arXiv subjects

S. Ryder

Publications and source records attributed to S. Ryder.

At least 19 recordsLinked to original sources

arXiv2026

SN 2007it on the RISE -- a radio detection of an interacting supernova 18 years post-explosion

We report the first detection of radio emission from the Type II supernova SN 2007it, located at a distance of 12.2 Mpc in NGC 5530. The observations were obtained with the Australian Telescope Compact Array (ATCA) more than 18 yr after the explosion as part of the Rebrightening in Interacting Supernova Emission (RISE) program, which monitors nearby core-collapse supernovae for late-time interaction with dense circumstellar material. SN 2007it was detected on 2026 April 8 (08:00-12:00 UTC) at 5.5 GHz with a flux density of $3.30 \pm 0.13$ mJy and at 9.0 GHz with $3.54 \pm 0.24$ mJy. Its non-detection in publicly available 0.88 GHz ASKAP data from 2026 January 11 suggests either rapidly rising emission or significant internal absorption at lower frequencies. We assess the prospects for detection at other wavelengths and encourage coordinated follow-up observations across the radio, optical, X-ray, and $\gamma$-ray band

astro-ph.HE↗

arXiv2024

Optical and near-infrared photometry of 94 type II supernovae from the Carnegie Supernova Project

Type II supernovae (SNeII) mark the endpoint in the lives of hydrogen-rich massive stars. Their large explosion energies and luminosities allow us to measure distances, metallicities, and star formation rates into the distant Universe. To fully exploit their use in answering different astrophysical problems, high-quality low-redshift data sets are required. Such samples are vital to understand the physics of SNeII, but also to serve as calibrators for distinct - and often lower-quality - samples. We present uBgVri optical and YJH near-infrared (NIR) photometry for 94 low-redshift SNeII observed by the Carnegie Supernova Project (CSP). A total of 9817 optical and 1872 NIR photometric data points are released, leading to a sample of high-quality SNII light curves during the first ~150 days post explosion on a well-calibrated photometric system. The sample is presented and its properties are analysed and discussed through comparison to literature events. We also focus on individual SNeII as examples of classically defined subtypes and outlier objects. Making a cut in the plateau decline rate of our sample (s2), a new subsample of fast-declining SNeII is presented. The sample has a median redshift of 0.015, with the nearest event at 0.001 and the most distant at 0.07. At optical wavelengths (V), the sample has a median cadence of 4.7 days over the course of a median coverage of 80 days. In the NIR (J), the median cadence is 7.2 days over the course of 59 days. The fast-declining subsample is more luminous than the full sample and shows shorter plateau phases. Of the non-standard SNeII highlighted, SN2009A particularly stands out with a steeply declining then rising light curve, together with what appears to be two superimposed P-Cygni profiles of H-alpha in its spectra. We outline the significant utility of these data, and finally provide an outlook of future SNII science.

astro-ph.CO↗

arXiv2022

Energetic nuclear transients in luminous and ultraluminous infrared galaxies

Energetic nuclear outbursts have been discovered in luminous and ultraluminous infrared galaxies (U/LIRGs) at unexpectedly high rates. To investigate this population of transients, we performed a search in mid-IR data from the Wide-field Infrared Survey Explorer (WISE) satellite and its NEOWISE survey to detect and characterise luminous and smoothly evolving transients in a sample of 215 U/LIRGs. We report three new transients, all with $\Delta L > 10^{43}$ erg s$^{-1}$, in addition to two previously known cases. Their host galaxies are all part of major galaxy mergers, and through radiative transfer model fitting we find that all have a significant contribution from an active galactic nucleus (AGN). We characterised the transients through measurements of their luminosities and resulting energetics, all of which are between 10$^{50.9}$ erg and 10$^{52.2}$ erg. The IR emission of the five transients was found to be consistent with re-radiation by the hot dust of emission at shorter wavelengths, presumably originating from an accretion event, onto the supermassive black hole. The corresponding transient rate of (1.6-4.6)$\times$10$^{-3}$ / yr / galaxy is over an order of magnitude higher than the rate of large amplitude flares shown by AGN in the optical. We suggest that the observed transients are part of a dust-obscured population of tidal disruption events (TDEs) that have remained out of the reach of optical surveys due to the obscuring dust. In one case, this is supported by our radio observations. We also discuss other plausible explanations. The observed rate of events is significantly higher than optical TDE rates, which can be expected in U/LIRG hosts undergoing a major galaxy merger with increased stellar densities in the nuclear regions. Continued searches for such transients and their multi-wavelength follow-up is required to constrain their rate and nature.

