Progenitor Mass Research Articles

Type II-P supernova progenitor star initial masses and SN 2020jfo: direct detection, light-curve properties, nebular spectroscopy, and local environment

ABSTRACT We present optical, ultraviolet, and infrared data of the type II supernova (SN II) 2020jfo at 14.5 Mpc. This wealth of multiwavelength data allows us to compare different metrics commonly used to estimate progenitor masses of SN II for the same object. Using its early light curve, we infer SN 2020jfo had a progenitor radius of ≈700 R⊙, consistent with red supergiants of initial mass MZAMS =11–13 M⊙. The decline in its late-time light curve is best fit by a 56Ni mass of 0.018 ± 0.007 M⊙ consistent with that ejected from SN II-P with ≈13 M⊙ initial mass stars. Early spectra and photometry do not exhibit signs of interaction with circumstellar matter, implying that SN 2020jfo experienced weak mass-loss within the final years prior to explosion. Our spectra at >250 d are best fit by models from 12 M⊙ initial mass stars. We analysed integral field unit spectroscopy of the stellar population near SN 2020jfo, finding its massive star population had a zero age main sequence mass of 9.7$\substack{+2.5\\ -1.3}~{\rm M}_{\odot }$. We identify a single counterpart in pre-explosion imaging and find it has an initial mass of at most $7.2\substack{+1.2\\ -0.6}~{\rm M}_{\odot }$. We conclude that the inconsistency between this mass and indirect mass indicators from SN 2020jfo itself is most likely caused by extinction with AV = 2–3 mag due to matter around the progenitor star, which lowered its observed optical luminosity. As SN 2020jfo did not exhibit extinction at this level or evidence for interaction with circumstellar matter between 1.6 and 450 d from explosion, we conclude that this material was likely confined within ≈3000 R⊙ from the progenitor star.

Subhalo abundance matching using progenitor mass at varying redshift: two modes of stellar mass growth imprinted into the Subaru HSC galaxy clustering

ABSTRACT We propose a novel subhalo abundance matching (SHAM) model that uses the virial mass of the main progenitor of each (sub)halo Mprog as a proxy of the galaxy stellar mass M* at the time of observation. This Mprog model predicts the two-point correlation functions depending on the choice of the epoch zprog at which Mprog is quoted. With zprog as a fitting parameter, we apply the Mprog model to the angular correlation functions measured with varying stellar mass thresholds from M*, lim/(h−2 M⊙) = 1011–108.6 using a sample of galaxies at z ≃ 0.4 from the Subaru Hyper Suprime-Cam survey. The Mprog model can reproduce the observations very well over 10 h−1kpc–10 h−1Mpc. We find that, for the samples of 109.2 ≤ M*, lim/(h−2 M⊙) ≤ 1010.2, the correlation functions predicted by the widely used Vpeak model lack amplitudes at ≲1 h−1 Mpc, suggesting that Mprog is a better proxy of the galaxy stellar mass than conventional Vpeak. The zprog parameter is highest (zprog ≃ 3) for intermediate mass galaxies at M* ≃ 109.9 h−2 M⊙, and becomes smaller down to zprog ≃ 1 for both lower and higher mass galaxies. We interpret these trends as reflecting the downsizing in the in situ star formation in lower mass galaxies and the larger contribution of the ex situ stellar mass growth in higher mass galaxies.

Inferring the Progenitor Mass–Kinetic Energy Relation of Stripped-envelope Core-collapse Supernovae from Nebular Spectroscopy

The relation between the progenitor mass and the kinetic energy of the explosion is a key toward revealing the explosion mechanism of stripped-envelope core-collapse supernovae (SESNe). Here, we present a method to derive this relation using the nebular spectra of SESNe, based on the correlation between [O i]/[Ca ii], which is an indicator of progenitor mass, and the width of [O i], which measures the expansion velocity of the oxygen-rich material. To explain the correlation, the kinetic energy (E K) is required to be positively correlated with the progenitor mass as represented by the CO core mass (M CO). We demonstrate that SNe IIb/Ib and SNe Ic/Ic-BL follow the same M CO–E K scaling relation, which suggests that helium-rich and helium-deficient SNe share the same explosion mechanism. The M CO–E K relation derived in this work is compared with the ones derived from early phase observations. The results are largely in good agreement. Combined with early phase observations, the method presented in this work provides a chance to scan through the ejecta from the outermost region to the dense inner core, which is important to reveal the global properties of the ejecta and constrain the explosion mechanism of core-collapse SNe.

