- ID:
- ivo://CDS.VizieR/J/A+A/560/A49
- Title:
- UV spectra of old novae
- Short Name:
- J/A+A/560/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an overview of the UV spectral properties of old novae as a class. The data and results of this paper, together with data from the outburst phases, will be utilized in a follow-up study to determine statistical properties and to investigate correlations among the physical parameters of the quiescent and eruptive phases.
« Previous |
41 - 48 of 48
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/367/759
- Title:
- Variable stars in IC 1613
- Short Name:
- J/A+A/367/759
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nearby galaxies IC 1613 and NGC 6822 were observed over four years to detect short period Cepheids and to obtain good light curves for Fourier decomposition. The program was carried out with a relatively small telescope, the Dutch 0.9m at ESO-La Silla, and the observations were performed without filter (white light), or Wh-band. In this paper we present the results of the observations of Fields C and D in IC 1613 (3.8'x3.8' each). The analysis of the light curves of 3297 stars in the two fields has allowed the detection of 92 variable stars. A total of 34 Population I Cepheids have been found, while only 7 of these objects were previously known in these fields. Most of the stars have short periods and some of them are first overtone mode pulsators. Among the other variable stars there are one eclipsing binary and five W Vir candidates. A nova event was observed in Field D.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A96
- Title:
- V407 Cyg spectral variations
- Short Name:
- J/A+A/600/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The outburst of the symbiotic recurrent nova V407 Cyg in 2010 has been studied by numerous authors. On the other hand, its spectral variations in the quiescent stage have not been well studied yet. This paper is probably the first report for the relation between the pulsation of the secondary Mira variable and the temperature of the primary hot component for V407 Cyg. The spectral variation in the post-outburst stage has been monitored to study the properties of this object. In the course of this work, we found some unexpected spectral variations around the light maximum of the secondary Mira variable in 2012. The relation between the mass transfer in the binary system and the pulsation of the secondary Mira variable is studied. High- and low-resolution optical spectra obtained at the Astronomical Observatories at Asiago were used. The photometric data depend on the database of the VSNET.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A17
- Title:
- VLBA SiO masers toward V838 Monocerotis
- Short Name:
- J/A+A/638/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch observations with the VLBA of SiO maser emission in the v=1, J=1-0 transition at 43GHz from the remnant of the red nova V838 Mon. We model the positions of maser spots to derive a parallax of 0.166+/-0.060mas. Combining this parallax with other distance information results in a distance of 5.6+/-0.5kpc, which agrees with an independent geometric distance of 6.1+/-0.6kpc from modeling polarimetry images of V838 Mon's light echo. Combining these results, and including a weakly constraining Gaia DR2 parallax, yields a best estimate of distance of 5.9+/-0.4kpc. The maser spots are located close to the peaks of continuum at ~225GHz and SiO J=5-4 thermal emission detected with ALMA. The proper motion of V838 Mon confirms its membership in a small open cluster in the Outer spiral arm of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A130
- Title:
- VLBI images of gamma-ray nova V407 Cygni
- Short Name:
- J/A+A/638/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 2010 March, the Large Area Telescope on board Fermi revealed a transient gamma-ray source that is positionally coincident with the optical nova in the symbiotic binary, V407 Cyg. This event marked the first discovery of gamma-ray emission from a nova. We aim to obtain resolved radio imaging of the material involved in the nova event, to determine the ejecta geometry and advance velocity directly in the image plane, and to constrain the physical conditions of the system. We observed the source with the European VLBI (Very Long Baseline Interferometry) Network in real time mode, at 1.6 and 5GHz, and the Very Long Baseline Array at 1.6, 5, and 8.4GHz. In total, we observed the source over 16 epochs, starting 20 days after the optical discovery and continuing for over six months. Milliarcsecond-scale radio emission is detected in 10/16 epochs of observations. The source is initially very dim but it later shows a substantial increase in brightness and a resolved shell-like structure 40-90 days after the optical event. The shell has a projected elliptical shape and is asymmetric in brightness and spectral index, being brighter and