White dwarf which undergoes characteristic variability
Giclas 29-38, also known as ZZ Piscium, is a variablewhite dwarf star of the DAV (or ZZ Ceti) type, whose variability is due to large-amplitude, non-radial pulsations known as gravity waves. It was first reported to be variable by Shulov and Kopatskaya in 1974.[7][8] DAV stars are like normal white dwarfs but have luminosity variations with amplitudes as high as 30%, arising from a superposition of vibrational modes with periods from 100 to 1,000 seconds. Large-amplitude DAVs generally differ from lower-amplitude DAVs by having lower temperatures, longer primary periodicities, and many peaks in their vibrational spectra with frequencies which are sums of other vibrational modes.[9]
G29-38, like other complex, large-amplitude DAV variables, has proven difficult to understand. The power spectrum or periodogram of the light curve varies over times which range from weeks to years. Usually, one strong mode dominates, although many smaller-amplitude modes are often observed. The larger-amplitude modes, however, fluctuate in and out of observability; some low-power areas show more stability. Asteroseismology uses the observed spectrum of pulsations from stars like G29-38 to infer the structure of their interiors.[9]
Debris disk
The circumstellar environment of G29-38 first attracted attention in the late 1980s during a near-infrared survey of 200 white dwarfs conducted by Ben Zuckerman and Eric Becklin to search for low mass companion stars and brown dwarfs.[11] G29-38 was shown to radiate substantial emission between 2 and 5 micrometres, far in excess of that expected from extrapolation of the visual and near infrared spectrum of the star.[12] Like other young, hot white dwarfs, G29-38 is thought to have formed relatively recently (600 million years ago) from its AGB progenitor, and therefore the excess was naturally explained by emission from a Jupiter-like brown dwarf with a temperature of 1200 K and a radius of 0.15 solar radius.[11][12] However, later observations, including speckle interferometry, failed to detect a brown dwarf.[13]
Infrared observations made in 2004 by NASA's Spitzer Space Telescope indicated the presence of a dust cloud around G29-38, which may have been created by tidal disruption of an exocomet or exoasteroid passing close to the white dwarf.[14] This may mean that G29-38 is still orbited by a ring of surviving comets and, possibly, outer planets. This is the first observation supporting the idea that comets persist to the white dwarf stage of stellar evolution.[15]
Infrared emission at 9-11 Mircons from Spitzer spectroscopy were interpreted as a mixture of amorphousolivine and a small amount of fosterite in the disk.[14] Modelling of the disk have shown that the inner edge of the disk lies at around 96±4 white dwarf radii and that the disk has a width of about 1-10 white dwarf radii. The dust mass of the disk is about 4-5 x 1018 g (about half the mass of a massive asteroid) and the disk has a temperature less than 1000 K.[16]
References
^ a b c dVallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
^ a b c d eThe general catalogue of trigonometric parallaxes, W. F. van Altena, J. T. Lee, E. D. Hoffleit, New Haven, CT: Yale University Observatory, c1995, 4th ed., completely revised and enlarged. CDS ID I/238A.
^Kirkpatrick, J. Davy; Marocco, Federico; Gelino, Christopher R.; Raghu, Yadukrishna; Faherty, Jacqueline K.; Bardalez Gagliuffi, Daniella C.; Schurr, Steven D.; Apps, Kevin; Schneider, Adam C.; Meisner, Aaron M.; Kuchner, Marc J.; Caselden, Dan; Smart, R. L.; Casewell, S. L.; Raddi, Roberto (2024-04-01). "The Initial Mass Function Based on the Full-sky 20 pc Census of ∼3600 Stars and Brown Dwarfs". The Astrophysical Journal Supplement Series. 271 (2): 55. Bibcode:2024ApJS..271...55K. doi:10.3847/1538-4365/ad24e2. ISSN 0067-0049.
