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[vsnet-preprint 97] V379 Peg preprint
V379 Peg preprint
Dear All,
The following paper is accepted for publication in IBVS No. 5342.
The PostScript version and figures are available at:
http://vsnet.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/V379_Peg/
Regards,
Taichi Kato
===
\documentstyle[twoside,epsf]{article}
\input{ibvs2.sty}
\begin{document}
\IBVShead{xxxx}{xx xxx 2002}
\IBVStitle{On the variability and nature of V379 Peg}
\IBVSauth{Kato,~Taichi$^1$; Yamaoka,~Hitoshi$^2$; Torii,~Ken'ichi$^3$;
Ishioka,~Ryoko$^1$; \\ Uemura,~Makoto$^1$}
\vskip 5mm
\IBVSinst{Dept. of Astronomy, Kyoto University, Kyoto 606-8502, Japan, \\
e-mail: (tkato,ishioka,uemura)@kusastro.kyoto-u.ac.jp}
\IBVSinst{Faculty of Science, Kyushu University, Fukuoka 810-8560, Japan,
e-mail: yamaoka@rc.kyushu-u.ac.jp}
\IBVSinst{Cosmic Radiation Laboratory, Institute of Physical and Chemical
Research (RIKEN), 2-1, Wako, Saitama, 351-0198, Japan,
e-mail: torii@crab.riken.go.jp}
\IBVSobj{V379 Peg}
\IBVStyp{CV:}
\IBVSkey{cataclysmic variable, proper motion, photometry, classification}
\begintext
V379 Peg = FBS 2351+228 = SVS 2550 = NSV 26158 was discovered as
a UV-excess object during the first Byurakan Survey (FBS).
Lipovetskii and Stepanyan (1981) detected the object on JD 2442329 (1974)
showing a spectrum of a B-A type blue star with a UV continuum.
Lipovetskii and Stepanyan (1981) also commented that the object appears
red on Palomar Sky Survey plates. The object was spectroscopically studied
by Kopylov et al. (1988).
Kopylov et al. (1988) described that FBS 2351+228 shows a late M-type
spectrum with prominent TiO bands, Ca I 4227\AA\, and Na D absorption lines.
The Balmer lines were in very narrow emission. Kopylov et al. (1988)
reported that the spectrum of FBS 2351+228 resembles those of the quiescent
states of the recurrent novae T CrB and RS Oph. According to this
suggestion, the star has been regarded as a candidate recurrent nova or
a symbiotic binary (cf. Downes et al. 1997, 2001). The star has been
given a designation as a suspected variable star (NSV 26158) in the
NSV Supplement (Kazarovets et al. 1998). The NSV Supplement gave
a variability range of 15--16 $m_{\rm pg}$ following Lipovetskii and
Stepanyan (1981).
We noticed, however, that this object has a significant proper motion,
suggesting that the object is a nearby object rather than a distant,
luminous symbiotic binary. Table 1 lists the available astrometry
(errors are typically less than 0\farcs 3). From these values, we have
determined a proper motion of 0\farcs065 $\pm$0\farcs 010 yr$^{-1}$,
PA = 236$^\circ$. This value has been confirmed by a direct
comparison of the DSS 1 and 2 scans, and a possible systematic error
is confirmed to be small by a overplotting the cataloged positions of
surrounding stars (see the figure in the electronic IBVS edition:
the yellow, green, and red circles represent USNO A2.0, GSC 2.2.1 and
2MASS positions, respectively. The large proper motion of V379 Peg
is apparent). The value is also in good agreement with the
proper motion of 0\farcs 063 yr$^{-1}$, PA = 240$^\circ$ in USNO B1.0
(Monet et al. 2002).
This large proper motion makes the object likely a nearby object.
Assuming an upper limit transverse velocity of 100 km s$^{-1}$, the upper
limit of the distance becomes $\sim$300 pc (see also Kato and Yamaoka 2002).
The upper limit of $M_{\rm V}$ of the secondary thus becomes +8,
which safely excludes the possibility of a symbiotic binary with a
giant secondary.
\begin{table}
\begin{center}
Table 1. Astrometry of V379 Peg. \\
\vspace{10pt}
\begin{tabular}{cccc}
\hline\hline
Source & R. A. & Decl. & Epoch \\
& \multicolumn{2}{c}{(J2000.0)} & \\
\hline
USNO A2.0 & 23 53 51.069 & +23 09 20.39 & 1953.608 \\
GSC 2.2.1 & 23 53 50.922 & +23 09 19.09 & 1990.661 \\
2MASS & 23 53 50.892 & +23 09 18.75 & 1998.751 \\
\hline
\end{tabular}
\end{center}
\end{table}
The spectrum published in Kopylov et al. (1988) also lacks the evidence
of a strong He~{\sc ii} line, which is usually seen in symbiotic binaries.
The likely presence of the CaH absorption at 6382\,\AA makes the low
luminosity classification more likely. From these data, we conclude that
V379 Peg is neither a symbiotic binary nor a recurrent nova candidate.
The variable star designation V379 Peg was given primarily based on
the 1999 and 2000 reports of the possible outburst detections
(Kazarovets et al. 2001). However, these detections were done with
unfiltered CCD observations by L. T. Jensen (Kato 1999) and T. Vanmunster
(Vanmunster 2000a). The maximum magnitude quoted in Kazarovets et al. (2001)
apparently refers to the unfiltered CCD observation by T. Vanmunster,
who reported a unfiltered CCD magnitude of 13.9 on 2002 August 9.
