DO Leonis - a new eclipsing cataclysmic variable

Photometric and spectroscopic observations of DO Leo have been obtained using the McDonald Observatory high-speed CCD photometer and a conventional two-channel photoelectric photometer. The data reveal eclipses that are approximately 1.5 m deep. A total of nine eclipses were observed in February and March 1988 and in April 1989. These data were used to establish an orbital period of 0.2345147(2) d. A low-resolution optical spectrum reveals significant He II 4686 emission in addition to the characteristic Balmer and He I emission lines

Optical and X-ray Observations of M31N 2007-12b: An Extragalactic Recurrent Nova with a Detected

We report combined optical and X-ray observations of nova M31N 2007-12b. Optical spectroscopy obtained 5 days after the 2007 December outburst shows evidence of very high ejection velocities (FWHM H$\alpha \simeq 4500$ km s$^{-1}$). In addition, Swift X-ray data show that M31N 2007-12b is associated with a Super-Soft Source (SSS) which appeared between 21 and 35 days post-outburst and turned off between then and day 169. Our analysis implies that M_{\rm WD} \ga 1.3 M$_{\odot}$ in this system. The optical light curve, spectrum and X-ray behaviour are consistent with those of a recurrent nova. Hubble Space Telescope observations of the pre-outburst location of M31N 2007-12b reveal the presence of a coincident stellar source with magnitude and color very similar to the Galactic recurrent nova RS Ophiuchi at quiescence, where the red giant secondary dominates the emission. We believe that this is the first occasion on which a nova progenitor system has been identified in M31. However, the greatest similarities of outburst optical spectrum and SSS behaviour are with the supposed Galactic recurrent nova V2491 Cygni. A previously implied association of M31N 2007-12b with nova M31N 1969-08a is shown to be erroneous and this has important lessons for future searches for recurrent novae in extragalactic systems. Overall, we show that suitable complementary X-ray and optical observations can be used not only to identify recurrent nova candidates in M31, but also to determine subtypes and important physical parameters of these systems. Prospects are therefore good for extending studies of recurrent novae into the Local Group with the potential to explore in more detail such important topics as their proposed link to Type Ia Supernovae.Comment: 10 pages, 4 figures, accepted for publication in the Astrophysical Journal. This paper - which replaces the original accepted paper - accounts for the positional coincidence of M31N 2007-12b and M31N 1969-08a and uses additional HST archival dat

Low Frequency Flickering of TT Arietis:Hard and Soft X-ray Emission Region

Using archival ASCA observations of TT Arietis, X-ray energy spectra and power spectra of the intensity time series are presented for the first time. The energy spectra are well-fitted by a two continuum plasma emission model with temperatures around 1 keV and 10 keV. A coherent feature at about 0.643 mHz appeared in the power spectra during the observation.Comment: 9 pages in PostScript including figures, accepted for publication in Astrophysics and Space Science, available at http://astroa.physics.metu.edu.tr/preprints.htm

The Rate and Spatial Distribution of Novae in M31 as Determined by a 20 Year Survey

A long-term (1995-2016) survey for novae in the nearby Andromeda galaxy (M31) was conducted as part of the Research-Based Science Education initiative. During the course of the survey 180 nights of observation were completed at Kitt Peak, Arizona. A total of 262 novae were either discovered or confirmed, 40 of which have not been previously reported. Of these, 203 novae form a spatially complete sample detected by the KPNO/WIYN 0.9 m telescope within a 20 ′ × 20 ′ field centered on the nucleus of M31. An additional 50 novae are part of a spatially complete sample detected by the KPNO 4 m telescope within a larger 36 ′ × 36 ′ field. Consistent with previous studies, it is found that the spatial distribution of novae in both surveys follows the bulge light of M31 somewhat more closely than the overall background light of the galaxy. After correcting for the limiting magnitude and the spatial and temporal coverage of the surveys, a final nova rate in M31 is found to be R = 40 − 4 + 5 yr−1, which is considerably lower than recent estimates. When normalized to the K-band luminosity of M31, this value yields a luminosity-specific nova rate, ν K = 3.3 ± 0.4 yr − 1 [ 10 10 L ⊙ , K ] − 1 . By scaling the M31 nova rate using the relative infrared luminosities of M31 and our Galaxy, a nova rate of R G = 28 − 4 + 5 yr−1 is found for the Milky Way. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Opt/NIR obs. of M31N 2008-12a 2015 eruption

VizieR online Data Catalogue associated with article published in journal Astronomical Journal (AAS) with title \u27M31N 2008-12a - the remarkable recurrent nova in M31: panchromatic observations of the 2015 eruption.\u27 (bibcode: 2016ApJ...833..149D