scholarly journals Radio and optical observations of the possible AE Aqr twin, LAMOST J024048.51+195226.9

2021 ◽  
Vol 503 (3) ◽  
pp. 3692-3697
Author(s):  
M L Pretorius ◽  
D M Hewitt ◽  
P A Woudt ◽  
R P Fender ◽  
I Heywood ◽  
...  
Keyword(s):  
White Dwarf ◽  
High Speed ◽  
Good Evidence ◽  
Optical Observations ◽  
Cataclysmic Variable ◽  
Radio Luminosity ◽  
Spin Modulation ◽  
Short Period ◽  
High Speed Photometry

ABSTRACT It was recently proposed that the cataclysmic variable (CV) LAMOST J024048.51+195226.9 may be a twin to the unique magnetic propeller system AE Aqr. If this is the case, two predictions are that it should display a short period white dwarf spin modulation, and that it should be a bright radio source. We obtained follow-up optical and radio observations of this CV, in order to see if this holds true. Our optical high-speed photometry does not reveal a white dwarf spin signal, but lacks the sensitivity to detect a modulation similar to the 33 s spin signal seen in AE Aqr. We detect the source in the radio, and measure a radio luminosity similar to that of AE Aqr and close to the highest so far reported for a CV. We also find good evidence for radio variability on a time-scale of tens of minutes. Optical polarimetric observations produce no detection of linear or circular polarization. While we are not able to provide compelling evidence, our observations are all consistent with this object being a propeller system.

scholarly journals Optical detection of the rapidly spinning white dwarf in V1460 Her

2021 ◽  
Author(s):  
Ingrid Pelisoli ◽  
R T Marsh ◽  
R P Ashley ◽  
Pasi Hakala ◽  
A Aungwerojwit ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Binary Systems ◽  
Hubble Space Telescope ◽  
Cataclysmic Variable ◽  
Optical Photometry ◽  
Arrival Times ◽  
Precise Ephemeris ◽  
History Of

Abstract Accreting magnetic white dwarfs offer an opportunity to understand the interplay between spin-up and spin-down torques in binary systems. Monitoring of the white dwarf spin may reveal whether the white dwarf spin is currently in a state of near-equilibrium, or of uni-directional evolution towards longer or shorter periods, reflecting the recent history of the system and providing constraints for evolutionary models. This makes the monitoring of the spin history of magnetic white dwarfs of high interest. In this paper we report the results of a campaign of follow-up optical photometry to detect and track the 39 sec white dwarf spin pulses recently discovered in Hubble Space Telescope data of the cataclysmic variable V1460 Her. We find the spin pulsations to be present in g-band photometry at a typical amplitude of 0.4 per cent. Under favourable observing conditions, the spin signal is detectable using 2-meter class telescopes. We measured pulse-arrival times for all our observations, which allowed us to derive a precise ephemeris for the white dwarf spin. We have also derived an orbital modulation correction that can be applied to the measurements. With our limited baseline of just over four years, we detect no evidence yet for spin-up or spin-down of the white dwarf, obtaining a lower limit of $|P/\dot{P}| > 4\times 10^{7}$ years, which is already 4 to 8 times longer than the timescales measured in two other cataclysmic variable systems containing rapidly rotating white dwarfs, AE Aqr and AR Sco.

scholarly journals RADIUS CONSTRAINTS FROM HIGH-SPEED PHOTOMETRY OF 20 LOW-MASS WHITE DWARF BINARIES

2014 ◽  
Vol 792 (1) ◽  
pp. 39 ◽  
Author(s):  
J. J. Hermes ◽  
Warren R. Brown ◽  
Mukremin Kilic ◽  
A. Gianninas ◽  
Paul Chote ◽  
...  
Keyword(s):  
White Dwarf ◽  
High Speed ◽  
High Speed Photometry ◽  
Low Mass

scholarly journals Cataclysmic Variable Stars

1998 ◽  
Vol 11 (1) ◽  
pp. 16-27
Author(s):  
Brian Warner
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Main Sequence ◽  
Variable Stars ◽  
Cataclysmic Variable ◽  
Common Envelope ◽  
Short Period ◽  
Orbital Periods ◽  
Probable Origin ◽  
Binary Orbit

