arXiv subjects

J. D. Lyman

Publications and source records attributed to J. D. Lyman.

At least 19 recordsLinked to original sources

arXiv2026

ENGRAVE follow-up of a type IIb supernova spatially coincident with the sub-threshold gravitational wave trigger S250818k

The candidate gravitational wave (GW) event S250818k was one of only three non-retracted LIGO-Virgo-KAGRA public alerts issued during the fourth observing run of the network (O4) with a binary neutron star (BNS) merger classification probability exceeding one percent. This triggered a prompt search for a potential electromagnetic (EM) counterpart in the large localisation error region (949 deg$^2$ projected in the sky at 90% credible level). The transient SN2025ulz, discovered by the Zwicky Transient Facility (ZTF) during the search, attracted a great deal of attention due to a potential spatial and temporal coincidence, and due to its initial fast decay and featureless spectrum. Here, we report on the follow up of this transient by the Electromagnetic counterparts of gravitational wave sources at the Very Large Telescope (ENGRAVE) Collaboration. We conducted an extensive multi-wavelength observational campaign, which led to the spectral classification of the transient as a type IIb supernova (SN), indicating that it is unrelated to the candidate GW event. In this article, we describe our observing strategies, data reduction, and interpretation. All of our results confirm and strengthen our classification of the source, and also show that shock cooling tails associated with type IIb SNe are one of the most prominent contaminants in kilonova searches.

astro-ph.HE↗

arXiv2026

Magnetar counterparts, kinematics and birth sites with HST and JWST

Magnetars are highly magnetised, isolated neutron stars with uncertain formation channels. They comprise a potentially significant fraction of the young neutron star population in the Milky Way, and are implicated in the explosion mechanisms of some of the most powerful explosions in nature. We aim to identify magnetars in the near-infrared with Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) imaging, in order to measure their proper motions and search for their birth sites. Candidate infrared counterparts are selected based on variability, colours and proper motions which are outliers with respect to sources in the field. Proper motions are obtained by tying HST and JWST images to the Gaia absolute astrometric reference frame. We newly identify infrared counterparts for PSRJ1622-4950, 1RXSJ170849.0-400910 and CXOUJ164710.2-455216, representing a substantial increase in the population. The past trajectory of the 1RXSJ170849.0-400910-associated source coincides with the supernova remnant G346.6-0.2. The transverse velocity distribution is found to be marginally inconsistent with young pulsars, due primarily to a dearth of high velocity magnetars. A candidate birth site is identified in nearly every case. We show, based on the inferred kinematic ages, that magnetar characteristic ages may frequently be lower than the true age, but caution that this depends on the reliability of the birth site associations. We conclude that magnetars are broadly similar in terms of their kinematics and birth sites to the wider Galactic neutron star population, consistent with magnetar formation being a common outcome of core-collapse. However, tentative evidence for a dearth of high-velocity magnetars is emerging. If real, this may arise from physical differences in the progenitor population giving rise to magnetars, or from differences in their post-formation velocity evolution.

astro-ph.SR↗

arXiv2026

The Gravitational-wave Optical Transient Observer (GOTO) data pipeline and workflow for transient discovery

Wide-field and high-cadence sky surveys are the first step in the chain of discovery and characterisation of astrophysical transients such as supernovae, kilonovae, and tidal disruption events, each linked to the varied demise of stellar systems. The Gravitational-wave Optical Transient Observer (GOTO) is a telescope array of thirty-two 40 cm unit telescopes split over two almost antipodal sites. It performs a regular time-domain sky-survey in the optical to ~20 mag in addition to immediate scheduling of follow-up observations at the locations of external multi-wavelength and -messenger triggers. To facilitate the timely recovery of optical counterparts to these triggers, as well as the presence of serendipitous discoveries of astrophysical transients in the regular sky-survey, a low-latency data pipeline and workflow was developed. The implementation of this workflow is described herein and the quality of GOTO data delivered by it assessed, alongside its performance for prompt transient recovery. Utilising difference image analysis to identify candidate discoveries, the process is typically complete ~7 minutes after shutter close on the telescope. We further describe later processing of these candidates -- both automated and human-in-the-loop -- including reporting to the wider community and the triggering of more detailed observations, with a focus on immediate, intra-night characterisation. The workflow is meeting the needs of GOTO to promptly discover, report and characterise infant transients. Nevertheless, areas for further development and improvements are also highlighted.

