WISEA J045921.21+154059.2: A Bright, Nearby Infrared Dwarf

Are you up for an observing challenge?  If you have a telescope equipped with a CCD camera and an infrared filter, you might be able to detect the brightest known L-type infrared dwarf star WISEA J045921.21+154059.2.  (This author prefers to use the term “infrared dwarf” rather than the more popular caconym brown dwarf.)

WISEA J045921.21+154059.2, also known as WISE J045921.20+154059.4 and 2MASS J04592088+1541054, is a high-proper-motion star located not far from Aldebaran in the constellation Taurus at α2000 = 4h 59m 20.89s, δ2000 = +15° 41′ 05.42″.  This cool star has a spectral classification of sdL0.  Though its parallax has not yet been measured, its high proper motion may indicate it’s a star just a few light years away.  The “sd” classification on the L0 spectral type indicates that it is a subdwarf star—underluminous in comparison with a “normal” L0 star.

Infrared dwarfs—as their name implies—radiate mostly in the infrared portion of the spectrum rather than at visible wavelengths.  You can see this in the apparent magnitudes listed below.  Remember, the lower the number the brighter the star is at that wavelength/passband.

g = 20.08 ± 0.03
(PS1 g magnitude: center wavelength 4866 Å; green light)

r = 18.70 ± 0.01
(PS1 r magnitude: center wavelength 6215 Å; red light)

i = 17.14 ± 0.01
(PS1 i magnitude: center wavelength 7545 Å; infrared)

z = 16.49 ± 0.01
(PS1 z magnitude: center wavelength 8679 Å; infrared)

y = 16.19 ± 0.01
(PS1 y magnitude: center wavelength 9633 Å; infrared)

J = 14.96 ± 0.03
(2MASS J magnitude: center wavelength 12,350 Å; infrared)

H = 14.61 ± 0.06
(2MASS H magnitude: center wavelength 16,620 Å; infrared)

Ks = 14.30 ± 0.06
(2MASS Ks magnitude: center wavelength 21,590 Å; infrared)

W1 = 14.09 ± 0.03
(AllWISE W1 magnitude: center wavelength 34,000 Å; infrared)

W2 = 13.85 ± 0.04
(AllWISE W2 magnitude: center wavelength 46,000 Å; infrared)

W3 = 11.86 or brighter
(AllWISE W3 magnitude: center wavelength 120,000 Å; infrared)

W4 = 8.99 or brighter
(AllWISE W4 magnitude: center wavelength 230,000 Å; infrared)

Best, W. M. J., Magnier, E. A., et al. 2017, arXiv:1701.00490 [astro-ph.SR]

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