Gliese 440 is known at least from 1917, when its
proper motion was published by
R. T. A. Innes and H. E. Wood in Volume 37 of Circular of the Union Observatory.[18] The corresponding designation is
UO 37.[10] (Note: this designation is not unique for this star, that is all other stars, listed in the table in the Volume 37 of this Circular, also could be called by this name).
Space motion
Gliese 440 may be a member of the Wolf 219
moving group, which has seven possible members. These stars share a similar motion through space, which may indicate a common origin.[19] This group has an estimated
space velocity of 160 km/s and is following a highly
eccentric orbit through the
Milky Way galaxy.[20]
Properties
White dwarfs are no longer generating energy at their cores through
nuclear fusion, and instead are steadily radiating away their remaining heat. Gliese 440 has a DQ
spectral classification, indicating that it is a rare type of white dwarf which displays evidence of atomic or molecular
carbon in its spectrum.[21]
In 2019, Gliese 440 was observed passing in front of a more distant star. The bending of starlight by the gravitational field of Gliese 440 observed by the
Hubble Space Telescope allowed its mass to be directly measured. The estimated mass of Gliese 440 is 0.56±0.08 M☉, which fits the expected range of a white dwarf with a carbon-oxygen core. This measurement marked the first direct gravitational mass determination of a single white dwarf.[6]
Gliese 440 has only 56% of the Sun's mass,[6] but it is the remnant of a massive
main-sequence star that had an estimated 4.4
solar masses.[22] While it was on the main sequence, it probably was a
spectral class B star (in the range B4–B9).[23] Most of the star's original mass was shed after it passed into the
asymptotic giant branch stage, just prior to becoming a white dwarf.
Search for companions
A survey with the
Hubble Space Telescope revealed no visible orbiting companions, at least down to the limit of detection.[24][5]
Its proximity, mass and temperature have led to it being considered a good candidate to look for Jupiter-like planets. Its relatively large mass and high temperature mean that the system is relatively short-lived and hence of more recent origin.[22]
^
abcdTable 2, P. Bergeron; S. K. Leggett; María Teresa Ruiz (April 2001). "Photometric and Spectroscopic Analysis of Cool White Dwarfs with Trigonometric Parallax Measurements". Astrophysical Journal Supplement Series. 133 (2): 413–449.
arXiv:astro-ph/0011286.
Bibcode:
2001ApJS..133..413B.
doi:
10.1086/320356.
S2CID15511301.
^Gliese, W.; Jahreiß, H. (1991).
"Gl 440". Preliminary Version of the Third Catalogue of Nearby Stars.
Archived from the original on 2016-03-04. Retrieved 2015-09-21.
^Perryman; et al. (1997).
"HIP 57367". The Hipparcos and Tycho Catalogues.
Archived from the original on 2016-03-04. Retrieved 2015-09-21.
^Luyten, Willem Jacob (1979).
"LHS 30". LHS Catalogue, 2nd Edition.
Archived from the original on 2016-03-04. Retrieved 2015-10-15.
^Luyten, Willem Jacob (1979).
"NLTT 28447". NLTT Catalogue.
Archived from the original on 2016-03-04. Retrieved 2015-10-15.
^Van Altena W. F.; Lee J. T.; Hoffleit E. D. (1995).
"GCTP 2716". The General Catalogue of Trigonometric Stellar Parallaxes (Fourth ed.).
Archived from the original on 2016-03-04. Retrieved 2015-09-21.
^Perryman; et al. (1997).
"HIP 57367". The Hipparcos and Tycho Catalogues.
Archived from the original on 2016-03-04. Retrieved 2015-09-21.
^Hog; et al. (2000).
"TYC 8981-4417-1". The Tycho-2 Catalogue.
Archived from the original on 2016-03-04. Retrieved 2015-10-15.
^Eggen, O. J.; Greenstein, J. L. (1965). "Spectra, colors, luminosities, and motions of the white dwarfs". Astrophysical Journal. 141: 83–108.
Bibcode:
1965ApJ...141...83E.
doi:
10.1086/148091. — see table 5.
^Bell, R. A. (1962). "Observations of some southern white dwarfs". The Observatory. 82: 68–71.
Bibcode:
1962Obs....82...68B.
^Siess, Lionel (2000).
"Computation of Isochrones". Institut d'Astronomie et d'Astrophysique, Université libre de Bruxelles. Archived from
the original on 2011-05-05. Retrieved 2007-03-24.