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Spectroscopy and Photometry of Multiple Populations along the Asymptotic Giant Branch of NGC 2808 and NGC 6121 (M4)
Milone, A. P.; Marino, A. F.; Bedin, L. R. +8 more
We present a photometric and spectroscopic study of multiple populations along the asymptotic giant branch (AGB) of the intermediate-metallicity globular clusters (GCs) NGC 2808 and NGC 6121 (M4). Chemical abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Zn, Y, and Ce in AGB stars from high-resolution FLAMES+UVES@VLT spectra are rep…
Evidence for multiple populations in the intermediate-age cluster Lindsay 1 in the SMC
Rejkuba, M.; Bastian, N.; Lardo, C. +6 more
Lindsay 1 is an intermediate-age (≈8 Gyr) massive cluster in the Small Magellanic Cloud. Using VLT FORS2 spectra of 16 probable cluster members on the lower red giant branch of the cluster, we measure CN and CH band strengths (at ≃ 3883 and 4300 Å, respectively), along with carbon and nitrogen abundances and find that a sub-population of stars has…
Near-infrared MOSFIRE Spectra of Dusty Star-forming Galaxies at 0.2 < z < 4
Casey, Caitlin M.; Sanders, D. B.; Capak, Peter +6 more
We present near-infrared and optical spectroscopic observations of a sample of 450 and 850 µm-selected dusty star-forming galaxies (DSFGs) identified in a 400 arcmin2 area in the COSMOS field. Thirty-one sources of the 114 targets were spectroscopically confirmed at 0.2< z< 4, identified primarily in the near-infrared with K…
Evolution of the reverberation lag in GX 339-4 at the end of an outburst
Ponti, G.; Tomsick, J. A.; Rodriguez, J. +13 more
We studied X-ray reverberation lags in the Black hole X-ray binary (BHXRB) GX 339-4 at the end of the 2014-2015 outburst. We analysed data from an XMM-Newton campaign covering the end of the transition from the soft to hard state, and the decrease of luminosity in the hard state. During all the observations we detected, at high frequencies, signif…
Extended Main-sequence Turn-offs in Intermediate-age Star Clusters: Stellar Rotation Diminishes, but Does Not Eliminate, Age Spreads
Girardi, Léo; Goudfrooij, Paul; Correnti, Matteo
Extended main-sequence turn-off (eMSTO) regions are a common feature in color-magnitude diagrams of young- and intermediate-age star clusters in the Magellanic Clouds. The nature of eMSTOs remains debated in the literature. The currently most popular scenarios are extended star formation activity and ranges of stellar rotation rates. Here we study…
A search for sterile neutrinos with the latest cosmological observations
Feng, Lu; Zhang, Jing-Fei; Zhang, Xin
We report the result of a search for sterile neutrinos with the latest cosmological observations. Both cases of massless and massive sterile neutrinos are considered in the
Constraints on the Lyman continuum escape fraction for faint star-forming galaxies
Tozzi, P.; Balestra, I.; Rosati, P. +6 more
Star-forming galaxies have long been considered the dominant sources of the cosmic ultraviolet background radiation at early epochs. However, observing and characterizing the galaxy population with significant ionizing emission have proven to be challenging. In particular, the fraction of ionizing radiation that escapes the local environment to th…
SNR 1E 0102.2-7219 as an X-ray calibration standard in the 0.5-1.0 keV bandpass and its application to the CCD instruments aboard Chandra, Suzaku, Swift and XMM-Newton
Miller, Eric D.; Haberl, Frank; Plucinsky, Paul P. +4 more
Context. The flight calibration of the spectral response of charge-coupled device (CCD) instruments below 1.5 keV is difficult in general because of the lack of strong lines in the on-board calibration sources typically available. This calibration is also a function of time due to the effects of radiation damage on the CCDs and/or the accumulation…
Dissecting the extended main-sequence turn-off of the young star cluster NGC 1850
Bellini, Andrea; Goudfrooij, Paul; Puzia, Thomas H. +2 more
We use the Wide Field Camera 3 onboard the Hubble Space Telescope to obtain deep, high-resolution photometry of the young (∼100 Myr) star cluster NGC 1850 in the Large Magellanic Cloud. We analyse the cluster colour-magnitude diagram (CMD) and find that it hosts an extended main-sequence turn-off (MSTO) and a double main sequence (MS). We demonstr…
Revealing the structure of the outer disks of Be stars
Carciofi, A. C.; Štefl, S.; Vieira, R. G. +9 more
Context. The structure of the inner parts of Be star disks (≲ 20 stellar radii) is well explained by the viscous decretion disk (VDD) model, which is able to reproduce the observable properties of most of the objects studied so far. The outer parts, on the other hand, are not observationally well-explored, as they are observable only at radio wave…