The evolution of single stars on and away from the main sequence is well understood. A degenerate core is formed in a star as the star leaves the main sequence and expands to a giant with a radius typically 50 - 500 Ro . Observationally it is known that most stars are members of binary systems, and among these many have orbital periods less than 100 y. It can happen, therefore, that the expanding envelope of the primary of a binary system can reach to the secondary. As this happens, the primary fills its Roche tidal lobe and transfers matter to the secondary; if the primary has a radiative envelope the rate at which this occurs exceeds the Eddington limit of the secondary, which therefore repels the incoming gas, forming a common envelope around the two stars. Friction within the envelope causes the stars to spiral towards each other until the energy and angular momentum extracted from the binary orbit and transferred to the envelope are sufficient to eject the common envelope as a planetary nebula, leaving a short period binary comprising a white dwarf and a main sequence star. This mechanism of producing short period binaries containing white dwarfs, proposed by Ostriker and by Paczynski (1976), is the probable origin of the class of objects known as Cataclysmic Variable Stars (CVs), which encompass the classical novae, dwarf novae, novalike variables and a variety of related objects. Evidence has been accumulating for forty years (Crawford & Kraft 1956, Warner 1995a) that every CV consists of a secondary star (usually a dwarf, but a few systems contain giants) filling its Roche lobe and transferring mass to a white dwarf primary. In systems of normal chemical composition the orbital periods lie between 75 mins and ~250 d, with the majority having . A few hydrogen-free systems are known for which 17 mins < Porb < 50 mins. It should be noted that CVs are very compact binary systems: for h such a binary would fit inside the Sun.

scholarly journals High Frequency Oscillations in SS Cygni

1989 ◽  
Vol 114 ◽  
pp. 462-464
Author(s):  
M.J. Arévalo ◽  
J.E. Solheim ◽  
C. Lázaro
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Cataclysmic Variable ◽  
Dwarf Novae ◽  
High Frequency Oscillations ◽  
Relative Brightness ◽  
High Speed Photometry

Because of its relative brightness (mv about 11.8 in quiescence and mv about 8.6 in outburst), SS Cygni is the Dwarf Novae most extensively studied since 1896 (Mattei et al., 1985; Bath and van Paradijs, 1983).Concerning its long-term behaviour, SS Cygni has short, long and anomalous out-bursts. Correlations between outburst characteristics and periodicities have been studied by van Paradijs (1983), Campbell (1934), and Sterne and Campbell (1934).SS Cygni, as any cataclysmic variable, also presents rapid variations. Since the discovery of this variability (Warner and Robinson, 1972) many long runs of high-speed photometry have been performed for different Dwarf Novae, both during out-bursts and in quiescence stages. Regarding to SS Cygni we can summarize these variations as:

High-Time-Resolution Astrophysics using the Thai 2.4-m Telescope with Ultraspec

2017 ◽  
Vol 14 (S339) ◽  
pp. 185-188
Author(s):  
P. Irawati
Keyword(s):  
Time Resolution ◽  
High Speed ◽  
Period Change ◽  
Low Noise ◽  
High Time ◽  
High Time Resolution ◽  
Third Body ◽  
Data Set ◽  
High Speed Photometry

AbstractThe Thai National Observatory (TNO) is equipped with a 2.4-m Ritchey-Chretien telescope and the high-speed versatile Ultraspec camera. The instrument employs a low-noise frame-transfer EMCCD, suitable for the observation of faint objects and for high-time-resolution astrophysics. We present some of the results obtained in the first four years of operation, focusing particularly on fast photometry of lunar and stellar occultations, and follow-up efforts on a few white-dwarf binaries. Among the latter is the polar cataclysmic variable UZ For. This system displays period changes and is suspected of hosting circumbinary planets. Our high-speed photometry data show a decreasing trend in the O–C diagram of UZ For. Using our new data set, we will investigate whether the period change in this binary is due to a possible third body, or to other mechanism(s).

scholarly journals The Mysterious Nature of HS 2331+3905

2004 ◽  
Vol 194 ◽  
pp. 190-191 ◽  
Author(s):  
S. Aranjo-Betancor ◽  
B. T. Gänsicke ◽  
H.-J. Hagen ◽  
T. R. Marsh ◽  
J. Thorstensen ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Optical Spectroscopy ◽  
Orbital Period ◽  
White Dwarf ◽  
Large Amplitude ◽  
Cataclysmic Variable ◽  
Ccd Photometry ◽  
Velocity Variations

AbstractWe report the discovery of one unique cataclysmic variable drawn from the Hamburg Quasar Survey, HS 2331 + 3905. Follow-up observations obtained over three years unveiled a very unusual picture. The large amplitude 3.5 h radial velocity variations obtained from our optical spectroscopy is not the orbital period of the system, as one would normally expect. Instead, extensive CCD photometry strongly suggests that HS 2331 + 3005 is a short orbital period cataclysmic variable with Рorb = 81.09 min, containing a cold white dwarf which appears to exhibit ZZ Ceti pulsations.

