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[vsnet-campaign 894] XTE J1118+480: IAUC 7617 tells superhumps still exist
XTE J1118+480: IAUC 7617 tells superhumps still exist
In IAU Circular 7617, J. Casares et al. reports that the
possible halo black hole X-ray nova, XTE J1118+480 is still
in the gradually fading phase to quiescence. They reported
the object is now at R=18.6mag and fading at 0.003mag/day during
Dec. 2000 - Apr 2001. They furthermore detected small amplitude
modulations on the normal orbital (ellipsoidal) modulation.
Their PDM period analysis yields a period of 0.17049(1) day and
they interpret them as superhumps since the period is slightly longer
than a reported orbital period.
On XTE J1118+480, the VSNET collaboration team performed the
extensive photometric campaign during the 2000 outburst and
revealed that superhumps exist throughout the outburst.
Our data set shows the mean superhump period during the outburst
is slightly longer than that reported in IAUC 7617, which may
imply a continuous period changing. In the case of SU UMa-type
dwarf nova, the "late superhump" is sometimes obvserved after
superoutburst which correspond to the main outburst of XTE J1118+480.
It is known that phases of the superhump and the late-superhump
are different and their mechanisms are also probably different.
To determine the peak time of the current superhumps are essential
to study the nature of them and accretion discs in low-mass X-ray
binaries. Further time-series photometry is encouraged.
Regards,
Makoto Uemura
vsnet-adm@kusastro.kyoto-u.ac.jp
Return to Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
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