astro-ph.IM↗

arXiv2026

Nested, asymmetric H-He circumstellar shells in the Type Icn/Ibn SN 2024abvb

Interacting transients probe mass loss in the final stages of stellar evolution; however, the geometry and timing of multi-episode mass loss remain poorly constrained. SN 2024abvb is a nearby interacting event with transitional Ibn/Icn spectroscopic properties and multi-epoch polarimetry, offering a rare opportunity to study structured circumstellar material (CSM). We aim to characterise the kinematics, composition and geometry of the CSM around SN 2024abvb and to identify plausible progenitor/ejection scenarios that can produce the observed spectro-polarimetric evolution. We present high-resolution (VLT/UVES and VLT/X-Shooter) optical/NIR spectroscopy across several epochs, complemented by broadband polarimetry and spectropolarimetry (VLT/FORS2 and NOT/ALFOSC). Line identifications, velocity decompositions and polarimetric time-series are used to trace multiple kinematic components and changes in scattering geometry. The high-resolution spectra reveal multiple narrow CSM components composed of He, C and O with absorption minima at $\sim150 - 400$ km s$^{-1}$ and additional faster material up to $\sim2000$ \kms. Low-velocity Balmer absorptions are present, indicating distant H-rich material, a first in SNe Ibn/Icn. Polarimetry shows a marked evolution ($P\sim1\%$ near peak, $\lesssim0.5\%$ after $\sim1$ week, rising to $\sim1.5\%$ at $\sim20$ d with $\sim50^\circ$ position-angle rotation and to $\sim4\%$ at $\sim30$ d, stronger in the blue), implying a time-variable, wavelength-dependent scattering/obscuration component. The combination of kinematics and polarimetric behaviour is consistent with multiple, concentric toroidal shells with differing orientations and partial dust content.

astro-ph.SR↗

arXiv2026

SN 2024abvb: a Type Ibn/Icn supernova with evidence of helium and an extreme offset from its host galaxy

We present spectroscopic and photometric observations and analysis of SN 2024abvb, a peculiar transitional Type Ibn/Icn supernova located at an unusually large projected distance from its host galaxy (21.5 kpc). SN 2024abvb displays an extended rise time in the $g$- and $o$-bands (10.1 and 10.6 days respectively), followed by a linear decline in all photometric bands. Comparisons with other supernova subclasses show that the photometric and spectroscopic evolution of SN 2024abvb are distinct from Type~Ibn and Type Icn events, with a higher peak $r$-band luminosity and lower blackbody temperatures. Spectra reveal an initial blue continuum and narrow P-Cygni profiles, with C {\sc ii} $λ$5890 dominating in emission, persisting at late phases, and showing a rapid decline in the expansion velocity. Weak He {\sc i} $λ$5876 features are tentatively detected at early times. Analysis of progenitor scenarios rules out thermonuclear origins based on incompatible light curve shapes and spectral signatures. A rare massive star progenitor appears unlikely given the low local star formation rate. The most plausible origin is an ultra-stripped supernova scenario involving a binary system; this best explains the observed separation from the host, the low circumstellar material mass, the fast photometric evolution and the low nickel production, although a discrepancy in model versus observed ejecta mass remains. These results reinforce the classification of SN 2024abvb as a distinctive Type Ibn/Icn event and highlight the diversity of progenitor channels for interacting supernovae.

astro-ph.SR↗

arXiv2025

A search for photometric variability towards the globular cluster M3 with the TWenty Inch Survey Telescope

We present the commissioning results and first scientific observations from the newly installed TWIST observatory - a 50 cm telescope equipped with an sCMOS camera providing a $36.1\times24.1$ arcmin$^2$ field of view - housed in the former SuperWASP-North enclosure. We conducted a 67-night, 199-day baseline white-light monitoring campaign centred on the globular cluster M3 aimed at characterizing stellar variability within the cluster while also assessing the photometric performance of the newly commissioned system. We report the discovery of four new SX Phoenicis variables (V301-304), confirm their cluster membership, and identify fundamental-mode pulsation in one, allowing an independent period-luminosity-based distance estimate to M3. We revisited 231 previously known RR Lyrae stars, providing updated period measurements for 203 and white-light amplitudes for 198. We detected Blazhko-like modulation in 53 stars and characterized the modulation parameters for 28. Notably, we measure periods and amplitudes for the unclassified variables V286 and V287 for the first time. We also identify three foreground flaring M dwarfs, and assess the feasibility of detecting microlensing events in M3, concluding that expected rates are negligible. Alongside the scientific results, we introduce a new correction technique for flat-field images affected by scattered light and present a full characterization of the observatory's photometric capabilities. These results demonstrate the scientific utility of TWIST for high-cadence time-domain surveys using modest-aperture instrumentation.

