Browsing by Subject "novae, cataclysmic variables"
Now showing 1 - 13 of 13
Results Per Page
Sort Options
- ItemOpen AccessAccurate classification of 29 objects detected in the 39 month Palermo Swift /BAT hard X-ray catalogue(2012) Parisi, P; Masetti, N; Jiménez-Bailón, E; Chavushyan, V; Palazzi, E; Landi, R; Malizia, A; Bassani, L; Bazzano, A; Bird, A J; Charles, P A; Galaz, G; Mason, E; McBride, V A; Minniti, D; Morelli, L; Schiavone, F; Ubertini, PThrough an optical campaign performed at 4 telescopes located in the northern and the southern hemispheres, plus archival data from two on-line sky surveys, we have obtained optical spectroscopy for 29 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/BAT and listed in the 39 months Palermo catalogue. All these objects have also observations taken with Swift/XRT or XMM-EPIC which not only allow us to pinpoint their optical counterpart, but also to study their X-ray spectral properties (column density, power law photon index and F2-10 keV flux). We find that 28 sources in our sample are AGN; 7 are classified as type 1 while 21 are of type 2; the remaining object is a galactic cataclysmic variable. Among our type 1 AGN, we find 5 objects of intermediate Seyfert type (1.2-1.9) and one Narrow Line Seyfert 1 galaxy; for 4 out of 7 sources, we have been able to estimate the central black hole mass. Three of the type 2 AGN of our sample display optical features typical of the LINER class and one is a likely Compton thick AGN. All galaxies classified in this work are relatively nearby objects since their redshifts lie in the range 0.008-0.075; the only galactic object found lies at an estimated distance of 90 pc. We have also investigated the optical versus X-ray emission ratio of the galaxies of our sample to test the AGN unified model. For them, we have also compared the X-ray absorption (due to gas) with the optical reddening (due to dust): we find that for most of our sources, specifically those of type 1.9-2.0 the former is higher than the latter confirming early results by Maiolino et al. (2001); this is possibly due to the properties of dust in the circumnuclear obscuring torus of the AGN.
- ItemOpen AccessDiscovery of an eclipsing dwarf nova in the ancient nova shell Te 11(2016) Miszalski, Brent; Woudt, P A; Littlefair, S P; Warner, B; Boffin, H M J; Corradi, R L M; Jones, D; Motsoaledi, M; Rodríguez-Gil, P; Sabin, L; Santander-García, MWe report on the discovery of an eclipsing dwarf nova (DN) inside the peculiar, bilobed nebula Te 11. Modelling of high-speed photometry of the eclipse finds the accreting white dwarf to have a mass 1.18 M
- ItemOpen AccessExploring inside-out Doppler tomography: magnetic cataclysmic variables(2016) Kotze, E J; Potter, S B; McBride, V AContext. Doppler tomography of magnetic cataclysmic variables is a valuable tool for the interpretation of the complex spectroscopic emission line profiles observed for these systems.
- ItemOpen AccessExploring inside-out Doppler tomography: non-magnetic cataclysmic variables(2015) Kotze, E J; Potter, S B; McBride, V AContext. Doppler tomography is a technique that has revolutionised the interpretation of the phase-resolved spectroscopic observations of interacting binary systems.
- ItemOpen AccessHigh-speed photometry of SDSS J013701.06 − 091234.9(2004) Pretorius, M L; Woudt, P A; Warner, B; Bolt, G; Patterson, J; Armstrong, EWe present high speed photometry of the Sloan Digital Sky Survey cataclysmic variable SDSS J013701.06-091234.9 in quiescence and during its 2003 December superoutburst. The orbital modulation at 79.71pm0.01 min is double humped; the superhump period is 81.702pm0.007 min. Towards the end of the outburst late superhumps with a period of 81.29pm0.01 min were observed. We argue that this is a system of very low mass transfer rate, and that it probably has a long outburst interval.