astro-ph.GA↗

arXiv2020

The Radio Luminosity-Risetime Function of Core-Collapse Supernovae

We assemble a large set of 2-10 GHz radio flux density measurements and upper limits of 294 different supernovae (SNe), from the literature and our own and archival data. Only 31% of the SNe were detected. We characterize the SN lightcurves near the peak using a two-parameter model, with $t_{\rm pk}$ being the time to rise to a peak and $L_{\rm pk}$ the spectral luminosity at that peak. Over all SNe in our sample at $D<100$ Mpc, we find that $t_{\rm pk} = 10^{1.7\pm0.9}$ d, and that $L_{\rm pk} = 10^{25.5\pm1.6}$ erg s$^{-1}$ Hz$^{-1}$, and therefore that generally, 50% of SNe will have $L_{\rm pk} < 10^{25.5}$ erg s$^{-1}$ Hz$^{-1}$. These $L_{\rm pk}$ values are ~30 times lower than those for only detected SNe. Types I b/c and II (excluding IIn's) have similar mean values of $L_{\rm pk}$ but the former have a wider range, whereas Type IIn SNe have ~10 times higher values with $L_{\rm pk} = 10^{26.5\pm1.1}$ erg s$^{-1}$ Hz$^{-1}$. As for $t_{\rm pk}$, Type I b/c have $t_{\rm pk}$ of only $10^{1.1\pm0.5}$ d while Type II have $t_{\rm pk} = 10^{1.6\pm1.0}$ and Type IIn the longest timescales with $t_{\rm pk} = 10^{3.1\pm0.7}$ d. We also estimate the distribution of progenitor mass-loss rates, $\dot M$, and find the mean and standard deviation of log$_{10}(\dot M/$Msol) yr$^{-1}$ are $-5.4\pm1.2$ (assuming $v_{\rm wind}=1000$ km s$^{-1}$) for Type I~b/c SNe, and $-6.9\pm1.4$ (assuming $v_{\rm wind} = 10$ km s$^{-1}$ for Type II SNe excluding Type IIn.

astro-ph.HE↗

arXiv2020

AT 2017gbl: a dust obscured TDE candidate in a luminous infrared galaxy

We present the discovery with Keck of the extremely infrared (IR) luminous transient AT 2017gbl, coincident with the Northern nucleus of the luminous infrared galaxy (LIRG) IRAS 23436+5257. Our extensive multi-wavelength follow-up spans ~900 days, including photometry and spectroscopy in the optical and IR, and (very long baseline interferometry) radio and X-ray observations. Radiative transfer modelling of the host galaxy spectral energy distribution and long-term pre-outburst variability in the mid-IR indicate the presence of a hitherto undetected dust obscured active galactic nucleus (AGN). The optical and near-IR spectra show broad 2000 km/s hydrogen, He I and O I emission features that decrease in flux over time. Radio imaging shows a fast evolving compact source of synchrotron emission spatially coincident with AT 2017gbl. We infer a lower limit for the radiated energy of 7.3 x 10^50 erg from the IR photometry. An extremely energetic supernova would satisfy this budget, but is ruled out by the radio counterpart evolution. Instead, we propose AT 2017gbl is related to an accretion event by the central supermassive black hole, where the spectral signatures originate in the AGN broad line region and the IR photometry is consistent with re-radiation by polar dust. Given the fast evolution of AT 2017gbl, we deem a tidal disruption event (TDE) of a star a more plausible scenario than a dramatic change in the AGN accretion rate. This makes AT 2017gbl the third TDE candidate to be hosted by a LIRG, in contrast to the so far considered TDE population discovered at optical wavelengths and hosted preferably by post-starburst galaxies.