Severe Head Injury linked to Subsequent Development of Malignant Brain Tumour within a Short Period- A Case Report

2018 ◽  
Vol 3 (2) ◽  
Keyword(s):  
Head Injury ◽  
Brain Tumour ◽  
Severe Head Injury ◽  
Case Reports ◽  
Subsequent Development ◽  
Malignant Brain Tumour ◽  
Tumour Development ◽  
Short Period ◽  
The Brain

There have been a few case reports of head injury leading to brain tumour development in the same region as the brain injury. Here we report a case where the patient suffered a severe head injury with contusion. He recovered clinically with conservative management. Follow up Computed Tomography scan of the brain a month later showed complete resolution of the lesion. He subsequently developed malignant brain tumour in the same region as the original contusion within a very short period of 15 months. Head injury patients need close follow up especially when severe. The link between severity of head injury and malignant brain tumour development needs further evaluation. Role of anti-inflammatory agents for prevention of post traumatic brain tumours needs further exploration.

scholarly journals SuperWASP variable stars: classifying light curves using citizen science

2021 ◽  
Vol 502 (1) ◽  
pp. 1299-1311
Author(s):  
Heidi B Thiemann ◽  
Andrew J Norton ◽  
Hugh J Dickinson ◽  
Adam McMaster ◽  
Ulrich C Kolb
Keyword(s):  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Data Set ◽  
Resultant Data ◽  
Sky Survey ◽  
Short Period ◽  
Contact Binaries ◽  
Analysis Of Results

ABSTRACT We present the first analysis of results from the SuperWASP variable stars Zooniverse project, which is aiming to classify 1.6 million phase-folded light curves of candidate stellar variables observed by the SuperWASP all sky survey with periods detected in the SuperWASP periodicity catalogue. The resultant data set currently contains &gt;1 million classifications corresponding to &gt;500 000 object–period combinations, provided by citizen–scientist volunteers. Volunteer-classified light curves have ∼89 per cent accuracy for detached and semidetached eclipsing binaries, but only ∼9 per cent accuracy for rotationally modulated variables, based on known objects. We demonstrate that this Zooniverse project will be valuable for both population studies of individual variable types and the identification of stellar variables for follow-up. We present preliminary findings on various unique and extreme variables in this analysis, including long-period contact binaries and binaries near the short-period cut-off, and we identify 301 previously unknown binaries and pulsators. We are now in the process of developing a web portal to enable other researchers to access the outputs of the SuperWASP variable stars project.

Endoscopy-assisted removal of periorbital inclusion cysts in children

2011 ◽  
Vol 7 (2) ◽  
pp. 161-164 ◽  
Author(s):  
George Chater-Cure ◽  
Caitlin Hoffman ◽  
Jared Knopman ◽  
Samuel Rhee ◽  
Mark M. Souweidane
Keyword(s):  
High Speed ◽  
Complete Removal ◽  
Skin Incision ◽  
Clinical Findings ◽  
Complete Excision ◽  
Alternative Approach ◽  
Cyst Recurrence ◽  
Scalp Incision ◽  
Access Technique

Object Surgical treatment for periorbital inclusion cysts typically involves a brow, pterional, or partial bicoronal scalp incision for sufficient exposure. The authors have recently employed an endoscopy-assisted technique as an alternative approach intended to minimize the length of the skin incision and avoid scarring in the brow. Methods Children having typical clinical findings of a dermoid cyst located on the hairless forehead were selected to undergo endoscopy-assisted cyst removal. For suspected intradiploic lesions, MR imaging was used to assess osseous involvement. After induction of general anesthesia, a 1–2-cm curvilinear incision was made posterior to the hairline. A 30°-angled endoscope (4 mm) was then used for dissection in the subgaleal compartment. Subgaleal dissection was followed by a circumferential periosteal incision in which the authors used an angled needle-tip unipolar cautery. For lesions within the diploe, a high-speed air drill was used to expose the lesion. Complete removal was accomplished with curettage of either the skull or dural surface. Results Eight patients (5–33 months of age) underwent outpatient endoscopic resection. Seven cysts were extracranial, and 1 cyst extended through the inner table. In all patients complete excision of the cyst was achieved. There was negligible blood loss, no dural violation, and no postoperative infection. There have been no recurrences at a mean follow-up of 15 months. Conclusions Endoscopy-assisted resection of inclusion cysts of the scalp and calvaria is a safe and effective surgical approach. The technique results in negligible incisions with less apparent scarring compared with previously described incisions. This limited-access technique does not appear to be associated with a higher incidence of cyst recurrence.

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