Search Publications
Velocity resolved [C ii], [C i], and CO observations of the N159 star-forming region in the Large Magellanic Cloud: a complex velocity structure and variation of the column densities
Wiesemeyer, Helmut; Güsten, Rolf; Okada, Yoko +4 more
Context. The [C ii] 158 µm fine structure line is one of the dominant cooling lines in star-forming active regions. Together with models of photon-dominated regions, the data is used to constrain the physical properties of the emitting regions, such as the density and the radiation field strength. According to the modeling, the [C ii] 158 &m…
The Flare-ona of EK Draconis
Ayres, Thomas R.
EK Draconis (HD 129333: G1.5 V) is a well-known young (50 Myr) solar analog. In 2012, Hubble Space Telescope returned to EK Dra to follow up a far-ultraviolet (FUV) SNAPshot visit by Cosmic Origins Spectrograph (COS) two years earlier. The brief SNAP pointing had found surprisingly redshifted, impulsively variable subcoronal “hot-line” emission of…
The growth index of matter perturbations using the clustering of dark energy
Basilakos, Spyros
We have put forward a new unified framework which provides a consistent and rather complete account of the growth index of matter perturbations in the regime where the dark energy is allowed to have clustering. In particular, we find that the growth index is not only affected by the cosmological parameters but rather it depends on the choice of th…
Radio Timing and Optical Photometry of the Black Widow System PSR J1953+1846A in the Globular Cluster M71
Dalessandro, E.; Ransom, S. M.; Ferraro, F. R. +6 more
We report on the determination of the astrometric, spin, and orbital parameters for PSR J1953+1846 A, a “black widow” binary millisecond pulsar in the globular cluster M71. By using the accurate position and orbital parameters obtained from radio timing, we identified the optical companion in Advanced Camera for Surveys/Hubble Space Telescope imag…
Observations and Modeling of North-South Asymmetries Using a Flux Transport Dynamo
Tripathi, Durgesh; Shetye, Juie; Dikpati, Mausumi
The peculiar behavior of solar cycle 23 and its prolonged minima has been one of the most studied problems over the past few years. In the present paper, we study the asymmetries in active region magnetic flux in the northern and southern hemispheres during the complete solar cycle 23 and the rising phase of solar cycle 24. During the declining ph…
Mars thermospheric scale height: CO Cameron and CO2+ dayglow observations from Mars Express
Montmessin, F.; Bertaux, J. -L.; Gérard, J. -C. +3 more
The CO Cameron (170-270 nm) and CO2+ ultraviolet doublet (298 and 299 nm) emissions have been observed on the Mars dayside with Mars Express Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM) instrument in the limb viewing mode. These ultraviolet emissions ultimately arise from the excitation…
Multiscale study of electron energization during unsteady reconnection events
Lapenta, Giovanni; El-Alaoui, Mostafa; Walker, Raymond J. +2 more
Understanding particle acceleration in the magnetotail during substorms requires knowledge of changes in the global magnetospheric configuration and the local regions of intense fields and microinstabilities caused by processes associated with reconnection. We simulated a substorm on 15 February 2008 by coupling the University of California, Los A…
Co-spatial Long-slit UV/Optical AL Spectra of 10 Galactic Planetary Nebulae with HST/STIS. I. Description of the Observations, Global Emission-line Measurements, and CNO Abundances
Corradi, Romano L. M.; Balick, Bruce; Shaw, Richard A. +3 more
We present observations and initial analysis from a Hubble Space Telescope (HST) Cycle 19 program using STIS to obtain the first co-spatial, UV-optical spectra of 10 Galactic planetary nebulae (PNs). Our primary objective was to measure the critical emission lines of carbon and nitrogen with unprecedented signal-to-noise ratio (S/N) and spatial re…
Chemical Abundances and Properties of the Ionized Gas in NGC 1705
Tosi, M.; Mignoli, M.; Aloisi, A. +3 more
We obtained [O iii] narrow-band imaging and multi-slit MXU spectroscopy of the blue compact dwarf (BCD) galaxy NGC 1705 with FORS2@VLT to derive chemical abundances of planetary nebulae and H ii regions and, more in general, to characterize the properties of the ionized gas. The auroral [O iii]λ 4363 line was detected in all but 1 of the 11 analyz…
Relativistic electron acceleration during HILDCAA events: are precursor CIR magnetic storms important?
Hajra, Rajkumar; Tsurutani, Bruce T.; Gonzalez, Walter D. +4 more
We present a comparative study of high-intensity long-duration continuous AE activity (HILDCAA) events, both isolated and those occurring in the "recovery phase" of geomagnetic storms induced by corotating interaction regions (CIRs). The aim of this study is to determine the difference, if any, in relativistic electron acceleration and magnetosphe…