astro-ph.HE↗

arXiv2020

WALLABY -- An SKA Pathfinder HI Survey

The Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a next-generation survey of neutral hydrogen (HI) in the Local Universe. It uses the widefield, high-resolution capability of the Australian Square Kilometer Array Pathfinder (ASKAP), a radio interferometer consisting of 36 x 12-m dishes equipped with Phased-Array Feeds (PAFs), located in an extremely radio-quiet zone in Western Australia. WALLABY aims to survey three-quarters of the sky (-90 degr < Dec < +30 degr) to a redshift of z < 0.26, and generate spectral line image cubes at ~30 arcsec resolution and ~1.6 mJy/beam per 4 km/s channel sensitivity. ASKAP's instantaneous field of view at 1.4 GHz, delivered by the PAF's 36 beams, is about 30 sq deg. At an integrated signal-to-noise ratio of five, WALLABY is expected to detect over half a million galaxies with a mean redshift of z ~ 0.05 (~200 Mpc). The scientific goals of WALLABY include: (a) a census of gas-rich galaxies in the vicinity of the Local Group; (b) a study of the HI properties of galaxies, groups and clusters, in particular the influence of the environment on galaxy evolution; and (c) the refinement of cosmological parameters using the spatial and redshift distribution of low-bias gas-rich galaxies. For context we provide an overview of previous large-scale HI surveys. Combined with existing and new multi-wavelength sky surveys, WALLABY will enable an exciting new generation of panchromatic studies of the Local Universe. - First results from the WALLABY pilot survey are revealed, with initial data products publicly available in the CSIRO ASKAP Science Data Archive (CASDA).

astro-ph.GA↗

arXiv2018

A dust-enshrouded tidal disruption event with a resolved radio jet in a galaxy merger

Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). We have observed a transient source in the western nucleus of the merging galaxy pair Arp 299 that radiated >1.5x10^52 erg in the infrared and radio, but was not luminous at optical or X-ray wavelengths. We interpret this as a TDE with much of its emission re-radiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the difference between theoretical predictions and observed luminosities of TDEs. The radio observations resolve an expanding and decelerating jet, probing the jet formation and evolution around a SMBH.

astro-ph.GA↗

arXiv2017

First results from GeMS/GSAOI for project SUNBIRD: Supernovae UNmasked By Infra-Red Detection

Core collapse supernova (CCSN) rates suffer from large uncertainties as many CCSNe exploding in regions of bright background emission and significant dust extinction remain unobserved. Such a shortfall is particularly prominent in luminous infrared galaxies (LIRGs), which have high star formation (and thus CCSN) rates and host bright and crowded nuclear regions, where large extinctions and reduced search detection efficiency likely lead to a significant fraction of CCSNe remaining undiscovered. We present the first results of project SUNBIRD (Supernovae UNmasked By Infra-Red Detection), where we aim to uncover CCSNe that otherwise would remain hidden in the complex nuclear regions of LIRGs, and in this way improve the constraints on the fraction that is missed by optical seeing-limited surveys. We observe in the near-infrared 2.15 {\mu}m $K_s$-band, which is less affected by dust extinction compared to the optical, using the multi-conjugate adaptive optics imager GeMS/GSAOI on Gemini South, allowing us to achieve a spatial resolution that lets us probe close in to the nuclear regions. During our pilot program and subsequent first full year we have discovered three CCSNe and one candidate with projected nuclear offsets as small as 200 pc. When compared to the total sample of LIRG CCSNe discovered in the near-IR and optical, we show that our method is singularly effective in uncovering CCSNe in nuclear regions and we conclude that the majority of CCSNe exploding in LIRGs are not detected as a result of dust obscuration and poor spatial resolution.

astro-ph.GA↗

arXiv2017

Predicting the Presence of Companions for Stripped-Envelope Supernovae: The Case of the Broad-Lined Type Ic SN 2002ap