astro-ph.IM↗

arXiv2025

SN 2024bfu, SN 2025qe, and the early light curves of type Iax supernovae

Type Iax supernovae (SNe Iax) are one of the most common subclasses of thermonuclear supernova and yet their sample size, particularly those observed shortly after explosion, remains relatively small. In this paper we present photometric and spectroscopic observations of two SNe Iax discovered shortly after explosion, SN 2024bfu and SN 2025qe. Both SNe were observed by multiple all-sky surveys, enabling tight constraints on the moment of first light and the shape of the early light curve. Our observations of SN 2025qe begin <2d after the estimated time of first light and represent some of the earliest observations of any SN Iax. Spectra show features consistent with carbon absorption throughout the evolution of SN 2025qe, potentially indicating the presence of unburned material throughout the ejecta. We gather a sample of SNe Iax observed by ATLAS, GOTO, and ZTF shortly after explosion and measure their rise times and early light curve power-law rise indices. We compare our results to a sample of normal SNe Ia and find indications that SNe Iax show systematically shorter rise times, consistent with previous work. We also find some indication that SNe Iax show systematically lower rise indices than normal SNe Ia. The low rise indices observed among SNe Iax are qualitatively consistent with extended $^{56}$Ni distributions and more thoroughly-mixed ejecta compared to normal SNe Ia, similar to predictions from pure deflagration explosions.

astro-ph.HE↗

arXiv2025

GRB 241105A: A test case for GRB classification and rapid r-process nucleosynthesis channels

Gamma-ray bursts (GRBs) offer a powerful window to probe the progenitor systems responsible for the formation of heavy elements through the rapid neutron capture (r-) process, thanks to their exceptional luminosity, which allows them to be observed across vast cosmic distances. GRB 241105A, observed at a redshift of z = 2.681, features a short initial spike (1.5 s) and a prolonged weak emission lasting about 64 s, positioning it as a candidate for a compact binary merger and potentially marking it as the most distant merger-driven GRB observed to date. However, the emerging ambiguity in GRB classification necessitates further investigation into the burst's true nature. Prompt emission analyses, such as hardness ratio, spectral lag, and minimum variability timescales, yield mixed classifications, while machine learning-based clustering places GRB 241105A near both long-duration mergers and collapsar GRBs. We conducted observations using the James Webb Space Telescope (JWST) to search for a potential supernova counterpart. Although no conclusive evidence was found for a supernova, the host galaxy's properties derived from the JWST observations suggest active star formation with low metallicity, and a sub-kpc offset of the afterglow from the host, which appears broadly consistent with a collapsar origin. Nevertheless, a compact binary merger origin cannot be ruled out, as the burst may plausibly arise from a fast progenitor channel. This would have important implications for heavy element enrichment in the early Universe.

astro-ph.HE↗

arXiv2025

MUSE Observations Reveal Optical Coronal Iron Lines from Shock Emission in Supernova Remnant 0540-69.3

We investigate the optical shock emission from the Large Magellanic Cloud supernova remnant 0540-69.3 (SNR 0540) using MUSE integral-field-unit data from the VLT. The observations cover the spectral range 4650-9300 $Å$ and provide a $1\times1$ arcmin$^{2}$ field of view, encompassing nearly the entire remnant. We analyse the spatial and spectral properties of shock-related emission lines, and identify clumpy optical shock emission e.g. from [S II] $λλ$6716,6731 doublet and the coronal [Fe XIV] $λ$5303 line (typically at radial velocities $\lesssim|100|$ km s$^{-1}$ and $\lesssim|170|$ km s$^{-1}$, respectively). These features trace the blast-wave shell seen in previous X-ray studies. Post-shock electron density estimates, based on the [S II]-line ratio, reveal spatial variation, with the highest densities ($\sim10^4$ cm$^{-3}$) in the bright knots in the west, and lower densities ($\sim3\times10^3$ cm$^{-3}$) in the east. The density in the north (southwest) appears significantly lower (higher) but remains unconstrained due to limited signal. We also estimate blast-wave shock velocities using the [Fe XIV] $λ$5303/[Fe XI] $λ$7892 ratio, finding low velocities ($\sim400$ km s$^{-1}$), consistent with previous studies. All these results support the scenario that the blast wave is interacting with the surrounding interstellar medium, particularly in the western regions. Additionally, we detect four unidentified emission lines, $\sim$2000-3000 km s$^{-1}$ south from the pulsar in transverse velocity, but their origin remains unclear. Possible explanations, including Fe lines from a high-velocity ejecta clump, all present challenges. Our findings highlight the complex nature of the circum- and interstellar medium surrounding SNR 0540.

