The spectroscopic evolution of V2467 Cyg (Nova Cygni 2007) in the first months after the outburst

We present the spectroscopy of nova V2467 Cyg acquired at the Loiano Observatory, Italy, during the first six months after the outburst. We have used the optical spectroscopy to study the physical properties of the ejected material and the photometry to estimate the nova distance. V2467 Cyg is a fast nova, with decline rates by two or three magnitudes of 7.6 and 14.6 days respectively. The light curve exhibited oscillations during the transition stage. The nova achieved an absolute magnitude at maximum in the range –8.5… –9.1. The distance is in the range 2.6… 3.6 kpc. V2467 Cyg showed an early appearance of forbidden lines during the transition stage. Its evolution is similar to the behavior of V1494 Aql (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The early spectroscopic evolution of nova V458 Vul (Nova Vulpeculae 2007)

The early spectral evolution of the nova V458 Vul has been monitored at the Loiano Observatory, Italy. The nova exhibited a couple of oscillations during the decline from initial maximum. We have performed spectroscopic observations to study the physical properties of the ejected material. The photometric light curve has been used to derive the nova distance and its absolute magnitude at maximum. V458 Vul is a fast nova, with decline rates by two or three magnitudes of 7 and 15 days respectively. The magnitude at maximum is M _V =?8.8. The nova distance is in the range 6.7–10.3 kpc. The spectra secured a few days after initial maximum showed emission lines of H I and Fe II, making V458 Vul a Fe II nova at this stage. After the oscillations V458 Vul came back to a standard decline curve, but evolved towards the He/N class. Thus V458 Vul is a hybrid nova.     

An analysis of the spectra and light curve of Nova Centauri 1995

The light curve and spectra of Nova Centauri 1995 (V888 Cen) are analysed. The spectra were obtained a few days post-maximum. The nova is found to be a very fast nova, declining by 2 mag within about 5±2 d of maximum. The light curve shows strong oscillations in the transition region, of peak-to-peak amplitude about 1.5 mag and period 12–15 d. The light curve of Nova Centauri resembles closely that of Nova Aquilae 1918 (V603 Aql).
The early blue and red spectra obtained at Mt John show broad emission lines, many with P Cygni profiles. The absorption lines are found in two velocity systems at about −1765 and −3010 km s⁻¹, in respectively the principal and diffuse-enhanced stages of spectral development, as defined by McLaughlin. Nova Centauri has many Fe  ii lines in emission, indicating that it is a member of the Williams Fe  ii class of classical novae.     

Spectral evolution of the classical symbiotic star V1413 Aql during a new activity cycle

We present the results of our spectroscopic observations for the classical symbiotic star V1413 Aql performed in 2008–2011. Various states of the hot component are considered: almost quiescence in 2008, very slow outburst onset in 2009, outburst maximum in 2010, and gradual brightness decline in the erupted hot component in 2011. We have established that, according to a spectroscopic criterion, in 2008 the system was in quiescence. We have shown that the parameters of the hot component during its outburst can be determined only by modeling the differences of the spectra taken at different eclipse phases. The active hot component of V1413 Aql at the outburst maximum is shown to have had the record late (for a symbiotic star) spectral type K2. At various stages of the new activity cycle, we have modeled the continuumenergy distribution based on a standard three-componentmodel, a model including a standard accretion disk and a red giant, and amodel including a supergiant (of various spectral types) and a red giant. The parameters of the system’s components have been determined.     

The absorption and emission spectrum of the magnetic Herbig Ae star HD 190073

We determine abundances from the absorption spectrum of the magnetic Herbig Ae star HD 190073 (V1295 Aql). The observations are primarily from HARPS spectra obtained at a single epoch. We accept arguments that the presence of numerous emission lines does not vitiate a classical abundance analysis, though it likely reduces the achievable accuracy. Most abundances are closely solar, but several elements show departures of a factor of two to three, as an earlier study has also shown. We present quantitative measurements of more than 60 emission lines, peak intensities, equivalent widths, and FWHM's. The latter range from over 200 km s^–1(Hα, He D₃) down to 10–20 km s^–1(forbidden lines). Metallic emission lines have intermediate widths. We eschew modeling, and content ourselves with a presentation of the observations a successful model must explain. Low‐excitation features such as the Na I D‐lines and [O I] appear with He I D₃, suggesting proximate regions with widely differing T_e and N_e as found in the solar chromosphere. The [O I] and [Ca II] lines show sharp, violet‐shifted features. Additionally, [Fe II] lines appear tobe weakly present in emission (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the further observations ofB E /shell star V 923 Aql

