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An Astrometric Calibration of the MV-Porb Relationship for Cataclysmic Variables based on Hubble Space Telescope Fine Guidance Sensor Parallaxes
Harrison, Thomas E.; Johnson, Joni J.; McArthur, B. E. +4 more
We present new, high-precision astrometric parallaxes for three cataclysmic variables: WZ Saggitae, YZ Cancri, and RU Pegasi, obtained using the Fine Guidance Sensors on the Hubble Space Telescope. The addition of these three parallaxes to the existing data set allows us to examine the outburst luminosities for dwarf novae spanning the orbital per…
Photometric redshifts with the Multilayer Perceptron Neural Network: Application to the HDF-S and SDSS
Popesso, P.; Fontana, A.; Vanzella, E. +8 more
We present a technique for the estimation of photometric redshifts based on feed-forward neural networks. The Multilayer Perceptron (MLP) Artificial Neural Network is used to predict photometric redshifts in the HDF-S from an ultra deep-multicolor catalog. Various possible approaches for the training of the neural network are explored, including t…
The Origin of Postflare Loops
Warren, H. P.; Sheeley, N. R., Jr.; Wang, Y. -M.
We apply a tracking technique, previously developed to study motions in the outer corona by Sheeley, Walters, Wang, and Howard, to 195 Å filtergrams obtained with the Transition Region and Coronal Explorer (TRACE) satellite and obtain height-time maps of the motions in the hot (10-20 MK) plasma clouds above postflare loop systems. These maps indic…
The Initial Mass Function and Stellar Content of NGC 3603
Bessell, Michael S.; Sung, Hwankyung
We present UBVRI and Hα photometry of the extremely compact, starburst cluster NGC 3603. Ground-based images, Hubble Space Telescope (HST) archival data, as well as Chandra X-ray data have been used for this study. We present, for the first time, optical color-magnitude diagrams (CMDs) for the stars in the cluster core down to V=22 mag. A well-def…
A New Probe of the Planet-forming Region in T Tauri Disks
Herczeg, Gregory J.; Russell, Ray W.; Qi, Chunhua +9 more
We present new observations of the far-ultraviolet (FUV; 1100-2200 Å) radiation field and the near- to mid-IR (3-13.5 µm) spectral energy distribution (SED) of a sample of T Tauri stars selected on the basis of bright molecular disks (GM Aur, DM Tau, and LkCa 15). In each source we find evidence for Lyα-induced H2 fluorescence and…
The XMM-Newton and BeppoSAX view of the Ultra Luminous Infrared Galaxy MKN 231
Cappi, M.; Franceschini, A.; Piconcelli, E. +11 more
We discuss XMM-Newton and BeppoSAX observations of MKN 231, the lowest-redshift Broad Absorption Line (BAL) QSO known so far and one of the best-studied Ultra Luminous Infrared Galaxies. By combining the XMM-Newton spectral resolution and the high-energy bandpass of BeppoSAX we have been able to study in more detail than previously possible its 0.…
E+A Galaxies and the Formation of Early-Type Galaxies at z~0
Lauer, Tod R.; Zabludoff, Ann I.; Zaritsky, Dennis +2 more
E+A galaxies, whose spectra have deep Balmer absorption lines but no significant [O II] emission, are the best candidates for an evolutionary link between star-forming, gas-rich galaxies and quiescent, gas-poor galaxies. However, their current morphologies are not well known. We present Hubble Space Telescope WFPC2 observations of the five bluest …
Coronal Heating through Braiding of Magnetic Field Lines
Peter, Hardi; Gudiksen, Boris V.; Nordlund, Åke
Cool stars such as our Sun are surrounded by a million degree hot outer atmosphere, the corona. For more than 60 years, the physical nature of the processes heating the corona to temperatures well in excess of those on the stellar surface have remained puzzling. Recent progress in observational techniques and numerical modeling now opens a new win…
Imaging X-Ray, Optical, and Infrared Observations of the Transient Anomalous X-Ray Pulsar XTE J1810-197
Gotthelf, E. V.; Halpern, J. P.; Buxton, M. +1 more
We report X-ray imaging, timing, and spectral studies of XTE J1810-197, a 5.54 s pulsar discovered by Ibrahim and coworkers in recent Rossi X-Ray Timing Explorer (RXTE) observations. In a set of short exposures with the High Resolution Camera on board the Chandra X-Ray Observatory, we detect a strongly modulated signal (55%+/-4% pulsed fraction) w…
Ultraviolet Emission from the Millisecond Pulsar J0437-4715
Pavlov, George G.; Kargaltsev, Oleg; Romani, Roger W.
We observed PSR J0437-4715 with the FUV-MAMA detector of the Space Telescope Imaging Spectrometer (STIS) to measure the pulsar's spectrum and pulsations. For the first time, UV emission from a millisecond pulsar has been detected. The measured flux, (2.0+/-0.2)×10-15 ergs s-1 cm-2 in the 1150-1700 Å range, correspo…