astro-ph.HE↗

arXiv2025

The infrared counterpart and proper motion of magnetar SGR0501+4516

Soft gamma repeaters (SGRs) are highly magnetised neutron stars (magnetars) notable for their gamma-ray and X-ray outbursts. In this paper, we use near-infrared (NIR) imaging of SGR 0501+4516 in the days, weeks, and years after its 2008 outburst to characterise the multi-wavelength emission, and to obtain a proper motion from our long temporal baseline observations. Unlike most magnetars, the source has only moderate foreground extinction with minimal crowding. Our observations began only 2 hours after the first activation of SGR 0501+4516 in August 2008, and continued for 4 years, including two epochs of Hubble Space Telescope (HST) imaging. The proper motion constraint is improved by a third HST epoch 10 years later. The near-infrared and X-rays faded slowly during the first week, thereafter following a steeper power-law decay. The behaviour is satisfactorily fit by a broken power-law. Three epochs of HST imaging with a 10-year baseline allow us to determine a quiescent level, and to measure a proper motion of 5.4+/-0.6 mas/yr. This corresponds to a low transverse peculiar velocity of 51+/-14 km/s (at 2 kpc). The magnitude and direction of the proper motion rules out supernova remnant HB9 as the birth-site. We can find no other supernova remnants or groups of massive stars within the region traversed by SGR 0501+4516 during its characteristic lifetime (20 kyr). Our observations of SGR 0501+4516 suggest that some magnetars may be either significantly older than expected, that their progenitors produce low supernova ejecta masses, or alternatively that they can be formed through accretion-induced collapse (AIC) or low-mass neutron star mergers. Although the progenitor of SGR 0501+4516 remains unclear, we propose that SGR 0501+4516 is the best Galactic candidate for a magnetar formed through a mechanism other than massive star core-collapse.

astro-ph.HE↗

arXiv2025

Constraints on optical and near-infrared variability in the localisation of the long-period radio transient GLEAM-X J1627-52

GLEAM-X J1627-52 was discovered as a periodic (~18 min) radio signal over a duration of three months in 2018. It is an enigmatic example of a growing population of 'long-period radio transients' consistent with Galactic origins. Their nature is uncertain, and leading models invoke magnetic neutron stars or white dwarfs, potentially in close binary systems, to power them. GLEAM-X J1627-52 resides in the Galactic plane with a comparatively coarse localisation (~2 arcsecond). Here we study the localisation region to search for spectrophotometric signatures of a counterpart using time-domain searches in optical and near-infrared imaging, and MUSE integral field spectroscopy. No sources in the localisation display clear white dwarf spectral signatures, although at the expected distance we can only provide modest limits on their presence directly. We rule out the presence of hot sub-dwarfs in the vicinity. We found no candidate within our search for variability or periodic behaviour in the light curves. Radial velocity curves additionally show only weak evidence of variation, requiring any realistic underlying system to have very low orbital inclination (i < 5 deg). Two Balmer emission line sources are reminiscent of white dwarf pulsar systems, but their characteristics fall within expected M-dwarf chromospheric activity with no signs of being in a close binary. Currently the white dwarf pulsar scenario is not supported, although longer baseline data and data contemporaneous with a radio active epoch are required before stronger statements. Isolated magnetars, or compact binaries remain viable. Our limits highlight the difficulty of these searches in dense environments at the limits of ground-based data.

astro-ph.SR↗

arXiv2024

Binary neutron star merger offsets from their host galaxies. GW 170817 as a case study

Aims. The locations of binary neutron star (BNS) mergers within their host galaxies encode the systemic kicks that these systems received in the supernova aftermath. We investigate how the galactic potential and the systemic kicks shape the offset distribution of BNS mergers with a case study of GW 170817 and its host NGC 4993. Methods. We derived dynamical constraints on the host potential from integral field spectroscopy with Jeans anisotropic modelling. We evolved the trajectories of synthetic BNSs from the BPASS code in the galactic potential, using two different kick prescriptions to investigate how the observed offsets might differentiate between these two possibilities. The simulation was repeated after swapping the host potential with that of a dwarf galaxy, to test the effect of the potential on the offsets. Results. The location of GW 170817 is entirely consistent with our predictions, regardless of large or small kicks, because the strong potential of NGC 4993 is only diagnostic of very large kicks. In galaxies of similar or greater mass, large offsets can constrain large kicks, while small offsets do not provide much information. In an old dwarf galaxy, on the other hand, small offsets can constrain small kicks, while large offsets would prevent host association.

