ORCID Profile
0000-0003-0371-2639
Current Organisations
UNSW Sydney
,
Royal Australian College of General Practitioners
,
Western Sydney University
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Publications
Spectroscopic and geometrical evolution of the ejecta of the classical nova ASASSN-18fv
Publisher: Oxford University Press (OUP)
Date: 05-05-2020
Abstract: The optical spectroscopic observations of ASASSN-18fv observed from 2018 March 24 to 2019 January 26 are presented. The optical spectra are obtained from Mirranook, Vainu Bappu, and South African Astronomical observatories. The spectra are dominated by the hydrogen Balmer, Fe ii, and O i lines with P-Cygni profiles in the early phase, typical of an Fe ii class nova. The spectra show He i lines along with H i and O i emission lines in the decline phase placing the nova in the hybrid class of novae. The spectra show rapid development in high-ionization lines in this phase. Analysis of the light curve indicates t2 and t3 values of about 50 and 70 d, respectively, placing the nova in the category of moderately fast nova. The ejectum geometry, inclination, and position angle are estimated using morpho-kinematic analysis. The geometry of the ejecta is found to be an asymmetric bipolar structure with an inclination angle of about 53○. The ejected mass using photoionization analysis is found to be 6.07 × 10−4 M⊙.
An ATCA radio-continuum study of the Small Magellanic Cloud - I. Source catalogues at 1.42, 2.37, 4.80 and 8.64 GHz
Publisher: Oxford University Press (OUP)
Date: 10-2002
V473 Lyr, a modulated, period-doubled Cepheid, and U TrA, a double-mode Cepheid observed by MOST
Publisher: Oxford University Press (OUP)
Date: 23-12-2016
Evolution of the disk of π Aqr: From near-disappearance to a strong maximum
Publisher: Elsevier BV
Date: 11-2019
Improved physical properties of the quadruple sub-system with the eclipsing binary QZ Carinae
Publisher: Central Library of the Slovak Academy of Sciences
Date: 03-2020
The 2016 January eruption of recurrent Nova LMC 1968
Publisher: Oxford University Press (OUP)
Date: 23-10-2019
Abstract: We present a comprehensive review of all observations of the eclipsing recurrent Nova LMC 1968 in the Large Magellanic Cloud which was previously observed in eruption in 1968, 1990, 2002, 2010, and most recently in 2016. We derive a probable recurrence time of 6.2 ± 1.2 yr and provide the ephemerides of the eclipse. In the ultraviolet–optical–IR photometry the light curve shows high variability right from the first observation around 2 d after eruption. Therefore no colour changes can be substantiated. Outburst spectra from 2016 and 1990 are very similar and are dominated by H and He lines longward of 2000 Å. Interstellar reddening is found to be E(B − V) = 0.07 ± 0.01. The super soft X-ray luminosity is lower than the Eddington luminosity and the X-ray spectra suggest the mass of the white dwarf (WD) is larger than 1.3 M⊙. Eclipses in the light curve suggest that the system is at high orbital inclination. On day 4 after the eruption a recombination wave was observed in Fe ii ultraviolet absorption lines. Narrow-line components are seen after day 6 and explained as being due to reionization of ejecta from a previous eruption. The UV spectrum varies with orbital phase, in particular a component of the He ii 1640 Å emission line, which leads us to propose that early-on the inner WD Roche lobe might be filled with a bound opaque medium prior to the re-formation of an accretion disc. Both this medium and the ejecta can cause the delay in the appearance of the soft X-ray source.
Early evolution of the extraordinary Nova Delphini 2013 (V339 Del)
Publisher: EDP Sciences
Date: 09-2014
X-ray response to disc evolution in two γ Cas stars
Publisher: Oxford University Press (OUP)
Date: 07-02-2022
Abstract: The Hα emission of a set of southern γ Cas stars was monitored since 2019, with the aim of detecting transition events and examining how their peculiar X-ray emission would react in such cases. Two stars, namely HD 119682 and V767 Cen, were found to display slowly decreasing disc emissions. These decreases were not perfectly monotonic and several temporary and limited rebuilding events were observed. For HD 119682, the emission component in Hα disappeared in 2020 mid-July. In X-rays, the X-ray flux was twice smaller than that recorded two decades ago but of a similar level as observed a decade ago. The X-ray flux decreased over the c aign by 30 per cent, but the hardness remained similar in data sets of all epochs. In particular, the γ Cas character remained as clear as before even when there was no trace of disc emission in the Hα line. For V767 Cen, the full disappearance of disc emission in Hα never occurred. We followed closely a disc rebuilding event, but no significant change in flux or hardness was detected. These behaviours are compared to those of other γ Cas stars and their consequences on the X-ray generation are discussed.
