286 research outputs found
Oscillations in Arcturus from WIRE photometry
Observations of the red giant Arcturus (Alpha Boo) obtained with the star
tracker on the Wide Field Infrared Explorer (WIRE) satellite during a baseline
of 19 successive days in 2000 July-August are analysed. The amplitude spectrum
has a significant excess of power at low-frequencies. The highest peak is at
about 4.1 micro-Hz (2.8 d), which is in agreement with previous ground-based
radial velocity studies. The variability of Arcturus can be explained by sound
waves, but it is not clear whether these are coherent p-mode oscillations or a
single mode with a short life-time.Comment: 6 pages, 1 Latex file, 4 .eps figures, 2 .sty files, ApJL, 591, L151
See erratum (astro-ph/0308424
One-dimensional behavior of elongated Bose-Einstein condensates
We study the properties of elongated Bose-Einstein condensates. First, we
show that the dimensions of the condensate after expansion differs from the 3D
Thomas-Fermi regime. We also study the coherence length of such elongated
condensates.Comment: proceeding of Quantum Gases in Low Dimension, Les Houches 2003, 8
pages, 5 figure
The Detection of a 3.5-h Period in the Classical Nova Velorum 1999 (V382 Vel) and the Long Term Behavior of the Nova Light Curve
We present CCD photometry, light curve and time series analysis of the
classical nova V382 Vel (N Vel 1999). The source was observed for 2 nights in
2000, 21 nights in 2001 and 7 nights in 2002 using clear filters. We report the
detection of a distinct period in the light curve of the nova P=0.146126(18) d
(3.5 h). The period is evident in all data sets, and we interpret it as the
binary period of the system. We also measured an increase in the amplitude
modulation of the optical light (in magnitude) by more than 55% from 2000 to
2001 and about 64% from 2001 to 2002. The pulse profiles in 2001 show
deviations from a pure sinusoidal shape which progressively become more
sinusoidal by 2002. The main cause of the variations in 2001 and 2002 can be
explained with the occultation of the accretion disk by the secondary star. We
interpret the observed deviations from a pure sinusoidal shape as additional
flux resulting from the aspect variations of the irradiated face of the
secondary star.Comment: 16 pages and 4 figures, accepted as it stands to be published in the
Astronomical Journal (AJ
Detection of orbital and superhump periods in Nova V2574 Ophiuchi (2004)
We present the results of 37 nights of CCD unfiltered photometry of nova
V2574 Oph (2004) from 2004 and 2005. We find two periods of 0.14164 d (~3.40 h)
and 0.14773 d (~3.55 h) in the 2005 data. The 2004 data show variability on a
similar timescale, but no coherent periodicity was found. We suggest that the
longer periodicity is the orbital period of the underlying binary system and
that the shorter period represents a negative superhump. The 3.40 h period is
about 4% shorter than the orbital period and obeys the relation between
superhump period deficit and binary period. The detection of superhumps in the
light curve is evidence of the presence of a precessing accretion disk in this
binary system shortly after the nova outburst. From the maximum magnitude -
rate of decline relation, we estimate the decay rate t_2 = 17+/-4 d and a
maximum absolute visual magnitude of M_Vmax = -7.7+/-1.7 mag.Comment: 6 pages, 6 figures, 2 .sty files, AJ accepted, minor change to one of
reference
A photometric study of the newly discovered eclipsing cataclysmic variable SDSS J040714.78-064425.1
We present the results obtained from unfiltered photometric CCD observations
of the newly discovered cataclysmic variable SDSS J040714.78-064425.1 made
during 7 nights in November 2003. We establish the dwarf nova nature of the
object as it was in outburst during our observations. We also confirm the
presence of deep eclipses with a period of 0.17017d+/-0.00003 in the optical
light curve of the star. In addition, we found periods of 0.166d+/-0.001 and
possibly also 5.3d+/-0.7 in the data. The 0.17017d periodicity is consistent
within the errors with the proposed orbital period of 0.165d (Szkody et. al.
2003) and 0.1700d (Monard 2004). Using the known relation between the orbital
and superhump periods, we interpret the 0.166d and 5.3d periods as the negative
superhump and the nodal precession period respectively. SDSS
J040714.78-064425.1 is then classified as a negative superhump system with one
of the largest orbital periods.Comment: 6 pages, 8 figures. accepted by PAS
Discovery of Irradiation Induced Variations in the Light Curve of the Classical Nova Cygni 2001 No.2 (V2275 Cyg)
We present the CCD photometry, light curve and time series analysis of the
classical nova V2275 Cyg (N Cyg 2001 No.2). The source was observed for 14
nights in total using an R filter in 2002 and 2003 with the 1.5 m
Russian-Turkish joint telescope (RTT150) at the TUBITAK (The Scientific and
Technical Research Council of Turkey) National Observatory in Antalya Turkey,
as part of a large program on the CCD photometry of Cataclysmic Variables
(CVs). We report the detection of two distinct periodicities in the light curve
of the nova : a) P_1=0.31449(15) d -- 7.6 h, b) P_2=0.017079(17) d -- 24.6 min.