- ItemOpen AccessHistorical light curve and search for previous outbursts of Nova KT Eridani (2009)(2012) Jurdana-Šepić, R; Ribeiro, V A R M; Darnley, M J; Munari, U; Bode, M FContext. Nova Eridani (2009) caught the eye of the nova community due to its fast decline from maximum, which was initially missed, and its subsequent development in the radio and X-ray wavelengths. This system also exhibits properties similar to those of the much smaller class of recurrent novae; themselves potential progenitors of Type Ia Supernovae. Aims. We aim to determine the nature and physical parameters of the KT Eri progenitor system. Methods. We searched the Harvard College Observatory archive plates for the progenitor of KT Eri to determine the nature of the system, particularly the evolutionary stage of the secondary.We used the data obtained to search for any periodic signal and the derived luminosity to estimate a recurrence timescale. Furthermore, by comparing the colours of the quiescent system on a colour-magnitude diagram we may infer the nature of the secondary star. Results. We identified the progenitor system of KT Eri and measured a quiescent magnitude of < B >= 14.7 pm 0.4. No previous outburst was found. However, we suggest that if the nova is recurrent it should be on a timescale of centuries. We find a periodicity at quiescence of 737 days which may arise from reflection effects and/or eclipses in the central binary. The periodicity and the quiescence magnitude of the system suggest that the secondary star is evolved and likely in, or ascending, the Red Giant Branch. A second period is evident at 376 days which has a sinusoidal like light curve. Furthermore, the outburst amplitude of ~ 9 magnitudes is inconsistent with those expected for fast classical novae (~ 17 magnitudes) which may lend further support for an evolved secondary. (Abridged)
- ItemOpen AccessHubble Space Telescope and Optical Observations of Three Pulsating Accreting White Dwarfs in Cataclysmic Variables(2007) Szkody, Paula; Mukadam, Anjum; Gänsicke, Boris T; Woudt, Patrick A; Solheim, Jan‐Erik; Nitta, Atsuko; Sion, Edward M; Warner, Brian; Sahu, D K; Prabhu, T; Henden, ArneUltraviolet observations using the Solar Blind Channel on the Hubble Space Telescope provide light curves and low-resolution spectra of three pulsating white dwarfs in the cataclysmic variables SDSS J013132.39-090122.3, SDSS J161033.64-010223.3, and SDSS J220553.98+115553.7. The UV light curves show enhanced pulsation amplitudes over those from simultaneous and previous optical photometry, while the UV-optical spectra are fit with white dwarf temperatures near 15,000 K. These temperatures place the accreting white dwarfs outside the instability zone for noninteracting DAV white dwarfs and show that the instability strip is complex for accreting white dwarfs
- ItemOpen AccessIrradiated accretion discs in post novae(2001) Schreiber, M R; Gänsicke, B TWe derive approximations for the
- ItemOpen AccessObscuration effects in super-soft-source X-ray spectra(2013) Ness, J-U; Osborne, J P; Henze, M; Dobrotka, A; Drake, J J; Ribeiro, V A R M; Starrfield, S; Kuulkers, E; Behar, E; Hernanz, M; Schwarz, G; Page, K L; Beardmore, A P; Bode, M FContext. Super-soft-source (SSS) X-ray spectra are blackbody-like spectra with effective temperatures ~3−7 × 105 K and luminosities of 1035−38 erg s-1. Grating spectra of SSS and novae in outburst that show SSS type spectra display atmospheric absorption lines. Radiation transport atmosphere models can be used to derive physical parameters. Blue-shifted absorption lines suggest that hydrostatic equilibrium is an insufficient assumption, and more sophisticated models are required.
- ItemOpen AccessQPOs in cataclysmic variables and in X-ray binaries(2005) Kluźniak, W; Lasota, J-P; Abramowicz, M A; Warner, BRecent observations, reported by Warner and Woudt, of Dwarf Nova Oscillations (DNOs) exhibiting frequency drift, period doubling, and 1:2:3 harmonic structure, can be understood as disc oscillations that are excited by perturbations at the spin frequency of the white dwarf or of its equatorial layers. Similar quasi-periodic disc oscillations in black hole low-mass X-ray binary (LMXB) transients in a 2:3 frequency ratio show no evidence of frequency drift and correspond to two separate modes of disc oscillation excited by an internal resonance. Just as no effects of general relativity play a role in white dwarf DNOs, no stellar surface or magnetic field effects need be invoked to explain the black hole QPOs.
