MACHO Project Photometry of RR Lyrae Stars in the Sagittarius Dwarf Galaxy

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Griest, K.; Guern, J.; Lehner, M. J.; Marshall, Stuart; Minniti, D.; Peterson, Bruce A.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Stubbs, C. W.; Sutherland, William J.; Welch, D. L.

doi:10.1086/303467

Cited by 50 publications

(63 citation statements)

References 28 publications

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“…From this Figure we conclude that their colors and reddening-independent magnitudes are consistent with bulge blue stragglers. This is confirmed also by the location of~Scuti stars (triangles) with respect to bulge RR Lyrae type ab (crosses, from Alcock et al 1997) in the color magnitude diagram shown in Figure 3b. use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0074180900116808 We assume that the line of sight distributions of d Scu and RR Lyrae stars are similar.…”

Section: The Evolutionary Status Of 6 Seu Stars In the Bulge Fieldssupporting

confidence: 67%

Bulge δ Scuti stars in the MACHO database

Minniti¹,

Alcock²,

Alves³

et al. 1997

Symp. - Int. Astron. Union

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Section: The Evolutionary Status Of 6 Seu Stars In the Bulge Fieldssupporting

confidence: 67%

Bulge δ Scuti stars in the MACHO database

Minniti¹,

Alcock²,

Alves³

et al. 1997

Symp. - Int. Astron. Union

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“…Even taking into account that Sgr RR Lyrae stars are mixed with the Milky Way halo variables, some RR Lyrae stars found towards these coordinates have been associated with the dwarf galaxy by MACHO (Alard 1996;Alcock et al 1997) and OGLE (Soszyński et al 2014).…”

Section: Distances and The 3d View Of The Outer Bulgementioning

confidence: 99%

Mapping the outer bulge with RRab stars from the VVV Survey

Gran

Minniti

Saito

et al. 2016

A&A

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Context. The VISTA Variables in the Vía Láctea (VVV) is a near-IR time-domain survey of the Galactic bulge and southern plane. One of the main goals of this survey is to reveal the 3D structure of the Milky Way through their variable stars. In particular, enormous numbers of RR Lyrae stars have been discovered in the inner regions of the bulge (−8• ) by optical surveys such as OGLE and MACHO, but leaving an unexplored window of more than ∼47 sq deg (−10.0• and −10.3• b −8.0 • ) observed by the VVV Survey. Aims. Our goal is to characterize the RR Lyrae stars in the outer bulge in terms of their periods, amplitudes, Fourier coefficients, and distances in order to evaluate the 3D structure of the bulge in this area. The distance distribution of RR Lyrae stars will be compared to that of red clump stars, which is known to trace a X-shaped structure, in order to determine whether these two different stellar populations share the same Galactic distribution. Methods. A search for RR Lyrae stars was performed in more than ∼47 sq deg at low Galactic latitudes (−10.3• ). In the procedure the χ 2 value and analysis of variance (AoV) statistic methods were used to determine the variability and periodic features of the light curves, respectively. To prevent misclassifications, the analysis was performed only on the fundamental mode RR Lyrae stars (RRab) owing to similarities found in the near-IR light curve shapes of contact eclipsing binaries (W UMa) and first overtone RR Lyrae stars (RRc). On the other hand, the red clump stars of the same analyzed tiles were selected, and cuts in the color-magnitude diagram were applied and the maximum distance restricted to ∼20 kpc in order to construct a similar catalog in terms of distances and covered area compared to the RR Lyrae stars. Results. We report the detection of more than 1000 RR Lyrae ab-type stars in the VVV Survey located in the outskirts of the Galactic bulge. A few of them are possibly associated with the Sagittarius Dwarf Spheroidal Galaxy. We calculated colours, reddening, extinction, and distances of the detected RR Lyrae stars in order to determine the outer bulge 3D structure. Our main result is that, at the low galactic latitudes mapped here, the RR Lyrae stars trace a centrally concentrated spheroidal distribution. This is a noticeably different spatial distribution to the one traced by red clump stars known to follow a bar and X-shaped structure. We estimate the completeness of our sample at 80% for K s ≤ 15 mag.

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“…RR Lyrae stars are excellent distance indicators, as well as superb tracers of stellar substructures away from the Galactic plane (Mateo et al 1993;Alcock et al 1997). In order to pinpoint RR Lyrae star candidates within the 3FGL 95% uncertainty ellipses, we adopted a simple SDSS color cut scheme based on Equations (1)-(4) derived by Sesar et al (2010).…”

Section: Globular Clusters/dwarf Galaxies: Optical Searchmentioning

confidence: 99%

3fgl Demographics Outside the Galactic Plane Using Supervised Machine Learning: Pulsar and Dark Matter Subhalo Interpretations

Mirabal

Charles

Ferrara

et al. 2016

ApJ

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Nearly one-third of the sources listed in the Third Fermi Large Area Telescope (LAT) catalog (3FGL) remain unassociated. It is possible that predicted and even unanticipated gamma-ray source classes are present in these data waiting to be discovered. Taking advantage of the excellent spectral capabilities achieved by the Fermi LAT, we use machine-learning classifiers (Random Forest and XGBoost) to pinpoint potentially novel source classes in the unassociated 3FGL sample outside the Galactic plane. Here we report a total of 34 high-confidence Galactic candidates at. The currently favored standard astrophysical interpretations for these objects are pulsars or low-luminosity globular clusters hosting millisecond pulsars (MSPs). Yet these objects could also be interpreted as dark matter annihilation taking place in ultra-faint dwarf galaxies or dark matter subhalos. Unfortunately, Fermi LAT spectra are not sufficient to break degeneracies between the different scenarios. Careful visual inspection of archival optical images reveals no obvious evidence for low-luminosity globular clusters or ultra-faint dwarf galaxies inside the 95% error ellipses. If these are pulsars, this would bring the total number of MSPs at   b 5 | | to 106, down to an energy flux ≈4.0 × 10 −12 erg cm −2 s −1 between 100 MeV and 100 GeV. We find this number to be in excellent agreement with predictions from a new population synthesis of MSPs that predicts 100-126 highlatitude 3FGL MSPs depending on the choice of high-energy emission model. If, however, these are dark matter substructures, we can place upper limits on the number of Galactic subhalos surviving today and on dark matter annihilation cross sections. These limits are beginning to approach the canonical thermal relic cross section for dark matter particle masses below ∼100 GeV in the bottom quark (bb) annihilation channel.

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MACHO Project Photometry of RR Lyrae Stars in the Sagittarius Dwarf Galaxy

Cited by 50 publications

References 28 publications

Bulge δ Scuti stars in the MACHO database

Bulge δ Scuti stars in the MACHO database

Mapping the outer bulge with RRab stars from the VVV Survey

3fgl Demographics Outside the Galactic Plane Using Supervised Machine Learning: Pulsar and Dark Matter Subhalo Interpretations

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