Many young, massive stars are found in close binaries. Using population synthesis simulations we predict the likelihood of a companion star being present when these massive stars end their lives as core-collapse supernovae (SNe). We focus on stripped-envelope SNe, whose progenitors have lost their outer hydrogen and possibly helium layers before explosion. We use these results to interpret new Hubble Space Telescope observations of the site of the broad-lined Type Ic SN 2002ap, 14 years post-explosion. For a subsolar metallicity consistent with SN 2002ap, we expect a main-sequence companion present in about two thirds of all stripped-envelope SNe and a compact companion (likely a stripped helium star or a white dwarf/neutron star/black hole) in about 5% of cases. About a quarter of progenitors are single at explosion (originating from initially single stars, mergers or disrupted systems). All the latter scenarios require a massive progenitor, inconsistent with earlier studies of SN 2002ap. Our new, deeper upper limits exclude the presence of a main-sequence companion star $>8$-$10$ Msun, ruling out about 40% of all stripped-envelope SN channels. The most likely scenario for SN 2002ap includes nonconservative binary interaction of a primary star initially $\lesssim 23$ Msun. Although unlikely ($<$1% of the scenarios), we also discuss the possibility of an exotic reverse merger channel for broad-lined Type Ic events. Finally, we explore how our results depend on the metallicity and the model assumptions and discuss how additional searches for companions can constrain the physics that governs the evolution of SN progenitors.

astro-ph.HE↗

arXiv2014

Core-collapse and Type Ia supernovae with the SKA

Core-collapse SNe (CCSNe): Systematic searches of radio emission from CCSNe are still lacking, and only targeted searches of radio emission from just some of the optically discovered CCSNe in the local universe have been carried out. Optical searches miss a significant fraction of CCSNe due to dust obscuration; CCSN radio searches are thus more promising for yielding the complete, unobscured star-formation rates in the local universe. The SKA yields the possibility to piggyback for free in this area of research by carrying out commensal, wide-field, blind transient survey observations. SKA1-SUR should be able to discover several hundreds of CCSNe in just one year, compared to about a dozen CCSNe that the VLASS would be able to detect in one year, at most. SKA, with an expected sensitivity ten times that of SKA1, is expected to detect CCSNe in the local Universe by the thousands. Therefore, commensal SKA observations could easily result in an essentially complete census of all CCSNe in the local universe, thus yielding an accurate determination of the volumetric CCSN rate. Type Ia SNe: We advocate for the use of the SKA to search for the putative prompt (~first few days after the explosion) radio emission of any nearby type Ia SN, via target-of-opportunity observations. The huge improvement in sensitivity of the SKA with respect to its predecessors will allow to unambiguously discern which progenitor scenario (single-degenerate vs. double-degenerate) applies to them.

astro-ph.HE↗

arXiv2014

SN 2005at - A neglected type Ic supernova at 10 Mpc

We present a photometric and spectroscopic study of a reddened type Ic supernova (SN) 2005at. We report our results based on the available data of SN 2005at, including late-time observations from the Spitzer Space Telescope and the Hubble Space Telescope. In particular, late-time mid-infrared observations are something rare for type Ib/c SNe. In our study we find SN 2005at to be very similar photometrically and spectroscopically to another nearby type Ic SN 2007gr, underlining the prototypical nature of this well-followed type Ic event. The spectroscopy of both events shows similar narrow spectral line features. The radio observations of SN 2005at are consistent with fast evolution and low luminosity at radio wavelengths. The late-time Spitzer data suggest the presence of an unresolved light echo from interstellar dust and dust formation in the ejecta, both of which are unique observations for a type Ic SN. The late-time Hubble observations reveal a faint point source coincident with SN 2005at, which is very likely either a declining light echo of the SN or a compact cluster. For completeness we study ground-based pre-explosion archival images of the explosion site of SN 2005at, however this only yielded very shallow upper limits for the SN progenitor star. We derive a host galaxy extinction of $A_{V} \approx 1.9$ mag for SN 2005at, which is relatively high for a SN in a normal spiral galaxy not viewed edge-on.

astro-ph.SR↗

arXiv2014

Constraints on the progenitor system and the environs of SN 2014J from deep radio observations