The first period is evident in both 2002 and 2003 whereas the second period is
only detected in the 2003 data set. We interpret the first period as the
orbital period of the system and attribute the orbital variations to aspect
changes of the secondary irradiated by the hot WD. We suggest that the nova was
a Super Soft X-ray source in 2002 and, perhaps, in 2003. The second period
could be a QPO originating from the oscillation of the ionization front (due to
a hot WD) below the inner Lagrange point as predicted by King (1989) or a beat
frequency in the system as a result of the magnetic nature of the WD if steady
accretion has already been re-established.Comment: 6 pages and 8 figures. Accepted to be published in MNRAS main Journal
as it stand
SDSS J210014.12+004446.0: A New Dwarf Nova with Quiescent Superhumps?
We report follow-up observations of the Sloan Digital Sky Survey Cataclysmic
Variable SDSS J210014.12+004446.0 (hereafter SDSS J2100). We obtained
photometry and spectroscopy in both outburst and quiescent states, providing
the first quiescent spectrum of this source. In both states, non-sinusoidal
photometric modulations are apparent, suggestive of superhumps, placing SDSS
J2100 in the SU UMa subclass of dwarf novae. However, the periods during
outburst and quiescence differ significantly, being 2.099 plus or minus 0.002
hr and 1.96 plus or minus 0.02 hr respectively. Our phase-resolved spectroscopy
during outburst yielded an estimate of about 2 hr for the orbital period,
consistent with the photometry. The presence of the shorter period modulation
at quiescence is unusual, but not unique. Another atypical feature is the
relative weakness of the Balmer emission lines in quiescence. Overall, we find
a close similarity between SDSS J2100 and the well-studied superhump
cataclysmic Variable V503 Cygni. By analogy, we suggest that the quiescent
modulation is due to a tilted accretion disk -- producing negative superhumps
-- and the modulation in outburst is due to positive superhumps from the
precession of an elliptical disk.Comment: 6 pages, 5 eps figures, accepted by PASP Dec. 16th, 200
Nova V4743 Sagittarii 2002: An Intermediate Polar Candidate
We present the results of 11 nights of CCD unfiltered photometry of V4743 Sgr
(Nova Sgr 2002 # 3) from 2003 and 2005. We find two periods of 0.2799 d ~ 6.7 h
and 0.01642 d ~ 24 min in the 2005 data. The long period is also present in the
2003 data, but only weak evidence of the shorter period is found in this year.
The 24-min period is somewhat longer than the 22-min period, which was detected
from X-ray observations. We suggest that the 6.7-h periodicity represents the
orbital period of the underlying binary system and that the 24-min period is
the beat periodicity between the orbital period and the X-ray period, which is
presumably the spin period of the white dwarf. Thus, V4743 Sgr should be
classified as an intermediate polar (DQ Her star). About six months after the
nova outburst, the optical light curve of V4743 Sgr seemed to show
quasi-periodic oscillations, which are typical of the transient phase in
classical nova. Therefore, our results support the previous suggestion that the
trans ition phase in novae may be related to intermediate polars.Comment: 7 pages, 6 figures, AJ accepte
Solar-like oscillations in the metal-poor subgiant nu Indi: II. Acoustic spectrum and mode lifetime
Convection in stars excites resonant acoustic waves which depend on the sound
speed inside the star, which in turn depends on properties of the stellar
interior. Therefore, asteroseismology is an unrivaled method to probe the
internal structure of a star. We made a seismic study of the metal-poor
subgiant star nu Indi with the goal of constraining its interior structure. Our
study is based on a time series of 1201 radial velocity measurements spread
over 14 nights obtained from two sites, Siding Spring Observatory in Australia
and ESO La Silla Observatory in Chile. The power spectrum of the high precision
velocity time series clearly presents several identifiable peaks between 200
and 500 uHz showing regularity with a large and small spacing of 25.14 +- 0.09
uHz and 2.96 +- 0.22 uHz at 330 uHz. Thirteen individual modes have been
identified with amplitudes in the range 53 to 173 cm/s. The mode damping time
is estimated to be about 16 days (1-sigma range between 9 and 50 days),
substantially longer than in other stars like the Sun, the alpha Cen system or
the giant xi Hya.Comment: 5 pages, 7 figures, A&A accepte
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