M. Childress

University of Southampton

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

C. Inserra

Cardiff University

F. Yuan

University of Michigan–Ann Arbor

S. J. Smartt

University of Oxford

B. Schmidt

Australian National University

D. R. Young

Queen's University Belfast

S. Valenti

Medical College of Wisconsin

M. Sullivan

University of Southampton

M. Fraser

University College Dublin

A. Gal‐Yam

Weizmann Institute of Science

R. Scalzo

Data61

Cooperative Institutions

Centre National de la Recherche Scientifique

Queen's University Belfast

Lawrence Berkeley National Laboratory

Osservatorio Astronomico di Padova

Cerro Tololo Inter-American Observatory

University of California, Berkeley

Institut National de Physique Nucléaire et de Physique des Particules

South African Radio Astronomy Observatory

Astronomical Observatory

European Southern Observatory

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

SN 2009ip à la PESSTO: no evidence for core collapse yet★

Monthly Notices of the Royal Astronomical Society (2013)

M. Fraser C. Inserra A. Jerkstrand R. Kotak G. Pignata

We present ultraviolet, optical and near-infrared observations of the interacting transient SN 2009ip, covering the period from the start of the outburst in 2012 October until the end of the 2012 observing season. The transient reached a peak magnitude of MV = −17.7 mag, with a total integrated luminosity of 1.9 × 1049 erg over the period of 2012 August–December. The light curve fades rapidly, dropping by 4.5 mag from the V-band peak in 100 d. The optical and near-infrared spectra are dominated by narrow emission lines with broad electron scattering wings, signalling a dense circumstellar environment, together with multiple components of broad emission and absorption in H and He at velocities in the range 0.5–1.2 × 104 km s−1. We see no evidence for nucleosynthesized material in SN 2009ip, even in late-time pseudo-nebular spectra. We set a limit of <0.02 M⊙ on the mass of any possible synthesized 56Ni from the late-time light curve. A simple model for the narrow Balmer lines is presented and used to derive number densities for the circumstellar medium in the range ∼109–1010 cm−3. Our near-infrared data do not show any excess at longer wavelengths, and we see no other signs of dust formation. Our last data, taken in 2012 December, show that SN 2009ip has spectroscopically evolved to something quite similar to its appearance in late 2009, albeit with higher velocities. It is possible that neither of the eruptive and high-luminosity events of SN 2009ip were induced by a core collapse. We show that the peak and total integrated luminosity can be due to the efficient conversion of kinetic energy from colliding ejecta, and that around 0.05–0.1 M⊙ of material moving at 0.5–1 × 104 km s−1 could comfortably produce the observed luminosity. We discuss the possibility that these shells were ejected by the pulsational pair instability mechanism, in which case the progenitor star may still exist, and will be observed after the current outburst fades. The long-term monitoring of SN 2009ip, due to its proximity, has given the most extensive data set yet gathered of a high-luminosity interacting transient and its progenitor. It is possible that some purported Type IIn supernovae are in fact analogues of the 2012b event and that pre-explosion outbursts have gone undetected.

Balmer series

10.1093/mnras/stt813

Cite

Citations (123)

Principal Component Analysis of Type Ia Supernova Spectrophotometric Time Series

American Astronomical Society Meeting Abstracts #223 (2014)

C. Saunders G. Aldering S. Bailey D. Birchall M. Childress

Component (thermodynamics)

Source

Cite

Citations (0)

WiFeS+FIRE classification of ASASSN-14lw as a young SN Ia

The astronomer's telegram (2014)

M. Childress T. Diamond R. Scalzo C. Contreras B. Tucker

Source

Cite

Citations (0)

Ages of Type Ia supernovae over cosmic time

Monthly Notices of the Royal Astronomical Society (2014)

