Hasan H. Esenoglu

Spectral evolution of Nova (V1494) Aql and its high velocity jets

Spectral evolution of the fast nova V1494 Aql was monitored soon after its discovery in December 1999 to September 2000. The first spectra showed prominent emission lines of H I and Fe II, while He I was seen in absorption. The radial velocities of the absorption components of H I, He I and N II rapidly increased (in the negative sense) during the early decline stage, while those of Fe II remained nearly constant. When a new spectrum was taken on February 6, 2000 after the seasonal interruption, this nova was in the transition stage. The spectra in the transition stage showed emission lines of H I, He I, He II, N II, N III, Si II, (N II), (O I), (O III), (Fe II), (Fe VI), (Ca V) etc., hence the emission lines of Fe II had disappeared. A quasi-periodic oscillation of luminosity with a time scale of about 16:5 1 days and a mean amplitude of about 1.2 mag in V band was seen from February to the middle of April 2000. The emission lines of He II and (Ca V) disappeared around a light maximum of the oscillation, while the emission lines of N II and N III strengthened. At the same time high velocity ( 2900 and+2830 km s 1 ) broad emission wings of H I lines appeared, which suggest an ejection of high velocity jets. The excitation state increased throughout the nebular stage. The last spectra taken in September 2000 showed highly excited emission lines up to (Fe VII) and (Fe X)6374.5. The interstellar extinction is estimated as E(B V) = 0:6 0:1 from the equivalent widths of the interstellar absorption components of Na I D1 and D2. Using this result, the distance to the nova is estimated as 1:6 0:2 kpc. The mass and the helium abundance of the ejecta are estimated as 6:2 1:4 10 5 M and N(He)/N(H)= 0:13 0:01, respectively. The electron density of the ejecta decreased as Ne / t 0:8 during the nebular stage, where t is time from light maximum. This low decline rate suggests that the ejecta had a ring like shape as well a large mass loss which may have continued throughout the nebular stage.

A Photometric Study of the Newly Discovered Eclipsing Cataclysmic Variable SDSS J040714.78–064425.1

We present the results obtained from unfiltered photometric CCD observations of the newly discovered cataclysmic variable SDSS J040714.78–064425.1 made during seven nights in 2003 November. We establish the dwarf nova nature of the object as it was in outburst during our observations. We also confirm the presence of deep eclipses with a period of 0.17017 ± 0.00003 d in the optical light curve of the star. In addition, we found periods of 0.166 ± 0.001 d and possibly also 5.3 ± 0.7 d in the data. The 0.17017 d periodicity is consistent within the errors with the proposed orbital period of 0.165 and 0.1700 d. Using the known relation between the orbital and superhump periods, we interpret the 0.166 and 5.3 d periods as the negative superhump and the nodal precession period respectively. SDSS J040714.78–064425.1 is then classified as a negative superhump system with one of the largest orbital periods.

Discovery of irradiation-induced variations in the light curve of the classical nova V2275 Cyg (N Cyg 2001 No. 2)

We present charge-coupled device (CCD) photometry, light curve and time-series analysis of the classical nova V2275 Cyg (N Cyg 2001 No. 2). The source was observed for 14 nights in total in 2002 and 2003 using an R filter with the 1.5-m Russian-Turkish joint telescope (RTT150) at the TUBITAK National Observatory in Antalya, Turkey, as part of a large programme on the CCD photometry of cataclysmic variables. We report the detection of two distinct periodicities in the light curve of the nova: (a) P 1 = 0.31449(15) d [7.6 h], and (b) P 2 = 0.017079(17) d [24.6 min]. The first period is evident in both 2002 and 2003 whereas the second period is only detected in the 2003 data set. We interpret the first period as the orbital period of the system and attribute the orbital variations to aspect changes of the secondary irradiated by the hot white dwarf (WD). We suggest that the nova was a supersoft X-ray source in 2002 and, perhaps, in 2003. The second period could be a quasi-periodic pscillation originating from the oscillation of the ionization front (due to a hot WD) below the inner Lagrange point or a beat frequency in the system as a result of the magnetic nature of the WD if steady accretion has already been re-established.

