A VIMOS spectroscopy study of photometric variables and straggler candidates in<i>ω</i> Centauri

Rozyczka, M.; Kałużny, J.; Pietrukowicz, P.; Pych, W.; Catelan, M.; Contreras, C.

doi:10.1051/0004-6361/201117668

Cited by 14 publications

(16 citation statements)

References 30 publications

(75 reference statements)

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“…We choose to include them here, and future metallicity measurements for these stars will be very important to confirm their identity as SSG/RS stars. Regardless of the nature of the Cool et al (2013) sources, Rozyczka et al (2012) identify an additional 13 3D kinematic cluster members in the SSG and RS regions in the cluster (not confined to the anomalous RGB/SGB). (Note, SSG candidate 23 lies blueward of the R vs. B −R isochrone in Figure 1, but inside the SSG region in other filter combinations.)…”

Section: Globular Cluster Observationsmentioning

confidence: 89%

On the Origin of Sub-subgiant Stars. I. Demographics

Geller

Leiner

Bellini

et al. 2017

ApJ

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Sub-subgiants are stars observed to be redder than normal main-sequence stars and fainter than normal subgiant (and giant) stars in an optical color-magnitude diagram. The red straggler stars, which lie redward of the red giant branch, may be related and are often grouped together with the sub-subgiants in the literature. These stars defy our standard theory of single-star evolution, and are important tests for binary evolution and stellar collision models. In total, we identify 65 sub-subgiants and red stragglers in 16 open and globular star clusters from the literature; 50 of these, including 43 sub-subgiants, pass our strict membership selection criteria (though the remaining sources may also be cluster members). In addition to their unique location on the color-magnitude diagram, we find that at least 58% (25/43) of sub-subgiants in this sample are X-ray sources with typical 0.5-2.5 keV luminosities of order 10 30−31 erg s −1 . Their X-ray luminosities and optical-to-X-ray flux ratios are similar to those of RS CVn active binaries. At least 65% (28/43) of the sub-subgiants in our sample are variables, 21 of which are known to be radial-velocity binaries. Typical variability periods are 15 days. At least 33% (14/43) of the sub-subgiants are Hα emitters. These observational demographics provide strong evidence that binarity is important for sub-subgiant formation. Finally, we find that the number of sub-subgiants per unit mass increases toward lower-mass clusters, such that the open clusters in our sample have the highest specific frequencies of sub-subgiants.

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Section: Globular Cluster Observationsmentioning

confidence: 89%

On the Origin of Sub-subgiant Stars. I. Demographics

Geller

Leiner

Bellini

et al. 2017

ApJ

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“…In the absence of both proper motion and radial velocity measurements suggesting otherwise, these stars would likely have been dismissed as unrelated to the cluster. Interestingly, Rozyczka et al (2012) find evidence that well over half are binaries, and surmise that they all may be. Given the extreme that ω Cen represents among globular clusters in many regards (including the recent and suprising discovery of a population of faint and very red main-sequence stars; King et al 2012), it remains to be seen whether such extreme red stragglers are commonplace in globulars.…”

