Nova Sagittarii 1998 (V4633 Sgr): a permanent superhump system or an asynchronous polar? Page: 1,169
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Mon. Not. R. Astron. Soc. 328, 1169-1180 (2001)
Nova Sagittarii 1998 (V4633 Sgr): a permanent superhump system or an
asynchronous polar?
Y. Lipkin,l* E. M. Leibowitz,'* A. Retter2,3* and 0. Shemmerl*
'School of Physics and Astronomy, and the Wise Observatory, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University,
Tel Aviv 69978, Israel
2Department of Physics, Keele University, Keele, Staffordshire ST5 5BG
3School of Physics, University of Sydney, 2006, Australia
Accepted 2001 August 23. Received 2001 July 11; in original form 2001 February 15
ABSTRACT
We report the results of observations of V4633 Sgr (Nova Sagittarii 1998) during 1998-2000.
Two photometric periodicities were present in the light curve during the three years of
observations: a stable one at P = 3.014 h, which is probably the orbital period of the
underlying binary system; and a second one of lower coherence, approximately 2.5 per cent
longer than the former. The latter periodicity may be a permanent superhump, or,
alternatively, the spin period of the white dwarf in a nearly synchronous magnetic system. A
third period, at P = 5.06 d, corresponding to the beat between the two periods was probably
present in 1999. Our results suggest that a process of mass transfer has taken place in the
binary system since no later than two-and-a-half months after the nova eruption. We derive an
interstellar reddening of E(B - V) ~i 0.21 from our spectroscopic measurements and
published photometric data, and estimate a distance of d - 9kpc to this nova.
Key words: accretion, accretion discs - stars: individual: V4633 Sgr - novae, cataclysmic
variables.1 INTRODUCTION
Nova Sagittarii 1998 (V4633 Sgr) was discovered on 1998 March
22 by Liller (1998). Brightest visual magnitude of 7.4 mag was
reported by Jones (1998) on March 23.7. Liller & Jones (1999)
classified V4633 Sgr as a fast nova, with t3 ~ 35 d for the visual
observations, and ~ 48 d in charge-coupled device (CCD) broad-
band V. An early spectrum of V4633 Sgr revealed slow expansion
velocities and massive presence of iron, implying a Fe ii
classification (Della Valle, Pizzella & Bernardi 1998).
Skiff (1998) reported no definite object at the location of V4633
Sgr in the Palomar Sky Survey, setting a lower limit of 12 mag on
the outburst amplitude.
Spectropolarimetry of V4633 Sgr shortly after maximum
brightness did not yield evidence for intrinsic polarization
(Ikeda, Kawabata & Akitaya 2000).
Infrared spectrophotometry indicated that V4633 Sgr was in the
early stages of its coronal phase in 1999 August (Rudy et al. 1999),
and revealed strong coronal lines, and a relatively low reddening in
2000 July (Rudy et al. 2000).
Lipkin, Retter & Leibowitz (1998) reported a photometric
*E-mail: yiftah@wise.tau.ac.il (YL); elia@wise.tau.ac.il (EML); ar@astro.
keele.ac.uk and/or retter@physics.usyd.edu.au (AR); ohad@wise.tau.ac.il
(OS)modulation in the light curve (LC) of V4633 Sgr, with a period of
0.17330 or 0.14765 +0.00011 d, which are 1-d aliases of each
other. The modulation was detected eleven weeks, and possibly as
early as six weeks, after the eruption. Later on, Lipkin & Leibowitz
(2000) found that another 1-d alias, at 0.128 791 d, is in fact the
dominant periodicity in the LC. They also reported the discovery of
a second photometric periodicity at 0.125 573 d, modulating the
brightness of the star along with the first one during 1999 and also
in 1998.
In this paper we describe in detail the photometric properties of
the V4633 Sgr during the 1998-2000 seasons. We also report on a
few spectroscopic observations that we performed on this star, and
on the implications of these data on some properties of this system.
2 OBSERVATIONS AND DATA REDUCTION
2.1 Photometry
We performed photometry of V4633 Sgr during 34 nights in 1998,
36 nights in 1999, and 26 nights in 2000, using the Tektronix 1K
back-illuminated CCD, mounted on the 1-m telescope at the Wise
Observatory (WO). Details on the telescope and instrument are
given by Kaspi et al. (1995).
Photometry was conducted either through an I filter, or
switching sequentially between I and V, or between I, V and B
filters. Logs of the observations are given in Appendix A.O 2001 RAS
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Lipkin, Yaacov; Leibowitz, E. M.; Retter, A. & Shemmer, Ohad. Nova Sagittarii 1998 (V4633 Sgr): a permanent superhump system or an asynchronous polar?, article, August 23, 2001; Oxford, UK. (https://digital.library.unt.edu/ark:/67531/metadc861698/m1/1/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT College of Arts and Sciences.