- 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.
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Search Results
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/147
- Title:
- RR Lyrae population in the Phoenix dwarf galaxy
- Short Name:
- J/ApJ/786/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first detailed study of the RR Lyrae variable population in the Local Group dSph/dIrr transition galaxy, Phoenix, using previously obtained HST/WFPC2 observations of the galaxy. We utilize template light curve fitting routines to obtain best fit light curves for RR Lyrae variables in Phoenix. Our technique has identified 78 highly probable RR Lyrae stars (54 ab-type; 24 c-type) with about 40 additional candidates. We find mean periods for the two populations of <P_ab_>=0.60+/-0.03 days and <P_c_>=0.353+/-0.002 days. We use the properties of these light curves to extract, among other things, a metallicity distribution function for ab-type RR Lyrae. Our analysis yields a mean metallicity of <[Fe/H]>=-1.68+/-0.06 dex for the RRab stars. From the mean period and metallicity calculated from the ab-type RR Lyrae, we conclude that Phoenix is more likely of intermediate Oosterhoff type; however the morphology of the Bailey diagram for Phoenix RR Lyraes appears similar to that of an Oosterhoff type I system. Using the RRab stars, we also study the chemical enrichment law for Phoenix. We find that our metallicity distribution is reasonably well fitted by a closed-box model. The parameters of this model are compatible with the findings of Hidalgo et al. (2009ApJ...705..704H; 2013ApJ...778..103H), further supporting the idea that Phoenix appears to have been chemically enriched as a closed-box-like system during the early stage of its formation and evolution.
- ID:
- ivo://CDS.VizieR/J/A+AS/125/313
- Title:
- RR Lyrae radial velocities and [Fe/H] I.
- Short Name:
- J/A+AS/125/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present systemic velocities and iron abundances for 56 RR Lyraes, the majority of which have been observed by the HIPPARCOS satellite. Comparison between our systemic velocities and previous values identifies several binary candidates only one of which, TU UMa, was previously suspected of being a binary. However, spectra of the unusual RR Lyrae BB Vir show no evidence of line doubling and hence do not support the recent claims that this star may have a Blue Horizontal Branch companion. Comparison between our abundances and previous determinations shows reasonable agreement except with the recent work of Layden (1994, Cat. <J/AJ/108/1016>) where we find systematic differences. Several of the stars included on the HIPPARCOS observing list as RR Lyraes are shown to be mis-classified. Of particular interest are the stars V363 Cas and AT And which, by analogy with XZ Cet, may be anomalous Cepheids.
- ID:
- ivo://CDS.VizieR/J/A+AS/125/321
- Title:
- RR Lyrae radial velocities and [Fe/H] II.
- Short Name:
- J/A+AS/125/321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second of the papers devoted to derive radial velocities and iron abundances of field RR Lyraes observed by HIPPARCOS. Our abundances show good agreement with those in the literature obtained both from photometric ({DELTA}S index) and spectroscopic methods. Binary candidates and stars misclassified as RR Lyraes in the original HIPPARCOS list have been also identified.
- ID:
- ivo://CDS.VizieR/J/MNRAS/398/1757
- Title:
- RR Lyraes in SDSS stripe 82
- Short Name:
- J/MNRAS/398/1757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the substructure revealed by RR Lyraes in Sloan Digital Sky Survey Stripe 82, which covers 2.5{deg} in declination on the celestial equator over the right ascension range {alpha}=20.7h to 3.3h. We use the new public archive of light-motion curves in Stripe 82, published by Bramich et al. in 2008 (Cat. V/141), to identify a set of high-quality RR Lyrae candidates. Period estimates are determined to high accuracy using a string-length method. A subset of 178 RR Lyraes with spectrally derived metallicities are employed to derive metallicity-period-amplitude relations, which are then used, together with archive magnitude data and light-curve Fourier decomposition, to estimate metallicities and hence distances for the entire sample. The RR Lyraes lie 5-115kpc from the Galactic Centre, with distance estimates accurate to ~8%. The RR Lyraes are further divided into subsets of 316 RRab types and 91 RRc types based on their period, colour and metallicity. We fit a smooth density law to the distribution as a simple representation of the data. For Galactocentric radii 5-25kpc the number density of RR Lyraes falls as r^-2.4^, but beyond 25kpc, the number density falls much more steeply, as r^-4.5^. However, we stress that in practice the density distribution is not smooth, but dominated by clumps and substructure. Samples of 55 and 237 RR Lyraes associated with the Sagittarius Stream and the Hercules-Aquila Cloud, respectively, are identified. Hence, ~70% of the RR Lyraes in Stripe 82 belong to known substructure, and the sharp break in the density law reflects the fact that the dominant substructure in Stripe 82 - the Hercules-Aquila Cloud and the Sagittarius Stream - lie within 40kpc. In fact, almost 60% of all the RR Lyraes in Stripe 82 are associated with the Hercules-Aquila Cloud alone, which emphasizes the cloud's pre-eminence. Additionally, evidence of a new and distant substructure - the Pisces Overdensity - is found, consisting of 28 faint RR Lyraes centred on Galactic coordinates (l~80{deg}, b~-55{deg}), with distances of ~80kpc. The total stellar mass in the Pisces Overdensity is ~10^4^M_{sun}_ and its metallicity is [Fe/H]~-1.5.