Optical Color of Type Ib and Ic Supernovae and Implications for Their Progenitors

Type Ib and Ic supernovae (SNe Ib/Ic) originate from hydrogen-deficient massive star progenitors, of which the exact properties are still much debated. Using SN data in the literature, we investigate the optical B − V color of SNe Ib/Ic at the V-band peak and show that SNe Ib are systematically bluer than SNe Ic. We construct SN models from helium-rich and helium-poor progenitors of various masses using the radiation hydrodynamics code STELLA and discuss how the B − V color at the V-band peak is affected by the 56Ni to ejecta mass ratio, 56Ni mixing, and the presence/absence of a helium envelope. We argue that the dichotomy in the amount of helium in the progenitors plays the primary role in making the observed systematic color difference at the optical peak, in favor of the most commonly invoked SN scenario that SNe Ib and SNe Ic progenitors are helium rich and helium poor, respectively.

Infrared Ejecta and Cold Dust in the Young Supernova Remnant N132D

We present Spitzer, Wide-field Infrared Survey Explorer (WISE), and Herschel observations of the young supernova remnant (SNR) N132D in the Large Magellanic Cloud, including 3–40 μm Spitzer Infrared Spectrograph (IRS) mapping, 12 μm WISE and 70, 100, 160, 250, 350, and 500 μm Herschel images. The high-velocity lines of [Ne ii] at 12.8 μm, [Ne iii] at 15.5 μm, and [O iv] 26 μm reveal infrared ejecta concentrated in a central ring and coincide with the optical and X-ray ejecta. Herschel images reveal far-IR emission coinciding with the central ejecta, which suggests that the IR emission is freshly formed, cold dust in the SN ejecta. The infrared spectra are remarkably similar to those of another young SNR of 1E0102 with Ne and O lines. Shock modeling of the Ne ejecta emission suggests a gas temperature of 300–600 K and densities in the range 1000–2 × 104 cm−3 in the postshock photoionized region. The IR continuum from the ejecta shows an 18 μm peak dust feature. We performed spectral fitting to the IRS dust continuum and Herschel photometry. The dust mass associated with the central ejecta is 1.25 ± 0.65 M ⊙, while the 18 μm dust feature requires forsterite grains. The dust mass of the central ejecta region in N132D is higher than those of other young SNRs, which is likely associated with its higher progenitor mass. We discuss the dust productivity in the ejecta of N132D and infer its plausible implications for dust in the early universe.

The Pristine Inner Galaxy Survey (PIGS) VII: a discovery of the first inner Galaxy CEMP-r/s star

ABSTRACT Well-studied very metal-poor (VMP, [Fe/H] <−2) stars in the inner Galaxy are few in number, and they are of special interest because they are expected to be among the oldest stars in the Milky Way. We present high-resolution spectroscopic follow-up of the carbon-enhanced metal-poor (CEMP) star Pristine_184237.56-260624.5 (hereafter Pr184237) identified in the Pristine Inner Galaxy Survey. This star has an apocentre of ∼2.6 kpc. Its atmospheric parameters (Teff = 5100 K, log g = 2.0, and [Fe/H] = −2.60) were derived based on the non-local thermodynamic equilibrium (NLTE) line formation. We determined abundances for 32 elements, including 15 heavy elements beyond the iron group. The NLTE abundances were calculated for 13 elements from Na to Pb. Pr184237 is strongly enhanced in C, N, and O, and both s- and r-process elements from Ba to Pb; it reveals a low carbon isotope ratio of 12C/13C = 7. The element abundance pattern in the Na–Zn range is typical of halo stars. With [Ba/Eu] = 0.32, Pr184237 is the first star of the CEMP-r/s subclass identified in the inner Galaxy. Variations in radial velocity suggest binarity. We tested whether a pollution by the s- or i-process material produced in the more massive and evolved companion can form the observed abundance pattern and find that an i-process in the asymptotic giant branch star with a progenitor mass of 1.0–2.0 $\, {\rm M}_{\odot }$ can be the solution.