A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray-luminous Classical Nova to Date
Publisher: American Astronomical Society
Date: 12-01-2018
The ambiguous transient ASASSN-17hx
Publisher: EDP Sciences
Date: 03-2020
DOI: 10.1051/0004-6361/201937025
Abstract: Aims. Some transients, although classified as novae based on their maximum and early decline optical spectra, cast doubts on their true nature, and raise the question of whether nova impostors might exist. Methods. We monitored a candidate nova that displayed a distinctly unusual light curve at maximum and early decline through optical spectroscopy (3000–10 000 Å, 500 R 100 000) complemented with Swift UV and AAVSO optical photometry. We use the spectral line series to characterize the ejecta dynamics, structure, and mass. Results. We find that the ejecta are in free ballistic expansion and have a typical classical nova structure. However, their derived mass is at least an order of magnitude higher than the typical ejecta masses obtained for classical novae. Specifically, we find M ej ≃9 × 10 −3 M ⊙ independent of the distance for a filling factor ε = 1. By constraining the distance we derived ε in the range 0.08–0.10, giving a mass 7 × 10 −4 ≲ M ej ≲ 9 × 10 −4 M ⊙ . The nebular spectrum, characterized by unusually strong coronal emission lines, confines the ionizing source energy to the range 20–250 eV, possibly peaking in the range 75–100 or 75–150 eV. Conclusions. We link this source to other slow novae that show similar behavior, and we suggest that they might form a distinct physical subgroup. The sources may result from a classical nova explosion occurring on a very low-mass white dwarf or they may be impostors for an entirely different type of transient.
NuSTAR Detection of X-Rays Concurrent with Gamma-Rays in the Nova V5855 Sgr
Publisher: American Astronomical Society
Date: 13-02-2019
An investigation of the photometric variability of confirmed and candidate Galactic Be stars using ASAS-3 data
Publisher: Oxford University Press (OUP)
Date: 18-05-2018
Discovery of a Hot Symbiotic Star in the Cold Antarctic Sky: Symbiotics Are Outliers in SkyMapper uvgriz Photometry
Publisher: American Astronomical Society
Date: 12-12-2018
Spectroscopic and photometric analysis of symbiotic candidates – I. Ten candidates on classical symbiotic stars
Publisher: Oxford University Press (OUP)
Date: 16-07-2021
Abstract: Symbiotic stars belong to a group of interacting binaries that display a wide variety of phenomena, including prominent outbursts connected with mass transfer, as well as stellar winds, jets, eclipses, or intrinsic variability of the components. Dozens of new symbiotic stars and candidates have been discovered in recent years. However, there are many objects that are still poorly studied. Some symbiotic candidates suspected in the literature have never been studied spectroscopically. In this contribution, we present the first results of the ongoing c aign focused on symbiotic candidates. In the first paper in the series, we study the nature of 10 candidate classical symbiotic stars suspected based on their photometric behaviour, colours or abundance pattern. To confirm or reject the symbiotic nature of the studied candidates, we obtained new spectra and analysed them in detail together with available multifrequency photometric and spectroscopic observations of the objects. Hen 3−860 and V2204 Oph are genuine symbiotic systems showing typical spectral features of burning symbiotic stars and outbursts in the last 100 yr. The first object belongs to the uncommon group of eclipsing symbiotic stars. V1988 Sgr cannot be classified as a genuine burning symbiotic star, but the scenario of an accreting-only symbiotic system cannot be ruled out. Hen 4−204 might be a bonafide symbiotic star due to its similarity with the known symbiotic binary BD Cam. Six other symbiotic candidates (V562 Lyr, IRAS 19050+0001, EC 19249−7343, V1017 Cyg, PN K1−6, V379 Peg) are either single dwarf or giant stars or non-symbiotic binaries.
An investigation of four chemically peculiar stars with photometric periods below 12 h
Publisher: Oxford University Press (OUP)
Date: 09-12-2016
Related Organisations
Royal Australian College Of General Practitioners
Location: Australia
Related Funding Activities
No related grants have been discovered for Terry Bohlsen.