Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userLife after eruption - VI. Recovery of the old novae EL Aql, V606 Aql, V908 Oph, V1149 Sgr, V1583 Sgr and V3964 Sgr
91
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report on the recovery of the six old novae EL Aql, V606 Aql, V908 Oph, V1149 Sgr, V1583 Sgr and V3964 Sgr, using photometric and spectroscopic data. Analysing several properties, we find that EL Aql is a good candidate for an intermediate polar. Furthermore, the system inclination of EL Aql, V606 Aql, V1583 Sgr and V3964 Sgr appears to be sufficiently high to suggest them as good targets for time series observations. We also eliminate some previously suggested candidates for the post-novae V1301 Aql and V1151 Sgr.
rate research
Read More
We report spectroscopic observations of the resonance lines of singly ionized $^{7}$Be in the blue-shifted absorption line systems found in the post-outburst spectra of two classical novae -- V5668 Sgr (Nova Sagittarii 2015 No.2) and V2944 Oph (Nova Ophiuchi 2015). The unstable isotope, $^{7}$Be, should has been created during the thermonuclear runaway (TNR) of these novae and decays to form $^{7}$Li within a short period (a half-life of 53.22 days). Confirmations of $^{7}$Be are the second and the third ones following the first case found in V339 Del by Tajitsu et al. (2015). The blue-shifted absorption line systems in both novae are clearly divided into two velocity components, both of which contain $^{7}$Be. This means that the absorbing gases in both velocity components consist of products of TNR. We estimate amounts of $^{7}$Be produced during outbursts of both novae and conclude that significant $^{7}$Li should have been created. These findings strongly suggest that the explosive production of $^{7}$Li via the reaction $^{3}$He($alpha$,$gamma$)$^{7}$Be and subsequent decay to $^{7}$Li occurs frequently among classical novae and contributes to the process of the Galactic Li enrichment.
The impact of nova eruptions on the long-term evolution of Cataclysmic Variables(CVs) is one of the least understood and intensively discussed topics in the field. Acrucial ingredient to improve with this would be to establish a large sample of post-novae with known properties, starting with the most easily accessible one, the orbitalperiod. Here we report new orbital periods for six faint novae: X Cir (3.71 h), ILNor (1.62 h), DY Pup (3.35 h), V363 Sgr (3.03 h), V2572 Sgr (3.75 h) and CQ Vel(2.7 h). We furthermore revise the periods for the old novae OY Ara, RS Car, V365Car, V849 Oph, V728 Sco, WY Sge, XX Tau and RW UMi. Using these new dataand critically reviewing the trustworthiness of reported orbital periods of old novae inthe literature, we establish an updated period distribution. We employ a binary-starevolution code to calculate a theoretical period distribution using both an empiricaland the classical prescription for consequential angular momentum loss. In comparisonwith the observational data we find that both models especially fail to reproduce thepeak in the 3 - 4 h range, suggesting that the angular momentum loss for CVs abovethe period gap is not totally understood.
V350 Sgr is a classical Cepheid suitable for mass determination. It has a hot companion which is prominent in the ultraviolet and which is not itself a binary. We have obtained two high resolution echelle spectra of the companion at orbital velocity maximum and minimum with the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) in the 1320 to 1510 AA/ region. By cross-correlating these spectra we obtained the orbital velocity amplitude of the companion with an uncertainty in the companion amplitude of 1.9 km sec$^{-1}$. This provides a mass ratio of the Cepheid to the companion of 2.1. The ultraviolet energy distribution of the companion provides the mass of the companion, yielding a Cepheid mass of 5.2 $pm$ 0.3 M$_odot$. This mass requires some combination of moderate main sequence core convective overshoot and rotation to match evolutionary tracks.
Spectral and timing studies of Suzaku ToO observations of two SGRs, 1900+14 and 1806-20, are presented. The X-ray quiescent emission spectra were well fitted by a two blackbody function or a blackbody plus a power law model. The non-thermal hard component discovered by INTEGRAL was detected by the PIN diodes and its spectrum was reproduced by the power law model reported by INTEGRAL. The XIS detected periodicity P = 5.1998+/-0.0002 s for SGR 1900+14 and P = 7.6022+/-0.0007 s for SGR 1806-20. The pulsed fraction was related to the burst activity for SGR 1900+14.
BVRI photometry and low-, medium- and high-resolution Echelle fluxed spectroscopy is presented and discussed for three faint, heavily reddened novae of the FeII-type which erupted in 2013. V1830 Aql reached a peak V=15.2 mag on 2013 Oct 30.3 UT and suffered from a huge E(B-V)~2.6 mag reddening. After a rapid decline, when the nova was Delta(V)=1.7 mag below maximum, it entered a flat plateau where it remained for a month until Solar conjunction prevented further observations. Similar values were observed for V556 Ser, that peaked near Rc=12.3 around 2013 Nov 25 and soon went lost in the glare of sunset sky. V809 Cep peaked at V=11.18 on 2013 Feb 3.6. The reddening is E(B-V)~1.7 and the nova is located within or immediately behind the spiral Outer Arm, at a distance of ~6.5 kpc as constrained by the velocity of interstellar atomic lines and the rate of decline from maximum. While passing at t_3, the nova begun to form a thick dust layer that caused a peak extinction of Delta(V)>5 mag, and took 125 days to completely dissolve. The dust extinction turned from neutral to selective around 6000 Ang. Monitoring the time evolution of the integrated flux of emission lines allowed to constrain the region of dust formation in the ejecta to be above the region of formation of OI 7774 Ang and below that of CaII triplet. Along the decline from maximum and before the dust obscuration, the emission line profiles of Nova Cep 2013 developed a narrow component (FWHM=210 km/sec) superimposed onto the much larger normal profile, making it a member of the so far exclusive but growing club of novae displaying this peculiar feature. Constrains based on the optical thickness of the innermost part of the ejecta and on the radiated flux, place the origin of the narrow feature within highly structured internal ejecta and well away from the central binary.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