The Masses of Supernova Remnant Progenitors in M33

Using resolved optical stellar photometry from the Panchromatic Hubble Andromeda Treasury Triangulum Extended Region survey, we measured the star formation history near the position of 85 supernova remnants (SNRs) in M33. We constrained the progenitor masses for 60 of these SNRs, finding that the remaining 25 remnants had no local star formation in the last 56 Myr, consistent with core-collapse supernovae, making them potential Type Ia candidates. We then infer a progenitor mass distribution from the age distribution, assuming single star evolution. We find that the progenitor mass distribution is consistent with being drawn from a power law with an index of . Additionally, we infer a minimum progenitor mass of M ⊙ from this sample, consistent with several previous studies, providing further evidence that stars with ages older than the lifetimes of single 8 M ⊙ stars are producing supernovae.

Hidden shock powering the peak of SN 2020faa

The link between the fate of the most massive stars and the resulting supernova (SN) explosion is still a matter of debate, in major part because of the ambiguity among light-curve powering mechanisms. When stars explode as SNe, the light-curve luminosity is typically sustained by a central engine (radioactive decay, magnetar spin-down, or fallback accretion). However, since massive stars eject considerable amounts of material during their evolution, there may be a significant contribution coming from interactions with the previously ejected circumstellar medium (CSM). Reconstructing the progenitor configuration at the time of explosion requires a detailed analysis of the long-term photometric and spectroscopic evolution of the related transient. In this paper, we present the results of our follow-up campaign of SN 2020faa. Given the high luminosity and peculiar slow light curve, it is purported to have a massive progenitor. We present the spectro-photometric dataset and investigate different options to explain the unusual observed properties that support this assumption. We computed the bolometric luminosity of the supernova and the evolution of its temperature, radius, and expansion velocity. We also fit the observed light curve with a multi-component model to infer information on the progenitor and the explosion mechanism. Reasonable parameters are inferred for SN 2020faa with a magnetar of energy Ep=1.5(+0.5,-0.2)x10^50 erg and spin-down time t(spin)=15+/-1 d, a shell mass M(shell)=2.4(+0.5,-0.4) Msun and kinetic energy Ekin(shell)=0.9(+0.5,-0.3)x 10^51 erg, and a core with M(core)=21.5(+1.4,-0.7) Msun and Ekin(core)=3.9(+0.1,-0.4)x10^51 erg. In addition, we need an extra source to power the luminosity of the second peak. We find that hidden interaction with either a CSM disc or delayed, choked jets is a viable mechanism for supplying the required energy to achieve this effect.

Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis

We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; [Fe/H] < –2.0) stars, selected as extremely metal-poor (EMP; [Fe/H] < –3.0) candidates from the Sloan Digital Sky Survey and Large sky Area Multi-Object Fiber Spectroscopic Telescope survey. High-resolution spectroscopic observations were performed using GEMINI-N/GRACES. We find 10 EMP stars among our candidates, and we newly identify three carbon-enhanced metal-poor stars with [Ba/Fe] < 0. Although chemical abundances of our VMP/EMP stars generally follow the overall trend of other Galactic halo stars, there are a few exceptions. One Na-rich star ([Na/Fe] = +1.14) with low [Mg/Fe] suggests a possible chemical connection with second-generation stars in a globular cluster. The progenitor of an extremely Na-poor star ([Na/Fe] = –1.02) with high K- and Ni-abundance ratios may have undergone a distinct nucleosynthesis episode, associated with core-collapse supernovae (SNe) having a high explosion energy. We have also found a Mg-rich star ([Mg/Fe] = +0.73) with slightly enhanced Na and extremely low [Ba/Fe], indicating that its origin is not associated with neutron-capture events. On the other hand, the origin of the lowest Mg abundance ([Mg/Fe] = –0.61) star could be explained by accretion from a dwarf galaxy, or formation in a gas cloud largely polluted by SNe Ia. We have also explored the progenitor masses of our EMP stars by comparing their chemical-abundance patterns with those predicted by Population III SNe models, and find a mass range of 10–26 M ⊙, suggesting that such stars were primarily responsible for the chemical enrichment of the early Milky Way.

