175 research outputs found
V803 Centauri: Helium Dwarf Nova Mimicking a WZ Sge-Type Superoutburst
We observed long-term behavior of the helium dwarf nova V803 Cen, and
clarified the existence of at least two distinct states (state with 77-d
supercycles and standstill-like state) which interchangeably appeared with a
time-scale of 1--2 yr. We also conducted a time-resolved CCD photometry
campaign during the bright outburst in 2003 June. The overall appearance of the
outburst closely resemble that of the late stage of the 2001 outburst of WZ
Sge, consisting of the initial peak stage (superoutburst plateau), the dip, and
the oscillating (rebrightening) states. During the initial peak stage, we
detected large-amplitude superhump-type variation with a period of 0.018686(4)
d = 1614.5(4) s, and during the oscillation stage, we detected variations with
a period of 0.018728(2) d = 1618.1(2) s. We consider that the former period
better represents the superhump period of this system, and the latter
periodicity may be better interpreted as arising from late superhumps. The
overall picture of the V803 Cen outburst resembles that of a WZ Sge-type
outburst, but apparently with a higher mass-transfer rate than in hydrogen-rich
WZ Sge-type stars. We suggest that this behavior may be either the result of
difficulty in maintaining the hot state in a helium disk, or the effect of an
extremely low tidal torque resulting from the extreme mass ratio.Comment: 13 pages, 11 figures, to appear in PAS
The 2011 Eruption of the Recurrent Nova T Pyxidis; the Discovery, the Pre-eruption Rise, the Pre-eruption Orbital Period, and the Reason for the Long Delay
We report the discovery by M. Linnolt on JD 2455665.7931 (UT 2011 April
14.29) of the sixth eruption of the recurrent nova T Pyxidis. This discovery
was made just as the initial fast rise was starting, so with fast notification
and response by observers worldwide, the entire initial rise was covered (the
first for any nova), and with high time resolution in three filters. The speed
of the rise peaked at 9 mag/day, while the light curve is well fit over only
the first two days by a model with a uniformly expanding sphere. We also report
the discovery by R. Stubbings of a pre-eruption rise starting 18 days before
the eruption, peaking 1.1 mag brighter than its long-time average, and then
fading back towards quiescence 4 days before the eruption. This unique and
mysterious behavior is only the fourth known anticipatory rise closely spaced
before a nova eruption. We present 19 timings of photometric minima from 1986
to February 2011, where the orbital period is fast increasing with
P/dot{P}=313,000 yrs. From 2008-2011, T Pyx had a small change in this rate of
increase, so that the orbital period at the time of eruption was
0.07622950+-0.00000008 days. This strong and steady increase of the orbital
period can only come from mass transfer, for which we calculate a rate of
1.7-3.5x10^-7 Mo/yr. We report 6116 magnitudes between 1890 and 2011, for an
average B=15.59+-0.01 from 1967-2011, which allows for an eruption in 2011 if
the blue flux is nearly proportional to the accretion rate. The
ultraviolet-optical-infrared spectral energy distribution is well fit by a
power law with flux proportional to nu^1.0, although the narrow ultraviolet
region has a tilt with a fit of \nu^{1/3}. We prove that most of the T Pyx
light is not coming from a disk, or any superposition of blackbodies, but
rather is coming from some nonthermal source.Comment: ApJ submitted, 62 pages, 8 figures; much added data, updated analysi
Photometric Studies of New Southern SU UMa-type dwarf novae, FL Triangulum Australe and CTCV J0549-4921
We report time-resolved optical CCD photometry on newly discovered SU
UMa-type dwarf novae, FL TrA and CTCV J0549-4921. During the 2006 August
outburst, we detected superhumps with a period of 0.59897(11) days for FL TrA,
clarifying the SU UMa nature of the system. On the first night of our
observations on FL TrA, the object showed no superhumps. This implies that it
takes a few days for full development of superhumps. The superhump period
variation diagram of FL TrA was similar to that observed in some WZ Sge stars
and short period SU UMa-type stars. This indicates that the system is closely
related to WZ Sge stars and SU UMa stars having short orbital periods. For CTCV
J0549-4921, the candidates of the mean superhump period are 0.083249(10) days
and 0.084257(8) days, respectively. Due to a lack of the observations, we
cannot determine the true superhump period, but the latter period is favorable.