- ItemOpen AccessStatistical properties of dwarf novae-type cataclysmic variables: the outburst catalogue(2016) Coppejans, Deanne L; Körding, Elmar G; Knigge, Christian; Pretorius, Magaretha L; Woudt, Patrick A; Groot, Paul J; Van Eck, Cameron L; Drake, Andrew JThe Outburst Catalogue contains a wide variety of observational properties for 722 dwarf nova-type (DN) cataclysmic variables (CVs) and 309 CVs of other types from the Catalina Real-time Transient Survey. In particular, it includes the apparent outburst and quiescent V-band magnitudes, duty cycles, limits on the recurrence time, upper- and lower-limits on the distance and absolute quiescent magnitudes, colour information, orbital parameters, and X-ray counterparts. These properties were determined by means of a classification script presented in this paper. The DN in the catalogue show a correlation between the outburst duty cycle and the orbital period (and outburst recurrence time), as well as between the quiescent absolute magnitude and the orbital period (and duty cycle). This is the largest sample of dwarf nova properties collected to date. Besides serving as a useful reference for individual systems and a means of selecting objects for targeted studies, it will prove valuable for statistical studies that aim to shed light on the formation and evolution of cataclysmic variables.
- ItemOpen AccessThe nature of 50 Palermo Swift -BAT hard X-ray objects through optical spectroscopy(2017) Rojas, A F; Masetti, N; Minniti, D; Jiménez-Bailón, E; Chavushyan, V; Hau, G; McBride, V A; Bassani, L; Bazzano, A; Bird, A J; Galaz, G; Gavignaud, I; Landi, R; Malizia, A; Morelli, L; Palazzi, E; Patiño-Álvarez, V; Stephen, J B; Ubertini, PWe present the nature of 50 hard X-ray emitting objects unveiled through an optical spectroscopy campaign performed at seven telescopes in the northern and southern hemispheres. These objects were detected with the Burst Alert Telescope (BAT) instrument onboard the Swift satellite and listed as of unidentified nature in the 54-month Palermo BAT catalogue. In detail, 45 sources in our sample are identified as active galactic nuclei of which, 27 are classified as type 1 (with broad and narrow emission lines) and 18 are classified as type 2 (with only narrow emission lines). Among the broad-line emission objects, one is a type 1 high-redshift quasi-stellar object, and among the narrow-line emission objects, one is a starburst galaxy, one is a X-ray bright optically normal galaxy, and one is a low ionization nuclear emission line region. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary probably with a low mass secondary star, and one is an active star.
- ItemOpen AccessUnveiling the nature of INTEGRAL objects through optical spectroscopy: X. A new multi-year, multi-observatory campaign(2013) Masetti, N; Parisi, P; Palazzi, E; Jiménez-Bailón, E; Chavushyan, V; McBride, V; Rojas, A F; Steward, L; Bassani, L; Bazzano, A; Bird, A J; Charles, P A; Galaz, G; Landi, R; Malizia, A; Mason, E; Minniti, D; Morelli, L; Schiavone, F; Stephen, J B; Ubertini, PWithin the framework of our program (running since 2004) of identification of hard X-ray INTEGRAL sources through optical spectroscopy, we present the results concerning the nature of 33 high-energy objects. The data were acquired with the use of six telescopes of different sizes and from one on-line archive. The results indicate that the majority of these objects (23 out of 33) are active galactic nuclei (AGNs), whereas 10 are sources in the local Universe with eight of which in the Galaxy and two in the Small Magellanic Cloud (SMC). Among the identified AGNs, 13 are of Type 1 (i.e., with broad emission lines), eight are of Type 2 (with narrow emissions only), and two are X-ray bright, optically normal galaxies with no apparent nuclear activity in the optical. Six of these AGNs lie at high redshift (z > 0.5). Concerning local objects, we found that five of them are Galactic cataclysmic variables, three are high-mass X-ray binaries (two of which lying in the SMC), one is a low-mass X-ray binary, and one is classified as a flare star that is likely of RS CVn type. The main optical properties and inferred physical characteristics of these sources are presented and discussed.