Number of results to display per page
Search Results
1152. RR Lyrae in NGC 6101
- ID:
- ivo://CDS.VizieR/J/other/PASA/29.72
- Title:
- RR Lyrae in NGC 6101
- Short Name:
- J/other/PASA/29.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- V- and I-band observations were taken over 9 months to study the RR Lyrae population in the metal-poor diffuse globular cluster NGC 6101. We identify one new variable, which is either a potential long-period red giant variable or eclipsing binary, and recover all previously identified RR Lyraes. One previously studied RR Lyrae is reclassified as an RRc type, while two period estimations have been significantly refined. We confirm that NGC 6101 is Oosterhoff type II with a high ratio of n(c)/n(ab+c)=0.833 with a very long mean RRab period of 0.86d. By using theoretical RR Lyrae period-luminosity-metallicity relations, we use our V- and I-band RR Lyrae data to gain an independent estimate of the reddening towards this cluster of E(B-V)=0.15+/-.04 and derive a distance of 12.8+/-0.8kpc. The majority of the work in this study was undertaken by upper secondary school students involved in the Space to Grow astronomy education project in Australia.
1153. RR Lyrae in NGC 6171
- ID:
- ivo://CDS.VizieR/J/AJ/113/1711
- Title:
- RR Lyrae in NGC 6171
- Short Name:
- J/AJ/113/1711
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations have been used to derive precise light curves and Fourier parameters for sixteen RR Lyrae variables in the Oosterhoff type I globular cluster NGC 6171. It is found that, for the RRab stars, the Fourier phase differences {phi}_21_, {phi}_31_ and {phi}_41_ all correlate with period, but the amplitude ratios R_21_, R_31_, and R_41_ do not. For the RRc stars, R_21_, {phi}_31_, and {phi}_41_ correlate with period, but {phi}_21_, R_31_, and R_41_ do not. It is also found that a plot of R_21_ against {phi}_21_ is a useful tool for distinguishing between RRc and RRab stars, regardless of color or chemical composition. Simon's method that relates physical properties of RRc stars to the pulsation period and Fourier phase parameter {phi}_31_ has been used to determine the mass, luminosity, temperature and a helium parameter for the RRc stars. A comparison with the parameters determined from CCD observations of RRc stars in six other galactic globular clusters indicates that mean masses and mean luminosities increase and mean temperatures and helium abundances decrease with decreasing cluster metal abundance. The formulae of Jurcsik & Kovacs (1996, Cat. <J/A+A/312/111>) for relating Fourier parameters of RRab stars to [Fe/H] and luminosity have been tested and the results are reasonable. (c) 1997 American Astronomical Society.
- ID:
- ivo://CDS.VizieR/J/AJ/132/1202
- Title:
- RR Lyrae in Northern Sky Variability Survey
- Short Name:
- J/AJ/132/1202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use data from the Northern Sky Variability Survey (NSVS), obtained from the first-generation Robotic Optical Transient Search Experiment (ROTSE-I), to identify and study RR Lyrae variable stars in the solar neighborhood. We initially identified 1197 RRab (RR0) candidate stars brighter than the ROTSE median magnitude V=14. Periods, amplitudes, and mean V magnitudes are determined for a subset of 1188 RRab stars with well-defined light curves. Metallicities are determined for 589 stars by the Fourier parameter method and by the relationship between period, amplitude, and [Fe/H]. We comment on the difficulties of clearly classifying RRc (RR1) variables in the NSVS data set. Distances to the RRab stars are calculated using an adopted luminosity-metallicity relation with corrections for interstellar extinction. The 589 RRab stars in our final sample are used to study the properties of the RRab population within 5kpc of the Sun. The Bailey diagram of period versus amplitude shows that the largest component of this sample belongs to Oosterhoff type I. Metal-rich ([Fe/H]>-1) RRab stars appear to be associated with the Galactic disk. Our metal-rich RRab sample may include a thin-disk, as well as a thick-disk population, although the uncertainties are too large to establish this. There is some evidence among the metal-rich RRab stars for a decline in scale height with increasing [Fe/H], as was found by Layden. The distribution of RRab stars with -1<[Fe/H]<-1.25 indicates that within this metallicity range the RRab stars are a mixture of stars belonging to halo and disk populations.
