Evidence from stellar rotation of enhanced disc dispersal: (I) The case of the triple visual system BD-21 1074 in the β\beta Pictoris association

The early stage of stellar evolution is characterized by a star-disc locking mechanism. The disc-locking prevents the star to spin its rotation up, and its timescale depends on the disc lifetime. Some mechanisms can significantly shorten this lifetime, allowing a few stars to start spinning up much earlier than other stars. In the present study, we aim to investigate how the properties of the circumstellar environment can shorten the disc lifetime. We have identified a few multiple stellar systems, composed of stars with similar masses, which belong to associations with a known age. Since all parameters that are responsible for the rotational evolution, with the exception of environment properties and initial stellar rotation, are similar for all components, we expect that significant differences among the rotation periods can only arise from differences in the disc lifetimes. A photometric timeseries allowed us to measure the rotation periods of each component, while high-resolution spectra provided us with the fundamental parameters, $v\sin{i}$ and chromospheric line fluxes. The rotation periods of the components differ significantly, and the component B, which has a closer companion C, rotates faster than the more distant and isolated component A. We can ascribe the rotation period difference to either different initial rotation periods or different disc-locking phases arising from the presence of the close companion C. In the specific case of BD$-$21 1074, the second scenario seems to be more favored. In our hypothesis of different disc-locking phase, any planet orbiting this star is likely formed very rapidly owing to a gravitational instability mechanism, rather than core accretion. Only a large difference of initial rotation periods alone could account for the observed period difference, leaving comparable disc lifetimes.Comment: Accepted by Astronomy & Astrophysics on July 31, 2014; Pages 12, Figs.

Photometric Studies of a WZ Sge-Type Dwarf Nova Candidate, ASAS160048-4846.2

We report on our time-resolved CCD photometry during the 2005 June superoutburst of a WZ Sge-type dwarf nova candidate, ASAS 160048-4846.2. The ordinary superhumps underwent a complex evolution during the superoutburst. The superhump amplitude experienced a regrowth, and had two peaks. The superhump period decreased when the superhump amplitude reached to the first maximum, successively gradually increased until the second maximum of the amplitude, and finally decreased again. Investigating other SU UMa-type dwarf novae which show an increase of the superhump period, we found the same trend of the superhump evolution in superoutbursts of them. We speculate that the superhump regrowth in the amplitude has a close relation to the increase of the superhump period, and all of SU UMa-type dwarf novae with a superhump regrowth follow the same evolution of the ordinary superhumps as that of ASAS 160048-4846.2.Comment: 7 pages, 4 figure

Discovery of a Promissing Candidate of WZ Sge-Type Dwarf Novae, ASAS 160048-4846.2: Evidence for Double-Peaked Humps

We report on time-resolved CCD photometry during the 2005 June outburst of a dwarf nova, ASAS160048-4846.2. The observed light curves unambiguously showed embryonic humps with a period of 0.063381(41) days, after which genuine superhumps emerged with a period of 0.064927(3) days. Based on evidence for double-peaked humps in the earlier stage of the outburst, this object might be qualified as the seventh member of WZ Sge-type dwarf novae after Var Her 04. If the former period is the same as, or very close to the orbital period of the system, as in other WZ Sge systems, the fractional superhump excess is about 2.4{%}. This value is unexpectedly larger than that of other WZ Sge-type dwarf novae. The early phase of our observing run provided evidence for the transition from chaotic humps to genuine superhumps, together with increasing the amplitude.Comment: 4 pages, 6 figures, submitted to PAS

Explosion of a massive, He-rich star at z=0.16

We present spectroscopic and photometric data of the peculiar SN 2001gh, discovered by the 'Southern inTermediate Redshift ESO Supernova Search' (STRESS) at a redshift z=0.16. SN 2001gh has relatively high luminosity at maximum (M_B = -18.55 mag), while the light curve shows a broad peak. An early-time spectrum shows an almost featureless, blue continuum with a few weak and shallow P-Cygni lines that we attribute to HeI. HeI lines remain the only spectral features visible in a subsequent spectrum, obtained one month later. A remarkable property of SN 2001gh is the lack of significant spectral evolution over the temporal window of nearly one month separating the two spectra. In order to explain the properties of SN 2001gh, three powering mechanism are explored, including radioactive decays of a moderately large amount of 56Ni, magnetar spin-down, and interaction of SN ejecta with circumstellar medium. We favour the latter scenario, with a SN Ib wrapped in a dense, circumstellar shell. The fact that no models provide an excellent fit with observations, confirms the troublesome interpretation of the nature of SN 2001gh. A rate estimate for SN 2001gh-like event is also provided, confirming the intrinsic rarity of these objects.Comment: 11 pages, 8 figures, 3 tables. Accepted by MNRA

Mission conjointe NMA/PRIFAS d´étude et de prospective dans Le Sudeste du Bresil, du 27 octobre au 10 novembre 1990.

