Search Publications
Eta Carinae’s 2014.6 Spectroscopic Event: The Extraordinary He II and N II Features
Humphreys, Roberta M.; Davidson, Kris; Mehner, Andrea +2 more
Eta Carinae’s spectroscopic events (periastron passages) in 2003, 2009, and 2014 differed progressively. He ii λ4687 and nearby N ii multiplet 5 have special significance because they respond to very soft X-rays and the ionizing UV radiation field (EUV). Hubble Space Telescope (HST)/STIS observations in 2014 show dramatic increases in both feature…
Hot Plasma from Solar Active Region Cores: a Test of AC and DC Coronal Heating Models?
Schmelz, J. T.; Pathak, S.; Christian, G. M. +2 more
Direct current (DC) models of solar coronal heating invoke magnetic reconnection to convert magnetic free energy into heat, whereas alternating current (AC) models invoke wave dissipation. In both cases the energy is supplied by photospheric footpoint motions. For a given footpoint velocity amplitude, DC models predict lower average heating rates …
Collisionally Excited Filaments in Hubble Space Telescope Hα and Hβ Images of HH 1/2
Bally, J.; Raga, A. C.; Reipurth, B. +2 more
We present new Hα and Hβ images of the HH 1/2 system, and we find that the Hα/Hβ ratio has high values in ridges along the leading edges of the HH 1 bow shock and of the brighter condensations of HH 2. These ridges have Hα/Hβ = 4 → 6, which is consistent with collisional excitation from the n = 1 to the n = 3 and 4 levels of hydrogen in a gas of t…
Suzaku Observation of the Classical Nova V2491 Cyg in Quiescence.
Mukai, K.; Orio, M.; Zemko, P.
We present the Suzaku XIS observation of V2491 Cyg (Nova Cyg 2008 No. 2) obtained in quiescence, more than two years after the outburst. The nova was detected as a very luminous source in a wide spectral range from soft to hard X-rays. A very soft blackbody-like component peaking at 0.5 keV indicates that we observe either remaining, localized hyd…
Dynamics of Rotation in M Dwarfs: Indications for a Change in the Dynamo Regime in Stars at the Onset of Complete Convection
Mullan, D. J.; Houdebine, E. R.
We have measured vsin i with high precision for a sample of dM3 stars (86 targets). We detected rotation in 82 stars (73 dM3 stars and nine dM3e stars). We compare our measurements of vsin i for all of the stars in our dM0, dM2, dM3, and dM4 samples to those from other authors. We find a good agreement down to vsin i values of less than 1 km s
An Embedded Active Nucleus in the OH Megamaser Galaxy IRAS16399-0937
Axon, D. J.; Robinson, A.; Elitzur, M. +7 more
We present a multiwavelength study of the OH megamaser galaxy IRAS16399-0937, based on new Hubble Space Telescope (HST)/Advanced Camera for Surveys F814W and Hα+[N II] images and archive data from HST, Two Micron All Sky Survey, Spitzer, Herschel and the Very Large Array. This system has a double nucleus, whose northern (IRAS16399N) and southern (…
Probing the Physical Properties of z = 4.5 Lyman Alpha Emitters with Spitzer
Finkelstein, Steven L.; Grogin, Norman A.; Tilvi, Vithal +10 more
We present the results from a stellar population modeling analysis of a sample of 162 z = 4.5 and 14 z = 5.7 Lyα emitting galaxies (LAEs) in the Boötes field, using deep Spitzer/IRAC data at 3.6 and 4.5 µm from the Spitzer Lyα Survey, along with Hubble Space Telescope NICMOS and WFC3 imaging at 1.1 and 1.6 µm for a subset of the LAEs. …
The Schmidt Law in Six Galactic Massive Star-forming Regions
Marengo, M.; Smith, H. A.; Allen, L. +3 more
We present a census of young stars in five massive star-forming regions in the 4th Galactic quadrant, G305, G326-4, G326-6, G333 (RCW 106), and G351, and combine this census with an earlier census of young stars in NGC 6334. Each region was observed at J, H, and Ks with the NOAO Extremely Wide-Field Infrared Imager and combined with dee…
A Newly Recognized Very Young Supernova Remnant in M83
Soria, Roberto; Blair, William P.; Whitmore, Bradley C. +7 more
As part of a spectroscopic survey of supernova remnant candidates in M83 using the Gemini-South telescope and Gemini Multi-Object Spectrograph, we have discovered one object whose spectrum shows very broad lines at Hα, [O I] λλ6300, 6363, and [O III] λλ4959, 5007, similar to those from other objects classified as "late time supernovae". Although s…
On the Possibility of Significant Electron Depletion due to Nanograin Charging in the Coma of Comet 67p/churyumov-gerasimenko near Perihelion
Wahlund, J. -E.; Vigren, E.; Galand, M. +2 more
We approach the complicated phenomena of gas-dust interactions in a cometary ionosphere, focusing in particular on the possibility of significant depletion in electron number density due to grain charging. Our one-dimensional ionospheric model, accounting for grain charging processes, is applied to the subsolar direction and the diamagnetic cavity…