Section: 2mentioning

confidence: 95%

HST/ACS IMAGING OF OMEGA CENTAURI: OPTICAL COUNTERPARTS OFCHANDRAX-RAY SOURCES

Cool

Haggard

Arias

et al. 2013

ApJ

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We present results of a search for optical counterparts of X-ray sources in and toward the globular cluster Omega Centauri (NGC 5139) using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. The ACS data consist of a mosaic of Wide Field Channel (WFC) images obtained using F625W, F435W, and F658N filters; with 9 pointings we cover the central ∼10 ′ ×10 ′ of the cluster and encompass 109 known Chandra sources. We find promising optical counterparts for 59 of the sources, ∼40 of which are likely to be associated with the cluster. These include 27 candidate cataclysmic variables (CVs), 24 of which are reported here for the first time. Fourteen of the CV candidates are very faint, with absolute magnitudes in the range M 625 = 10.4 − 12.6, making them comparable in brightness to field CVs near the period minimum discovered in the SDSS (Gänsicke et al. 2009). Additional optical counterparts include three BY Dra candidates, a possible blue straggler, and a previously-reported quiescent low-mass X-ray binary (Haggard et al. 2004). We also identify three foreground stars and 11 probable active galactic nuclei. Finally, we report the discovery of a group of seven stars whose X-ray properties are suggestive of magnetically active binaries, and whose optical counterparts lie on or very near the metal-rich anomalous giant and subgiant branches in ω Cen. If the apparent association between these seven stars and the RGB/SGB-a stars is real, then the frequency of X-ray sources in this metal-rich population is enhanced by a factor of at least five relative to the other giant and subgiant populations in the cluster. If these stars are not members of the metal-rich population, then they bring to 20 the total number of red stragglers (also known as sub-subgiants) that have been identified in ω Cen, the largest number yet known in any globular cluster.

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“…SB2 EBs that contain at least one low-mass main-sequence star (M   M 0.7 ☉ ) are especially useful for testing the treatment of convection and degeneracy in evolutionary models (e.g., Feiden & Chaboyer 2013). To date, several dozen low-mass SB2 EBs are known (e.g., Torres & Ribas 2002;Ribas 2003;Bayless & Orosz 2006;López-Morales & Shaw 2007;Vaccaro et al 2007;Devor 2008;Fernandez et al 2009;Huélamo et al 2009;Irwin et al 2009;Morales et al 2009aMorales et al , 2009bRozyczka et al 2009;Irwin et al 2011;Kraus et al 2011;Birkby et al 2012;Lee et al 2013;Zhou et al 2015). Many have larger radii than predicted by evolutionary models for their mass, effective temperature, and age.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Inflation and Stellar Mass. I. Revised Parameters for the Component Stars of the Kepler Low-mass Eclipsing Binary T-Cyg1-12664

Han

Muirhead

Swift³

et al. 2017

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Several low-mass eclipsing binary stars show larger than expected radii for their measured mass, metallicity, and age. One proposed mechanism for this radius inflation involves inhibited internal convection and starspots caused by strong magnetic fields. One particular eclipsing binary, T-Cyg1-12664, has proven confounding to this scenario. Çakırlı et al. measured a radius for the secondary component that is twice as large as model predictions for stars with the same mass and age, but a primary mass that is consistent with predictions. Iglesias-Marzoa et al. independently measured the radii and masses of the component stars and found that the radius of the secondary is not in fact inflated with respect to models, but that the primary is, which is consistent with the inhibited convection scenario. However, in their mass determinations, Iglesias-Marzoa et al. lacked independent radial velocity measurements for the secondary component due to the star's faintness at optical wavelengths. The secondary component is especially interesting, as its purported mass is near the transition from partially convective to a fully convective interior. In this article, we independently determined the masses and radii of the component stars of T-Cyg1-12664 using archival Kepler data and radial velocity measurements of both component stars obtained with IGRINS on the Discovery Channel Telescope and NIRSPEC and HIRES on the Keck Telescopes. We show that neither of the component stars is inflated with respect to models. Our results are broadly consistent with modern stellar evolutionary models for main-sequence M dwarf stars and do not require inhibited convection by magnetic fields to account for the stellar radii.

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A VIMOS spectroscopy study of photometric variables and straggler candidates inω Centauri

Cited by 14 publications

References 30 publications

On the Origin of Sub-subgiant Stars. I. Demographics

On the Origin of Sub-subgiant Stars. I. Demographics

HST/ACS IMAGING OF OMEGA CENTAURI: OPTICAL COUNTERPARTS OFCHANDRAX-RAY SOURCES

Magnetic Inflation and Stellar Mass. I. Revised Parameters for the Component Stars of the Kepler Low-mass Eclipsing Binary T-Cyg1-12664

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