Search Publications
An Empirical Measure of the Rate of White Dwarf Cooling in 47 Tucanae
Tremblay, P. -E.; Stetson, P. B.; Bergeron, P. +8 more
We present an empirical determination of the white dwarf cooling sequence in the globular cluster 47 Tucanae. Using spectral models, we determine temperatures for 887 objects from Wide Field Camera 3 data, as well as 292 objects from data taken with the Advanced Camera for Surveys. We make the assumption that the rate of white dwarf formation in t…
First Observation in the South of Titan's Far-infrared 220 cm-1 Cloud
Teanby, N. A.; Calcutt, S. B.; de Kok, R. +15 more
An emission feature at 220 cm-1 which has been attributed to a cloud of condensed material in Titan's winter stratosphere has been seen for the first time in the south. This feature had previously been found only at high northern latitudes during northern winter and spring. The material emitting at 220 cm-1, as yet unidentifi…
The S4G Perspective on Circumstellar Dust Extinction of Asymptotic Giant Branch Stars in M100
Holwerda, Benne; Ho, Luis C.; Meidt, Sharon E. +19 more
We examine the effect of circumstellar dust extinction on the near-IR (NIR) contribution of asymptotic giant branch (AGB) stars in intermediate-age clusters throughout the disk of M100. For our sample of 17 AGB-dominated clusters we extract optical-to-mid-IR spectral energy distributions (SEDs) and find that NIR brightness is coupled to the mid-IR…
Dynamical Mass Constraints on the Ultraluminous X-Ray Source NGC 1313 X-2
Orosz, Jerome; Bregman, Joel N.; Liu, Jifeng
Dynamical mass measurements hold the key to answering whether ultraluminous X-ray sources (ULXs) are intermediate-mass black holes (IMBHs) or stellar-mass black holes with special radiation mechanisms. NGC 1313 X-2 is so far the only ULX with Hubble Space Telescope light curves, the orbital period, and the black hole's radial velocity amplitude ba…
The First Confirmed Microlens in a Globular Cluster
Minniti, D.; Udalski, A.; Pietrukowicz, P. +2 more
In 2000 July/August a microlensing event occurred at a distance of 2.33 arcmin from the center of the globular cluster M22 (NGC 6656), observed against the dense stellar field of the Milky Way bulge. We have used the adaptive optics system NACO at the ESO Very Large Telescope to resolve the two objects that participated in the event: the lens and …
Short Gas Dissipation Timescales: Diskless Stars in Taurus and Chamaeleon I
Briceño, Cesar; Calvet, Nuria; Herczeg, Gregory +1 more
We present an Advanced Camera for Surveys/Solar Blind Channel far-ultraviolet (FUV) study of H2 gas in 12 weak T Tauri stars in nearby star-forming regions. The sample consists of sources which have no evidence of inner disk dust. Our new FUV spectra show that in addition to the dust, the gas is depleted from the inner disk. This sample…
Counterrotation in Magnetocentrifugally Driven Jets and Other Winds
Tsinganos, K.; Cayatte, V.; Lima, J. J. G. +2 more
Rotation measurement in jets from T Tauri stars is a rather difficult task. Some jets seem to be rotating in a direction opposite to that of the underlying disk, although it is not yet clear if this affects the totality or part of the outflows. On the other hand, Ulysses data also suggest that the solar wind may rotate in two opposite ways between…
On the Distribution of Quiet-Sun Magnetic Fields at Different Heliocentric Angles
Katsukawa, Y.; Orozco Suárez, D.
This paper presents results from the analysis of high signal-to-noise ratio spectropolarimetric data taken at four heliocentric angles in quiet-Sun internetwork regions with the Hinode satellite. First, we find that the total circular and total linear polarization signals vary with heliocentric angle, at least for fields with large polarization si…
Cluster 77 in NGC 4449: The Nucleus of a Satellite Galaxy Being Transformed into a Globular Cluster?
Tosi, M.; van der Marel, R. P.; Aloisi, A. +2 more
We report the discovery in our Hubble Space Telescope Advanced Camera for Surveys B, V, and I images of NGC 4449 of a globular cluster (GC) which appears associated with two tails of blue stars. The cluster is massive (M ~ 1.7 × 106 M ⊙) and highly flattened (epsilon ~ 0.24). From the color-magnitude diagrams of the resolved …
Bubbles and Knots in the Kinematical Structure of the Bipolar Planetary Nebula NGC 2818
Vázquez, Roberto
High-resolution Hubble Space Telescope archive imaging and high-dispersion spectroscopy are used to study the complex morphological and kinematical structure of the planetary nebula, NGC 2818. We analyze narrowband Hα, [O III], [N II], [S II], and He II images, addressing important morphological features. Ground-based long-slit echelle spectra wer…