Context. The structure of the wind from the cool giants in symbiotic binaries carries important information for understanding the wind mass transfer to their white dwarf companions, its fuelling, and ...thus the path towards different phases of symbiotic-star evolution. Aims. In this paper, we indicate a non-spherical distribution of the neutral wind zone around the red giant (RG) in the symbiotic binary star, EG And. We concentrate in particular on the wind focusing towards the orbital plane and its asymmetry alongside the orbital motion of the RG. Methods. We achieved this aim by analysing the periodic orbital variations of fluxes and radial velocities of individual components of the Hα and O III λ5007 lines observed on our high-cadence medium (R ∼ 11 000) and high-resolution (R ∼ 38 000) spectra. Results. The asymmetric shaping of the neutral wind zone at the near-orbital-plane region is indicated by: (i) the asymmetric course of the Hα core emission fluxes along the orbit; (ii) the presence of their secondary maximum around the orbital phase φ = 0.1, which is possibly caused by the refraction effect; and (iii) the properties of the Hα broad wing emission originating by Raman scattering on H0 atoms. The wind is substantially compressed from polar directions to the orbital plane as constrained by the location of the O III λ5007 line emission zones in the vicinity of the RG at/around its poles. The corresponding mass-loss rate from the polar regions of ≲10−8 M⊙ yr−1 is a factor of ≳10 lower than the average rate of ≈10−7 M⊙ yr−1 derived from nebular emission of the ionised wind from the RG. Furthermore, it is two orders of magnitude lower than that measured in the near-orbital-plane region from Rayleigh scattering. Conclusions. The startling properties of the nebular O III λ5007 line in EG And provides an independent indication of the wind focusing towards the orbital plane – the key to understanding the efficient wind mass transfer in symbiotic binary stars.
Abstract
We report the Fermi LAT
γ
-ray detection of the 2021 outburst of the symbiotic recurrent nova RS Ophiuchi. In this system, unlike classical novae from cataclysmic binaries, the ejecta from ...the white dwarf form shocks when interacting with the dense circumstellar wind environment of the red giant companion. We find the LAT spectra from 50 MeV to ∼20–23 GeV, the highest-energy photons detected in some subintervals, are consistent with
π
0
-decay emission from shocks in the ejecta as proposed by Tatischeff & Hernanz for its previous 2006 outburst. The LAT light curve displayed a fast rise to its peak >0.1 GeV flux of ≃6 × 10
−6
ph cm
−2
s
−1
beginning on day 0.745 after its optically constrained eruption epoch of 2021 August 8.50. The peak lasted for ∼1 day and exhibited a power-law decline up to the final LAT detection on day 45. We analyze the data on shorter timescales at early times and found evidence of an approximate doubling of emission over ∼200 minutes at day 2.2, possibly indicating a localized shock-acceleration event. Comparing the data collected by the American Association of Variable Star Observers, we measured a constant ratio of ∼ 2.8 × 10
−3
between the
γ
-ray and optical luminosities except for a ∼5×smaller ratio within the first day of the eruption likely indicating attenuation of
γ
rays by ejecta material and lower high-energy proton fluxes at the earliest stages of the shock development. The hard X-ray emission due to bremsstrahlung from shock-heated gas traced by the Swift-XRT 2–10 keV light curve peaked at day ∼6, later than at GeV and optical energies. Using X-ray derived temperatures to constrain the velocity profile, we find the hadronic model reproduces the observed >0.1 GeV light curve.
ABSTRACT
Symbiotic stars belong to a group of interacting binaries that display a wide variety of phenomena, including prominent outbursts connected with mass transfer, as well as stellar winds, ...jets, eclipses, or intrinsic variability of the components. Dozens of new symbiotic stars and candidates have been discovered in recent years. However, there are many objects that are still poorly studied. Some symbiotic candidates suspected in the literature have never been studied spectroscopically. In this contribution, we present the first results of the ongoing campaign focused on symbiotic candidates. In the first paper in the series, we study the nature of 10 candidate classical symbiotic stars suspected based on their photometric behaviour, colours or abundance pattern. To confirm or reject the symbiotic nature of the studied candidates, we obtained new spectra and analysed them in detail together with available multifrequency photometric and spectroscopic observations of the objects. Hen 3−860 and V2204 Oph are genuine symbiotic systems showing typical spectral features of burning symbiotic stars and outbursts in the last 100 yr. The first object belongs to the uncommon group of eclipsing symbiotic stars. V1988 Sgr cannot be classified as a genuine burning symbiotic star, but the scenario of an accreting-only symbiotic system cannot be ruled out. Hen 4−204 might be a bonafide symbiotic star due to its similarity with the known symbiotic binary BD Cam. Six other symbiotic candidates (V562 Lyr, IRAS 19050+0001, EC 19249−7343, V1017 Cyg, PN K1−6, V379 Peg) are either single dwarf or giant stars or non-symbiotic binaries.
