- ID:
- ivo://CDS.VizieR/J/ApJ/780/L25
- Title:
- 1898-2013 BV and visual photometry for V603 Aql
- Short Name:
- J/ApJ/780/L25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the light curve of the old nova V603 Aql (Nova Aql 1918) from 1898-1918 and 1934-2013 using 22721 archival magnitudes. All of our magnitudes are either in, or accurately transformed into, the Johnson B and V magnitude systems. This is vital because offsets in old sequences and the visual-to-V transformation can cause errors of 0.1-1.0mag if not corrected. Our V603 Aql light curve is the first time that this has been done for any nova. Our goal was to see the evolution of the mass accretion rate on a century timescale, and to test the long-standing prediction of the Hibernation model that old novae should be fading significantly in the century after their eruption is over. The 1918 nova eruption was completely finished by 1938 when the nova decline stopped, and when the star had faded to fainter than its pre-nova brightness of B=11.43+/-0.03mag. We find that the nova light from 1938 to 2013 was significantly fading, with this being seen consistently in three independent data sets (the Sonneberg plates in B, the American Association of Variable Star Observers (AAVSO) V light curve, and the non-AAVSO V light curve). We find that V603 Aql has been declining in brightness at an average rate of 0.44+/-0.04mag per century since 1938. This work provides remarkable confirmation of an important prediction of the Hibernation model.
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- ID:
- ivo://CDS.VizieR/J/A+A/463/981
- Title:
- BV CCD photometry in Westerlund 2
- Short Name:
- J/A+A/463/981
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The properties of the early-type stars in the core of the Westerlund 2 cluster are examined in order to establish a link between the cluster and the very massive Wolf-Rayet binary WR20a as well as the H II complex RCW 49. Photometric monitoring as well as spectroscopic observations of Westerlund 2 are used to search for light variability and to establish the spectral types of the early-type stars in the cluster core. The first light curves of the eclipsing binary WR 20a in B and V filters are analysed and a distance of 8kpc is inferred. Three additional eclipsing binaries, which are probable late O or early B-type cluster members, are discovered, but none of the known early O-type stars in the cluster displays significant photometric variability above 1% at the 1-sigma level. The twelve brightest O-type stars are found to have spectral types between O3 and O6.5, significantly earlier than previously thought. The distance of the early-type stars in Westerlund 2 is established to be in excellent agreement with the distance of WR20a, indicating that WR20a actually belongs to the cluster. Our best estimate of the cluster distance thus amounts to 8.0+/-1.4kpc. Despite the earlier spectral types, the currently known population of early-type stars in Westerlund 2 does not provide enough ionizing photons to account for the radio emission of the RCW 49 complex. This suggests that there might still exist a number of embedded early O-stars in RCW49.
- ID:
- ivo://CDS.VizieR/J/PASP/104/1063
- Title:
- BV Color-Magnitude Diagram for NGC 1851
- Short Name:
- J/PASP/104/1063
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BV photometry is provided for 1,234 stars in the magnitude range 13-18 in an annulus between 5 and 20 arc seconds from the center of NGC 1851 and for 1,247 stars in the magnitude range 18-23 at a distance of more than 240 arc seconds from the center. For stars in the magnitude range 16-21, the errors in B-V increase with magnitude from 0.005 mag. to 0.022 mag. See the document file (walker.txt or walker.tex) by Nancy G. Roman for more details.
- ID:
- ivo://CDS.VizieR/J/A+A/344/263
- Title:
- B-V colour excess of Miras
- Short Name:
- J/A+A/344/263
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A study of 73 carbon-rich Miras (see Subsec. 6.1) with suitable solution for 56 stars at one or several phase of their variations. In the second part, preliminary and incomplete results are reported for 17 additional Miras observed at only one phase. Table 5 contains our HC-CV-classification (see text) for the stars and their colour excess E(B-V) as determined by the method described in Subsec. 2.2.
- ID:
- ivo://CDS.VizieR/J/MNRAS/381/602
- Title:
- BV differential light curves of EQ Tau
- Short Name:
- J/MNRAS/381/602
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present two new sets of complete light curves of EQ Tauri (EQ Tau) observed in 2000 October and 2004 December. These were analysed, together with the light curves obtained by Yang & Liu (2002AJ....124.3358Y) in 2001 December, with the 2003 version of the Wilson-Devinney code. In the three observing seasons, the light curves show a noticeable variation in the time-scale of years. The more massive component of EQ Tau is a solar-type star (G2) with a very deep convective envelope, which rotates about 80 times as fast as the Sun. Therefore, the change can be explained by dark-spot activity on the common convective envelope. The assumed unperturbed part of the light curve and the radial velocities published by Rucinski et al. (2001AJ....122.1974R) were used to determine the basic parameters of the system, which were kept fixed for spot modelling in the three sets of light curves. The results reveal that the total spotted area on the more massive component covers 18, 3 and 20 per cent of the photospheric surface in the three observing seasons, respectively. Polar spots and high-latitude spots are found. The analysis of the orbital period has demonstrated that it undergoes cyclical oscillation, which is due to either a tertiary component or periodic magnetic activity in the more massive component.
