- ID:
- ivo://CDS.VizieR/J/A+A/399/365
- Title:
- ROTSE delta Scuti stars
- Short Name:
- J/A+A/399/365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed a sample of delta Scuti stars discovered by the ROTSE collaboration in 1999 with Super-LOTIS in order to characterize changes in their pulsation periods over a time baseline of roughly three years. Achieving these goals required the creation of an automated astrometric and photometric data reduction pipeline for the Super-LOTIS camera. Applying this pipeline to data from a June 2002 observing campaign, we detect pulsations in 18 objects, and find that in two cases the periods have changed significantly over the three years between the ROTSE and Super-LOTIS observations. Since theory predicts that evolutionary period changes should be quite small, sources of non-evolutionary period changes due to the interactions of pulsations modes are discussed.
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- ID:
- ivo://CDS.VizieR/J/ApJ/776/26
- Title:
- RRab stars in the Orphan stream distances
- Short Name:
- J/ApJ/776/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report positions, velocities, and metallicities of 50 ab-type RR Lyrae (RRab) stars observed in the vicinity of the Orphan stellar stream. Using about 30 RRab stars classified as being likely members of the Orphan stream, we study the metallicity and the spatial extent of the stream. We find that RRab stars in the Orphan stream have a wide range of metallicities, from -1.5dex to -2.7dex. The average metallicity of the stream is -2.1dex, identical to the value obtained by Newberg et al. (2010ApJ...711...32N) using blue horizontal branch stars. We find that the most distant parts of the stream (40-50kpc from the Sun) are about 0.3dex more metal-poor than the closer parts (within ~30kpc), suggesting a possible metallicity gradient along the stream's length. We have extended the previous studies and have mapped the stream up to 55kpc from the Sun. Even after a careful search, we did not identify any more distant RRab stars that could plausibly be members of the Orphan stream. If confirmed with other tracers, this result would indicate a detection of the end of the leading arm of the stream. We have compared the distances of Orphan stream RRab stars with the best-fit orbits obtained by Newberg et al. We find that model 6 of Newberg et al. cannot explain the distances of the most remote Orphan stream RRab stars, and conclude that the best fit to distances of Orphan stream RRab stars and to the local circular velocity is provided by potentials where the total mass of the Galaxy within 60kpc is M_60_~2.7x10^11^M_{sun}_, or about 60% of the mass found by previous studies. More extensive modeling that would consider non-spherical potentials and the possibility of misalignment between the stream and the orbit is highly encouraged.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/47
- Title:
- RRab stars of Monoceros Ring & A13 overdensities
- Short Name:
- J/ApJ/854/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Monoceros Ring (also known as the Galactic Anticenter Stellar Structure) and A13 are stellar overdensities at estimated heliocentric distances of d~11kpc and 15kpc observed at low Galactic latitudes toward the anticenter of our Galaxy. While these overdensities were initially thought to be remnants of a tidally disrupted satellite galaxy, an alternate scenario is that they are composed of stars from the Milky Way (MW) disk kicked out to their current location due to interactions between a satellite galaxy and the disk. To test this scenario, we study the stellar populations of the Monoceros Ring and A13 by measuring the number of RR Lyrae and M giant stars associated with these overdensities. We obtain low-resolution spectroscopy for RR Lyrae stars in the two structures and measure radial velocities to compare with previously measured velocities for M giant stars in the regions of the Monoceros Ring and A13, to assess the fraction of RR Lyrae to M giant stars (f_RR:MG_) in A13 and Mon/GASS. We perform velocity modeling on 153 RR Lyrae stars (116 in the Monoceros Ring and 37 in A13) and find that both structures have very low f_RR:MG_. The results support a scenario in which stars in A13 and Mon/GASS formed in the MW disk. We discuss a possible association between Mon/GASS, A13, and the Triangulum-Andromeda overdensity based on their similar velocity distributions and f_RR:MG_.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/30
- Title:
- RRab stars toward Baade's window with Blanco/DECam
- Short Name:
- J/ApJ/874/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained repeated images of six fields toward the Galactic bulge in five passbands (u, g, r, i, z) with the DECam imager on the Blanco 4m telescope at CTIO. From more than 1.6 billion individual photometric measurements in the field centered on Baade's window, we have detected 4877 putative variable stars. A total of 474 of these have been confirmed as fundamental mode RR Lyrae stars, whose colors at minimum light yield line-of-sight reddening determinations, as well as a reddenning law toward the Galactic Bulge, which differs significantly from the standard R_V_=3.1 formulation. Assuming that the stellar mix is invariant over the 3 square-degree field, we are able to derive a line-of-sight reddening map with sub-arcminute resolution, enabling us to obtain de-reddened and extinction corrected color-magnitude diagrams (CMDs) of this bulge field using up to 2.5 million well-measured stars. The corrected CMDs show unprecedented detail and expose sparsely populated sequences: for example, delineation of the very wide red giant branch, structure within the red giant clump, the full extent of the horizontal branch, and a surprising bright feature that is likely due to stars with ages younger than 1Gyr. We use the RR Lyrae stars to trace the spatial structure of the ancient stars and find an exponential decline in density with Galactocentric distance. We discuss ways in which our data products can be used to explore the age and metallicity properties of the bulge, and how our larger list of all variables is useful for learning to interpret future LSST alerts.