We report deep EVN and eMERLIN observations of the Type Ia SN 2014J in the nearby galaxy M 82. Our observations represent, together with JVLA observations of SNe 2011fe and 2014J, the most sensitive radio studies of Type Ia SNe ever. By combining data and a proper modeling of the radio emission, we constrain the mass-loss rate from the progenitor system of SN 2014J to $\dot{M} \lesssim 7.0\times 10^{-10}\, {\rm M_{\odot}\, yr^{-1}}$ (3-$\sigma$; for a wind speed of $100\, {\rm km s^{-1}}$). If the medium around the supernova is uniform, then $n_{\rm ISM} \lesssim 1.3 {\rm cm^3}$ (3-$\sigma$), which is the most stringent limit for the (uniform) density around a Type Ia SN. Our deep upper limits favor a double-degenerate (DD) scenario--involving two WD stars--for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast, most single-degenerate (SD) scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to a exploding WD, are ruled out by our observations. Our estimates on the limits to the gas density surrounding SN 2011fe, using the flux density limits from Chomiuk et al. (2012), agree well with their results. Although we discuss possibilities for a SD scenario to pass observational tests, as well as uncertainties in the modeling of the radio emission, the evidence from SNe 2011fe and 2014J points in the direction of a DD scenario for both.

astro-ph.SR↗

arXiv2014

The nature of supernovae 2010O and 2010P in Arp 299 - I. Near-infrared and optical evolution

We present near-infrared and optical photometry, plus optical spectroscopy of two stripped-envelope supernovae (SNe) 2010O and 2010P that exploded in two different components of an interacting luminous infrared galaxy Arp 299 within only a few days of one another. SN 2010O is found to be photometrically and spectroscopically similar to many normal Type Ib SNe and our multiwavelength observations of SN 2010P suggest it to be a Type IIb SN. No signs of clear hydrogen features or interaction with the circumstellar medium are evident in the optical spectrum of SN 2010P. We derive estimates for the host galaxy line-of-sight extinctions for both SNe, based on both light-curve and spectroscopic comparison finding consistent results. These methods are also found to provide much more robust estimates of the SN host galaxy reddening than the commonly used empirical relations between extinction and equivalent width of Na I D absorption features. The SN observations also suggest that different extinction laws are present in different components of Arp 299. For completeness, we study high-resolution pre-explosion images of Arp 299 and find both SNe to be close to, but not coincident with, extended sources that are likely massive clusters. A very simple model applied to the bolometric light curve of SN 2010O implies a rough estimate for the explosion parameters of $E_{\mathrm{k}} \approx 3 \times 10^{51}$ erg, $M_{\mathrm{ej}} \approx 2.9$ M$_{\odot}$ and $M_{\mathrm{Ni}} \approx 0.16$ M$_{\odot}$.

astro-ph.SR↗

arXiv2014

Super Star Clusters in Luminous Infrared Galaxies: the SUNBIRD Survey

We present recent results from an adaptive optics imaging survey of 40 Luminous IR Galaxies (LIRGs) searching for obscured core collapse supernovae and studying the galaxies themselves. Here, in particular, we discuss the Super Star Clusters (SSC) populations in the LIRGs. We have constructed the first statistically significant samples of Luminosity Functions (LF) of SSCs in the near-IR, and find evidence that the LF slopes in LIRGs are shallower than in more quiescent spiral galaxies. Distance and blending effects were investigated in detail paving the way for SSC studies further out than done previously. We have also correlated the luminosities of the brightest clusters with the star formation rates (SFR) of the hosts. The relation is similar, though somewhat steeper than that found in the optical and at lower SFR levels, suggesting systematic extinction and/or age effects. We find that the characteristics of the relation suggest an underlying physical driver rather than solely a size-of-sample effect. In particular, a truncated luminosity/mass function would naturally explain the small scatter we find. Finally, we are modelling the ages and masses of our near-IR detected clusters in conjunction with HST optical data and present early results of using SSC properties to trace the histories of the target LIRG systems.

astro-ph.GA↗

arXiv2013

The circumnuclear environment of NGC613: a nuclear starburst caught in the act?