V 923 Aql is one of the candidateB _E stars to be a binary star. In this research, optical and near-infrared spectral measurements of V 923 Aql is presented. V 923 Aql presents variable H Balmer line profiles with shell components. H profiles present R/V, E/C and radial velocity variation. Shell parameters of the envelope are calculated.Near infra-red and optical spectra obtained from Haute-Provence Observatory and bibliographic data obtained from SIMBAD database of C.D.S., Strasbourg Observatory, France.     

A photometric and spectroscopic study of the binary V1430 Aql

We present the first infrared light curves of the binary V1430 Aql, in the bands J and K, plus V, R and I light curves and spectra covering the ranges of H_β, H_α and Ca II-IRT lines. Our VRIJK data, together with published radial velocity curves, are analyzed to determine the orbital and stellar parameters of the system. Both stellar components present spectroscopic evidence of chromospheric activity, with emission excesses in the H_β, H_α and Ca II-IRT lines. The measured ratio of the lines H_β/H_α emission excesses can be interpreted as originated in plages. Our light curves also show photometric evidence of cool spots at least on one of the stars.     

Spectroscopic studies of three novae

We present our spectroscopic observations of the novae V1425, V1493, and V1494 Aql carried out with the 125-cm telescope at the Crimean Station of the Sternberg Astronomical Institute in the wavelength range 4000–11000 Å. We measured the emission-line intensities, determined the nova shell expansion velocities from the line profile FWHMs and components, and estimated the interstellar reddening from the first members of the Balmer series. The chemical composition of the nova shells is analyzed. Nitrogen and oxygen were found to be overabundant in V1425 and V1494 Aql; the helium abundance turned out to be normal in the two stars.     

CK Vul: reborn perhaps, but not hibernating

It has been claimed that CK Vul (the remnant of Nova Vul 1670) may be the oldest recovered 'old nova' and as such provides evidence in support of the hibernation scenario for classical nova systems. However this interpretation has been challenged. We present 450- and 850-μm photometry of CK Vul which cast further doubt on its old nova status. It displays a large far infrared-submillimetre flux excess, inconsistent with the properties of an old nova. Furthermore, IRAS images show that CK Vul is located in a 'cavity' in the infrared emission, a feature often associated with planetary nebulae. It seems more likely that CK Vul – and hence Nova Vul 1670 – is (like V605 Aql and V4334 Sgr) an evolved star in the throes of a final thermal pulse.     

On nova Scorpii 2007 N.1 (V1280 Sco)

We present the results of our photometric and spectroscopic observations of Nova Sco 2007 N.1 (V1280 Sco). The photometric data was represented by a single data point in the light curve since the observation was carried out only for one night. The spectra cover two different phases of the object’s evolution during the outburst, i.e. pre-maximum and post-maximum. Measurements of the P-Cygni profile on Na I ‘D’ line (5889 Å) was derived as the velocity of shell expansion, yielding 1567.43±174.14 km s^?1. We conclude that V1280 Sco is a fast Fe II-type nova.     

Near-infrared observations of the novae V2491 Cygni and V597 Puppis

We present results obtained from near-infrared JHK spectroscopic observations of novae V2491 Cygni and V597 Puppis in the early declining phases of their 2007 and 2008 outbursts, respectively. In both objects, the spectra displayed emission lines of H  i , O  i , He  i and N  i . In V597 Pup, the He  i lines were found to strengthen rapidly with time. Based on the observed spectral characteristics, both objects are classified as He/N novae. We have investigated the possibility of V2491 Cyg being a recurrent nova as has been suggested. By studying the temporal evolution of the linewidths in V2491 Cyg, it appears unlikely that the binary companion is a giant star with heavy wind as in recurrent novae of the RS Oph type. Significant deviations from that of recombination case B conditions are observed in the strengths of the H  i lines. This indicates that the H  i lines, in both novae, are optically thick during the span of our observations. The slope of the continuum spectra in both cases was found to have a  λ^−(3−3.5)  dependence which deviates from a Rayleigh–Jeans spectral distribution. Both novae were detected in the post-outburst supersoft X-ray phase; V2491 Cyg being very bright in X-rays has been the target of several observations. We discuss and correlate our infrared observations with the observed X-ray properties of these novae.     

