- ID:
- ivo://CDS.VizieR/J/A+A/496/765
- Title:
- R light-curve of TT Ari
- Short Name:
- J/A+A/496/765
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the variability of the nova-like cataclysmic variable TT Ari, on time-scales of between minutes and months. The observations in the filter R were obtained at the 40-cm telescope of the Chungbuk National University (Korea), 51 observational runs cover 226 hours. In our analysis, we applied several methods: periodogram, wavelet, and scalegram analysis. TT Ari remained in a "negative superhump" state after its return from the "positive superhump" state, which lasted for 8 years. The ephemeris for 12 of the best pronounced minima is T_min_=BJD 2453747.0700(47)+0.132322(53)E, where numbers in digits are errors in units of the last digit. The phases of minima may reach 0.2, which reflects the non-eclipse nature of these minima. The quasi-periodic oscillations (QPO) are present with a mean "period" of 21.6min and mean semi-amplitude of 36mmag.This value is consistent with the range 15-25min reported for previous "negative superhump" states and does not support the hypothesis of secular decrease in the QPO period. Either the period, or the semi-amplitude show significant night-to-night variations. According to the position at the two-parameter diagrams (i.e. diagrams of pairs of parameters: time, mean brightness of the system, brightness of the source of QPO, amplitude, and timescale of the QPOs), the interval of observations was divided into 5 parts, showing different characteristics: 1) the "pre-outburst" stage, 2) the "rise to outburst", 3) "top of the outbursts", 4) "post- outburst QPO" state, and 5) "slow brightening". The the QPO source was significantly brighter during the 10-day outburst, than during the preceding interval. However, after the outburst, the large brightness of the QPO source still existed for about 30 days, producing the stage "4". The diagram for m_QPO_({bar}{m}) exhibits two groups in the brightness range 10.6-10.8, which correspond to larger and smaller amplitudes of the QPO. For the group "5" only, statistically significant correlations were found, for which, with increasing mean brightness, the period, amplitude, and brightness of the of QPO source also increase. The mean brightness at the "negative superhump state" varies within 10.3-11.2, so the system is brighter than at the "positive superhump" (11.3), therefore the "negative superhump" phenomenon may be interpreted by a larger accretion rate. The system is an excellent laboratory for studying processes resulting in variations on timescales of between seconds and decades and needs further monitoring at various states of activity.
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- ID:
- ivo://CDS.VizieR/J/AZh/81/925
- Title:
- R light curves of 5 blazars
- Short Name:
- J/AZh/81/925
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We monitored five active galactic nuclei in the R optical band with a CCD mounted on the 1-m Zeiss-1000 telescope of the Special Astrophysical Observatory from April 2001 to August 2003. Three sources displayed intraday variability on several nights. Stronger variability was detected on time scales from two days to a week. The two-year light curves are presented for four of the observed objects.
- ID:
- ivo://CDS.VizieR/J/A+AS/120/357
- Title:
- R magnitudes in four ESO fields
- Short Name:
- J/A+AS/120/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables present a R-band CCD photometric sequence of stars for calibrating ESO/SERC(R) survey plates in the region of the Shapley supercluster of galaxies. The observations were carried out on 1993 Ferbruary 17 to 22 at the 0.6m telescope of the University of Toronto at Las Campanas Observatory in Chile, using a 513x516pix CCD with a resolution of 0.46''.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A38
- Title:
- Robust automatic photometry for SDSS gal.
- Short Name:
- J/A+A/591/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an automatic procedure to perform reliable photometry of galaxies on SDSS images. We selected a sample of 5853 galaxies in the Coma and Virgo superclusters. For each galaxy, we derive Petrosian g and i magnitudes, surface brightness and color profiles. Unlike the SDSS pipeline, our procedure is not affected by the well known shredding problem and efficiently extracts Petrosian magnitudes for all galaxies. Hence we derived magnitudes even from the population of galaxies missed by the SDSS which represents ~25% of all Local supercluster galaxies and 95% of galaxies with g<11mag. After correcting the g and i magnitudes for Galactic and internal extinction, the blue and red sequences in the color magnitude diagram are well separated, with similar slopes. In addition, we study (i) the color-magnitude diagrams in different galaxy regions, the inner (r<=1kpc), intermediate (0.2R_{Pet}_>=r>=0.3R_{Pet}_) and outer, disk-dominated (r>=0.35R_{Pet}_)) zone, and (ii), we compute template color profiles, discussing the dependences of the templates on the galaxy masses and on their morphological type. The two analyses consistently lead to a picture where elliptical galaxies show no color gradients, irrespective of their masses. Spirals, instead, display a steeper gradient in their color profiles with increasing mass, which is consistent with the growing relevance of a bulge and/or a bar component above 10^10^M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/110/1229
- Title:
- ROSAT X-ray survey in NGC 6475
- Short Name:
- J/AJ/110/1229
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A ROSAT X-ray survey, with complementary optical photometry, of the open cluster NGC 6475 has enabled the detection of ~50 late-F to K0 and ~70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low galactic latitude, 220Myr old cluster. The X-ray observations reported here have a typical limiting sensitivity of L_X_ ~ 10^29^erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the X-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the X-rays. The ratio between X-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of X-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in X-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of X-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/430/1049
- Title:
- RR Gem BV(RI)c differential photometry
- Short Name:
- J/A+A/430/1049
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extended CCD monitoring of RR Gem revealed that it is a Blazhko type RRab star with the shortest Blazhko period (7.23d) and smallest modulation amplitude (delta_Mmax_<0.1mag) currently known. The short period of the modulation cycle enabled us to obtain complete phase coverage of the pulsation at each phase of the modulation. This is the first multicolour observation of a Blazhko star which is extended enough to define accurate mean magnitudes and colours of the variable at different Blazhko phases. Small, but real, changes in the intensity mean colours at different Blazhko phases have been detected. The Fourier analysis of the light curves shows that, in spite of the mmag and smaller order of the amplitudes, the triplet structure is noticeable up to about the 14th harmonic. The modulation is concentrated to a very narrow, 0.2 phase range of the pulsation, centred on the supposed onset of the H emission during rising light. These observational results raise further complications for theoretical explanation of the long known but poorly understood Blazhko phenomenon.