Hydrodynamics and Nucleosynthesis of Jet-driven Supernovae. I. Parameter Study of the Dependence on Jet Energetics

Rotating massive stars with initial progenitor masses M prog ∼ 25–140 M ⊙ can leave rapidly rotating black holes to become collapsars. The black holes and the surrounding accretion disks may develop powerful jets by magnetohydrodynamics instabilities. The propagation of the jet in the stellar envelope provides the necessary shock heating for triggering nucleosynthesis unseen in canonical core-collapse supernovae. However, the energy budget of the jet and its effects on the final chemical abundance pattern are unclear. In this exploratory work, we present a survey on the parameter dependence of collapsar nucleosynthesis on jet energetics. We use the zero-metallicity star with M prog ∼ 40 M ⊙ as the progenitor. The parameters include the jet duration, its energy deposition rate, deposited energy, and the opening angle. We examine the correlations of the following observables: (1) the ejecta and remnant masses; (2) the energy deposition efficiency; (3) the 56Ni production and its correlation with the ejecta velocity, deposited energy, and the ejected mass; (4) the Sc–Ti–V correlation as observed in metal-poor stars; and (5) the [Zn/Fe] ratio as observed in some metal-poor stars. We also provide the chemical abundance table of these explosion models for the use of the galactic chemical evolution and stellar archeology.

Spectroscopic and evolutionary analyses of the binary system AzV 14 outline paths toward the WR stage at low metallicity

Context. The origin of the observed population of Wolf-Rayet (WR) stars in low-metallicity galaxies, such as the Small Magellanic Cloud (SMC), is not yet understood. Standard, single-star evolutionary models predict that WR stars should stem from very massive O-type star progenitors, but these are very rare. On the other hand, binary evolutionary models predict that WR stars could originate from primary stars in close binaries. Aims. We conduct an analysis of the massive O star, AzV 14, to spectroscopically determine its fundamental and stellar wind parameters, which are then used to investigate evolutionary paths from the O-type to the WR stage with stellar evolutionary models. Methods. Multi-epoch UV and optical spectra of AzV 14 are analyzed using the non-local thermodynamic equilibrium (LTE) stellar atmosphere code PoWR. An optical TESS light curve was extracted and analyzed using the PHOEBE code. The obtained parameters are put into an evolutionary context, using the MESA code. Results. AzV 14 is a close binary system with a period of P = 3.7058 ± 0.0013 d. The binary consists of two similar main sequence stars with masses of M1, 2 ≈ 32 M⊙. Both stars have weak stellar winds with mass-loss rates of log Ṁ/(M⊙ yr−1) = −7.7 ± 0.2. Binary evolutionary models can explain the empirically derived stellar and orbital parameters, including the position of the AzV 14 components on the Hertzsprung-Russell diagram, revealing its current age of 3.3 Myr. The model predicts that the primary will evolve into a WR star with Teff ≈ 100 kK, while the secondary, which will accrete significant amounts of mass during the first mass transfer phase, will become a cooler WR star with Teff ≈ 50 kK. Furthermore, WR stars that descend from binary components that have accreted significant amount of mass are predicted to have increased oxygen abundances compared to other WR stars. This model prediction is supported by a spectroscopic analysis of a WR star in the SMC. Conclusions. Inspired by the binary evolutionary models, we hypothesize that the populations of WR stars in low-metallicity galaxies may have bimodal temperature distributions. Hotter WR stars might originate from primary stars, while cooler WR stars are the evolutionary descendants of the secondary stars if they accreted a significant amount of mass. These results may have wide-ranging implications for our understanding of massive star feedback and binary evolution channels at low metallicity.

Inference of protoneutron star properties in core-collapse supernovae from a gravitational-wave detector network

The next Galactic core-collapse supernova (CCSN) will be a unique opportunity to study within a fully multimessenger approach the explosion mechanism responsible for the formation of neutron stars and stellar-mass black holes. State-of-the-art numerical simulations of those events reveal the complexity of the gravitational-wave emission which is highly stochastic. This challenges the possibility to infer the properties of the compact remnant and of its progenitor using the information encoded in the waveforms. In this paper we take further steps in a program we recently initiated to overcome those difficulties. In particular we show how oscillation modes of the protoneutron star (PNS), highly visible in the gravitational-wave signal, can be used to reconstruct the time evolution of their physical properties. Extending our previous work where only the information from a single detector was used, we here describe a new data-analysis pipeline that coherently combines gravitational-wave detectors' data and infers the time evolution of a combination of the mass and radius of the compact remnant. The performance of the method is estimated employing waveforms from 2D and 3D CCSN simulations covering a progenitor mass range between $11{M}_{\ensuremath{\bigodot}}$ and $40{M}_{\ensuremath{\bigodot}}$ and different equations of state for both a network of up to five second-generation detectors and the proposed third-generation detectors Einstein Telescope and Cosmic Explorer. Our study shows that it will be possible to infer PNS properties for CCSN events occurring in the vicinity of the Milky Way, up to the Large Magellanic Cloud, with the current generation of gravitational-wave detectors.

