IQ Aurigae
A magnetic Ap star with rotationally modulated variability.
IQ Aurigae is a likely solitary variable star in the northern constellation Auriga. To the naked eye, it appears as a faint, white point of light, with its apparent visual magnitude typically hovering around 5.38. Based on parallax measurements, the star lies roughly 460 light-years from the Sun and is moving away at a radial velocity of +28.6 km/s.
In 1953, Sanford S. Provin noted that the star—then cataloged as HD 34452—showed possible signs of variability, though the evidence was not definitive. Karl D. Rakos later confirmed its variable nature in 1962.
This is a magnetic Ap star, classified as A0pSi, and is known as a silicon star due to a strong spectral line from singly ionized silicon. It may also be helium-deficient, as its helium lines are weaker than expected. As an Alpha² Canum Venaticorum-type variable, its brightness ranges from magnitude 5.35 to 5.43, modulated by rotation with a period of 2.4660 days. The star emits X-rays with a high luminosity of 4×10²⁹ erg s⁻¹, likely produced by a combination of shocks in its stellar wind and magnetic reconnection well above the surface. It has been observed to flare, during which X-ray output jumped to 3.2×10³¹ erg s⁻¹.
IQ Aurigae is about 6.3 million years old and rotates with a projected velocity of 49 km/s, giving a rotation period of 2.47 days. It has roughly four times the Sun’s mass and 2.6 times its radius. From its active photosphere, the star radiates 263 times the Sun’s luminosity at an effective temperature of 14,454 K.
- type
- Variable star (Alpha2 Canum Venaticorum-type)
- constellation
- Auriga
- apparent magnitude
- 5.35 to 5.43
- distance
- ~460 light-years
- spectral type
- A0pSi
- rotation period
- 2.4660 days
- age
- 6.3 million years
Lore & Background
IQ Aurigae is a magnetic Ap star with a stellar classification of A0pSi. It is known as a silicon star, having a strong line of singly ionized silicon, and may also be helium deficient as the lines of helium are weaker than expected. The star is an Alpha2 Canum Venaticorum-type variable, ranging in magnitude from 5.35 down to 5.43 with a rotationally-modulated period of 2.4660 days. It is an X-ray source with a high luminosity of 4×10^29 erg s−1, which may be caused by a combination of shocks in the stellar wind and magnetic reconnection occurring well above the stellar surface. The star has been observed to flare, during which the X-ray emission rose to 3.2×10^31 erg s−1.
Reader's Guide
IQ Aurigae is significant as a well-studied example of a magnetic Ap star, specifically a silicon star, whose variability was first suspected in 1953 and confirmed in 1962. Its rotationally modulated brightness changes and strong magnetic field make it a key object for understanding stellar magnetism and the behavior of chemically peculiar stars. The star's high X-ray luminosity and flaring activity provide insights into magnetic reconnection and shock processes in stellar atmospheres. Its youth (6.3 million years) and rapid rotation (2.47 days) contribute to its active photosphere and high luminosity (263 times the Sun's). As a naked-eye variable, it serves as a benchmark for studying the evolution and magnetic properties of intermediate-mass stars.
Did You Know?
- IQ Aurigae is an Alpha2 Canum Venaticorum-type variable star with a rotation period of 2.4660 days.
- The star is a silicon star, showing a strong line of singly ionized silicon and possibly helium deficiency.
- It has been observed to flare, with X-ray emission rising to 3.2×10^31 erg s−1.
- IQ Aurigae is 6.3 million years old and has nearly four times the mass of the Sun.
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