characterised by a rising spectrum at the south-eastern edge. We determine a projected expansion velocity of ~3500km/s in the initial phase (for an adopted 2.7kpc distance), and ~2100km/s between day 20 and 91. We also found an emitting feature about 350 mas (940AU) to the north-west, advancing at a projected velocity of ~700km/s along the polar axis of the binary. The total flux density in the VLBI images is significantly lower than that previously reported at similar epochs and over much wider angular scales with the VLA. Optical spectra convincingly demonstrated that in 2010 we were viewing V407 Cyg along the equatorial plane and from behind the Mira. Our radio observations image the bipolar flow of the ejecta perpendicular to the orbital plane, where deceleration is much lower than through the equatorial plane probed by the truncated profile of optical emission lines. The separated polar knot at 350 mas and the bipolar flow strictly resemble a similar arrangement seen in Hen 2-104, another symbiotic Mira seen equator-on that went through a large outburst ~5700yrs ago. The observed ~700km/s expansion constrains the launch date of the polar knot around 2004, during the accretion-fed active phase preceding the 2010 nova outburst.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A52
- Title:
- X-ray monitoring of M31 novae
- Short Name:
- J/A+A/533/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context. Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of the galaxy M31. We performed a dedicated monitoring of the M31 central region with XMM-Newton and Chandra between Nov 2007 and Feb 2008 and between Nov 2008 and Feb 2009, respectively, to find SSS counterparts of CNe, determine the duration of their SSS phase, and derive physical outburst parameters. We systematically searched our data for X-ray counterparts of CNe, determined their X-ray light curves and characterised their spectra using blackbody fits and white dwarf (WD) atmosphere models. Additionally, we determined luminosity upper limits for all previously known X-ray emitting novae that are not detected any more and for all CNe in our field of view with optical outbursts between one year before the start of the X-ray monitoring (Oct 2006) and its end (Feb 2009).
- ID:
- ivo://CDS.VizieR/J/A+A/563/A2
- Title:
- X-ray monitoring of M31 novae
- Short Name:
- J/A+A/563/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M 31. We performed a dedicated monitoring of the M 31 central region, which aimed to detect SSS counterparts of CNe, with XMM-Newton and Chandra between Nov and Mar of the years 2009/10, 2010/11, and 2011/12. We systematically searched our data for X-ray counterparts of CNe and determined their X-ray light curves and also their spectral properties in the case of XMM-Newton data. Additionally, we determined luminosity upper limits for all previously known X-ray emitting novae, which are not detected anymore, and for all CNe in our field of view with recent optical outbursts.
- ID:
- ivo://CDS.VizieR/J/A+A/465/375
- Title:
- X-ray monitoring of optical novae in M31
- Short Name:
- J/A+A/465/375
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical novae have recently been identified as the major class of supersoft X-ray sources in M 31 based on ROSAT and early XMM-Newton and Chandra observations. This paper reports on a search for X-ray counterparts of optical novae in M 31 based on archival Chandra HRC-I and ACIS-I as well as XMM-Newton observations of the galaxy center region obtained from July 2004 to February 2005. We systematically determine X-ray brightness or upper limit for counterparts of all known optical novae with outbursts between November 2003 to the end of the X-ray coverage. In addition, we determine the X-ray brightnesses for counterparts of four novae with earlier outbursts. For comparison with the X-ray data we created a catalogue of optical novae in M 31 based on our own nova search programs and on all novae reported in the literature. We collected all known properties and named the novae consistently following the CBAT scheme. We detect eleven out of 34 novae within a year after the optical outburst in X-rays. While for eleven novae we detect the end of the supersoft source phase, seven novae are still bright more than 1200, 1600, 1950, 2650, 3100, 3370 and 3380d after outburst. One nova is detected to turn on 50d, another 200d after outburst. Three novae unexpectedly showed short X-ray outbursts starting within 50d after the optical outburst and lasting only two to three months. The X-ray emission of several of the novae can be characterized as supersoft from hardness ratios and/or X-ray spectra or by comparing HRC-I count rates with ACIS-I count rates or upper limits. The number of detected optical novae at supersoft X-rays is much higher than previously estimated (>30%). We use the X-ray light curves to estimate the burned masses of the White Dwarf and of the ejecta.
