Search Publications
Hunting for Planetary Nebulae toward the Galactic Center
Hong, Jihye; An, Deokkeun; Ramírez, Solange V. +2 more
We present near-infrared (IR) spectra of two planetary nebula (PN) candidates in close lines of sight toward the Galactic center (GC) using the Gemini Near-Infrared Spectrograph at Gemini North. High-resolution images from radio continuum and narrowband IR observations reveal ringlike or barrel-shaped morphologies of these objects, and their mid-I…
X-ray reverberation models of the disc wind in ultraluminous X-ray source NGC 5408 X-1
Chainakun, P.; Luangtip, W.; Loekkesee, S. +3 more
Majority of ultraluminous X-ray sources (ULXs) are believed to be super-Eddington objects, providing a nearby prototype for studying an accretion in supercritical regime. In this work, we present the study of time-lag spectra of the ULX NGC 5408 X-1 using a reverberation mapping technique. The time-lag data were binned using two different methods:…
On the Origin of Hard X-Ray Emissions from the Behind-the-limb Flare on 2014 September 1
Kouloumvakos, Athanasios; Rouillard, Alexis P.; Warmuth, Alexander +6 more
The origin of hard X-rays and γ-rays emitted from the solar atmosphere during occulted solar flares is still debated. The hard X-ray emissions could come from flaring loop tops rising above the limb or coronal mass ejection shock waves, two by-products of energetic solar storms. For the shock scenario to work, accelerated particles must be release…
Restoration of the K and F Components of the Solar Corona from LASCO-C2 Images over 24 Years [1996 - 2019]
Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine +2 more
We present a photometrically accurate restoration of the K- and F-coronae from white-light images obtained over 24 years [1996 - 2019] by the Large-Angle Spectrometric COronagraph (LASCO-C2) onboard the Solar and Heliospheric Observatory (SOHO). The procedure starts with the data set of unpolarized images of 512 × 512 pixels produced by the polari…
Potential and sky coverage for off-axis fringe tracking in optical long baseline interferometry
Hadjara, Massinissa; Benkhaldoun, Zouhair; Boskri, Abdelkarim +6 more
The spectacular results provided by the second-generationVLTI instruments GRAVITY and MATISSE on active galactic nuclei (AGN) trigger and justify a strong increase in the sensitivity limit of optical interferometers. A key component of such an upgrade is off-axis fringe tracking. To evaluate its potential and limitations, we describe and analyse i…
Optical Variability of ICRF3 Quasars in the Pan-STARRS 3Pi Survey with Functional Principal Component Analysis
Makarov, V. V.; Goldman, B.; Berghea, C. T. +1 more
We make use of individual (epoch) detection data from the Pan-STARRS 3 survey for 2863 optical ICRF3 counterparts in the five wavelength bands g, r, i, z, and y, published as part of the Data Release 2. A dedicated method based on the Functional Principal Component Analysis is developed for these sparse and irregularly sampled data. With certain r…
Gaseous nebulae and massive stars in the giant H I ring in Leo
Venturi, Giacomo; Cresci, Giovanni; Thilker, David +2 more
Context. Chemical abundances in the Leo ring, the largest H I cloud in the local Universe, have recently been determined to be close to or above Solar values. This is a finding that is incompatible with prior claims that the ring was primordial in origin. The gas, pre-enriched in a galactic disk and tidally stripped, did not manage to efficiently …
The fractions of post-binary-interaction stars and evolved blue straggler stars on the red giant branch of globular clusters
Wang, Hai-Feng; Jiang, Deng-Kai; Wang, Bo +4 more
The red giant branch (RGB) of globular clusters (GCs) is home to some exotic stars, which may provide clues on the formation of multiple stellar populations in GCs. It is well known that binary interactions are responsible for many exotic stars. Thus, it is important to understand what fraction of stars on the RGB of GCs is the result of binary in…
Fundamental parameters and non local thermodynamic equilibrium abundances of key light elements for nine bright and nearby K giants
Lee, Byeong-Cheol; Han, Inwoo; Lyubimkov, Leonid S. +4 more
For nine bright K giants within 100 pc of the sun, the fundamental parameters and the non local thermodynamic equilibrium (LTE) abundances of three key light elements (Li, C, and O) are accurately determined. These stars are of special interest due to the planets detected around them. Their fundamental parameters are found to be typical for K gian…
ASASSN-14lp: two possible solutions for the observed ultraviolet suppression
Foley, Ryan J.; Kerzendorf, Wolfgang; Kromer, Markus +10 more
We test the adequacy of ultraviolet (UV) spectra for characterizing the outer structure of Type Ia supernova (SN) ejecta. For this purpose, we perform spectroscopic analysis for ASASSN-14lp, a normal SN Ia showing low continuum in the mid-UV regime. To explain the strong UV suppression, two possible origins have been investigated by mapping the ch…