bitstream/item/116959/1/1589.pd

The Peculiar 2004 Superoutburst in the Helium Dwarf Nova, 2003aw

We conducted a time-resolved photometric campaign of the helium dwarf nova, 2003aw in 2004 May--June. 2003aw stayed at 14.7--15.7 mag for the first several days during this campaign, which is the plateau phase of this superoutburst. This variable then rapidly decayed to $\sim$18.0 mag, still brighter by about 2 mag than its quiescence magnitude, and maintained this brightness for about 20 days, having short flares of $\sim$2 mag. A long fading tail followed it. We detected superhumps with a period of 0.02357(4) d [= 2036(3) s] during the plateau phase. The whole light curve of the superoutburst in 2003aw, taking into account the present data and those in the literature, perfectly resembles that of the 1996-1997 superoutburst of the peculiar WZ Sge-type hydrogen-rich dwarf nova, EG Cnc.Comment: 5 pages, 4 figures, PASJ Letter in pres

Recurrent mini-outbursts and a magnetic white dwarf in the symbiotic system FN Sgr

AIMS: We investigated the optical variability of the symbiotic binary FN Sgr, with photometric monitoring during $\simeq$55 years and with a high-cadence Kepler light curve lasting 81 days. METHODS: The data obtained in the V and I bands were reduced with standard photometric methods. The Kepler data were divided into subsamples and analyses with the Lomb-Scargle algorithm. RESULTS: The V and I band light curves showed a phenomenon never before observed with such recurrence in any symbiotic system, namely short outbursts, starting between orbital phase 0.3 and 0.5 and lasting about a month, with a fast rise and a slower decline, and amplitude of 0.5-1 mag. In the Kepler light curve we discovered three frequencies with sidebands. We attribute a stable frequency of 127.5 d$^{-1}$ (corresponding to an 11.3 minutes period) to the white dwarf rotation. We suggest that this detection probably implies that the white dwarf accretes through a magnetic stream, like in intermediate polars. The small outbursts may be ascribed to the stream-disc interaction. Another possibility is that they are due to localized thermonuclear burning, perhaps confined by the magnetic field, like recently inferred in intermediate polars, albeit on different timescales. We measured also a second frequency around 116.9 d$^{-1}$ (corresponding to about 137 minutes), which is much less stable and has a drift. It may be due to rocky detritus around the white dwarf, but it is more likely to be caused by an inhomogeneity in the accretion disk. Finally, there is a third frequency close to the first one that appears to correspond to the beating between the rotation and the second frequency.Comment: Accepted for publication in Astronomy and Astrophysic

Cytokine hemoadsorption with CytoSorb^® in post-cardiac arrest syndrome, a pilot randomized controlled trial.

Hemoadsorption (HA) might mitigate the systemic inflammatory response associated with post-cardiac arrest syndrome (PCAS) and improve outcomes. Here, we investigated the feasibility, safety and efficacy of HA with CytoSorb <sup>®</sup> in cardiac arrest (CA) survivors at risk of PCAS. In this pilot randomized controlled trial, we included patients admitted to our intensive care unit following CA and likely to develop PCAS: required norepinephrine (> 0.2 µg/kg/min), and/or had serum lactate > 6 mmol/l and/or a time-to-return of spontaneous circulation (ROSC) > 25 min. Those requiring ECMO or renal replacement therapy were excluded. Eligible patients were randomly allocated to either receive standard of care (SOC) or SOC plus HA. Hemoadsorption was performed as stand-alone therapy for 24 h, using CytoSorb <sup>®</sup> and regional heparin-protamine anticoagulation. We collected feasibility, safety and clinical data as well as serial plasma cytokines levels within 72 h of randomization. We enrolled 21 patients, of whom 16 (76%) had out-of-hospital CA. Median (IQR) time-to-ROSC was 30 (20, 45) minutes. Ten were assigned to the HA group and 11 to the SOC group. Hemoadsorption was initiated in all patients allocated to the HA group within 18 (11, 23) h of ICU admission and conducted for a median duration of 21 (14, 24) h. The intervention was well tolerated except for a trend for a higher rate of aPTT elevation (5 (50%) vs 2 (18%) p = 0.18) and mild (100-150 G/L) thrombocytopenia at day 1 (5 (50%) vs 2 (18%) p = 0.18). Interleukin (IL)-6 plasma levels at randomization were low (< 100 pg/mL) in 10 (48%) patients and elevated (> 1000 pg/mL) in 6 (29%). The median relative reduction in IL-6 at 48 h was 75% (60, 94) in the HA group versus 5% (- 47, 70) in the SOC group (p = 0.06). In CA survivors at risk of PCAS, HA was feasible, safe and was associated with a nonsignificant reduction in cytokine plasma levels. Future trials are needed to further define the role of HA after CA. Those studies should include cytokine assessment to enrich the study population. NCT03523039, registered 14 May 2018

The 2005 July Superoutburst of the Dwarf Nova 2QZ J021927.9-304545: the SU UMa Nature Confirmed

We report on time-resolved photometry of the 2005 July superoutburst of the dwarf nova, 2QZ J021927.9-304545. The resultant light curves showed conspicuous superhumps with a period of 0.081113(19) days, confirming the SU UMa nature of the object. Although we missed the maximum phase of the outburst, the amplitude of the superoutburst well exceeded 5 mag. This value is slightly larger than that of typical SU UMa-type dwarf novae. The superhump period decreased as time elapsed, as can be seen in most SU UMa-type dwarf novae. Based on the archive of ASAS-3, the recurrence time of a superoutburst of the variable turned out to be about 400 days. This value is typical of well known SU UMa stars. The distance to this system was roughly estimated as 370(+20, -60) pc using an empirical relation.Comment: 6 pages, 7 figures, accepted for publication in PAS