G 29-38

Variable star designation	ZZ Psc
Variable type	DAV
Right ascension (J 2000)	23h 28m 49s
Declination (J2000)	+5° 15.5′
Range (magnitudes)	13.03
Period	110 - 1016 seconds

G29-38 (Giclas 29-38, ZZ Psc, WD 2326+049, EG 159, LTT 16907) is a large-amplitude DAV (ZZ Ceti) pulsator White Dwarf with variability first reported by Shulov & Kopatskaya in 1974. G29-38 died around half a billion years ago and probably consumed any inner planets it may have had in the process. Recently, NASA's Spitzer Space Telescope has observed what may be comet dust spread around G29-38. This data may mean that G29-38 is still orbited by a ring of surviving comets and possibly outer planets. This is the first observational data to support the idea that comets may outlive their stars. "The dust seen by Spitzer around G29-38 was probably generated relatively recently when one such outlying comet may have been knocked into the inner region of the system and ripped into dust shreds by the tidal forces of the star," said astronomer William Reach of the Spitzer Science Center at the California Institute of Technology in Pasadena, Calif.

DAV stars are like normal white dwarfs but have luminosity variations in amplitudes as high as 30% and periods from 100 to 1,000 seconds. Asteroseismology uses the observed spectrum of pulsations like G29-38 to observe their stellar interior. G29-38 is one of the more complex large-amplitude DAV pulsators that, to date, are more difficult to understand.

The power spectrum of G29-38 varies in periods from weeks to years which are usually dominated by one large mode, although many smaller amplitude modes can also be observed. The bigger amplitude modes evidence complex and variable behavior commonly seen in other large-amplitude DAVs. Interspersed among the major variable modes are a few areas with less power that demonstrate a lot more stability by lingering in the light curve while the larger modes come and go. Large-amplitude DAVs, generally differ from the lower amplitude DAVs by their: lower temperatures; longer primary periodicities; and presence of many peaks with frequencies that are sums of other modes present in the white dwarf.

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