- ID:
- ivo://CDS.VizieR/J/AJ/152/170
- Title:
- RRLs in globulars. IV. UBVRI photometry in Omega Cen
- Short Name:
- J/AJ/152/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular cluster {omega} Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years and a sky area of 84x48arcmin. The current data were complemented with data available in the literature and provided new, homogeneous pulsation parameters (mean magnitudes, luminosity amplitudes, periods) for 187 candidate {omega} Cen RR Lyrae (RRLs). Among them we have 101 RRc (first overtone) and 85 RRab (fundamental) variables, and a single candidate RRd (double-mode) variable. Candidate Blazhko RRLs show periods and colors that are intermediate between the RRc and RRab variables, suggesting that they are transitional objects. A comparison of the period distribution and the Bailey diagram indicates that RRLs in {omega} Cen show a long-period tail not present in typical Oosterhoff II (OoII) globulars. The RRLs in dwarf spheroidals and in ultra-faint dwarfs have properties between Oosterhoff intermediate and OoII clusters. Metallicity plays a key role in shaping the above evidence. These findings do not support the hypothesis that {omega} Cen is the core remnant of a spoiled dwarf galaxy. Using optical period-Wesenheit relations that are reddening-free and minimally dependent on metallicity we find a mean distance to {omega} Cen of 13.71+/-0.08+/-0.01mag (semi-empirical and theoretical calibrations). Finally, we invert the I-band period-luminosity-metallicity relation to estimate individual RRLs' metal abundances. The metallicity distribution agrees quite well with spectroscopic and photometric metallicity estimates available in the literature.
- ID:
- ivo://CDS.VizieR/J/AJ/155/137
- Title:
- RRLs in globulars. V.{omega} Centauri NIR photometry
- Short Name:
- J/AJ/155/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new complete near-infrared (NIR, JHK_s_) census of RR Lyrae stars (RRLs) in the globular {omega} Cen (NGC 5139). We collected 15472 JHK_s_ images with 4-8 m class telescopes over 15 years (2000-2015) covering a sky area around the cluster center of 60x34 arcmin^2^. These images provided calibrated photometry for 182 out of the 198 cluster RRL candidates with 10 to 60 measurements per band. We also provide new homogeneous estimates of the photometric amplitude for 180 (J), 176 (H) and 174 (K_s_) RRLs. These data were supplemented with single-epoch JK_s_ magnitudes from VHS (Mcmahon et al. 2013Msngr.154...35M) and with single-epoch H magnitudes from 2MASS (Cat. VII/233). Using proprietary optical and NIR data together with new optical light curves (ASAS-SN) we also updated pulsation periods for 59 candidate RRLs. As a whole, we provide JHK_s_ magnitudes for 90 RRab (fundamentals), 103 RRc (first overtones) and one RRd (mixed-mode pulsator). We found that NIR/optical photometric amplitude ratios increase when moving from first overtone to fundamental and to long-period (P>0.7 days) fundamental RRLs. Using predicted period-luminosity-metallicity relations, we derive a true distance modulus of 13.674+/-0.008+/-0.038 mag (statistical error and standard deviation of the median) based on spectroscopic iron abundances, and of 13.698+/-0.004+/-0.048 mag based on photometric iron abundances. We also found evidence of possible systematics at the 5%-10% level in the zero-point of the period-luminosity relations based on the five calibrating RRLs whose parallaxes had been determined with the HST.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/L96
- Title:
- RR Lyrae AllWise photometry
- Short Name:
- J/MNRAS/440/L96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use photometry from the recent AllWISE Data Release of the Wide-field Infrared Survey Explorer (WISE) of 129 calibration stars, combined with prior distances obtained from the established M_V_-[Fe/H] relation and Hubble Space Telescope trigonometric parallax, to derive mid-infrared period-luminosity relations for RR Lyrae pulsating variable stars. We derive relations in the W1, W2 and W3 wavebands (3.4, 4.6 and 12um, respectively), and for each of the two main RR Lyrae sub-types (RRab and RRc). We report an error on the period-luminosity relation slope for RRab stars of 0.2. We also fit posterior distances for the calibration catalogue and find a median fractional distance error of 0.8 per cent.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/165