The minimum magnitude in Kazarovets et al. (2001) apparently refers to
T. Kinnunen's visual observations preceding these detections.
We must note, however, V379 Peg is a red object (GSC 2.2.1
magnitudes: $r$ = 14.04, $b$ = 15.96, 2MASS magnitudes: $J$ = 11.35,
$H$ = 10.76, $K_s$ = 10.51), which is consistent with the above spectroscopic
classification. Since the reported ``outburst'' red-sensitive CCD
observations had magnitude close to the $r$ magnitude in GSC 2.2.1,
it is most likely these CCD detections were not true outbursts, but
were simply bright detections of a red object on red-sensitive CCDs.
The lack of short-term variation during the claimed outburst
(Vanmunster 2000b) is also suggestive of this interpretation.
The lack of significant variability was also confirmed by our follow-up
snapshot CCD observations (Table 2, taken at RIKEN, 20-cm telescope and
an unfiltered AP-7 camera), following the claimed 1999 outburst detection.
Although there was a historical hint of variability of 15--16 $m_{\rm pg}$
(Lipovetskii and Stepanyan 1981), we conclude that the claimed large-amplitude
variability of V379 Peg has not yet been confirmed.
\begin{table}
\begin{center}
Table 2. Snapshot CCD photometry of V379 Peg. \\
\vspace{10pt}
\begin{tabular}{cccc}
\hline\hline
JD & mag$^a$ & error & N \\
\hline
2451775.173 & 14.37 & 0.04 & 3 \\
2451782.188 & 14.42 & 0.03 & 11 \\
2451783.211 & 14.44 & 0.19 & 2 \\
2451785.272 & 14.33 & 0.02 & 19 \\
\hline
\multicolumn{4}{l}{$^a$ Unfiltered CCD magnitude, zero point} \\
\multicolumn{4}{l}{\phantom{$^a$} adjusted to $R_{\rm c}$} \\
\end{tabular}
\end{center}
\end{table}
We further obtained time-resolved unfiltered CCD photometry on 2002
November 5, with two telescopes (RIKEN: 25-cm reflector, AP-6E CCD,
40 s exposure, 130 frames; Kyoto: 25-cm Schmidt--Cassegrain telescope,
ST-7E CCD, 30 s exposure, 84 frames). The magnitudes were determined
relative to GSC 2252.2143, whose constancy during the observation was
confirmed by a comparison with GSC 2252.1995. A 0.061 mag was added to
the Kyoto magnitudes to correct the systematic difference between the
instruments. The resultant light curve (Figure 1) did not reveal significant
variation larger than the observational errors.
\IBVSfig{8cm}{v379-fig1.eps}{Light curve of V379 Peg on 2002 November 5.
The filled and open squares represent RIKEN and Kyoto observations,
respectively.
No significant variation was detected larger than the observational errors.
}
From the presence of a UV excess (in 1974) and Balmer emission lines,
V379 Peg seems to be a binary of a white dwarf and a red dwarf. If this
object is indeed a cataclysmic (CV) type binary, the lack of a blue
continuum in the spectrum (in Kopylov et al. 1988)
suggests that the object has a very low accretion rate. This object,
together with RX J2309.8+2135 (Kato and Yamaoka 2002), may comprise a
previously overlooked nearby population of CV-type binaries with low
mass-transfer rates. However, if the very blue object detected in 1974
was indeed the presently identified V379 Peg, the reported magnitude
(15 $m_{\rm pg}$) corresponds to $M_V \leq$ +7, which is unusually faint
for a CV-type outburst (cf. Warner 1987). V379 Peg can alternatively
be a detached binary of a white dwarf and a red dwarf. The narrowness of
the emission lines and the lack of short-term photometric variability
may prefer the detached binary interpretation. In either cases,
the claimed very blue appearance of the spectrum in 1974
(Lipovetskii and Stepanyan 1981) still remains a mystery.
\vskip 3mm
This work is partly supported by a grant-in aid [13640239 (TK),
14740131 (HY)] from the Japanese Ministry of Education, Culture, Sports,
Science and Technology.
Part of this work is supported by a Research Fellowship of the
Japan Society for the Promotion of Science for Young Scientists (MU).
This research has made use of the Digitized Sky Survey producted by STScI,
the ESO Skycat tool, and the VizieR catalogue access tool.
\references
Downes, R., Webbink, R. F., Shara, M. M., 1997, PASP, {\bf 109}, 345
Downes, R. A.. Webbink, R. F., Shara, M. M., Ritter, H., Kolb, U.,
Duerbeck, H. W., 2001, PASP, {\bf 113}, 764
Kato, T. 1999, VSNET alert 3526,
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/alert3000/\\msg00526.html
Kato, T., Yamaoka, H., 2002, IBVS No. 5334
Kazarovets, E. V., Durlevich, O. V., Samus, N. N., 1998,
New Catalogue of Suspected Variable Stars. Supplement
(http://vsnet.sai.msu.ru/groups/cluster/gcvs/gcvs/nsvsup/)
Kazarovets, E. V., Samus, N. N., Durlevich, O. V., 2001, IBVS No. 5135
Kopylov, I. M., Lipovetsky, V. A. and Somov, N. N., Somova, T. A.,
Stepanian, J. A., 1988, Astrofizika, {\bf 28}, 287
Lipovetskii, V. A., Stepanyan, J. A., 1981, Astrofizika, {\bf 17}, 573
Monet, D., Levine, S., Canzian, B., Ables, H., Bird, A., Dahn, C. et al.,
2002, AJ in press (astro-ph/0210694)
Vanmunster, T., 2000a, VSNET alert 5176,
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/\\alert5000/msg00176.html
Vanmunster, T., 2000b, VSNET alert 5183,
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/\\alert5000/msg00183.html
Warner, B., 1987, MNRAS, {\bf 227}, 23
\endreferences
\end{document}
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