M. Childress Christian Wolf H. Jabran Zahid

We derive empirical models for galaxy mass assembly histories, and convolve these with theoretical delay time distribution (DTD) models for Type Ia supernovae (SNe Ia) to derive the distribution of progenitor ages for all SNe Ia occurring at a given epoch of cosmic time.In actively star-forming galaxies, the progression of the star formation rate is shallower than a t -1 SN Ia DTD, so mean SN Ia ages peak at the DTD peak in all star-forming galaxies at all epochs of cosmic history.In passive galaxies which have ceased star formation through some quenching process, the SN Ia age distribution peaks at the quenching epoch, which in passive galaxies evolves in redshift to track the past epoch of major star formation.Our models reproduce the SN Ia rate evolution in redshift, the relationship between SN Ia stretch and host mass, and the distribution of SN Ia host masses in a manner qualitatively consistent with observations.Our model naturally predicts that low-mass galaxies tend to be actively star-forming while massive galaxies are generally passive, consistent with observations of galaxy "downsizing".Consequently, the mean ages of SNe Ia undergo a sharp transition from young ages at low host mass to old ages at high host mass, qualitatively similar to the transition of mean SN Ia Hubble residuals with host mass.The age discrepancy evolves with redshift in a manner currently not accounted for in SN Ia cosmology analyses.We thus suggest that SNe Ia selected only from actively star-forming galaxies will yield the most cosmologically uniform sample, due to the homogeneity of young SN Ia progenitor ages at all cosmological epochs.

Stellar mass

10.1093/mnras/stu1892

Cite

Citations (99)

On the diversity of superluminous supernovae: ejected mass as the dominant factor

Monthly Notices of the Royal Astronomical Society (2015)

M. Nicholl S. J. Smartt A. Jerkstrand C. Inserra Stuart Sim

We assemble a sample of 24 hydrogen-poor super-luminous supernovae (SLSNe). Parameterizing the light curve shape through rise and decline timescales shows that the two are highly correlated. Magnetar-powered models can reproduce the correlation, with the diversity in rise and decline rates driven by the diffusion timescale. Circumstellar interaction models can exhibit a similar rise-decline relation, but only for a narrow range of densities, which may be problematic for these models. We find that SLSNe are approximately 3.5 magnitudes brighter and have light curves 3 times broader than SNe Ibc, but that the intrinsic shapes are similar. There are a number of SLSNe with particularly broad light curves, possibly indicating two progenitor channels, but statistical tests do not cleanly separate two populations. The general spectral evolution is also presented. Velocities measured from Fe II are similar for SLSNe and SNe Ibc, suggesting that diffusion time differences are dominated by mass or opacity. Flat velocity evolution in most SLSNe suggests a dense shell of ejecta. If opacities in SLSNe are similar to other SNe Ibc, the average ejected mass is higher by a factor 2-3. Assuming $κ=0.1\,$cm$^2\,$g$^{-1}$, we estimate a mean (median) SLSN ejecta mass of 10$\,$M$_\odot$ (6$\,$M$_\odot$), with a range of 3-30$\,$M$_\odot$. Doubling the assumed opacity brings the masses closer to normal SNe Ibc, but with a high-mass tail. The most probable mechanism for generating SLSNe seems to be the core-collapse of a very massive hydrogen-poor star, forming a millisecond magnetar.

Opacity

Magnetar

10.1093/mnras/stv1522

Cite

Citations (167)

Correction: Corrigendum: The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole

Nature Astronomy (2016)

G. Leloudas M. Fraser Nicholas C. Stone Sjoert van Velzen P. G. Jonker

Transient (computer programming)

10.1038/s41550-016-0034

Cite

Citations (3)

High-velocity features in Type Ia supernova spectra

Monthly Notices of the Royal Astronomical Society (2013)

