IM Normae: The Death Spiral of a Cataclysmic Variable?

We present a study of the orbital light curves of the recurrent nova IM Normae since its 2002 outburst. The broad "eclipses" recur with a 2.46 hour period, which increases on a timescale of 1.28(16)x10^6 years. Under the assumption of conservative mass-transfer, this suggests a rate near 10^-7 M_sol/year, and this agrees with the estimated /accretion/ rate of the postnova, based on our estimate of luminosity. IM Nor appears to be a close match to the famous recurrent nova T Pyxidis. Both stars appear to have very high accretion rates, sufficient to drive the recurrent-nova events. Both have quiescent light curves which suggest strong heating of the low-mass secondary, and very wide orbital minima which suggest obscuration of a large "corona" around the primary. And both have very rapid orbital period increases, as expected from a short-period binary with high mass transfer from the low-mass component. These two stars may represent a final stage of nova -- and cataclysmic-variable -- evolution, in which irradiation-driven winds drive a high rate of mass transfer, thereby evaporating the donor star in a paroxysm of nova outbursts.Comment: PDF, 30 pages, 3 tables, 6 figures; accepted, in press, ApJ; more info at http://cbastro.org

TU Tau B: The Peculiar 'Eclipse' of a possible proto-Barium Giant

TU Tau (= HD 38218 = HIP 27135) is a binary system consisting of a C-N carbon star primary and an A-type secondary. We report on new photometry and spectroscopy which tracked the recent disappearance of the A-star secondary. The dimming of the A-star was gradual and irregular, with one or more brief brightenings, implying the presence of nonhomogeneities in the carbon star outflow. We also present evidence that the A-star is actively accreting s-process enriched material from the carbon star and suggest that it will therefore eventually evolve into a Barium giant. This is an important system as well because the A-type star can serve as a probe of the outer atmosphere of the carbon star.Comment: 9 pages, 9 figures, 4 tables, a number of amateur observatories made significant contributions to this research. Paper accepted for publication in The Astronomical Journa

The rise and fall of the king : the correlation between FO Aquarii's low states and the White Dwarf's Spindown

The intermediate polar FO Aquarii experienced its first-reported low-accretion states in 2016, 2017, and 2018. We establish that these low states occurred shortly after the system's white dwarf (WD) began spinning down, after having spent a quarter-century spinning up. FO Aquarii is the only intermediate polar whose period derivative has undergone a sign change, and it has now done so twice. By combining our spin-pulse timings with previous data, we determine that the WD's spin period has varied quasi-sinusoidally since the system's discovery, and an extrapolation predicts that the white dwarf was spinning down during newly discovered low states in photographic plates from 1964, 1965, and 1974. Thus, FO Aquarii's low states appear to occur exclusively during epochs of spindown. Additionally, our time-series photometry of the 2016-18 low states reveals that the mode of accretion is extremely sensitive to the accretion rate; when the system is fainter than V~14.0, the accretion onto the WD is largely stream-fed, but when it is brighter, it is almost exclusively disk-fed. The system's grazing eclipse remained detectable throughout all observations, confirming the uninterrupted presence of a disk-like structure, regardless of the accretion state. Our observations are consistent with theoretical predictions that during the low states, the accretion disk dissipates into a ring of diamagnetic blobs. Finally, a new XMM-Newton observation from 2017 indicates that the system's anomalously soft X-ray spectrum and diminished X-ray luminosity in the wake of the 2016 low state appear to be long-lasting changes compared to pre-2016 observations.peer-reviewe

Method-comparison study between a watch-like sensor and a cuff-based device for 24-h ambulatory blood pressure monitoring.

The use of 24-h ambulatory blood pressure monitoring (ABPM) has been continuously increasing over the last decades. However, cuff-based devices may cause discomfort, particularly at night, leading to potentially non-representative blood pressure (BP) values. We investigated the feasibility of a cuff-less BP monitoring solution in 67 subjects undergoing conventional 24-h ABPM. A watch-like optical sensor was attached at the upper arm or wrist at the contralateral side of the cuff. Systolic (SBP) and diastolic BP (DBP) values were estimated from the measured optical signals by pulse wave analysis. Average 24-h, daytime and nighttime BP values were compared between the conventional monitor and the cuff-less sensor. The differences between both methods-expressed as mean ± standard deviation (95% limits of agreement)-were of - 1.8 ± 6.2 mmHg (- 13.9, 10.3) on SBP and - 2.3 ± 5.4 mmHg (- 13.0, 8.3) on DBP for 24-h averages, of - 1.5 ± 6.6 mmHg (- 14.4, 11.4) on SBP and - 1.8 ± 5.9 mmHg (- 13.4, 9.9) on DBP for daytime averages, and of 0.4 ± 7.5 mmHg (- 14.4, 15.1) on SBP and - 1.3 ± 6.8 mmHg (- 14.7, 12.0) on DBP for nighttime averages. These results encouragingly suggest that cuff-less 24-h ABPM may soon become a clinical possibility

Lateral river erosion impacts the preservation of Neolithic enclosures in alluvial plains