Using the ASAS-3 archive, it turned out that the system shows only four
outbursts over the past 6 years. The outburst amplitude of CTCV J0549-4921 was
relatively small, with about 4.5 mag. One possibility is that mass evaporation
may play a role during quiescence.Comment: 7 pages, 8 figures, published for PASJ vol.6
Two X-Ray Bright Cataclysmic Variables with Unusual Activities: GZ Cnc and NSV 10934
We report on a discovery of unexpected activities in two X-ray bright dwarf novae. GZ Cnc showed an anomalous clustering of outbursts in 2002, in contrast to a low outburst frequency in the past record. The activity resembles an increased activity seen in some intermediate polars or candidates. We identified NSV 10934, X-ray selected high-amplitude variable star, as a dwarf nova with unusually rapid decline. The outburst characteristics make NSV 10934 a twin of recently discovered intermediate polar (HT Cam) with dwarf nova-type outbursts. We propose that these activities in X-ray strong dwarf novae may be a previously overlooked manifestation of outburst activities in magnetic cataclysmic variables
Photometric study of new southern SU UMa-type dwarf novae and candidates: V877 Ara, KK Tel and PU CMa
We photometrically observed three dwarf novae V877 Ara, KK Tel and PU CMa. We
discovered undisputed presence of superhumps in V877 Ara and KK Tel, with mean
periods of 0.08411(2) d and 0.08808(3) d, respectively. Both V877 Ara and KK
Tel are confirmed to belong to long-period SU UMa-type dwarf novae. In V877
Ara, we found a large decrease of the superhump period (dot(P)/P = -14.5 +/-
2.1 x 10^(-5)). There is evidence that the period of KK Tel decreased at a
similar or a more exceptional rate. Coupled with the past studies of superhump
period changes, these findings suggest that a previously neglected diversity of
phenomena is present in long-period SU UMa-type dwarf novae. The present
discovery of a diversity in long-period SU UMa-type systems would become an
additional step toward a full understanding the dwarf nova phenomenon. PU CMa
is shown to be an excellent candidate for an SU UMa-type dwarf nova. We
examined the outburst properties of these dwarf novae, and derived
characteristic outburst recurrence times. Combined with the recently published
measurement of the orbital period of PU CMa, we propose that PU CMa is the
first object filling the gap between the extreme WZ Sge-type and ER UMa-type
stars.Comment: 12 pages, 14 figures, accepted for publication in MNRA
Cancer symptom awareness and barriers to symptomatic presentation in England – Are we clear on cancer?
Background: Low cancer awareness may contribute to delayed diagnosis and poor cancer survival. We aimed to quantify socio-demographic differences in cancer symptom awareness and barriers to symptomatic presentation in the English population.
Methods: Using a uniquely large data set (n=49?270), we examined the association of cancer symptom awareness and barriers to presentation with age, gender, marital status and socio-economic position (SEP), using logistic regression models to control for confounders.
Results: The youngest and oldest, the single and participants with the lowest SEP recognised the fewest cancer symptoms, and reported most barriers to presentation. Recognition of nine common cancer symptoms was significantly lower, and embarrassment, fear and difficulties in arranging transport to the doctor’s surgery were significantly more common in participants living in the most deprived areas than in the most affluent areas. Women were significantly more likely than men to both recognise common cancer symptoms and to report barriers. Women were much more likely compared with men to report that fear would put them off from going to the doctor.
Conclusions: Large and robust socio-demographic differences in recognition of some cancer symptoms, and perception of some barriers to presentation, highlight the need for targeted campaigns to encourage early presentation and improve cancer outcomes
Risk factors for delay in symptomatic presentation: a survey of cancer patients
Background: Delay in symptomatic presentation leading to advanced stage at diagnosis may contribute to poor cancer survival. To inform public health approaches to promoting early symptomatic presentation, we aimed to identify risk factors for delay in presentation across several cancers.
Methods: We surveyed 2371 patients with 15 cancers about nature and duration of symptoms using a postal questionnaire. We calculated relative risks for delay in presentation (time from symptom onset to first presentation >3 months) by cancer, symptoms leading to diagnosis and reasons for putting off going to the doctor, controlling for age, sex and deprivation group.
Results: Among 1999 cancer patients reporting symptoms, 21% delayed presentation for >3 months. Delay was associated with greater socioeconomic deprivation but not age or sex. Patients with prostate (44%) and rectal cancer (37%) were most likely to delay and patients with breast cancer least likely to delay (8%). Urinary difficulties, change of bowel habit, systemic symptoms (fatigue, weight loss and loss of appetite) and skin symptoms were all common and associated with delay. Overall, patients with bleeding symptoms were no more likely to delay presentation than patients who did not have bleeding symptoms. However, within the group of patients with bleeding symptoms, there were significant differences in risk of delay by source of bleeding: 35% of patients with rectal bleeding delayed presentation, but only 9% of patients with urinary bleeding. A lump was a common symptom but not associated with delay in presentation. Twenty-eight percent had not recognised their symptoms as serious and this was associated with a doubling in risk of delay. Embarrassment, worry about what the doctor might find, being too busy to go to the doctor and worry about wasting the doctor’s time were also strong risk factors for delay, but were much less commonly reported (<6%).
Interpretation: Approaches to promote early presentation should aim to increase awareness of the significance of cancer symptoms and should be designed to work for people of the lowest socioeconomic status. In particular, awareness that rectal bleeding is a possible symptom of cancer should be raised
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