Models for the soft X-ray emission of post-outburst classical novae

A hydrostatic and stationary white dwarf envelope model has been developed for the study of the post-outburst phases of classical novae and their soft X-ray emission. Several white dwarf masses and chemical compositions typical for classical novae have been considered. The results show that the luminosity, maximum effective temperature and envelope masses depend on the white dwarf mass and on the chemical composition. Envelope masses for which equilibrium solutions exist are pretty small ~10^{-7}-10^{-6} Msun, thus leading to a short duration of the soft X-ray emitting phase of classical novae, in agreement with most of the observations. The models presented provide a useful tool for the determination of the white dwarf properties from observable parameters in the X-ray range.Comment: 15 pages, 11 figures, 2 tables, accepted for publication in Astronomy & Astrophysic

V5116 Sgr, an Eclipsing Supersoft Post-Outburst Nova?

V5116 Sgr (Nova Sgr 2005 No. 2), discovered on 2005 July 4, was observed with XMM-Newton in March 2007, 20 months after the optical outburst. The X-ray spectrum shows that the nova had evolved to a pure supersoft X-ray source, with no significant emission at energies above 1 keV. The X-ray light-curve shows abrupt decreases and increases of the flux by a factor ~8. It is consistent with a periodicity of 2.97 h, the orbital period suggested by Dobrotka et al. (2007), although the observation lasted just a little more than a whole period. We estimate the distance to V5116 Sgr to be 11+/-3 kpc. A simple blackbody model does not fit correctly the EPIC spectra, with reduced chi^2>4. In contrast, ONe rich white dwarf atmosphere models provide a good fit, with nH=1.3(+/-0.1)e21 cm^-2, T=6.1(+/-0.1)e5 K, and L=3.9(+/-0.8)e37(D/10kpc)^2 erg/s (during the high-flux periods). This is consistent with residual hydrogen burning in the white dwarf envelope. The white dwarf atmosphere temperature is the same both in the low and the high flux periods, ruling out an intrinsic variation of the X-ray source as the origin of the flux changes. We speculate that the X-ray light-curve may result from a partial coverage by an asymmetric accretion disk in a high inclination system.Comment: 2 figures, emulateapj, to appear in ApJ

Dos fermalls i altres joies d'Alfons el Magnànim, segons un inventari de la Taula de Canvi de la ciutat de Barcelona

Translation de l’ inventaire d’une série de bijoux du roi Alfons el Magnànim, celui qui fut deposé a “La Taula de Canvi” de la ville de Barcelone, le l8 de mai de l429 et elle fut retiré cinc mois aprés. L’inventaire nous donne une description trés précise de chacun des bijoux: forme, composition avec indication de pierres précieuses et perles, poids et valoration. Parmi eux, on souligne les deux fermaux et l’importance qui eurent au Moyen- Âge, comme indiquent les documents, textes littéraires et l’iconographie

The supersoft X-ray source in V5116 Sagittarii: I. the high resolution spectra

Context. Classical nova explosions occur on the surface of an accreting white dwarf in a binary system. After ejection of a fraction of the envelope and when the expanding shell becomes optically thin to X-rays, a bright source of supersoft X-rays arises, powered by residual H burning on the surface of the white dwarf. While the general picture of the nova event is well established, the details and balance of accretion and ejection processes in classical novae are still full of unknowns. The long-term balance of accreted matter is of special interest for massive accreting white dwarfs, which may be promising supernova Ia progenitor candidates. Nova V5116 Sgr 2005b was observed as a bright and variable supersoft X-ray source by XMM-Newton in March 2007, 610 days after outburst. The light curve showed a periodicity consistent with the orbital period. During one third of the orbit the luminosity was a factor of seven brighter than during the other two thirds of the orbital period. Aims. In the present work we aim to disentangle the X-ray spectral components of V5116 Sgr and their variability. Methods. We present the high resolution spectra obtained with XMM-Newton RGS and Chandra LETGS/HRC-S in March and August 2007. Results. The grating spectrum during the periods of high-flux shows a typical hot white dwarf atmosphere dominated by absorption lines of N VI and N VII. During the low-flux periods, the spectrum is dominated by an atmosphere with the same temperature as during the high-flux period, but with several emission features superimposed. Some of the emission lines are well modeled with an optically thin plasma in collisional equilibrium, rich in C and N, which also explains some excess in the spectra of the high-flux period. No velocity shifts are observed in the absorption lines, with an upper limit set by the spectral resolution of 500 km s-1, consistent with the expectation of a non-expanding atmosphere so late in the evolution of the post-nova.Postprint (published version

