Search Publications
Multiwavelength observations of the EUV variable metal-rich white dwarf GD 394
Redfield, Seth; Casewell, Sarah L.; Burleigh, Matthew R. +13 more
We present new Hubble Space Telescope (HST) ultraviolet and ground-based optical observations of the hot, metal-rich white dwarf GD 394. Extreme-ultraviolet (EUV) observations in 1992-1996 revealed a 1.15 d periodicity with a 25 per cent amplitude, hypothesized to be due to metals in a surface accretion spot. We obtained phase resolved HST/Space T…
Superstrong photospheric magnetic fields in sunspot penumbrae
Solanki, S. K.; Lagg, A.; van Noort, M. +2 more
Context. Recently, there have been some reports of unusually strong photospheric magnetic fields (which can reach values of over 7 kG) inferred from Hinode SOT/SP sunspot observations within penumbral regions. These superstrong penumbral fields are even larger than the strongest umbral fields on record and appear to be associated with supersonic d…
Fine-scale structure in cometary dust tails I: Analysis of striae in Comet C/2006 P1 (McNaught) through temporal mapping
Morgan, Huw; Jones, Geraint H.; Battams, Karl +5 more
Striated features, or striae, form in cometary dust tails due to an as-yet unconstrained process or processes. For the first time we directly display the formation of striae, at C/2006 P1 McNaught, using data from the SOHO LASCO C3 coronagraph. The nature of this formation suggests both fragmentation and shadowing effects are important in the form…
Polarimetric and Photometric Investigation of the Dark Globule LDN 1225: Distance, Extinction Law, and Magnetic Fields
Jose, Jessy; Wang, Jia-Wei; Lai, Shih-Ping +7 more
We present results based on the optical R-band observations of the polarization of 280 stars distributed toward the dark globule LDN 1225. Parallaxes from Gaia data release 2 along with the polarization data of ∼200 stars have been used to (a) constrain the distance of LDN 1225 as 830 ± 83 pc, (b) determine the contribution of interstellar polariz…
Observations of the Venus Dramatic Response to an Extremely Strong Interplanetary Coronal Mass Ejection
Xu, Qi; Zhang, Tielong; Rong, Zhaojin +4 more
On 2011 November 5, Venus Express observed the impact of an extremely strong interplanetary coronal mass ejection (ICME) on Venus. As a result, the Venusian induced magnetosphere dramatically fluctuated during the ICME passage: the bow shock was compressed and broadened by the sheath and the body of the ICME, respectively; an atypically strong mag…
Discovery of a White Dwarf Companion to HD 159062
Fulton, Benjamin J.; Hirsch, Lea A.; Howard, Andrew W. +11 more
We report on the discovery of a white dwarf companion to the nearby late G dwarf star, HD 159062. The companion is detected in 14 years of precise radial velocity (RV) data, and in high-resolution imaging observations. RVs of HD 159062 from 2003 to 2018 reveal an acceleration of -13.3 ± 0.12 {{m}} {{{s}}}-1 {yr}}-1, indicatin…
The GALAH Survey: lithium-strong KM dwarfs
Zwitter, T.; Buder, S.; Casagrande, L. +10 more
Identifying and characterizing young stars in the Solar neighbourhood is essential to find and describe planets in the early stages of their evolution. This work seeks to identify nearby young stars showing a lithium 6708 Å absorption line in the GALAH survey. A robust, data-driven approach is used to search for corresponding templates in the pool…
Statistical Study of Chromospheric Evaporation in Impulsive Phase of Solar Flares
Kerr, Graham S.; Kosovichev, Alexander G.; Sadykov, Viacheslav M. +1 more
We present a statistical study of chromospheric evaporation in solar flares using simultaneous observations by the RHESSI X-ray telescope and the Interface Region Imaging Spectrograph UV spectrograph. The results are compared with radiation hydrodynamic flare models from the F-CHROMA RADYN database. For each event, we study spatially resolved Dopp…
Deriving star cluster parameters with convolutional neural networks. I. Age, mass, and size
Narbutis, D.; Vansevičius, V.; Bialopetravičius, J.
Context. Convolutional neural networks (CNNs) have been proven to perform fast classification and detection on natural images and have the potential to infer astrophysical parameters on the exponentially increasing amount of sky-survey imaging data. The inference pipeline can be trained either from real human-annotated data or simulated mock obser…
The Origin of [C II] 158 µm Emission toward the H II Region Complex S235
Schneider, N.; Tremblin, P.; Zavagno, A. +9 more
Although the {}2{{{P}}}3/2-{}2{{{P}}}1/2 transition of [C II] at λ ≃ 158 µ {{m}} is known to be an excellent tracer of active star formation, we still do not have a complete understanding of where within star formation regions the emission originates. Here, we use SOFIA upGREAT observations of [C I…