Search Publications
Resistive Emergence of Undulatory Flux Tubes
Aulanier, G.; Schmieder, B.; Pariat, E. +3 more
During its 2000 January flight, the Flare Genesis Experiment observed the gradual emergence of a bipolar active region, by recording a series of high-resolution photospheric vector magnetograms and images in the blue wing of the Hα line. Previous analyses of these data revealed the occurrence of many small-scale, transient Hα brightenings identifi…
Resolution of the MACHO-LMC-5 Puzzle: The Jerk-Parallax Microlens Degeneracy
Gould, Andrew
By extending the constant-acceleration analysis of Smith, Mao, & Paczyński to include jerk, I show that microlens parallax measurements are subject to a four-fold discrete degeneracy. The new degeneracy is characterized by a projected velocity vj=-(3/4)cscβec(cos2ψsin2βec+sin2ψ)3/2v⊕, wher…
Interstellar Carbon in Translucent Sight Lines
Sofia, Ulysses J.; Meyer, David M.; Lauroesch, James T. +1 more
We report interstellar C II column densities or upper limits determined from weak absorption of the 2325.4029 Å intersystem transition observed in six translucent sight lines (AV>~1) with the Space Telescope Imaging Spectrograph (STIS). The sight lines sample a wide range of interstellar characteristics, including total to selective …
The Effect of Metallicity on Cepheid-based Distances
Ferrarese, Laura; Saha, Abhijit; Sakai, Shoko +1 more
We have used the Wide Field Planetary Camera 2 on board the Hubble Space Telescope to obtain V and I images of seven nearby galaxies. For each, we have measured a distance using the tip of the red giant branch (TRGB) method. By comparing the TRGB distances with published Cepheid distances, we investigate the metallicity dependence of the Cepheid p…
Magnetic Reconnection and Mass Acceleration in Flare-Coronal Mass Ejection Events
Qiu, Jiong; Wang, Haimin; Gary, Dale E. +1 more
An observational relationship has been well established among magnetic reconnection, high-energy flare emissions and the rising motion of erupting flux ropes. In this paper, we verify that the rate of magnetic reconnection in the low corona is temporally correlated with the evolution of flare nonthermal emissions in hard X-rays and microwaves, all…
A Probable z~7 Galaxy Strongly Lensed by the Rich Cluster A2218: Exploring the Dark Ages
Richard, Johan; Ellis, Richard S.; Kneib, Jean-Paul +1 more
We discuss the observational properties of a remarkably faint triply imaged galaxy revealed in a deep z'-band Advanced Camera for Surveys observation of the lensing cluster A2218 (z=0.175). A well-constrained mass model for the cluster, which incorporates the outcome of recent Keck spectroscopic campaigns, suggests that the triple syste…
A Composite Extreme-Ultraviolet QSO Spectrum from FUSE
Green, Richard F.; Shull, J. Michael; Scott, Jennifer E. +4 more
The Far Ultraviolet Spectroscopic Explorer (FUSE) has surveyed a large sample (>100) of active galactic nuclei (AGNs) in the low-redshift universe (z<1). Its response at short wavelengths makes it possible to measure directly the far-ultraviolet spectral properties of quasi-stellar objects (QSOs) and Seyfert 1 galaxies at z<0.3. Using arc…
ILCT: Recovering Photospheric Velocities from Magnetograms by Combining the Induction Equation with Local Correlation Tracking
Welsch, B. T.; Fisher, G. H.; Abbett, W. P. +1 more
We present three methods for deriving the velocity field in magnetized regions of the Sun's photosphere. As a preliminary step, we introduce a Fourier-based local correlation tracking (LCT) routine that we term ``FLCT.'' By explicitly employing the observation made by Démoulin & Berger, that results determined by LCT applied to magnetograms in…
Changes in the X-Ray Emission from the Magnetar Candidate 1E 2259+586 during Its 2002 Outburst
Heyl, J.; Marshall, H. L.; Chakrabarty, D. +6 more
An outburst of more than 80 individual bursts, similar to those seen from Soft Gamma Repeaters (SGRs), was detected from the anomalous X-ray pulsar (AXP) 1E 2259+586 in 2002 June. Coincident with this burst activity were gross changes in the pulsed flux, persistent flux, energy spectrum, pulse profile, and spin-down of the underlying X-ray source.…
A Survey of Extended Radio Jets with Chandra and the Hubble Space Telescope
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +5 more
We present the results from an X-ray and optical survey of a sample of 17 radio jets in active galactic nuclei performed with Chandra and the Hubble Space Telescope. The sample was selected from the radio and is unbiased toward detection at shorter wavelengths, but preferentially it includes beamed sources. We find that X-ray emission is common on…