Context. Classical novae are the product of thermonuclear runaway-initiated explosions occurring on accreting white dwarfs. Aims. V339 Del (Nova Delphinus 2013) was one of the brightest classical ...novae of the last hundred years. Spectroscopy and photometry are available from γ-rays through infrared at stages that have frequently not been observed well. The complete data set is intended to provide a benchmark for comparison with modeling and for understanding more sparsely monitored historical classical and recurrent novae. This paper is the first in the series of reports on the development of the nova. We report here on the early stages of the outburst, through the X-ray active stage. Methods. A time sequence of optical, flux calibrated high resolution spectra was obtained with the Nordic Optical Telescope (NOT) using FIES simultaneously, or contemporaneously, with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope during the early stages of the outburst. These were supplemented with Mercator/HERMES optical spectra. High resolution IUE ultraviolet spectra of OS And 1986, taken during the Fe curtain phase, served as a template for the distance determination. We used standard plasma diagnostics (e.g., O III and N II line ratios, and the Hβ line flux) to constrain electron densities and temperatures of the ejecta. Using Monte Carlo modeling of the ejecta, we derived the structure, filling factor, and mass from comparisons of the optical and ultraviolet line profiles. Results. We derive an extinction of E(B − V) = 0.23 ± 0.05 from the spectral energy distribution, the interstellar absorption, and H I emission lines. The distance, about 4−4.5 kpc, is in agreement with the inferred distance from near infrared interferometry. The maximum velocity was about 2500 km s-1, measured from the UV resonance and optical profiles. The ejecta showed considerable fine structure in all transitions, much of which persisted as emission knots. The line profiles were modeled using a bipolar conical structure for the ejecta within a relatively restricted range of parameters. For V339 Del, we find that an inclination to the line of sight of about 35°−55°, an opening angle of 60°−80°, and an inner radius ΔR/R(t) ≈ 0.3 based on vrad,max matches the permitted and intercombination lines. The filling factor is f ≈ 0.1, and the derived range in the ejecta mass is (2−3) × 10-5M⊙.
Context. AG Peg is known as the slowest symbiotic nova, which experienced its nova-like outburst around 1850. After 165 yr, during June of 2015, it erupted again showing characteristics of the Z ...And-type outburst. Aims. The primary objective is to determine basic characteristics, the nature and type of the 2015 outburst of AG Peg. Methods. We achieved this aim by modelling the spectral energy distribution using low-resolution spectroscopy (330–750 nm; R = 500–1000), medium-resolution spectroscopy (420–720 nm; R ~ 11 000), and UBVRCIC photometry covering the 2015 outburst with a high cadence. Optical observations were complemented with the archival HST and FUSE spectra from the preceding quiescence. Results. During the outburst, the luminosity of the hot component was in the range of 2–11 × 1037 (d/ 0.8 kpc)2 erg s-1, being in correlation with the light curve (LC) profile. To generate the maximum luminosity by the hydrogen burning, the white dwarf (WD) had to accrete at ~ 3 × 10-7 M⊙ yr-1, which exceeds the stable-burning limit and thus led to blowing optically thick wind from the WD. We determined its mass-loss rate to a few × 10-6 M⊙ yr-1. At the high temperature of the ionising source, 1.5–2.3 × 105 K, the wind converted a fraction of the WD’s photospheric radiation into the nebular emission that dominated the optical. A one order of magnitude increase of the emission measure, from a few × 1059 (d/ 0.8 kpc)2 cm-3 during quiescence, to a few × 1060 (d/ 0.8 kpc)2 cm-3 during the outburst, caused a 2 mag brightening in the LC, which is classified as the Z And-type of the outburst. Conclusions. The very high nebular emission and the presence of a disk-like H i region encompassing the WD, as indicated by a significant broadening and high flux of the Raman-scattered O vi 6825 Å line during the outburst, is consistent with the ionisation structure of hot components in symbiotic stars during active phases.
Aims. We determine the temporal evolution of the luminosity (LWD), radius (RWD) and effective temperature (Teff) of the white dwarf (WD) pseudophotosphere of V339 Del from its discovery to around day ...40. Another main objective was studying the ionization structure of the ejecta. Methods. These aims were achieved by modelling the optical/near-IR spectral energy distribution (SED) using low-resolution spectroscopy (3500–9200 Å), UBVRCIC and JHKLM photometry. Important insights in the physical conditions of the ejecta were gained from an analysis of the evolution of the Hα and Raman-scattered 6825 Å O vi line using medium-resolution spectroscopy (R ~ 10 000). Results. During the fireball stage (Aug. 14.8–19.9, 2013), Teff was in the range of 6000–12 000 K, RWD was expanding non-uniformly in time from ~66 to ~300 (d/ 3 kpc) R⊙, and LWD was super-Eddington, but not constant. Its maximum of ~9 × 1038 (d/ 3 kpc)2 erg s-1 occurred around Aug. 16.0, at the maximum of Teff, half a day before the visual maximum. After the fireball stage, a large emission measure of 1.0−2.0 × 1062 (d/ 3 kpc)2 cm-3 constrained the lower limit of LWD to be well above the super-Eddington value. The mass of the ionized region was a few × 10-4 M⊙, and the mass-loss rate was decreasing from ~5.7 (Aug. 22) to ~0.71 × 10-4 M⊙ yr-1 (Sept. 20). The evolution of the Hα line and mainly the transient emergence of the Raman-scattered O vi 1032 Å line suggested a biconical ionization structure of the ejecta with a disk-like H i region persisting around the WD until its total ionization, around day 40. On Sept. 20 (day 35), the model SED indicated a dust emission component in the spectrum. The dust was located beyond the H i zone, where it was shielded from the hard, ≳105 K, radiation of the burning WD at that time. Conclusions. Our extensive spectroscopic observations of the classical nova V339 Del allowed us to map its evolution from the very early phase after its explosion. It is evident that the nova was not evolving according to the current theoretical prediction. The unusual non-spherically symmetric ejecta of nova V339 Del and its extreme physical conditions and evolution during and after the fireball stage represent interesting new challenges for the theoretical modelling of the nova phenomenon.
