Search Publications
Deep HST/ACS Photometry of the M81 Halo
Chandar, Rupali; Sarajedini, Ata; Durrell, Patrick R.
We present a deep color-magnitude diagram (CMD) for individual stars in the halo of the nearby spiral galaxy M81, at a projected distance of 19 kpc, based on data taken with the Advanced Camera for Surveys on the Hubble Space Telescope (HST). The CMD reveals a red giant branch (RGB) that is narrow and fairly blue, and a horizontal branch that has …
A mid-IR study of Hickson compact groups. I. Probing the effects of environment in galaxy interactions
Le Floc'h, E.; Charmandaris, V.; Díaz-Santos, T. +4 more
Hickson compact groups (HCGs) are among the densest galaxy environments of the local universe. To examine the effects of the environment on the infrared properties of these systems, we present an analysis of Spitzer and ISO mid-infrared imaging, as well as of deep ground-based near-infrared imaging of 14 HCGs containing a total of 69 galaxies. Bas…
A plasmapause-like density boundary at high latitudes in Saturn's magnetosphere
Gurnett, D. A.; Persoon, A. M.; Krupp, N. +8 more
Here we report the discovery of a well-defined plasma density boundary at high latitudes in Saturn's magnetosphere. The boundary separates a region of relatively high density at L less than about 8 to 15 from a region with densities nearly three orders of magnitude lower at higher L values. Magnetic field measurements show that strong field-aligne…
A close look at the Centaurus A group of galaxies. I. Metallicity distribution functions and population gradients in early-type dwarfs
Crnojević, D.; Grebel, E. K.; Koch, A.
Aims: We study dwarf galaxies in the Centaurus A group to investigate their metallicity and possible environmental effects. The Centaurus A group (at ~4 Mpc from the Milky Way) contains about 50 known dwarf companions of different morphologies and stellar contents, thus making it a very interesting target to study how these galaxies evolve. <…
Meridional distribution of CH3C2H and C4H2 in Saturn’s stratosphere from CIRS/Cassini limb and nadir observations
Fletcher, Leigh N.; Bézard, Bruno; Guerlet, Sandrine +4 more
Limb and nadir spectra acquired by Cassini/CIRS (Composite InfraRed Spectrometer) are analyzed in order to derive, for the first time, the meridional variations of diacetylene (C 4H 2) and methylacetylene (CH 3C 2H) mixing ratios in Saturn's stratosphere, from 5 hPa up to 0.05 hPa and 80°S to 45°N. We fi…
Discovery of the 51.47-d orbital period in the supergiant fast X-ray transient XTE J1739-302 with INTEGRAL
Hill, A. B.; Bird, A. J.; Scaringi, S. +5 more
Timing analysis of ∼12.4 Ms of INTEGRAL/IBIS data has revealed a period of 51.47 ± 0.02 d in the supergiant fast X-ray transient source XTE J1739-302/IGR J17391-3021 that can be interpreted as an orbital period. An outburst history showing 35 epochs of activity has been produced, showing X-ray outbursts throughout the orbit of XTE J1739-302. Possi…
The SARS algorithm: detrending CoRoT light curves with Sysrem using simultaneous external parameters
Aigrain, Suzanne; Guillot, Tristan; Erikson, Anders +31 more
Surveys for exoplanetary transits are usually limited not by photon noise but rather by the amount of red noise in their data. In particular, although the CoRoT space-based survey data are being carefully scrutinized, significant new sources of systematic noises are still being discovered. Recently, a magnitude-dependant systematic effect was disc…
Detection of Strong Short-term Variability in NGC 6946 X-1
Feng, Hua; Kaaret, Philip; Rao, Fengyun
Using two archival XMM-Newton observations, we identify strong X-ray flux variations in NGC 6946 X-1 indicating that it is the most variable ultraluminous X-ray source (ULX) on mHz timescales known so far. The 1-10 keV light curve exhibits variability with a fractional rms amplitude of 60% integrated in the frequency range of 1-100 mHz. The power …
Enhanced dust heating in the bulges of early-type spiral galaxies
Roussel, H.; Murphy, E. J.; Armus, L. +38 more
Stellar density and bar strength should affect the temperatures of the cool (T ~ 20-30 K) dust component in the inner regions of galaxies, which implies that the ratio of temperatures in the circumnuclear regions to the disk should depend on Hubble type. We investigate the differences between cool dust temperatures in the central 3 kpc and disk of…
X-ray emission from optical novae in M 31
Pietsch, W.
The first supersoft source (SSS) identification with an optical nova in