Body image, aging, and identity in women over 50: The Gender and Body Image (GABI) study

We conducted a qualitative study of 1,849 women over age 50 to capture the thoughts, feelings, and attitudes that women at middle age have about their bodies and the experience of aging. Via an open-ended question online survey, four primary themes emerged: 1) the physical and psychological experience of aging; 2) the injustices, inequities, and challenges of aging; 3) the importance of self-care; and 4) a plea for recognition of the need to maintain a contributory role in society. Results highlight the complexities of women’s psychological and physical aspects of aging and point toward important topics worthy of further study in this growing population

The orbital period of the recurrent nova V2487 Oph revealed

We present the first reliable determination of the orbital period of the recurrent nova V2487 Oph (Nova Oph 1998). We derived a value of $0.753 \pm 0.016$ d ($18.1 \pm 0.4$ h) from the radial velocity curve of the intense He II $\lambda$4686 emission line as detected in time-series X-shooter spectra. The orbital period is significantly shorter than earlier claims, but it makes V2487 Oph one of the longest period cataclysmic variables known. The spectrum of V2487 Oph is prolific in broad Balmer absorptions that resemble a white dwarf spectrum. However, we show that they come from the accretion disc viewed at low inclination. Although highly speculative, the analysis of the radial velocity curves provides a binary mass ratio $q \approx 0.16$ and a donor star mass $M_2 \approx 0.21$ M$_\odot$, assuming the reported white dwarf mass $M_1 = 1.35$ M$_\odot$. A subgiant M-type star is tentatively suggested as the donor star. We were lucky to inadvertently take some of the spectra when V2487 Oph was in a flare state. During the flare, we detected high-velocity emission in the Balmer and He II $\lambda$4686 lines exceeding $-2000$ km s$^{-1}$ at close to orbital phase 0.4. Receding emission up to $1200$ km s$^{-1}$ at about phase 0.3 is also observed. The similarities with the magnetic cataclysmic variables may point to magnetic accretion on to the white dwarf during the repeating flares.Comment: Accepted for publication in MNRAS (October 9, 2023

High growth potential of long-term starved deep ocean opportunistic heterotrophic bacteria

Experiments with bacteria in culture have shown that they often display “feast and famine” strategies that allow them to respond with fast growth upon pulses in resource availability, and enter a growth-arrest state when resources are limiting. Although feast responses have been observed in natural communities upon enrichment, it is unknown whether this blooming ability is maintained after long periods of starvation, particularly in systems that are energy limited like the bathypelagic ocean. Here we combined bulk and single-cell activity measurements with 16S rRNA gene amplicon sequencing to explore the response of a bathypelagic community, that had been starved for 1.6 years, to a sudden organic carbon supply. We observed a dramatic change in activity within 30 h, with leucine incorporation rates increasing over two orders of magnitude and the number of translationally active cells (mostly Gammaproteobacteria) increasing 4-fold. The feast response was driven by a single operational taxonomic unit (OTU) affiliated with the Marinobacter genus, which had remained rare during 7 months of starvation. Our work suggests that bathypelagic communities harbor a seed bank of highly persistent and resourceful “feast and famine” strategists that might disproportionally contribute to carbon fluxes through fast responses to occasional pulses of organic matter