TY - JOUR
T1 - Hubble Space Telescope stis spectroscopy of VW hydri during Early quiescence following a superoutburst
AU - Sion, Edward M.
AU - Cheng, Fu Hua
AU - Szkody, Paula
AU - Gänsicke, Boris
AU - Sparks, Warren M.
AU - Hubeny, Ivan
N1 - Funding Information:
We are grateful to Janet Mattei and AAVSO for their invaluable optical monitoring, required for scheduling our HST observations. We thank an anonymous referee for helpful comments. This work is supported by NASA through grant GO8139.01-97A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support was also provided in part by NSF grant 99-01195 and NASA ADP grant NAG5-8388.
Publisher Copyright:
© 2001. The American Astronomical Society. All rights reserved. Printed in U.S.A.
PY - 2001/11/1
Y1 - 2001/11/1
N2 - Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) observations of VW Hydri 2 and 7 days after the end of a superoutburst reveal a heated white dwarf with deep broad Lya, narrow metallic absorption features and evidence of a hotter Keplerian-broadened component.We confirm the existence of enhanced abundances of odd-numbered nuclear species P, Mn, and Al as well as an N/C ratio indicative of CNO H-burning thermonuclear processing. Our best single-temperature white dwarf reduced x2 fit to the first spectrum reveals (1) a DAZQ white dwarf with T=22,500±500 K, log g=8.0, and photospheric abundances C=0.3 solar, N=3.0 solar, eff O=3.0 solar, Si=0.3 solar, Al=2 solar, Fe=0.5 solar, Mg=3.0 solar, Mn=50 solar, Ni=0.3 solar, P=15 solar, and Ti=0.1 solar. The best-fit white dwarf + accretion belt composite model yields a large improvement in the reduced χ2 value. The accretion belt temperature is 32,000 K and covers a fractional area of 3%, contributing 11% of the flux. The second spectrum 5 days later reveals slightly increased metal abundances except that P is elevated to 20 times solar while Fe has declined to 0.05 times solar. The white dwarf has cooled by ≈1000 K, the belt temperature is 32,000 K, and the fractional area and flux contribution of the belt are 5% and 20%, respectively. These STIS observations confirm that a past (prehistoric?) thermonuclear runaway has occurred on the white dwarf in VW Hyi. It is expected that the thermonuclear runaway would be strong enough to produce a nova outburst. Therefore, these two classes of close binaries, namely, dwarf novae and classical novae, are linked and can overlap.
AB - Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) observations of VW Hydri 2 and 7 days after the end of a superoutburst reveal a heated white dwarf with deep broad Lya, narrow metallic absorption features and evidence of a hotter Keplerian-broadened component.We confirm the existence of enhanced abundances of odd-numbered nuclear species P, Mn, and Al as well as an N/C ratio indicative of CNO H-burning thermonuclear processing. Our best single-temperature white dwarf reduced x2 fit to the first spectrum reveals (1) a DAZQ white dwarf with T=22,500±500 K, log g=8.0, and photospheric abundances C=0.3 solar, N=3.0 solar, eff O=3.0 solar, Si=0.3 solar, Al=2 solar, Fe=0.5 solar, Mg=3.0 solar, Mn=50 solar, Ni=0.3 solar, P=15 solar, and Ti=0.1 solar. The best-fit white dwarf + accretion belt composite model yields a large improvement in the reduced χ2 value. The accretion belt temperature is 32,000 K and covers a fractional area of 3%, contributing 11% of the flux. The second spectrum 5 days later reveals slightly increased metal abundances except that P is elevated to 20 times solar while Fe has declined to 0.05 times solar. The white dwarf has cooled by ≈1000 K, the belt temperature is 32,000 K, and the fractional area and flux contribution of the belt are 5% and 20%, respectively. These STIS observations confirm that a past (prehistoric?) thermonuclear runaway has occurred on the white dwarf in VW Hyi. It is expected that the thermonuclear runaway would be strong enough to produce a nova outburst. Therefore, these two classes of close binaries, namely, dwarf novae and classical novae, are linked and can overlap.
KW - Accretion
KW - Accretion disks stars: abundances stars: dwarf novae stars: individual (VW Hydri)-white dwarfs
UR - http://www.scopus.com/inward/record.url?scp=85033384976&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85033384976&partnerID=8YFLogxK
U2 - 10.1086/324558/pdf
DO - 10.1086/324558/pdf
M3 - Article
AN - SCOPUS:85033384976
SN - 2041-8205
VL - 561
SP - L127-L130
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
ER -