^§1, The Dust cloud around the White Dwarf G 29-38. 2. Spectrum from 5-40 microns and mid-infrared variability, William T. Reach, Carey Lisse, Ted von Hippel, and Fergal Mullally, Astrophysical Journal, in press, Bibcode:2008arXiv0810.3276R.
^ a b cTable 1, The Formation Rate and Mass and Luminosity Functions of DA White Dwarfs from the Palomar Green Survey, James Liebert, P. Bergeron, and J. B. Holberg, The Astrophysical Journal Supplement Series156, #1 (January 2005), pp. 47–68, doi:10.1086/425738, Bibcode:2005ApJS..156...47L.
^O. S. Shulov and E. N. Kopatskaya, Astrofizika10, #1 (January–March, 1974), pp. 117–120. Translated into English as Variability of the white dwarf G 29-38, Astrophysics, 10, #1 (January, 1974), pp. 72–74. DOI 10.1007/BF01005183.
^G 29-38 and G 38-29: two new large-amplitude variable white dwarfs, J. T. McGraw and E. L. Robinson, Astrophysical Journal200 (September 1975), pp. L89–L93.
^ a bObservational limits on companions to G29-38, S. J. Kleinman, R. E. Nather, D. E. Winget, J. C. Clemens, P. A. Bradley, A. Kanaan, J. L. Provencal, C. F. Claver, T. K. Watson, K. Yanagida, J. S. Dixson, M. A. Wood, D. J. Sullivan, E. Meistas, E. M. Leibowitz, P. Moskalik, S. Zola, G. Pajdosz, J. Krzesinski, J.-E. Solheim, A. Bruvold, D. O'Donoghue, M. Katz, G. Vauclair, N. Dolez, M. Chevreton, M. A. Barstow, S. O. Kepler, O. Giovannini, C. J. Hansen, and S. D. Kawaler, Astrophysical Journal436, #2 (December 1994), pp. 875–884.
^Fontaine, G.; Brassard, P. (October 2008). "The Pulsating White Dwarf Stars". Publications of the Astronomical Society of the Pacific. 120 (872): 1043. Bibcode:2008PASP..120.1043F. doi:10.1086/592788. S2CID 119685025.
^ a bA low-temperature companion to a white dwarf star, E. E. Becklin & B. Zuckerman, Nature336 (Dec. 15, 1988), pp. 656-658
^ a bExcess infrared radiation from a white dwarf - an orbiting brown dwarf? B. Zuckerman & E. E. Becklin, Nature330, (Nov. 12, 1987), pp. 138-140
^Keck Speckle Imaging of the White Dwarf G29-38: No Brown Dwarf Companion Detected, Marc J. Kuchner, Christopher D. Koresko, and Michael E. Brown, The Astrophysical Journal508, #1 (November 20, 1998), pp. L81–L83. doi:10.1086/311725. Bibcode:1998ApJ...508L..81K.
^ a bThe Dust Cloud around the White Dwarf G29-38, William T. Reach, Marc J. Kuchner, Ted von Hippel, Adam Burrows, Fergal Mullally, Mukremin Kilic, and D. E. Winget, Astrophysical Journal635, #2 (December 2005), pp. L161–L164.
^NASA's Spitzer Finds Possible Comet Dust Around Dead Star Archived 2006-02-17 at the Wayback Machine, NASA press release, January 11, 2006.
^Ballering, Nicholas P.; Levens, Colette I.; Su, Kate Y. L.; Cleeves, L. Ilsedore (2022-11-01). "The Geometry of the G29-38 White Dwarf Dust Disk from Radiative Transfer Modeling". The Astrophysical Journal. 939 (2): 108. arXiv:2211.00118. Bibcode:2022ApJ...939..108B. doi:10.3847/1538-4357/ac9a4a. ISSN 0004-637X.
External links
Britt, Robert Roy (7 February 2002). "Tales From the Stellar Grave: Born Again Planets". Space.com. Archived from the original on 2008-03-31. Retrieved 2006-12-24.