Search Publications
Coronal height constraint in IRAS 13224-3809 and 1H 0707-495 by the random forest regressor
Chainakun, P.; Young, A. J.; Luangtip, W. +1 more
We develop a random forest regressor (RFR) machine learning model to trace the coronal evolution in two highly variable active galactic nuclei (AGNs) IRAS 13224-3809 and 1H 0707-495 observed with XMM-Newton, by probing the X-ray reverberation features imprinted on their power spectral density (PSD) profiles. Simulated PSDs in the form of a power l…
NGC 4388: a test case for relativistic disc reflection and Fe K fluorescence features
LaMassa, S.; Yaqoob, Tahir; Tzanavaris, P.
We present a new analysis of the Suzaku X-ray spectrum of the Compton-thin Seyfert 2 galaxy NGC 4388. The spectrum above ~2 keV can be described by a remarkably simple and rather mundane model, consisting of a uniform, neutral spherical distribution of matter, with a radial column density of $2.58\pm 0.02 \times 10^{23} \ \rm cm^{-2}$, and an Fe a…
New evidence about HW Vir's circumbinary planets from Hipparcos-Gaia astrometry and a reanalysis of the eclipse timing variations using nested sampling
Triaud, Amaury H. M. J.; Kervella, Pierre; Baycroft, Thomas A.
The post common-envelope eclipsing binary HW Virginis (HW Vir) has had many circumbinary companions proposed based on eclipse timing variations. Each proposed solution has lacked in predictability and orbital stability, leaving the origin of the eclipse timing variations an active area of research. Leveraging the catalogue of Hipparcos and Gaia pr…
Wavelet spectral timing: X-ray reverberation from a dynamic black hole corona hidden beneath ultrafast outflows
Wilkins, D. R.
Spectral timing analyses based upon wavelet transforms provide a new means to study the variability of the X-ray emission from accreting systems, including AGN, stellar mass black holes, and neutron stars, and can be used to trace the time variability of X-ray reverberation from the inner accretion disc. The previously missing iron K reverberation…
Detection of optical emission from the supernova remnant G7.7-3.7
Boumis, P.; Vink, J.; Chiotellis, A. +6 more
We present the first optical study of the supernova remnant (SNR) G7.7-3.7, with the aim of determining its evolutionary phase since it has been suggested to be the remnant of SN 386 AD. We obtained narrow-band images in the filters H α + [N II], H β, [O III], [S II] that revealed faint optical emission in the southern region of the SNR consisting…
Observed dust surface density across cosmic times
Howk, J. Christopher; Péroux, Céline; De Cia, Annalisa
Our ability to interpret observations of galaxies and trace their stellar, gas, and dust content over cosmic time critically relies on our understanding of how the dust abundance and properties vary with environment. Here, we compute the dust surface density across cosmic times to put novel constraints on simulations of the build-up of dust. We pr…
The spectroscopic orbit of Polaris and its pulsation properties
Torres, Guillermo
Polaris is the nearest and brightest classical Cepheid, and pulsates with a period of about 4 d. It has long been known as a single-lined spectroscopic binary with an orbital period of 30 yr. Historical photometric and spectroscopic records indicate that, until recently, the pulsation period has been increasing at a rate of about 4.5 s yr-1
KDG 64: a large dwarf spheroidal or a small ultradiffuse satellite of Messier 81
Caldwell, Nelson; Makarova, Lidia; Makarov, Dmitry +5 more
Low-mass early-type galaxies, including dwarf spheroidals (dSph) and brighter dwarf ellipticals (dE), dominate the galaxy population in groups and clusters. Recently, an additional early-type population of more extended ultradiffuse galaxies (UDGs) has been identified, sparking a discussion on the potential morphological and evolutionary connectio…
A hard look at the X-ray spectral variability of NGC 7582
Nardini, Emanuele; Zoghbi, Abderahmen; Miller, Jon M. +5 more
NGC 7582 (z = 0.005264; D = 22.5 Mpc) is a highly variable, changing-look AGN. In this work, we explore the X-ray properties of this source using XMM-Newton and NuSTAR archival observations in the 3 - 40 keV range, from 2001 to 2016. NGC 7582 exhibits a long-term variability between observations but also a short-term variability in two observation…
Exotica in the globular cluster M4, studied with Chandra, HST, and the VLA
Anderson, Jay; Zhao, Jiaqi; Heinke, Craig O. +3 more
Using the Hubble Ultraviolet Globular Cluster Survey (HUGS) and additional HST archival data, we have carried out a search for optical counterparts to the low-luminosity Chandra X-ray sources in the globular cluster M4 (NGC 6121). We have also searched for optical or X-ray counterparts to radio sources detected by the VLA. We find 24 new confident…