- ID:
- ivo://CDS.VizieR/J/A+A/603/A72
- Title:
- R light curves of MN Dra
- Short Name:
- J/A+A/603/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of an extensive world-wide observing campaign of MN Draconis. MN Draconis is a poorly known active dwarf nova in the period gap and is one of the only two known cases of period gap SU UMa objects showing the negative superhumps. Photometric behaviour of MN Draconis poses a challenge for existing models of the superhump and superoutburst mechanisms. Therefore, thorough investigation of peculiar systems, such as MN Draconis, is crucial for our understanding of evolution of the close binary stars. To measure fundamental parameters of the system, we collected photometric data in October 2009, June-September 2013 and June-December 2015. Analysis of the light curves, O-C diagrams and power spectra was carried out. During our three observational seasons we detected four superoutburts and several normal outbursts. Based on the two consecutive superoutbursts detected in 2015, the supercycle length was derived P_sc_=74+/-0.5-days and it has been increasing with a rate of P_dot_=3.3x10^-3^ during last twelve years. Based on the positive and negative superhumps we calculated the period excess {epsilon}=5.6%+/-0.1%, the period deficit {epsilon}_=2.5%+/-0.6%, and in result, the orbital period P_orb_=0.0994(1)days (143.126+/-0.144min). We updated the basic light curve parameters of MN Draconis. MN Draconis is the first discovered SU UMa system in the period gap with increasing supercycle length.
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- ID:
- ivo://CDS.VizieR/J/A+A/549/A77
- Title:
- SDSS J080434.20+510349.2 spectra and photometry
- Short Name:
- J/A+A/549/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study of SDSS J080434.20+510349.2 (SDSS0804) is primarily concerned with the double-hump shape in the light curve and its connection with the accretion disk in this bounce-back system. Time-resolved photometric and spectroscopic observations were obtained to analyze the behavior of the system between superoutbursts. A qualitative geometric model of a binary system containing a disk with two outer annuli spiral density waves was applied to explain the light curve and the Doppler tomography. Observations were carried out during 2008-2009, after the object's magnitude decreased to V~17.7+/-0.1 from the March 2006 eruption. The light curve clearly shows a sinusoid-like variability with a 0.07mag amplitude and a 42.48min periodicity, which is half of the orbital period of the system. In September 2010, the system underwent yet another superoutburst and returned to its quiescent level by the beginning of 2012. This light curve once again showed a double-hump-shape, but with a significantly smaller (~0.01mag) amplitude. Other types of variability like a "mini-outburst" or SDSS1238-like features were not detected. Doppler tomograms, obtained from spectroscopic data during the same period of time, show a large accretion disk with uneven brightness, implying the presence of spiral waves. We constructed a geometric model of a bounce-back system containing two spiral density waves in the outer annuli of the disk to reproduce the observed light curves. The Doppler tomograms and the double-hump-shape light curves in quiescence can be explained by a model system containing a massive >=0.7M_{sun}_ white dwarf with a surface temperature of ~12000K, a late-type brown dwarf, and an accretion disk with two outer annuli spirals. According to this model, the accretion disk should be large, extending to the 2:1 resonance radius, and cool ~2500K. The inner parts of the disk should be optically thin in the continuum or totally void.
- ID:
- ivo://CDS.VizieR/J/MNRAS/373/687
- Title:
- Spectra of 5 faint cataclysmic variables
- Short Name:
- J/MNRAS/373/687
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present medium-resolution VLT/FORS2 spectroscopy of six cataclysmic variables (CVs) discovered by the Sloan Digital Sky Survey (SDSS). We determine orbital periods for SDSS J023322.61+005059.5 (96.08+/-0.09min), SDSS J091127.36+084140.7 (295.74+/-0.22min), SDSS J103533.02+055158.3 (82.10+/-0.09min) and SDSS J121607.03+052013.9 (most likely 98.82+/-0.16min, but the one-day aliases at 92 and 107min are also possible) using radial velocities measured from their H{alpha} and H{beta} emission lines. Three of the four orbital periods measured here are close to the observed 75-80min minimum period for CVs, indicating that the properties of the population of these objects discovered by the SDSS are substantially different to those of the CVs found by other means. Additional photometry of SDSS J023322.61+005059.5 reveals a periodicity of approximately 60min which we interpret as the spin period of the white dwarf, suggesting that this system is an intermediate polar with a low accretion rate. SDSS J103533.02+055158.3 has a period right at the observed minimum value, a spectrum dominated by the cool white dwarf primary star and exhibits deep eclipses, so is an excellent candidate for an accurate determination of the parameters of the system. The spectroscopic orbit of SDSS J121607.03+052013.9 has a velocity amplitude of only 13.8+/-1.6km/s, implying that this system has an extreme mass ratio. From several physical constraints we find that this object must contain either a high-mass white dwarf or a brown-dwarf-mass secondary component or both.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A101
- Title:
- Spectra of 29 Swift/BAT optical counterparts
- Short Name:
- J/A+A/545/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Through an optical campaign performed at four telescopes located in the northern and the southern hemispheres, plus archival data from two on-line sky surveys, we obtained optical spectroscopy for 29 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/Burst Alert Telescope (BAT) and listed in the 39 month Palermo catalogue. All these objects also have observations taken with Swift/X-ray Telescope (XRT) or XMM-European Photon Imaging Camera (EPIC) which not only allow us to pinpoint their optical counterpart, but also study their X-ray spectral properties (column density, power law photon index, and F2-10keV flux).
