11 research outputs found
The symbiotic binary system RX Puppis: a possible recurrent nova with a Mira companion
We present an analysis of photometric and spectroscopic observations of the
symbiotic binary system RX Pup with the aims of developing a reliable binary
for the system and identifying mechanisms responsible for its spectacular
activity. The binary is composed of a long-perod Mira variable surrounded by a
thick dust shell and a hot white dwarf companion. The hot component produces
practically all activity observed in the UV, optical and radio range, while
variable obscuration of the Mira by circumstellar dust is responsible for
long-term changes in the near-IR magnitudes. The observations show RX Pup
underwent a nova-like eruption during the last three decades. The hot component
contracted in radius at roughly constant luminosity from 1975 to 1986, and was
the source of a strong stellar wind which prevented it from accreting material
lost in the Mira wind. Around 1988/9 the hot component turned over in the HR
diagram and by 1991 its luminosity had faded by a factor of about 30 with
respect to the maximum plateau value and the hot wind had practically ceased.
By 1995 the nova remnant started to accrete material from the Mira wind, as
indicated by a general increase in intensity of the optical continuum and HI
emission. The quiescent spectrum resembles the quiescent spectra of symbiotic
recurrent novae, and its intensity indicates the hot component must accrete as
much as about 1 per cent of the Mira wind, which is more or less the amount
predicted by Bondi-Hoyle theory. The earliest observational records from the
1890s suggest that another nova-like eruption of RX Pup occurred around 1894.Comment: 23 pages, 12 figues, MNRAS - accepte
The symbiotic binary system RX Puppis: a possible recurrent nova with a Mira companion
We present an analysis of photometric and spectroscopic observations of the symbiotic binary system RX Pup with the aim of developing a reliable binary model for the system and identifying mechanisms responsible for its spectacular activity. The binary is composed of a long-period Mira variable surrounded by a thick dust shell and a hot ,0:8M( white dwarf companion. The hot component produces practically all activity observed in the UV, optical and radio range, while variable obscuration of the Mira by circumstellar dust is responsible for long-term changes in the near-infrared magnitudes. The observations show that RX Pup underwent a nova-like eruption during the last three decades. The hot component contracted in radius at roughly constant luminosity from 1975 to 1986, and was the source of a strong stellar wind, which prevented it from accreting material lost in the Mira wind. Around 1988/9 the hot component turned over in the Hertzsprung±Russell (HR) diagram and by 1991 its luminosity had faded by a factor of ,30 with respect to the maximum plateau value and the hot wind had practically ceased. By 1995 the nova remnant started to accrete material from the Mira wind, as indicated by a general increase in intensity of the optical continuum and Hi emission. The quiescent spectrum resembles the quiescent spectra of symbiotic recurrent novae, and its intensity indicates that the hot component must accrete as much as ,1 per cent of the Mira wind, which is more or less the amount predicted by Bondi±Hoyle theory. The earliest observational records from the 1890s suggest that another nova-like eruption of RX Pup occurred around 1894.Facultad de Ciencias Astronómicas y Geofísica
The symbiotic binary system RX Puppis: a possible recurrent nova with a Mira companion
We present an analysis of photometric and spectroscopic observations of the symbiotic binary system RX Pup with the aim of developing a reliable binary model for the system and identifying mechanisms responsible for its spectacular activity. The binary is composed of a long-period Mira variable surrounded by a thick dust shell and a hot ,0:8M( white dwarf companion. The hot component produces practically all activity observed in the UV, optical and radio range, while variable obscuration of the Mira by circumstellar dust is responsible for long-term changes in the near-infrared magnitudes. The observations show that RX Pup underwent a nova-like eruption during the last three decades. The hot component contracted in radius at roughly constant luminosity from 1975 to 1986, and was the source of a strong stellar wind, which prevented it from accreting material lost in the Mira wind. Around 1988/9 the hot component turned over in the Hertzsprung±Russell (HR) diagram and by 1991 its luminosity had faded by a factor of ,30 with respect to the maximum plateau value and the hot wind had practically ceased. By 1995 the nova remnant started to accrete material from the Mira wind, as indicated by a general increase in intensity of the optical continuum and Hi emission. The quiescent spectrum resembles the quiescent spectra of symbiotic recurrent novae, and its intensity indicates that the hot component must accrete as much as ,1 per cent of the Mira wind, which is more or less the amount predicted by Bondi±Hoyle theory. The earliest observational records from the 1890s suggest that another nova-like eruption of RX Pup occurred around 1894.Facultad de Ciencias Astronómicas y Geofísica
Variability of eta Carinae III
Spectra (1951-78) of the central object in eta Car, taken by A.D. Thackeray,
reveal three previously unrecorded epochs of low excitation. Since 1948, at
least, these states have occurred regularly in the 2020 day cycle proposed by
Damineli et al. They last about 10 percent of each cycle. Early slit spectra
(1899-1919) suggest that at that time the object was always in a low state.
