Search Publications
Measuring the Probabilistic Photometric Redshifts of X-ray Quasars Based on the Quantile Regression of Ensembles of Decision Trees
Meshcheryakov, A. V.; Glazkova, V. V.; Gerasimov, S. V. +1 more
We present empirical machine learning algorithms for measuring the probabilistic photometric redshifts (photo-z) of X-ray quasars based on the quantile regression of ensembles of decision trees. Relying on the data of present-day photometric sky surveys (e.g., SDSS, GALEX, WISE, UKIDSS, 2MASS, FIRST), the proposed methods allow one to make high-qu…
Spotting stellar activity cycles in Gaia astrometry
Hawley, Suzanne L.; Davenport, James R. A.; Agol, Eric +1 more
Astrometry from Gaia will measure the positions of stellar photometric centroids to unprecedented precision. We show that the precision of Gaia astrometry is sufficient to detect starspot-induced centroid jitter for nearby stars in the Tycho-Gaia Astrometric Solution (TGAS) sample with magnetic activity similar to the young G-star KIC 7174505 or t…
Galactic cold cores. IX. Column density structures and radiative-transfer modelling
Juvela, M.; Ristorcelli, I.; Montillaud, J. +3 more
Context. The Galactic Cold Cores (GCC) project has made Herschel photometric observations of interstellar clouds where Planck detected compact sources of cold dust emission. The fields are in different environments and stages of star formation.
Aims: Our aim is to characterise the structure of the clumps and their parent clouds, and to study …
Project AMIGA: Distance and Metallicity Gradients along Andromeda’s Giant Southern Stream from the Red Clump
Brown, Thomas M.; Cohen, Roger E.; Gilbert, Karoline M. +7 more
The Giant Southern Stream (GSS) of M31, a keystone signature of a major accretion event, yields crucial constraints on M31 formation and evolution models. Currently, our understanding of the GSS, in terms of both its geometry and its chemistry, results from either wide-field imaging probing only a few magnitudes below the red giant branch tip, or …
A Deep Pulse Search in 11 Low Mass X-Ray Binaries
Messenger, C.; Wette, K.; Patruno, A.
We present a systematic coherent X-ray pulsation search in 11 low mass X-ray binaries (LMXBs). We select a relatively broad variety of LMXBs, including persistent and transient sources, spanning orbital periods between 0.3 and 17 hr. We use about 3.6 Ms of data collected by the Rossi X-Ray Timing Explorer and XMM-Newton and apply a semi-coherent s…
Stellar pulsation and granulation as noise sources in exoplanet transit spectroscopy in the ARIEL space mission
Vandenbussche, Bart; Pascale, Enzo; Argyriou, Ioannis +2 more
Stellar variability from pulsations and granulation presents a source of correlated noise that can impact the accuracy and precision of multiband photometric transit observations of exoplanets. This can potentially cause biased measurements in the transmission or emission spectrum or underestimation of the final error bars on the spectrum. ARIEL i…
Vibration isolation system for cryocoolers of soft x-ray spectrometer on-board ASTRO-H (Hitomi)
Eckart, Megan E.; Kilbourne, Caroline A.; Kokubun, Motohide +32 more
The soft x-ray spectrometer (SXS) onboard ASTRO-H (named Hitomi after launch) is a microcalorimeter-type spectrometer, installed in a dewar to be cooled at 50 mK. The energy resolution of the SXS engineering model suffered from microvibration from cryocoolers mounted on the dewar. This is mitigated for the flight model (FM) by introducing vibratio…
Coordinated Assembly of Brightest Cluster Galaxies
Conroy, Charlie; Brammer, Gabriel; Gu, Meng
Brightest Cluster Galaxies (BCGs) in massive dark matter halos are shaped by complex merging processes. We present a detailed stellar population analysis in the central region of Abell 3827 at z ∼ 0.1, including five-nucleus galaxies involved in a BCG assembly. Based on deep spectroscopy from the Multi Unit Spectroscopic Explorer, we fit the optic…
Parallaxes of Southern Extremely Cool objects III: 118 L and T dwarfs
Sozzetti, A.; Lattanzi, M. G.; Bucciarelli, B. +17 more
We present new results from the Parallaxes of Southern Extremely Cool dwarfs program to measure parallaxes, proper motions and multiepoch photometry of L and early T dwarfs. The observations were made on 108 nights over the course of 8 yr using the Wide Field Imager on the ESO 2.2m telescope. We present 118 new parallaxes of L and T dwarfs of whic…
Cyclic Changes of the Sun’s Seismic Radius
Rozelot, Jean-Pierre; Kosovichev, Alexander
The questions asking whether the Sun shrinks with the solar activity and what causes this have been a subject of debate. Helioseismology provides a means to measure with high precision the radial displacement of subsurface layers, the so-called “seismic radius,” through the analysis of oscillation frequencies of surface gravity (f) modes. Here, we…