1155. RR Lyrae in omega Cen
- ID:
- ivo://CDS.VizieR/J/A+A/574/A15
- Title:
- RR Lyrae in omega Cen
- Short Name:
- J/A+A/574/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey of RR Lyrae stars in an area of 50deg^2^ around the globular cluster {omega} Centauri, aimed at detecting debris material from the alleged progenitor galaxy of the cluster. We detected 48 RR Lyrae stars, only 11 of which have been previously reported. Ten of the eleven previously known stars were found inside the tidal radius of the cluster. The rest were located outside the tidal radius up to distances of ~6-degrees from the center of the cluster. Several of these stars are located at distances similar to that of {omega} Centauri. We investigate the probability that they may have been stripped off the cluster. To do this, we studied their properties (mean periods) by calculating the expected halo and thick-disk population of RR Lyrae stars in this part of the sky, analyzing the radial velocity of a sub-sample of the RR Lyrae stars, and finally, studying the probable orbits of this sub-sample around the Galaxy. The results of these investigations do not support the scenario that there is significant tidal debris around {omega} Centauri, which confirms previous studies on the region. It is puzzling that tidal debris has been found elsewhere but not near the cluster itself.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/2528
- Title:
- RR Lyrae in SDSS Stripe 82
- Short Name:
- J/MNRAS/424/2528
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose a robust principal component analysis framework for the exploitation of multiband photometric measurements in large surveys. Period search results are improved using the time-series of the first principal component due to its optimized signal-to-noise ratio. The presence of correlated excess variations in the multivariate time-series enables the detection of weaker variability. Furthermore, the direction of the largest variance differs for certain types of variable stars. This can be used as an efficient attribute for classification. The application of the method to a subsample of Sloan Digital Sky Survey Stripe 82 data yielded 132 high-amplitude delta Scuti variables. We also found 129 new RR Lyrae variables, complementary to the catalogue of Sesar et al., extending the halo area mapped by Stripe 82 RR Lyrae stars towards the Galactic bulge. The sample also comprises 25 multiperiodic or Blazhko RR Lyrae stars.
- ID:
- ivo://CDS.VizieR/J/AJ/158/223
- Title:
- RR Lyrae members of the Pal 5 stellar stream
- Short Name:
- J/AJ/158/223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Thin stellar streams, formed from the tidal disruption of globular clusters, are important gravitational tools, sensitive to both global and small-scale properties of dark matter. The Palomar 5 stellar stream (Pal 5) is an exemplar stream within the Milky Way: its ~20{deg} tidal tails connect back to the progenitor cluster, and the stream has been used to study the shape, total mass, and substructure fraction of the dark matter distribution of the Galaxy. However, most details of the phase-space distribution of the stream are not fully explained, and dynamical models that use the stream for other inferences are therefore incomplete. Here we aim to measure distance and kinematic properties along the Pal 5 stream in order to motivate improved models of the system. We use a large catalog of RR Lyrae-type stars (RRLs) with astrometric data from the Gaia mission to probabilistically identify RRLs in the Pal 5 stream. RRLs are useful because they are intrinsically luminous standard candles and their distances can be inferred with small relative precision (~3%). By building a probabilistic model of the Pal 5 cluster and stream in proper motion and distance, we find 27 RRLs consistent with being members of the cluster (10) and stream (17). Using these RRLs, we detect gradients in distance and proper motion along the stream, and provide an updated measurement of the distance to the Pal 5 cluster using the RRLs, d=20.6+/-0.2 kpc. We provide a catalog of Pal 5 RRLs with inferred membership probabilities for future modeling work.