- ID:
- ivo://CDS.VizieR/J/AJ/127/861
- Title:
- RR Lyrae in Draco dSph
- Short Name:
- J/AJ/127/861
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first CCD variability study of the Draco dwarf spheroidal galaxy. The data were obtained with the Fred Lawrence Whipple Observatory 1.2m telescope on Mount Hopkins, Arizona, between 1998 August 19 and 1999 June 20, over 22 nights, over a period of 10 months, covering a 22'x22' field centered at {alpha}=17h19m57.5s, {delta}=57{deg}50'05" (J2000.0). The analysis of the BVI images produced 163 variable stars, 146 of which were RR Lyrae: 123 RRab, 16 RRc, 6 RRd, and one RR12. The other variables include a SX Phe star, four anomalous Cepheids, and a field eclipsing binary. Using the short distance scale statistical parallax calibration of Gould & Popowski (1998ApJ...508..844G) and 94 RRab stars from our field, we obtain a distance modulus of (m-M)_0_=19.40+/-0.02(stat)+/-0.15(syst)mag for Draco, corresponding to a distance of 75.8+/-0.7(stat)+/-5.4(syst)kpc. By comparing the spread in magnitudes of RRab stars in B, V, and I, we find no evidence for internal dust in the Draco dwarf spheroidal galaxy. The catalog of all variables, as well as their photometry and finding charts, is available electronically via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request.
- ID:
- ivo://CDS.VizieR/J/other/IBVS/6106
- Title:
- RR Lyrae stars in GCVS observed by the QES
- Short Name:
- J/other/IBVS/610
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the light curve archive of the Qatar Exoplanet Survey to investigate the RR Lyrae variable stars listed in the GCVS. Of 588 variables studied, we reclassified 14 as eclipsing binaries, one as an RS CVn type variable, one as an irregular variable, four as classical Cepheids, and one as a type II Cepheid, while also improving their periods. We also report new RR Lyrae sub-type classifications for 65 variables and improve on the GCVS period estimates for 135 RR Lyrae variables. There are seven double-mode RR Lyrae stars in the sample for which we measured their fundamental and first overtone periods. Finally, we detected the Blazhko effect in 38 of the RR Lyrae stars for the first time and we successfully measured the Blazhko period for 26 of them.
- ID:
- ivo://CDS.VizieR/J/AJ/110/704
- Title:
- RR Lyrae Variables in M15
- Short Name:
- J/AJ/110/704
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD photometry is presented for RR Lyrae variable stars in the globular cluster M15. This photometry, mainly in V and R, with some additional B and I, is used to construct lightcurves of 44 RR Lyraes and one Cepheid in M15. One new low-amplitude RR Lyrae star was discovered. The observable parameters of the light curves are used, in conjunction with theoretical photometric indices, to obtain effective temperatures and bolometric magnitudes in the RR Lyrae stars. We confirm that the regions occupied by RRab and RRcd variables in M15 have little or no overlap in effective temperature. Photometry for variable and nonvariable horizontal branch stars in M15 is used to establish the high and low temperature boundaries of the instability strip. There is evidence that the blue edge of the M15 RR Lyrae instability strip becomes cooler at higher luminosities. Employing Cox's value of the mass of RRd stars, 0.75 Msun, and the pulsation equation, the absolute magnitude of the RR Lyrae stars in M15 is estimated to be <M_V_> = +0.36+/-0.12 mag. However, this result depends upon the adopted mass, bolometric correction, and color-temperature relation, which remain significantly uncertain. The implications of the absolute magnitude determination for the ages of the globular clusters are discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/115/193
- Title:
- RR Lyrae V light curves
- Short Name:
- J/AJ/115/193
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present V-band CCD photometry for a sample of 103 RR Lyrae variables selected from the General Catalogue of Variable Stars to lie in the inner halo of the Galaxy. I also describe a method for obtaining the mean apparent magnitude and the epoch at maximum light of an RR Lyrae star. The method requires as few as five photometric observations, and simulations demonstrate that the associated errors are relatively small. I employ this method to derive the mean magnitudes and maximum light epochs of the 103 RR Lyrae stars observed. These stars were selected, based on their Galactic coordinates and original photographic photometry, to lie near their orbital tangent points, thus providing a sample well suited for measuring the rotational kinematics of the inner halo. Using interstellar reddenings from the literature and the observed mean V magnitudes, I derive distances for these stars and show that their actual locations in the Galaxy are indeed suitable for use in a kinematic study, despite the large zero-point errors in the survey photographic photometry.
