganese star. It is also an 'sn' star, displaying a spectrum with generally sharp lines for most elements in combination with broad, diffuse lines of helium. 36 Lyncis has been classified as an SX Arietis variable with an amplitude of 0.03 in visual magnitude and a rotationally-modulated period of 3.834 days. The star is spinning with a projected rotational velocity of 49 km/s and a rotation rate of 3.83476 days. It has 4.21 times the Sun's radius and is radiating 443 times the luminosity of the Sun from its photosphere at an effective temperature of 13,700 K.

Aries (constellation)

Aries is one of the constellations of the zodiac. It is located in the northern celestial hemisphere between Pisces to the west and Taurus to the east. The name Aries is Latin for ram, and its symbol is (Unicode ♈), representing a ram's horns. It is one of the 48 constellations described by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. It is a mid-sized constellation, ranking 39th overall size, with an area of 441 square degrees (1.1% of the celestial sphere).

Although Aries came to represent specifically the ram whose fleece became the Golden Fleece of Ancient Greek mythology, it has represented a ram since late Babylonian times. Before that, the stars of Aries formed a farmhand. Different cultures have incorporated the stars of Aries into different constellations including twin inspectors in China and a porpoise in the Marshall Islands. Aries is a relatively dim constellation, possessing only four bright stars: Hamal (Alpha Arietis, second magnitude), Sheratan (Beta Arietis, third magnitude), Mesarthim (Gamma Arietis, fourth magnitude), and 41 Arietis (also fourth magnitude). The few deep-sky objects within the constellation are quite faint and include several pairs of interacting galaxies. Several meteor showers appear to radiate from Aries, including the Daytime Arietids and the Epsilon Arietids.

K Puppis

k Puppis (k Pup, k Puppis) is a Bayer designation given to an optical double star in the constellation Puppis, the two components being k1 Puppis and k2 Puppis.

List of stars in Lynx

This is the list of notable stars in the constellation Lynx, sorted by decreasing brightness.

Sigma Lupi

Sigma Lupi, Latinized from σ Lupi, is a star in the southern constellation of Lupus. It is visible to the naked eye with an apparent visual magnitude of 4.4. Based upon an annual parallax shift of 5.67 mas as seen from Earth, it is located about 580 light years from the Sun. It is a member of the Upper Centaurus Lupus subgroup of the nearby Sco OB2 association.This is a B-type main sequence star with a stellar classification of B1/B2 V. Sigma Lupi is a Helium strong star with an enhanced abundance nitrogen and an underabundance of carbon. Jerzykiewicz and Sterken (1992) showed a small amplitude variability with a period of 3.02 days. This suggests it is a close binary system forming a rotating ellipsoidal variable, although other causes such as rotational modulation can not be ruled out. There is a higher frequency photometric variability with a rate of 10.93482 per day and an amplitude of 0.0031 in visual magnitude, but the cause of this is unknown.At an age of just 13.4 million years, Sigma Lupi is spinning with a projected rotational velocity of 68 km/s giving it a rotation period of 3.02 days. A magnetic field has been detected with a polar field strength of around 500 G, which is varying longitudinally with an amplitude of around 100 G. The star has an estimated nine times the mass of the Sun and 4.8 times the Sun's radius. It is radiating 5,754 times the solar luminosity from its outer atmosphere at an effective temperature of around 23,000 K.

Sigma Orionis

Sigma Orionis or Sigma Ori (σ Orionis, σ Ori) is a multiple star system in the constellation Orion, consisting of the brightest members of a young open cluster. It is found at the eastern end of the belt, south west of Alnitak and west of the Horsehead Nebula which it partially illuminates. The total brightness of the component stars is magnitude 3.80.

Stellar magnetic field

A stellar magnetic field is a magnetic field generated by the motion of conductive plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material. A localized magnetic field exerts a force on the plasma, effectively increasing the pressure without a comparable gain in density. As a result, the magnetized region rises relative to the remainder of the plasma, until it reaches the star's photosphere. This creates starspots on the surface, and the related phenomenon of coronal loops.


This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.