Episodic absorption in the outflow of the old nova V603 Aquilae

We report on the time-dependent behaviour of ultraviolet spectral lines in Hubble Space Telescope Goddard High-Resolution Spectrograph data of the classical nova V603 Aql. In particular, episodic blueshifted absorption (extending to ∼−2500 km s⁻¹) is present, with a variability time-scale down to ∼1 min. The data provide a rare opportunity to study the rapid evolution of absorption structures that may be associated with accretion-disc winds in cataclysmic variables. At least three absorption events are recorded (at blueward velocities only) over ∼5 h, each lasting ∼10–15 min. The derived velocity, acceleration and optical depth properties provide an empirical picture of stochastically variable structures in the outflow, with no evidence for short-term (less than ∼1 h) cyclic or modulated behaviour in the overall absorption properties. In contrast, the emission components of the ultraviolet resonance lines are very stable in velocity and strength in this low-inclination system. On at least two occasions there is an intriguing short-term 'flare' in the ultraviolet continuum flux (of up to ∼40 per cent). Though there is no clear one-to-one relation in these data between the continuum fluctuations and the occurrence of the absorption events, the time-scales for the two variable phenomena are essentially the same. The irregular absorption episodes in the ultraviolet data of V603 Aql presently defy a clear physical interpretation. Their overall characteristics are discussed in the context of instabilities in radiation-pressure-driven disc winds.     

The early spectroscopy of V2670 Oph (Nova Oph 2008)

We report the spectroscopic observations of nova V2670 Oph secured at the Loiano Observatory, Italy, 39 days after the outburst. The spectra of V2670 Oph showed auroral lines, suggesting that ionization was increasing. V2670 Oph is a fast nova, with a decline rate by three magnitudes of 42 days. We have estimated the absolute magnitude at maximum and the distance of V2670 Oph. The nova achieved an absolute magnitude at maximum in the interval −7.9,…,−7.4. The distance of V2670 Oph is in the range 4.7–5.8 kpc.     

Deductions from the Indication of Eclipses of Nova V1493 Aql

Our mainly R band photometry of V1493 Aql (1999) during its outburst, indicates periodic variations with a period of 0.156 days, seen only 5 days after the maximum in V. This period can be orbital. The light curve indicates in addition, the presence of a faint eclipse like feature. We try to explain its extremely low amlitude, as being due to the eclipse of an expanded white dwarf component of the binary below an optically thick wind. We discuss what conditions would be required for such an interpretation to work.     

Echoes from an irradiated disc in GRO J1655–40

Oscillations observed in the light curve of Nova V1974 Cygni 1992 since the summer of 1994 have been interpreted as permanent superhumps. From simple calculations based on the tidal disc instability model of Osaki, and assuming that the accretion disc is the dominant optical source in the binary system, we predict that the nova will evolve to become an SU UMa system as its brightness declines from its present value by another 2–3 mag. Linear extrapolation of its current rate of fading (in magnitude units) puts the time of this phase transition within the next 2–4 yr. Alternatively, the brightness decline will stop before the nova reaches that level, and the system will continue to show permanent superhumps in its light curve. It will then be similar to two other old novae, V603 Aql and CP Pup, which still display the permanent superhump phenomenon 80 and 56 yr, respectively, after their eruptions. We suggest that non-magnetic novae with short orbital periods could be progenitors of permanent superhump systems.     