International audienceSituating prehistoric sites in their past environment helps us to understand their functionality and the organization of early sedentary human societies. However, this is a challenge as the natural environment constantly evolves through time and erases these constructions, especially along riverbanks, thus biasing the archaeological record. This study introduces a reassessment of the paleo-landscape evolution around the Neolithic enclosures at the Noyen-sur-Seine site based on new field observations as well as the synthesis of (un)published and new radiocarbon dating. Contrary to the initial hypothesis, our results show that the Noyen enclosures were not built along a Neolithic Seine River: the nearby channels were active in the Middle Age and Early Modern periods. Therefore, the results show that the enclosures were originally much larger: only a fraction that survived river erosion (lateral migration rates up to 2–3 m yr −1 estimated during the nineteenth century) has been preserved. Instead, an abandoned Mesolithic Seine River served as a natural delimitation of the SE part of the Neolithic enclosures. These results indicate that Neolithic enclosures in alluvial settings are often only partly preserved and that societies from that period lived farther away from active rivers than originally thought, where they were protected from floods

Pulse Oximetry at the Wrist During Sleep: Performance, Challenges and Perspectives.

The state-of-the-art non-invasive measurement of peripheral oxygen saturation (SpO2) during sleep is mainly based on pulse oximetry at the fingertip. Although this approach is noninvasive, it can still be obtrusive and cumbersome to apply, in particular for ambulatory monitoring over several nights.We developed a wrist-worn reflectance pulse oximetry device which can be embedded in a watch, making it less obtrusive and easy to apply. This device was tested in an ongoing clinical study on 57 subjects (33 patients and 24 healthy volunteers) undergoing a full overnight polysomnography recording. The accuracy was evaluated against state-of-the-art fingertip SpO2 measurements.In the 54 subjects available for analysis we obtained an SpO2 accuracy (ARMS) of 3.4 % when automatically rejecting 17.7 % of signals due to low quality. When further excluding measurements suffering from insufficient contact of the watch with the skin an ARMS of 2.7 % was obtained while rejecting a total of 23.2 % measurements. These accuracies comply with the ISO standard and the FDA guidance for pulse oximeters.The present results are promising and pave the way for unobtrusive and continuous monitoring of SpO2 to screen for sleep disordered breathing. Nonetheless, contact pressure and venous blood have shown to adversely affect the SpO2 estimation and remain a challenge for wrist-based reflectance pulse oximetry

IM normae: The death spiral of a cataclysmic variable?

We present a study of the orbital light curves of the recurrent nova IM Normae since its 2002 outburst. The broad "eclipses"recur with a 2.46 hr period, which increases on a timescale of 1.28(16) × 106 yr. Under the assumption of conservative mass transfer, this suggests a rate near 10-7 M o˙ yr-1, and this agrees with the estimated accretion rate of the postnova, based on our estimate of luminosity. IM Nor appears to be a close match to the famous recurrent nova T Pyxidis. Both stars appear to have very high accretion rates, sufficient to drive the recurrent-nova events. Both have quiescent light curves, which suggest strong heating of the low-mass secondary, and very wide orbital minima, which suggest obscuration of a large "corona"around the primary. And both have very rapid orbital period increases, as expected from a short-period binary with high mass transfer from the low-mass component. These two stars may represent a final stage of nova - and cataclysmic variable - evolution, in which irradiation-driven winds drive a high rate of mass transfer, thereby evaporating the donor star in a paroxysm of nova outbursts.</p

The Periodic Signals of Nova V1674 Herculis (2021)

We present time-series photometry during eruption of the extremely fast nova V1674 Herculis (Nova Her 2021). The 2021 light curve showed periodic signals at 0.152921(3) d and 501.486(5) s, which we interpret as respectively the orbital and white dwarf spin-periods in the underlying binary. We also detected a sideband signal at the /difference/ frequency between these two clocks. During the first 15 days of outburst, the spin-period appears to have increased by 0.014(1)%. This increase probably arose from the sudden loss of high-angular-momentum gas ("the nova explosion") from the rotating, magnetic white dwarf. Both periodic signals appeared remarkably early in the outburst, which we attribute to the extreme speed with which the nova evolved (and became transparent to radiation from the inner binary). After that very fast initial increase of ~71 ms, the spin-period commenced a steady decrease of ~160 ms/year -- about 100x faster than usually seen in intermediate polars. This is probably due to high accretion torques from very high mass-transfer rates, which might be common when low-mass donor stars are strongly irradiated by a nova outburst.Comment: PDF, 10 pages, 1 table, 3 figures; in preparation; more info at http://cbastro.org

The Periodic Signals of Nova V1674 Herculis (2021)

We present time-series photometry during eruption of the extremely fast nova V1674 Herculis (Nova Her 2021). The 2021 light curve showed periodic signals at 0.152921(3) d and 501.486(5) s, which we interpret as respectively the orbital and white dwarf spin-periods in the underlying binary. We also detected a sideband signal at the /difference/ frequency between these two clocks. During the first 15 days of outburst, the spin-period appears to have increased by 0.014(1)%. This increase probably arose from the sudden loss of high-angular-momentum gas ("the nova explosion") from the rotating, magnetic white dwarf. Both periodic signals appeared remarkably early in the outburst, which we attribute to the extreme speed with which the nova evolved (and became transparent to radiation from the inner binary). After that very fast initial increase of ~71 ms, the spin-period commenced a steady decrease of ~160 ms/year -- about 100x faster than usually seen in intermediate polars. This is probably due to high accretion torques from very high mass-transfer rates, which might be common when low-mass donor stars are strongly irradiated by a nova outburst.</p