- ID:
- ivo://CDS.VizieR/J/A+A/561/A67
- Title:
- Spectra of 75 Swift/BAT optical counterparts
- Short Name:
- J/A+A/561/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Through an optical campaign performed at four telescopes located in the northern and the southern hemispheres, we obtained optical spectroscopy for 75 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/Burst Alert Telescope (BAT) and listed in the 54 month Palermo catalogue. All these objects also have observations taken with Swift/X-ray Telescope (XRT) or Chandra satellites, which allowed us to reduce the high-energy error box and pinpoint the most likely optical counterparts.
- ID:
- ivo://CDS.VizieR/J/AJ/144/81
- Title:
- Spectroscopy and photometry of CV candidates
- Short Name:
- J/AJ/144/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Catalina Real Time Survey (CRTS) has found over 500 cataclysmic variable (CV) candidates, most of which were previously unknown. We report here on follow-up spectroscopy of 36 of the brighter objects. Nearly all of the spectra are typical of CVs at minimum light. One object appears to be a flare star, while another has a spectrum consistent with a CV but lies, intriguingly, at the center of a small nebulosity. We measured orbital periods for eight of the CVs, and estimated distances for two based on the spectra of their secondary stars. In addition to the spectra, we obtained direct imaging for an overlapping sample of 37 objects, for which we give magnitudes and colors. Most of our new orbital periods are shortward of the so-called period gap from roughly 2 to 3hr. By considering the cross-identifications between the Catalina objects and other catalogs such as the Sloan Digital Sky Survey, we argue that a large number of CVs remain uncataloged. By comparing the CRTS sample to lists of previously known CVs that CRTS does not recover, we find that the CRTS is biased toward large outburst amplitudes (and hence shorter orbital periods). We speculate that this is a consequence of the survey cadence.
- ID:
- ivo://CDS.VizieR/J/MNRAS/383/845
- Title:
- Spectroscopy of AE Circinus
- Short Name:
- J/MNRAS/383/845
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new optical spectroscopy and photometry, Two-Micron All-Sky Survey (2MASS) infrared observations and 24yr of combined American Association of Variable Star Observers (AAVSO) and Association Francaise des Observateurs d'Etoiles Variables (AFOEV) photometry of the symbiotic star candidate AE Cir. The long-term light curve is characterized by outbursts lasting several years and having a slow decline of ~2x10^-4^mag/d. The whole range of variability of the star in the V band is about 4mag. The periodogram of the photometric data reveals strong signals at ~342 and 171d. The presence of the emission feature at {lambda}6830{AA} at minimum and the detection of absorption lines of a ~K5 type star confirm the symbiotic classification and suggest that AE Cir is a new member of the small group of s-type yellow symbiotic stars. We estimate a distance of 9.4kpc. Our spectrum taken at the high state shows a much flatter spectral energy distribution, the disappearance of the {lambda}6830{AA} emission feature and the weakness of the HeII 4686 emission relative to the Balmer emission lines. Our observations indicate the presence of emission-line flickering in time-scales of minutes in 2001. The peculiar character of AE Cir is revealed in the visibility of the secondary star at the high and low state, the light curve resembling a dwarf nova superoutburst and the relatively short low states. The data are hard to reconciliate with standard models for symbiotic star outbursts.
- ID:
- ivo://CDS.VizieR/J/A+A/275/201
- Title:
- Stroemgren photometry of Dwarf Novae
- Short Name:
- J/A+A/275/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 26 dwarf novae was observed in the Stroemgren photometric system. The observations were performed on 3 different seasons in 1986 January, February and July, with a 6-channel photometer attached to the 1.5m telescope if the Observatorio Astronomicao Nacional at San Pedro Martir, Baja California, Mexico. A number of standard stars were observed, and a nearby comparison star was observed for each object.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/2695
- Title:
- Symbiotic recurrent nova T CrB spectroscopy
- Short Name:
- J/MNRAS/462/2695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- T CrB is a symbiotic recurrent nova known to exhibit active phases, characterized by apparent increases in the hot component temperature and the appearance of flickering, i.e. changes in the observed flux on the time-scale of minutes. Historical UV observations have ruled out orbital variability as an explanation for flickering and instead suggest flickering is caused by variable mass transfer. We have analysed optical and X-ray observations to investigate the nature of the flickering as well as the active phases in T CrB. The spectroscopic and photometric observations confirm that the active phases follow two periods of ~1000d and ~5000d. Flickering in the X-rays is detected and follows an amplitude-flux relationship similar to that observed in the optical. The flickering is most prominent at harder X-ray energies, suggesting that it originates in the boundary layer between the accretion disc and the white dwarf. The X-ray radiation from the boundary layer is then reprocessed by a thick accretion disc or a nebula into UV radiation. A more detailed understanding of flickering would benefit from long-term simultaneous X-ray and optical monitoring of the phenomena in symbiotic recurrent novae and related systems such as Z And type symbiotic stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/194/28
- Title:
- The evolution of cataclysmic variables
- Short Name:
- J/ApJS/194/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an attempt to reconstruct the complete evolutionary path followed by cataclysmic variables (CVs), based on the observed mass-radius relationship of their donor stars. Along the way, we update the semi-empirical CV donor sequence presented previously by one of us, present a comprehensive review of the connection between CV evolution and the secondary stars in these systems, and reexamine most of the commonly used magnetic braking (MB) recipes, finding that even conceptually similar ones can differ greatly in both magnitude and functional form.
