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[vsnet-preprint 30] Nova Aql 2001 = V1548 Aql preprint
Nova Aql 2001 = V1548 Aql preprint
Dear Colleagues,
The following article is accepted for publication as IBVS No. 5100.
The figures are placed at:
http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/V1548_Aql/
Regards,
Taichi Kato
===
\documentstyle[twoside,epsf]{article}
\input{ibvs2.sty}
\begin{document}
\IBVShead{xxxx}{xx May 2001}
\IBVStitletl{Nova Aql 2001: another V723 Cas-type slow nova?}
\IBVSauth{Taichi~Kato$^1$, Kesao~Takamizawa$^2$}
\vskip 5mm
\IBVSinst{Dept. of Astronomy, Kyoto University, Kyoto 606-8502, Japan,
e-mail: tkato@kusastro.kyoto-u.ac.jp}
\IBVSinst{Variable Star Observers League in Japan (VSOLJ), 65-1 Oohinata,
Saku-machi, Nagano 384-0502, Japan,
e-mail: k-takamizawa@nifty.ne.jp}
\IBVSobj{Nova Aql 2001}
\IBVStyp{NB}
\IBVSkey{photometry}
\begintext
Nova Aql 2001 was originally discovered by M. Collins as a variable star
TAV J1907+117 (Hurst 2001a). The object was reported to be at photographic
magnitude 10.9 on 2001 May 11.99 UT. The object was suspected at magnitude
12.1 on Apr. 25, but the measurement may have been affected by crowding
of the field (Hurst 2001a,b). The possibility as some sort of an eruptive
variable was suggested based on the lack of bright infrared counterpart
on IRAS surveys (Kato 2001). The object was announced as a possible nova
(Hurst 2001b). Spectroscopic confirmation as a nova was made by several
groups (Benn et al., 2001; Shemmer 2001). The nova was observed already
very faint ($\sim$12.5--13.0) on May 16--17, suggesting a rapid fade.
However, prediscovery photographs by Takamizawa (2001) revealed that
the nova was already bright in late February. This suggests that the
nova had a long premaximum halt before its final rise to maximum.
\IBVSfig{10cm}{fig1.ps}{Comparison of light curves between Nova Aql 2001
and V723 Cas. The symbols in the upper panels: discovery and prediscovery
photographic observations by Collins (open triangles), photographic
observations by Takamizawa (filled squares), visual and $V$-band CCD
observations reported to VSNET (open circles, including some observations
reported to IAU Circulars) and photographic upper limits (``v"-marks).
The light curve of V723 Cas (lower panel) are drawn from reports to
VSNET.}
\vskip 3mm
Such behavior was also observed in previous novae, most notably in
V723 Cas = Nova Cas 1995. Figure 1 shows the comparison between
light curvs of Nova Aql 2001 and V723 Cas. The horizontal scales
were slightly different between these objects, but the overall features
resemble each other within a factor of $\sim$40\% difference in time
scales. This striking similarity makes Nova Aql 2001 as a ``twin"
nova to V723 Cas, the best-observed slowest nova in the modern times.
This similarity is consistent with the low expansion velocity
(mean FWHM of 1100 km s$^{-1}$, Shemmer 2001), which is comparable
to the small FWHM of 600 km s$^{-1}$, observed in H$\alpha$ emission
line of V723 Cas (Della Valle et al. 1995). The small difference
in the FWHM between these two objects may suggest that the evolution
of Nova Aql 2001 may be more rapid, which looks consistent with the
time scales in the light curves, but the direct comparison of values
may be still premature because the spectra were taken at different
stages of nova explosions. The likely progenitor of Nova Aql 2001
was identified as a star having USNO A2.0 magnitudes of r=18.7 and b=19.6
(Uemura et al. 2001). This makes the outburst amplitude of $\sim$8 mag,
which is roughly comparable to that of V723 Cas ($\sim$10 mag).
\vskip 3mm
Long premaximum halts were also observed
in historical novae, HR Del and possibly in DO Aql. The almost
identical appearance of premaximum halts and sharp maxima suggest
that the common mechanism is responsible for producing such, still
poorly understood, features in slow novae. Both V723 Cas and HR Del
showed oscillations after the main peak (as is also seen in the lower
panel of Figure 1). If similar phenomenon occurs in Nova Aql 2001,
the expected time of the second maximum is around JD 2452080--2452090
(late June, 2001), but the expected dates should be treated as
approximate since the early stage of Nova Aql 2001 was not very well
sampled. The cause of such nova oscillations still being poorly
understood, intensive observations around this period would be
encouraged.
\vskip 3mm
The authors are grateful to VSNET (http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/)
members for providing vital observations of both novae.
\references
Benn, C. R., Vigotti, M., Holt., J., 2001, IAUC No. 7628
Della Valle, M., Marchiotto, W., Lercher, G., 1995, IAUC No. 6214
Hurst, G. M., 2001a, The Astronomer Electronic Circular No. 1633
Hurst, G. M., 2001b, IAUC No. 7627
Kato, T., 2001, {\it VSNET alert circulation}, No. 5876 \\
(available from
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert5000/msg05876.html).
Shemmer, O., 2001, IAUC No. 7628
Takamizawa, K., 2001, IAUC No. 7628
Uemura, M., Kato, T., Yamaoka, H., 2001, IAUC No. 7628
\end{document}
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