- Title:
- RR Lyrae as tracers in the Virgo overdensity region
- Short Name:
- J/ApJ/831/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a combination of spatial distribution and radial velocity to search for halo substructures in a sample of 412 RR Lyrae stars (RRLSs) that covers a region of ~525 square degrees of the Virgo overdensity (VOD) and spans distances from the Sun from 4 to 75kpc. With a friends-of-friends algorithm we identified six high-significance groups of RRLSs in phase space, which we associate mainly with the VOD and with the Sagittarius stream. Four other groups were also flagged as less significant overdensities. Three high-significance and three lower-significance groups have distances between ~10 and 20kpc, which places them in the distance range attributed by others to the VOD. The largest of these is the Virgo stellar stream at 19kpc, which has 18 RRLSs, a factor of two increase over the number known previously. While these VOD groups are distinct according to our selection criteria, their overlap in position and distance and, in a few cases, similarity in radial velocity are suggestive that they may not all stem from separate accretion events. Even so, the VOD appears to be caused by more than one overdensity. The Sagittarius (Sgr) stream is a very obvious feature in the background of the VOD at a mean distance of 44kpc. Two additional high-significance groups were detected at distances >40kpc. Their radial velocities and locations differ from the expected path of the Sgr debris in this part of the sky, and they are likely to be remnants of other accretion events.
- ID:
- ivo://CDS.VizieR/J/other/NewA/27.1
- Title:
- RR Lyrae candidates in Aqr halo stream
- Short Name:
- J/other/NewA/27.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Aquarius stream has been recently discovered in the course of the RAVE Survey. It is a chemically coherent structure, originating from the tidal disruption of a 12Gyr, [Fe/H]=-1.0 globular cluster. We have surveyed a ~284deg^2^ area of the sky containing the 15 known members of the Aquarius stream looking for RR Lyr variables. RR Lyr variables are primary distance indicators and discovering some of them firmly associated with the Aquarius stream would provide a 3D representation of its Galactic orbit and would probe the spatial structure of the Galactic gravitational potential. During September and October 2012, we have obtained on-purpose, epoch photometry in the Landolt BV and Sloan gri bands with the APASS South telescopes located at Cerro Tololo. Our data are uniformly complete to V=15.2mag over the whole surveyed area, the faintest recorded stars reaching V=18mag. We have found 71 RR Lyr variables, and a firm pulsation period was derived for 53 of them. Our census of RR Lyr variables is complete to a distance of 8kpc from the Sun. For all objects we provide distances and light- and color-curves, mean values and amplitudes in all five BVgri passbands, finding charts and accurate local photometric sequences. About half of the RR Lyr variables we have discovered were previously known, but we provide the first multi-band photometric data. They were in fact mostly discovered as by-products of white-light patrol searches for optical counterparts to gamma-ray bursters or potentially hazardous asteroids.
- ID:
- ivo://CDS.VizieR/J/ApJ/849/150
- Title:
- RR Lyrae candidates in the MW outer halo
- Short Name:
- J/ApJ/849/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- RR Lyrae stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way (MW). This is because they are easy to find in the light-curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112 RR Lyr stars beyond 50kpc in the outer halo of the MW, excluding the Sgr streams, for which we have obtained moderate-resolution spectra with Deimos on the Keck II Telescope. Four of these have distances exceeding 100kpc. These were selected from a much larger set of 447 candidate RR Lyr stars that were data-mined using machine-learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112 RR Lyr stars we determine the radial velocity dispersion in the outer halo of the MW to be ~90km/s at 50kpc, falling to about 65km/s near 100 kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447 candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as r^-4^.