Our previous results demonstrated that expressing the GTPase ras homolog gene family, member B (RhoB) in radiosensitive NIH3T3 cells increases their survival following 2 Gy irradiation (SF2). We have ...first demonstrated here that RhoB expression inhibits radiation-induced mitotic cell death. RhoB is present in both a farnesylated and a geranylgeranylated form in vivo. By expressing RhoB mutants encoding for farnesylated (RhoB-F cells), geranylgeranylated or the CAAX deleted form of RhoB, we have then shown that only RhoB-F expression was able to increase the SF2 value by reducing the sensitivity of these cells to radiation-induced mitotic cell death. Moreover, RhoB-F cells showed an increased G2 arrest and an inhibition of centrosome overduplication following irradiation mediated by the Rho-kinase, strongly suggesting that RhoB-F may control centrosome overduplication during the G2 arrest after irradiation. Overall, our results for the first time clearly implicate farnesylated RhoB as a crucial protein in mediating cellular resistance to radiation-induced nonapoptotic cell death.
Context.
The structure of the wind from the cool giants in symbiotic binaries carries important information for understanding the wind mass transfer to their white dwarf companions, its fuelling, and ...thus the path towards different phases of symbiotic-star evolution.
Aims.
In this paper, we indicate a non-spherical distribution of the neutral wind zone around the red giant (RG) in the symbiotic binary star,
EG And
. We concentrate in particular on the wind focusing towards the orbital plane and its asymmetry alongside the orbital motion of the RG.
Methods.
We achieved this aim by analysing the periodic orbital variations of fluxes and radial velocities of individual components of the H
α
and O
III
λ
5007 lines observed on our high-cadence medium (
R
∼ 11 000) and high-resolution (
R
∼ 38 000) spectra.
Results.
The asymmetric shaping of the neutral wind zone at the near-orbital-plane region is indicated by: (i) the asymmetric course of the H
α
core emission fluxes along the orbit; (ii) the presence of their secondary maximum around the orbital phase
φ
= 0.1, which is possibly caused by the refraction effect; and (iii) the properties of the H
α
broad wing emission originating by Raman scattering on H
0
atoms. The wind is substantially compressed from polar directions to the orbital plane as constrained by the location of the O
III
λ
5007 line emission zones in the vicinity of the RG at/around its poles. The corresponding mass-loss rate from the polar regions of ≲10
−8
M
⊙
yr
−1
is a factor of ≳10 lower than the average rate of ≈10
−7
M
⊙
yr
−1
derived from nebular emission of the ionised wind from the RG. Furthermore, it is two orders of magnitude lower than that measured in the near-orbital-plane region from Rayleigh scattering.
Conclusions.
The startling properties of the nebular O
III
λ
5007 line in
EG And
provides an independent indication of the wind focusing towards the orbital plane – the key to understanding the efficient wind mass transfer in symbiotic binary stars.
The Compact Muon Solenoid (CMS) experiment prepares its Phase-2 upgrade for the high-luminosity era of the LHC operation (HL-LHC). Due to the increase of occupancy, trigger latency and rates, the ...full electronics of the CMS Drift Tube (DT) chambers will need to be replaced. In the new design, the time bin for the digitization of the chamber signals will be of around 1 ns, and the totality of the signals will be forwarded asynchronously to the service cavern at full resolution. The new backend system will be in charge of building the trigger primitives of each chamber. These trigger primitives contain the information at chamber level about the muon candidates position, direction, and collision time, and are used as input in the L1 CMS trigger. The added functionalities will improve the robustness of the system against ageing. An algorithm based on analytical solutions for reconstructing the DT trigger primitives, called Analytical Method, has been implemented both as a software C++ emulator and in firmware. Its performance has been estimated using the software emulator with simulated and real data samples, and through hardware implementation tests. Measured efficiencies are 96 to 98% for all qualities and time and spatial resolutions are close to the ultimate performance of the DT chambers. A prototype chain of the HL-LHC electronics using the Analytical Method for trigger primitive generation has been installed during Long Shutdown 2 of the LHC and operated in CMS cosmic data taking campaigns in 2020 and 2021. Results from this validation step, the so-called Slice Test, are presented.
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