M. Childress A. V. Filippenko M. Ganeshalingam B. Schmidt

We use a sample of 58 low-redshift (z ≤ 0.03) Type Ia supernovae (SNe Ia) having well-sampled light curves and spectra near maximum light to examine the behaviour of high-velocity features (HVFs) in SN Ia spectra. We take advantage of the fact that Si ii λ6355 is free of HVFs at maximum light in all SNe Ia, while HVFs are still strong in the Ca ii near-infrared feature in many SNe, allowing us to quantify the strength of HVFs by comparing the structure of these two lines. We find that the average HVF strength increases with decreasing light-curve decline rate, and rapidly declining SNe Ia (Δm15(B) ≥ 1.4 mag) show no HVFs in their maximum-light spectra. Comparison of HVF strength to the light-curve colour of the SNe Ia in our sample shows no evidence of correlation. We find a correlation of HVF strength with the velocity of Si ii λ6355 at maximum light (vSi), such that SNe Ia with lower vSi have stronger HVFs, while those SNe Ia firmly in the 'high-velocity' (i.e. vSi ≥ 12 000 km s−1) subclass exhibit no HVFs in their maximum-light spectra. While vSi and Δm15(B) show no correlation in the full sample of SNe Ia, we find a significant correlation between these quantities in the subset of SNe Ia having weak HVFs. In general, we find that slowly declining (low Δm15(B)) SNe Ia, which are more luminous and more energetic than average SNe Ia, tend to produce either high photospheric ejecta velocities (i.e. high vSi) or strong HVFs at maximum light, but not both. Finally, we examine the evolution of HVF strength for a sample of SNe Ia having extensive pre-maximum spectroscopic coverage and find significant diversity of the pre-maximum HVF behaviour.

10.1093/mnras/stt1892

Cite

Citations (68)

450 d of Type II SN 2013ej in optical and near-infrared

Monthly Notices of the Royal Astronomical Society (2016)

F. Yuan A. Jerkstrand S. Valenti J. Sollerman I. R. Seitenzahl

We present optical and near-infrared photometric and spectroscopic observations of SN 2013ej, in galaxy M74, from 1 to 450 d after the explosion. SN 2013ej is a hydrogen-rich supernova, classified as a Type IIL due to its relatively fast decline following the initial peak. It has a relatively high peak luminosity (absolute magnitude MV = −17.6) but a small 56Ni production of ∼0.023 M⊙. Its photospheric evolution is similar to other Type II SNe, with shallow absorption in the Hα profile typical for a Type IIL. During transition to the radioactive decay tail at ∼100 d, we find the SN to grow bluer in B − V colour, in contrast to some other Type II supernovae. At late times, the bolometric light curve declined faster than expected from 56Co decay and we observed unusually broad and asymmetric nebular emission lines. Based on comparison of nebular emission lines most sensitive to the progenitor core mass, we find our observations are best matched to synthesized spectral models with a MZAMS = 12–15 M⊙ progenitor. The derived mass range is similar to but not higher than the mass estimated for Type IIP progenitors. This is against the idea that Type IIL are from more massive stars. Observations are consistent with the SN having a progenitor with a relatively low-mass envelope.

Absolute magnitude

10.1093/mnras/stw1419

Cite

Citations (67)

Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction

Monthly Notices of the Royal Astronomical Society (2014)

R. Scalzo M. Childress C. Tucker F. Yuan B. Schmidt

We present photospheric-phase observations of LSQ12gdj, a slowly declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude MB = −19.8, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600–23 800 Å) light curve out to 45 d past B-band maximum light. We estimate that LSQ12gdj produced 0.96 ± 0.07 M⊙ of 56Ni, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27 per cent of the flux at the earliest observed phases, and 17 per cent at maximum light, is emitted bluewards of 3300 Å. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 Å and the absence of narrow line emission and strong Na i D absorption all argue against a significant contribution from ongoing shock interaction. However, ∼10 per cent of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius <1013 cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios.

Chandrasekhar limit

Spectral energy distribution

Blanketing

10.1093/mnras/stu1723

Cite

Citations (27)

Spectroscopic Classification of PSN J01241425-3443364 and ASASSN-13bb with WiFeS

ATel (2013)

M. Childress R. Scalzo F. Yuan B. Schmidt B. Tucker

Source

Cite

Citations (0)