astro-ph.HE↗

arXiv2024

Bidimensional Exploration of the warm-Temperature Ionised gaS (BETIS) I. Showcase sample and first results

We present the Bidimensional Exploration of the warm-Temperature Ionised gaS (BETIS) project, designed for the spatial and spectral study of the diffuse ionised gas (DIG) in a selection of nearby spiral galaxies observed with the MUSE integral-field spectrograph. Our primary objective is to investigate the various ionisation mechanisms at play within the DIG. We analysed the distribution of high- and low-ionisation species in the optical spectra of the sample on a spatially resolved basis. We introduced a new methodology for spectroscopically defining the DIG, optimised for galaxies of different resolutions. We also examined the suitability of using Ha equivalent width (EWha) as a proxy for defining the DIG and its associated ionisation regime. The average radial distribution of the main line ratios are enhanced in the DIG. It follows similar trends between the DIG regime and the HII regions, as well as the Ha surface brightness, indicating a correlation between the ionisation of these species in both the DIG and the HII regions. The DIG loci in diagnostic diagrams are found within the line ratios that correspond to photoionisation due to the star formation. There is a noticeable offset correspondent to fast shocks. However, an individual diagnosis performed for each galaxy reveals that all the DIG in these galaxies can be attributed to photoionisation from star formation. The offset is primarily due to the contribution of Seyfert galaxies in our sample, which is closely aligned with models of ionisation from fast shocks and galactic outflows, thus mimicking the DIG emission. Our results indicate that galaxies exhibiting active galactic nucleus activity should be considered separately when conducting a general analysis of the DIG ionisation mechanisms, since this emission is indistinguishable from high-excitation DIG.

astro-ph.GA↗

arXiv2024

Spatial Variations and Breaks in the Optical-NIR spectra of the Pulsar and PWN in SNR 0540-69.3

The supernova remnant SNR 0540-69.3, twin of the Crab Nebula, offers an excellent opportunity to study the continuum emission from a young pulsar and pulsar-wind nebula (PWN). We present observations taken with the VLT instruments MUSE and X-shooter in the wavelength range 3000-25,000 Å, which allow us to study spatial variations of the optical spectra, along with the first near-infrared (NIR) spectrum of the source. We model the optical spectra with a power law (PL) $F_ν\proptoν^{-α}$ and find clear spatial variations (including a torus-jet structure) in the spectral index across the PWN. Generally, we find spectral hardening toward the outer parts, from $α\sim1.1$ to $\sim0.1$, which may indicate particle reacceleration by the PWN shock at the inner edge of the ejecta or alternatively time variability of the pulsar wind. The optical-NIR spectrum of the PWN is best described by a broken PL, confirming that several breaks are needed to model the full spectral energy distribution of the PWN, suggesting the presence of more than one particle population. Finally, subtracting the PWN contribution from the pulsar spectrum we find that the spectrum is best described with a broken-PL model with a flat and a positive spectral index, in contrast to the Crab pulsar that has a negative spectral index and no break in the optical. This might imply that pulsar differences propagate to the PWN spectra.

astro-ph.HE↗

arXiv2023

Panning for gold, but finding helium: discovery of the ultra-stripped supernova SN2019wxt from gravitational-wave follow-up observations

We present the results from multi-wavelength observations of a transient discovered during the follow-up of S191213g, a gravitational wave (GW) event reported by the LIGO-Virgo Collaboration as a possible binary neutron star merger in a low latency search. This search yielded SN2019wxt, a young transient in a galaxy whose sky position (in the 80\% GW contour) and distance ($\sim$150\,Mpc) were plausibly compatible with the localisation uncertainty of the GW event. Initially, the transient's tightly constrained age, its relatively faint peak magnitude ($M_i \sim -16.7$\,mag) and the $r-$band decline rate of $\sim 1$\,mag per 5\,days appeared suggestive of a compact binary merger. However, SN2019wxt spectroscopically resembled a type Ib supernova, and analysis of the optical-near-infrared evolution rapidly led to the conclusion that while it could not be associated with S191213g, it nevertheless represented an extreme outcome of stellar evolution. By modelling the light curve, we estimated an ejecta mass of $\sim 0.1\,M_\odot$, with $^{56}$Ni comprising $\sim 20\%$ of this. We were broadly able to reproduce its spectral evolution with a composition dominated by helium and oxygen, with trace amounts of calcium. We considered various progenitors that could give rise to the observed properties of SN2019wxt, and concluded that an ultra-stripped origin in a binary system is the most likely explanation. Disentangling electromagnetic counterparts to GW events from transients such as SN2019wxt is challenging: in a bid to characterise the level of contamination, we estimated the rate of events with properties comparable to those of SN2019wxt and found that $\sim 1$ such event per week can occur within the typical GW localisation area of O4 alerts out to a luminosity distance of 500\,Mpc, beyond which it would become fainter than the typical depth of current electromagnetic follow-up campaigns.