SPECTROSCOPIC AND PHOTOMETRIC ANALYSIS OF NOVAE: A NEW CLASSIFICATION METHOD

This study deals with the relationship between the absolute visual magnitude at maximum and the rate of decline (MMRD or Mv -- t3) for classical novae. Considering the most reliable data including the nebular expansion parallax method for 24 galactic novae, we find that there are two distinct kinds of galactic novae. Slopes of very fast and fast novae were found from a least-squares fit to their MMRD relation. The values of these two slope angles are similar. A similar result was found for moderately fast and slow novae, whose mean slopes differ by only a small amount. Therefore very fast novae can be grouped with fast novae, and moderately fast novae can be grouped with slow novae, so that we have only two separate novae groups. These two groups of novae are distinguished from each other by the Eddington luminosity. Our conclusions agree well with those of Duerbeck (1981, PASP, 93, 165), based on the light curves of approximately 100 galactic novae. Considering numerical nova model calculations (Livio 1992, ApJ, 393, 516), it seems that there is a good agreement between the observed and the theoretical MMRD relation. Moreover, we applied the same classification method to novae in M31 (Massimo and Livio, 1995, ApJ, 452, 704), and found the same two separate groups. We also determined expansion parallaxes for QZ Aur, V1974 Cyg, FH Ser, XX Tau, RW UMi, and QU Vul, and expansion velocities for Nova Aql 1995, V1974 Cyg and FH Ser. These results were found from H-alpha imaging and spectroscopic observations made by the author and A.Bianchini and T.Iijima (University of Padova), using the 1.82- and 1.22-m telescopes at the Ekar and Asiago Observatories. When we compare our images with those in the literature, we can obtain expansion parallaxes for QU Vul, QZ Aur, V1974 Cyg, and RW UMi. Shell diameters in the light of H-alpha for QU Vul, QZ Aur, V1974 Cyg and RW UMi were found to be 0.82, 0.83, 0.76 and 2.94 arcsec, respectively (epoch 1994-5). The literature gives nebular expansion parallaxes for 22 galactic novae. To these we can now add expansion parallaxes for QZ Aur and QU Vul, thus increasing the number to 24. Two high-dispersion spectra of FH Ser and N Aql 1995, and a low-dispersion spectrum of V1974 Cyg, give the following expansion velocities: 425 ± 25, 675 ± 25, and 1600 ± 100 km/s, respectively. (c) Society of

Photometric Observations of Cataclysmic Variables with the 1.5-m Telescope at the TÜBITAK National Observatory (TUG): V2275 Cyg, RW UMi, PX And and FO Per

We present the light curve and time series analysis of classical novae and dwarf novae systems monitored/observed with the 1.5 m Russian-Turkish Joint telescope (RTT150) at the TUBITAK (The Scientific and Technical Research Council of Turkey) National Observatory in Antalya, Turkey. As part of a large program on CCD photometry of Cataclysmic Variables, V2275 Cyg (N 2001 No.2), RW UMi, FO Per and PX And were observed for a total of about 25 nights. The results on V2275 Cyg show that the system has a period of 0.463±0.014 or the 1-d alias 0.316±0.007 with a wide eclipse-like pattern (IAUC 8074). The power spectral analysis of the data on RW UMi reveal possible periodicities at around several frequencies (eg., 14.4, 16.7, 19, 30, 39, 46, 68, 108 in cycles per day) that could be interpreted as the binary period, spin period of the white dwarf and/or orbital sidebands of the system. We find that the radial velocity profiles of H-alpha lines and the photometry of the Dwarf Nova FO Per indicates the possible presence of a period around 0.1828 d.

A Possible Detected Faint Shell of the Classical Nova QZ Aurigae

We observed the faint shell of QZ Aur (Nova Aurigae 1964) nearly 30 years of its outburst. Despite a diameter of 0.55+0.12−0.16 arcsec of the intrinsic point source of QZ Aur, a narrow‐band Hα image shows that the diameter of the nova shell in 1995 was 0.86+0.14−0.17 arcsec. This rather faint shell exists for a nova suggests that QZ Aur is an object worthy of further study.

Accretion Disk Winds in Dwarf Novae

It is well known that the International Ultraviolet Explorer observations of high-excitation P Cygni profiles of C IV and S IV lines provide direct evidence for winds in cataclysmic variables which reach speeds of ~5000 km s -1. We present in this paper our analysis of P Cygni profile for C IV line in seven dwarf novae based on 195 low-resolution IUE spectra. This work aims to do two things: i) to examine them in terms of wind properties, and ii) to seek time dependence of the lines indicating departure from axial symmetry in the outflow and/or disk and changes in the wind ionisation and/or mass loss rate. We infer the optical depth of C IV, the column density and the number density of absorbing and scattering ions in the region where the wind ionized.

IUE Spectra of Three Z Cam Type Dwarf Novae: A Study of P Cygni Profiles

We study the P Cygni profiles in three dwarf novae. In a study of Z Cam by Szkody and Mateo (1986), it was claimed that the mass loss continues for 1 month after the start of a standstill and ceases within 6 months. This results of the work depends on only one standstill spectrum. On the other hand, in another work carried out by Ozkan and Esenoglu (1994) it was found that the case may not be true for Z Cam, because two ultraviolet spectra obtained during the sixth month of another standstill configuration shows the P Cygni profile having a stronger absorption component and a weaker emission component which implies that the mass loss may continue during the standstill. Following these works in the present study, we aimed to investigate this situation for Z Cam and two other Z Cam type dwarf novae, RX And and HL CMa. considering all ultraviolet spectra obtained with IUE and AAVSO observations (Mattei, 1994).

Time dependence of the UV resonance lines in the cataclysmic variable star VW Hyi

In this work, we study orbital variations in the ultraviolet resonance lines of the SU UMa type dwarf nova VW Hyi examining spectra in the data archive of the International Ultraviolet Explorer (IUE). We show that VW Hyi exhibits an orbital and long term variability in terms of UV line profiles and continuum flux at 1450 A during superoutburst.