JHKL photometry is reported for the period 1994-2000. This shows that the
secular increase in brightness found in 1972-94 has continued and its rate has
increased at the shorter wavelengths. Modulation of the infrared brightness in
a period near 2020 days continues. There is a dip in the JHKL light curves near
1998.0, coincident with a dip in the X-ray light curve. Evidence is given that
this dip in the infrared repeats in the 2020 day cycle. As suggested by
Whitelock & Laney, the dip is best interpreted as an eclipse phenomenon in an
interacting binary system; the object eclipsed being a bright region (`hot
spot'), possibly on a circumstellar disc or produced by interacting stellar
winds. The eclipse coincides in phase and duration with the state of low
excitation. It is presumably caused by a plasma column and/or by one of the
stars in the system.Comment: 10 pages, 7 postscript figures, accepted for MNRA
Near-Infrared Photometry of Carbon Stars
Near-infrared, JHKL, photometry of 239 Galactic carbon-rich variable stars is
presented and discussed. From these and published data the stars were
classified as Mira or non-Mira variables and amplitudes and pulsation periods,
ranging from 222 to 948 days for the Miras, were determined for most of them. A
comparison of the colour and period relations with those of similar stars in
the Large Magellanic Cloud indicates minor differences, which may be the
consequence of sample selection effects. Apparent bolometric magnitudes were
determined by combining the mean JHKL fluxes with mid-infrared photometry from
IRAS and MSX. Then, using the Mira period luminosity relation to set the
absolute magnitudes, distances were determined -- to greater accuracy than has
hitherto been possible for this type of star. Bolometric corrections to the K
magnitude were calculated and prescriptions derived for calculating these from
various colours. Mass-loss rates were also calculated and compared to values in
the literature.
Approximately one third of the C-rich Miras and an unknown fraction of the
non-Miras exhibit apparently random obscuration events that are reminiscent of
the phenomena exhibited by the hydrogen deficient RCB stars. The underlying
cause of this is unclear, but it may be that mass loss, and consequently dust
formation, is very easily triggered from these very extended atmospheres.Comment: 35 pages, 21 figs, accepted for publication in MNRAS. Large data
table will be available on-line onl
The 2003 Shell Event in eta Carinae
Near-infrared, JHKL, photometry of eta Car is reported covering the period
2000 to 2004. This includes the 2003 shell event which was the subject of an
international multi-wavelength campaign. The fading that accompanied this event
was similar to, although slightly deeper than, that which accompanied the
previous one. The period between these events is 2023+/-3 days and they are
strictly periodic. Their cause, as well as that of the quasi-periodic
variations and secular brightening are discussed. It seems possible that all
three types of variability are consequences of the binary nature of the star.Comment: 11 pages, 5 figures, to appear in MNRA
The Case for Asymmetric Dust Around a C-Rich AGB star
JHKL observations of the mass-losing carbon Mira variable IRAS 15194-5115 (II
Lup) extending over about 18 years are presented and discussed. The pulsation
period is 575 days and has remained essentially constant over this time span.
The star has undergone an extensive obscuration minimum during this time. This
is complex and, like such minima in similar objects, e.g. R For, does not fit
the model predictions of a simple long term periodicity. Together with the high
resolution observations of Lopez et al. the results suggest that the
obscuration changes are due to the formation of dust clouds of limited extent
in the line-of-sight. This is an RCB-type model. The effective reddening law at
J and H is similar to that found for R For.Comment: 8 pages, 2 figures, accepted for publication in MNRA