- ID:
- ivo://CDS.VizieR/J/AJ/133/1421
- Title:
- BV differential photometry of 11 gamma Dor stars
- Short Name:
- J/AJ/133/1421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used precise photometric and high-dispersion spectroscopic observations to study 11 gamma Doradus stars, 10 of them newly confirmed. Only five of these 11 gamma Doradus stars appear to be single; two are primaries of double-lined spectroscopic binaries, one is the secondary of a double-lined binary, two are primaries of visual binaries and, in the case of the double-lined binary (HD 86371), either or both components could be a pulsating gamma Doradus star. We have determined a preliminary orbital period of 5.32 days for the double-lined binary HD 41547. Several of the stars show spectroscopic line-profile and low-amplitude radial velocity variability indicative of pulsation. All 11 stars are photometrically variable with amplitudes between 4 and 94 mmag in Johnson B and periods between 0.38 and 1.86 days. The 11 stars have between two and five independent periods.
- ID:
- ivo://CDS.VizieR/J/A+A/499/567
- Title:
- BV differential photometry of HR 7224
- Short Name:
- J/A+A/499/567
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although photometric variations of chemically peculiar (CP) stars are frequently used to determine their rotational periods, the detailed mechanism of their light variability remains poorly understood. We simulate the light variability of the star HR 7224 using the observed surface distribution of silicon and iron. We used the TLUSTY model atmospheres calculated for the appropriate silicon and iron abundances to obtain the emergent flux and to predict the rotationally modulated light curve of the star. We also obtained additional photometric measurements and employed our own regression procedure to derive a more precise estimate of the light elements. We show that the light variation of the star can be explained as a result of i) the uneven surface distribution of the elements, ii) the flux redistribution from the ultraviolet to the visible part of the spectrum, and iii) rotation of the star. We show that the silicon bound-free transitions and iron bound-bound transitions provide the main contribution to the flux redistribution, although an additional source of opacity is needed. We confirm that numerous iron lines significantly contribute to the well-known depression at 5200{AA} and discuss the connection between iron abundance and the value of peculiarity index a. The uneven surface distribution of silicon and iron is able to explain most of the rotationally modulated light variation in the star HR 7224.
- ID:
- ivo://CDS.VizieR/J/A+A/420/1039
- Title:
- 2001-2003 BV differential photometry of SW Lac
- Short Name:
- J/A+A/420/1039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the present study, the activity of the eclipsing binary of the W UMa-type system SW Lac is examined by analysing the new BV photoelectric observations obtained in 2001, 2002 and 2003 at the Ankara University Observatory. During this period, the seasonal light curves show significant differences and asymmetries. A simultaneous analysis of the light curves is made using Djurasevic's inverse-problem method.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A36
- Title:
- BV differential photometry of V711 Tau
- Short Name:
- J/A+A/521/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We attempt to establish the real nature of the orbital period variation and its relation to the spot activity of V711 Tau, and determine why the (B-V) colour of the star appears to be nearly independent of its V magnitude. We wish to verify whether existing predictions in the literature for the long-term spot activity of the star are true or not by making extended photometric observations, and whether the broad component of H{alpha} emission originates in more localised active regions, as suggested by some chromospheric models, by searching for any correlation between the base-line width of the emission and the light modulation.
- ID:
- ivo://CDS.VizieR/J/A+A/465/943
- Title:
- BVI and RV curves of 5 eclipsing binaries
- Short Name:
- J/A+A/465/943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We detected tertiary components of close binaries from spectroscopy and light curve modelling, investigated the light-travel time effect and the possibility of magnetic activity cycles, measured mass ratios for unstudied systems, and derived absolute parameters. We carried out new photometric and spectroscopic observations of five bright close eclipsing binaries, predominantly in the southern skies. We obtained full Johnson BV light curves, which were modelled with the Wilson-Devinney code. Radial velocities were measured with the cross-correlation method using IAU radial velocity standards as spectral templates. Period changes were studied with the O-C method, utilising published epochs of minimum light (XY Leo) and ASAS photometry (VZ Lib). For three objects (DX Tuc, QY Hya, V870 Ara), absolute parameters have been determined for the first time. We spectroscopically detected the tertiary components in XY Leo and VZ Lib and discovered one in QY Hya. For XY Leo we updated the light-time effect parameters and detected a secondary periodicity of about 5100d in the O-C diagram that may hint at the existence of short-period magnetic cycles. A combination of recent photometric data shows that the orbital period of the tertiary star in VZ Lib is likely to be over 1500d. QY Hya is a semi-detached X-ray active binary in a triple system with K and M-type components, while V870 Ara is a contact binary with the third smallest spectroscopic mass ratio for a W UMa star to date. Being close to the theoretical minimum for contact binaries, this small mass ratio suggests that V870 Ara has the potential of constraining evolutionary scenarios of binary mergers. The inferred distances to these systems are compatible with the Hipparcos parallaxes.