We present near-infrared ($H$- and $K$-band) integral-field observations of the inner $\sim$700pc of the active spiral galaxy NGC613, obtained with SINFONI on the Very Large Telescope. We use emission-line ratios to determine the dominant excitation mechanisms in different regions within our field-of-view, in particular the active nucleus and the star-forming circum-nuclear ring. Diagnostic diagrams involving [FeII] and H$_2$ fluxes indicate that the gas is not only photoionized by the AGN in the nucleus of NGC613, but also shock-heated. On the other hand, the emission line ratios measured in the ``hot spots'' along the ring are fully consistent with them being young star forming regions. We find no sign of radial gas transport from the ring into the core region dominated by the AGN. The ring morphology appears disturbed by a radial outflow of material from the AGN, which is confirmed by the existence of a weak jet in archival radio maps. However, this jet does not seem to have any significant effect on the morphology of the large ($\sim$8$\times$10$^7$ solar masses) reservoir of molecular gas that has accumulated inside the central $\sim$100pc. Such a concentration of molecular gas around an AGN is unusual, and supports a scenario in which star formation is recurrent and episodic in spiral galaxies. In this context, NGC613 appears to be in final stages of the gas accumulation phase, and is likely to undergo a nuclear starburst in the near future.

astro-ph.GA↗

arXiv2012

Core-collapse supernovae missed by optical surveys

We estimate the fraction of core-collapse supernovae (CCSNe) that remain undetected by optical SN searches due to obscuration by large amounts of dust in their host galaxies. This effect is especially important in luminous and ultraluminous infrared galaxies, which are locally rare but dominate the star formation at redshifts of z~1-2. We perform a detailed investigation of the SN activity in the nearby luminous infrared galaxy Arp 299 and estimate that up to 83% of the SNe in Arp 299 and in similar galaxies in the local Universe are missed by observations at optical wavelengths. For rest-frame optical surveys we find the fraction of SNe missed due to high dust extinction to increase from the average local value of ~19% to ~38% at z~1.2 and then stay roughly constant up to z~2. It is therefore crucial to take into account the effects of obscuration by dust when determining SN rates at high redshift and when predicting the number of CCSNe detectable by future high-z surveys such as LSST, JWST, and Euclid. For a sample of nearby CCSNe (distances 6-15 Mpc) detected during the last 12 yr, we find a lower limit for the local CCSN rate of 1.5 +0.4/-0.3 x 10^-4 yr^-1 Mpc^-3, consistent with that expected from the star formation rate. Even closer, at distances less than ~6 Mpc, we find a significant increase in the CCSN rate, indicating a local overdensity of star formation caused by a small number of galaxies that have each hosted multiple SNe.

astro-ph.CO↗

arXiv2011

Discovery of Two Supernovae in the Nuclear Regions of the Luminous Infrared Galaxy IC 883

We report the discovery of two consecutive supernovae (SNe), 2010cu and 2011hi, located at 0.37" (180 pc) and 0.79" (380 pc) projected distance respectively from the centre of the K-band nucleus of the luminous infrared galaxy IC 883. The SNe were discovered in an ongoing near-infrared K-band search for core-collapse SNe in such galaxies using the ALTAIR/NIRI adaptive optics system with laser guide star at the Gemini-North Telescope. These are thus the closest SNe yet discovered to a LIRG nucleus in optical or near-infrared wavelengths. The near-infrared light curves and colours of both SNe are consistent with core-collapse events. Both SNe seem to suffer from relatively low host galaxy extinction suggesting that regardless of their low projected galactocentric distances, they are not deeply buried in the nuclear regions of the host galaxy.

astro-ph.SR↗

arXiv2009

Radio Supernovae: Circum-Stellar Investigation (C.S.I.) of Supernova Progenitor Stars

Prior to explosion, a supernova progenitor slowly loses significant amounts of its hydrogen envelope in a stellar wind. After the explosion, the blastwave interacts with this wind producing synchrotron emission. A year of radio observations allows us to probe the progenitor evolution for a thousand years. The EVLA and SKA would represent more than an order of magnitude improvement in our ability to explore the pre-explosion lives of a significantly large population of supernova progenitor stars. It will allow us to move beyond the crude optical classifications and develop a deeper physical understanding of how massive stars live and die.

astro-ph.HE↗