Search Publications
Galaxy clustering in the VVV near-IR galaxy catalogue
Minniti, Dante; Alonso, M. Victoria; Valotto, Carlos +7 more
Mapping galaxies at low Galactic latitudes and determining their clustering status are fundamental steps in defining the large-scale structure in the nearby Universe. The VISTA Variables in the Vía Láctea (VVV) near-IR galaxy catalogue (VVV NIRGC) allows us to explore this region in great detail. Our goal is to identify galaxy overdensities and ch…
Identifying RR Lyrae in the ZTF DR3 data set
Koposov, Sergey E.; Huang, Kuan-Wei
We present an RR Lyrae (RRL) catalogue based on the combination of the third data release of the Zwicky Transient Facility (ZTF DR3) and Gaia EDR3. We use a multistep classification pipeline relying on the Fourier decomposition fitting to the multiband ZTF light curves and random forest classification. The resulting catalogue contains 71 755 RRLs …
An X-ray view of the ambiguous nuclear transient AT2019pev
Kochanek, C. S.; Grupe, D.; Mathur, S. +3 more
AT2019pev is a nuclear transient in a narrow-line Seyfert 1 galaxy at z = 0.096. The archival ultraviolet, optical, and infrared data showed features of both tidal disruption events and active galactic nuclei (AGNs), and its nature is not fully understood. We present detailed X-ray observations of AT2019pev taken with Swift, Chandra, and NICER ove…
Double-lined spectroscopic binaries in M11
Kovalev, Mikhail; Straumit, Ilya
We have developed a new method for spectral analysis of binaries. Our method successfully identifies double-lined spectroscopic binary (SB2) candidates from high-resolution Gaia-ESO spectra. Compared to the commonly used cross-correlation function analysis, it works for binaries with rapidly rotating components. We test our method on synthetic and…
Galactic H II region IRAS 17149 - 3916 - a multiwavelength study
Tej, Anandmayee; Das, Swagat R.; Vig, Sarita +3 more
This paper presents a multiwavelength investigation of the Galactic H II region IRAS 17149 - 3916. Using the Giant Meterwave Radio Telescope, India, first low-frequency radio continuum observations at 610 and 1280 MHz for this region are presented. The ionized gas emission displays an interesting cometary morphology, which is likely powered by the…
Semi-supervised classification and clustering analysis for variable stars
Catelan, M.; Protopapas, P.; Pichara, K. +1 more
The immense amount of time series data produced by astronomical surveys has called for the use of machine learning algorithms to discover and classify several million celestial sources. In the case of variable stars, supervised learning approaches have become commonplace. However, this needs a considerable collection of expert-labelled light curve…
Path-lengths in the quiet Sun transition region using O IV lines from IRIS
Del Zanna, Giulio; Rao, Yamini K.; Mason, Helen E. +1 more
We use spectroscopic diagnostics to determine different plasma parameters in the transition region of the quiet Sun. The electron number density from O IV lines using high-resolution spectral observations from the Interface Region Imaging Spectrograph (IRIS) are estimated to be around 1010 cm-3, in agreement with literature v…
Broad-band spectral analysis of Mrk 926 using multi-epoch X-ray observations
Buisson, D. J. K.; Russell, T. D.; Lohfink, A. M. +3 more
The X-ray spectra of some active galactic nuclei (AGNs) show a soft X-ray excess, emission in excess to the extrapolated primary X-ray continuum below 2 keV. Recent studies have shown that this soft excess can be described well as originating from either a relativistic ionized reflection, the extreme blurring of the reprocessed emission from the i…
Discovery of non-equilibrium ionization plasma associated with the North Polar Spur and Loop I
Kataoka, Jun; Sofue, Yoshiaki; Yamamoto, Marino
We investigated the detailed plasma condition of the North Polar Spur (NPS)/Loop I using archival Suzaku data. In previous research, collisional ionization equilibrium (CIE) have been assumed for X-ray plasma state, but we also assume non-equilibrium ionization (NEI) to check the plasma condition in more detail. We found that most of the plasma in…
A WHIM origin for the soft excess emission in the Coma cluster
Bonamente, Massimiliano; Lieu, Richard; Mirakhor, Mohammad +1 more
This paper provides a new analysis of ROSAT observations of the Coma cluster, to determine the amount of soft X-ray radiation in excess of the contribution from the hot intracluster medium (ICM). The re-analysis is made possible by a high-resolution study of the hot ICM with the XMM-Newton and Planck telescopes out to the cluster's virial radius. …