1158. RR Lyrae Metallicities
- ID:
- ivo://CDS.VizieR/III/176
- Title:
- RR Lyrae Metallicities
- Short Name:
- III/176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog presents metal abundance, distance and radial velocity data on a sample of 302 ab-type RR Lyrae variables within about 2.5 kpc of the Sun. The metal abundance information was obtained from low-medium resolution spectra, using the pseudo-equivalent widths of the Ca II K line and the the H-delta, H-gamma and H-beta lines. The technique employed was similar to Preston's (1959ApJ...130..507P) {Delta}-S method, though significant differences exist; see the source reference for details. The data were calibrated to the Zinn & West (1984ApJS...55...45Z) globular cluster abundance scale. The photometry employed in the distance determinations was primarily taken from the General Catalog of Variable Stars (1985, hereafter GCVS4). Exceptions are noted in column 29; the letters match the footnotes in Table 10 of Layden (1994AJ....108.1016L). The minimum and maximum light photometry, and rise-time were combined following Barnes & Hawley (1986ApJ...307L...9B) to give an estimate of the intensity- averaged magnitude, i.e. the magnitude the star would have if it were not variable. When the GCVS4 quoted magnitudes in passbands other than V, the GCVS4 magnitudes were transformed to the V passband using the relations established in Layden (1994AJ....108.1016L). The interstellar absorption estimates are from Burstein & Heiles (1982AJ.....87.1165B), modified by a simple dust-distribution model. The distances were computed assuming the Mv(RR)-[Fe/H] relation of Carney, Storm & Jones (1992ApJ...386..663C). Radial velocities were measured from the spectra via cross-correlation with secondary velocity standards. The velocities from the individual spectra were fit with a standard radial velocity curve in the (phase, velocity) plane, to give an estimate of the systemic (center of mass) velocity of each star. The error in this value was estimated from the scatter about the best-fit velocity curve, and the quality of the spectra employed. Other methods were used to combine the individual velocities when the situation demanded (cm = 2,3 in column 70; see Layden (1994AJ....108.1016L) for details). The observed velocities were combined with values from the literature to produce a final, best estimate of the systemic radial velocity of each star, and its error.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/4283
- Title:
- 33 RR Lyrae observed in Pisces with K2-E2
- Short Name:
- J/MNRAS/452/4283
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A detailed analysis is presented of 33 RR Lyrae stars in Pisces observed with the Kepler space telescope over the 8.9-d long K2 Two-Wheel Concept Engineering Test. The sample includes not only fundamental-mode and first-overtone (RRab and RRc) stars but the first two double-mode (RRd) stars that Kepler detected and the only modulated first-overtone star ever observed from space so far. The precision of the extracted K2 light curves made it possible to detect low-amplitude additional modes in all subtypes. All RRd and non-modulated RRc stars show the additional mode at P_X_/P_1_~0.61 that was detected in previous space-based photometric measurements. A periodicity longer than the fundamental mode was tentatively identified in one RRab star that might belong to a gravity mode. We determined the photometric [Fe/H] values for all fundamental-mode stars and provide the preliminary results of our efforts to fit the double-mode stars with non-linear hydrodynamic pulsation models. The results from this short test run indicate that the K2 mission will be, and has started to be, an ideal tool to expand our knowledge about RR Lyrae stars. As a by-product of the target search and analysis, we identified 165 bona fide double-mode RR Lyrae stars from the Catalina Sky Survey observations throughout the sky, 130 of which are new discoveries.
- ID:
- ivo://CDS.VizieR/J/A+A/330/515
- Title:
- RR Lyrae parallaxes & proper motions
- Short Name:
- J/A+A/330/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used HIPPARCOS proper motions and the method of Statistical Parallax to estimate the absolute magnitude of RR Lyrae stars. In addition we used the HIPPARCOS parallax of RR Lyrae itself to determine it's absolute magnitude. These two results are in excellent agreement with each other and give a zero-point for the RR Lyrae M_v_,[Fe/H] relation of 0.77+/-0.15 at [Fe/H]=-1.53. This zero-point is in good agreement with that obtained recently by several groups using Baade-Wesselink methods which, averaged over the results from the different groups, gives M_v_=0.73+/-0.14 at [Fe/H]=-1.53. Taking the HIPPARCOS based zero-point and a value of 0.18+/-0.03 for the slope of the M_v_,[Fe/H] relation from the literature we find firstly, the distance modulus of the LMC is 18.26+/-0.15 and secondly, the mean age of the Globular Clusters is 17.4+/-3.0 GYrs. These values are compared with recent estimates based on other "standard candles" that have also been calibrated with HIPPARCOS data. It is clear that, in addition to astrophysical problems, there are also problems in the application of HIPPARCOS data that are not yet fully understood.