astro-ph.HE↗

arXiv2023

Searching for ejected supernova companions in the era of precise proper motion and radial velocity measurements

The majority of massive stars are born in binaries, and most unbind upon the first supernova. With precise proper motion surveys such as Gaia, it is possible to trace back the motion of stars in the vicinity of young remnants to search for ejected companions. Establishing the fraction of remnants with an ejected companion, and the photometric and kinematic properties of these stars, offers unique insight into supernova progenitor systems. In this paper, we employ binary population synthesis to produce kinematic and photometric predictions for ejected secondary stars. We demonstrate that the unbound neutron star velocity distribution from supernovae in binaries closely traces the input kicks. Therefore, the observed distribution of neutron star velocities should be representative of their natal kicks. We evaluate the probability for any given filter, magnitude limit, minimum measurable proper motion (as a function of magnitude), temporal baseline, distance and extinction that an unbound companion can be associated with a remnant. We compare our predictions with results from previous companion searches, and demonstrate that the current sample of stars ejected by the supernova of their companion can be increased by a factor of 5-10 with Gaia data release 3. Further progress in this area is achievable by leveraging the absolute astrometric precision of Gaia, and by obtaining multiple epochs of deep, high resolution near-infrared imaging with the Hubble Space Telescope, JWST and next-generation wide-field near-infrared observatories such as Euclid or the Nancy Grace Roman Space Telescope.

astro-ph.HE↗

arXiv2022

The impostor revealed: SN 2016jbu was a terminal explosion

In this letter, we present recent observations from the Hubble Space Telescope of the interacting transient, SN 2016jbu, at +5 years. We find no evidence for any additional outburst from SN 2016jbu, and the optical source has now faded significantly below the progenitor magnitudes from early 2016. Similar to recent observations of SN 2009ip and SN 2015bh, SN 2016jbu has not undergone a significant change in colour over the past 2 years, suggesting that there is a lack of on-going dust formation. We find SN 2016jbu is fading slower than that expected from radioactive nickel, but faster than the decay of SN 2009ip. The late time light curve displays a non-linear decline and follows on from a re-brightening event that occurred $\sim$8 months after peak brightness, suggesting CSM interaction continues to dominate SN 2016jbu. While our optical observations are plausibly consistent with a surviving, hot, dust-enshrouded star, this would require an implausibly large dust mass. These new observations suggest that SN 2016jbu is a genuine, albeit strange, supernova, and we discuss the plausibility of a surviving binary companion.

astro-ph.HE↗

arXiv2022

Where are the magnetar binary companions? Candidates from a comparison with binary population synthesis predictions

It is well established that magnetars are neutron stars with extreme magnetic fields and young ages, but the evolutionary pathways to their creation are still uncertain. Since most massive stars are in binaries, if magnetars are a frequent result of core-collapse supernovae, some fraction are expected to have a bound companion at the time of observation. In this paper, we utilise literature constraints, including deep Hubble Space Telescope imaging, to search for bound stellar companions to magnetars. The magnitude and colour measurements are interpreted in the context of binary population synthesis predictions. We find two candidates for stellar companions associated with CXOU J171405.7-381031 and SGR 0755-2933, based on their J-H colours and H-band absolute magnitudes. Overall, the proportion of the Galactic magnetar population with a plausibly stellar near-infrared counterpart candidate, based on their magnitudes and colours, is between 5 and 10 per cent. This is consistent with a population synthesis prediction of 5 per cent, for the fraction of core-collapse neutron stars arising from primaries which remain bound to their companion after the supernova. These results are therefore consistent with magnetars being drawn in an unbiased way from the natal core-collapse neutron star population, but some contribution from alternative progenitor channels cannot be ruled out.

astro-ph.HE↗