New activity cycle of the classical symbiotic star V1413 Aql

We present the results of our photometric UBV JHKLM observations in 2008?C2011 for the classical symbiotic star V1413 Aql. At the end of 2008, the hot component of V1413 Aql experienced the next strong outburst (??V > 2 _· ^m 5). According to the photometric criterion (B-V ?? 0 _· ^m 9 ± 0 _· ^m 2), the star was in an active state even in the period preceding the strong 2008 outburst. Two eclipsing minima of the same amplitude were observed for V1413 Aql in 2010 and 2011. Our analysis of the 2011 eclipse has allowed us to estimate the sizes of the components with respect to the orbital semimajor axis if the system is seen edge-on: the radius of the cool component is R _g/a = 0.28 and the radius of the hot component is R _h/a = 0.17. However, judging by the B-V color index, the eclipse may be noncentral.     

V533 Herculis: the second SW Sex old nova displaying emission-line flaring

We present high-time-resolution spectroscopy of the non-eclipsing old nova V533 Herculis (N Her 1963). It is the second nova remnant affected by the 'SW Sex syndrome'. A modulation of the equivalent width of the emission lines with a period of 23.33 min has been detected. This, together with the strong He ii λ4686 emission characteristic of magnetic systems, leads us to link this period to the spin of a magnetic white dwarf. Similar flaring activity has been recorded in other SW Sex stars, namely, the old nova BT Mon, LS Peg and DW UMa, supporting the idea of these systems being magnetic accretors. Stationary emission features are also observed in the Balmer lines, which we attribute to the ejected nova shell.     

Multicolor Photometric Study of the NOVA V1494 Aql in 2002

R and I band CCD observations of the nova V1494 Aql during July-November 2002 are reported and the V, R, and I light curves are analyzed. The orbital light curve of this nova has an eclipse-like form with two unequal humps before and after the eclipse. The approach to the eclipse lasts twice as long as the emergence from it. The overall duration of the eclipse is about 0.45P _orb. The depth of eclipse increases with wavelength and averages 0^m.3 (V), 0^m.5 (R), and 0^m.7 (I). The secondary, shallow minimum has an average depth of 0^m.1 in R and I and about 0^m.03 in V. The hump at phase 0.65 is higher than the one at phase 0.17. The most probable explanation for the observed variations in the light with the phase of the orbital period may be self eclipsing of the accretion column in the magnetic exploding variable (white dwarf) together with partial eclipsing of the accretion region by the secondary component.     

Detection and evolution of the CO (Δv= 2) emission in Nova V2615 Ophiuchi (2007)

We present near-infrared (1–2.5 μm) spectroscopic and photometric results of Nova V2615 Ophiuchi which was discovered in outburst in 2007 March. Our observations span a period of ∼80 d starting from 2007 March 28 when the nova was at its maximum light. The evolution of the spectra is shown from the initial P Cygni phase to an emission-line phase and finally to a dust formation stage. The characteristics of the JHK spectra are very similar to those observed in a nova outburst occurring on a carbon–oxygen white dwarf. We analyse an observed line at 2.088 μm and suggest that it could be due to Fe  ii excited by Lyman α fluorescence. The highlight of the observations is the detection of the first overtone bands of carbon monoxide (CO) in the 2.29–2.40 μm region. The CO bands are modelled to estimate the temperature and mass of the emitting CO gas and also to place limits on the ¹²C/¹³C ratio. The CO bands are recorded over several epochs, thereby allowing a rare opportunity to study the evolution from a phase of constant strength through a stage when the CO is destroyed fairly rapidly. We compare the observed time-scales involved in the evolution of the CO emission and find a good agreement with model predictions that investigate the chemistry in a nova outflow during the early stages.     

The evolution of nova V5558 Sgr during the decline stage

We report the spectroscopic follow-up of the nova V5558 Sgr carried out in 2008 and 2009 at the Loiano Observatory, Italy, during the decline stage, as a part of an ongoing monitoring campaign. The spectra suggest that V5558 Sgr has entered the nebular stage, as shown by the presence of high ionization lines, and confirm that it is very similar to the slow nova V723 Cas, as previously suggested. We have estimated the decline time by three magnitudes, 170 ± 2 days, typical of slow novae. We have revised the estimation of the absolute magnitude at maximum (?6.3 to ?5.9) and the distance (1.3–1.6 kpc) of V5558 Sgr, in agreement with previous results. The revised white dwarf mass (0.58–0.63 M_⊙) confirms that V5558 Sgr is a critical system whose mass is close to the lower limit to trigger the nova outburst.