Abstract NG07: Targeting polyamines metabolism in acute myeloid leukemia stem cells

Abstract NG07: Targeting polyamines metabolism in acute myeloid leukemia stem cells

On the Anticorrelation between Duration and Redshift in Gamma-Ray Bursts

For gamma-ray bursts (GRBs) with durations greater than two seconds (so-called long GRBs), the intrinsic prompt gamma-ray emission appears, on average, to last longer for bursts at lower redshifts. We explore the nature of this duration–redshift anticorrelation, describing systems and conditions in which this cosmological evolution could arise. In particular, we explore its dependence on the metallicity of a massive star progenitor, because we can securely count on the average stellar metallicity to increase with decreasing redshift. Although stars with higher metallicity/lower redshift lose mass and angular momentum through line-driven winds, in some cases these stars are able to form more extended accretion disks when they collapse, potentially leading to longer-duration GRBs. We also examine how this duration–redshift trend may show up in interacting binary models composed of a massive star and compact object companion, recently suggested to be the progenitors of radio-bright GRBs. Under certain conditions, mass loss and equation-of-state effects from massive stars with higher metallicity and lower redshift can decrease the binary separation. This can then lead to spin-up of the massive star and allow for a longer-duration GRB upon the massive star’s collapse. Finally, the duration–redshift trend may also be supported by a relatively larger population of small-separation binaries born in situ at low redshift.

Raising the observed metallicity floor with a 3D non-LTE analysis of SDSS J102915.14+172927.9

Context. The first stars marked the end of the cosmic dark ages, produced the first heavy elements, and set the stage for the formation of the first galaxies. Accurate chemical abundances of ultra metal-poor stars ([Fe/H] &lt; −4) can be used to infer the properties of the first stars and thus the formation mechanism for low-mass second-generation stars in the early Universe. Spectroscopic studies have shown that most second-generation stars are carbon enhanced. A notable exception is SDSS J102915.14+172927.9, which is the most metal-poor star known to date, largely by virtue of the low upper limits of the carbon abundance reported in earlier studies. Aims. We re-analysed the composition of SDSS J102915.14+172927.9 with the aim of providing improved observational constraints on the lowest metallicity possible for low-mass star formation and constraining the properties of its Population III progenitor star. Methods. We developed a tailored three-dimensional model atmosphere for SDSS J102915.14+172927.9 with the Stagger code, making use of an improved surface gravity estimate based on the Gaia DR3 parallax. Snapshots from the model were used as input in the radiative transfer code Balder to compute 3D non-local thermodynamic equilibrium (non-LTE) synthetic spectra. These spectra were then used to infer abundances for Mg, Si, Ca, Fe, and Ni as well as upper limits on Li, Na, and Al. Synthetic 3D LTE spectra were computed with Scate to infer the abundance of Ti and upper limits on C and N. Results. In contrast to earlier works based on 1D non-LTE corrections applied to 3D LTE results, we are able to achieve ionisation balance for Ca I and Ca II when employing our consistent 3D non-LTE treatment. The elemental abundances are systematically higher than those found in earlier works. In particular, [Fe/H] is increased by 0.57 dex, and the upper limits of C and N are larger by 0.90 dex and 1.82 dex, respectively. Conclusions. We find that Population III progenitors with masses 10–20 M⊙ exploding with energy E ⪅ 3 × 1051 erg can reproduce our 3D non-LTE abundance pattern. Our 3D non-LTE abundances are able to better constrain the progenitor mass and explosion energy as compared to our 1D LTE abundances. Contrary to previous work, we obtain higher upper limits on the carbon abundance that are ‘marginally consistent’ with star formation through atomic line cooling, and consequently, these results prevent us from drawing strong conclusions about the formation mechanism of this low-mass star.

Spectroscopic Study of Ba and CEMP-s Stars: Mass Distribution of AGB Progenitors* * Based [in part] on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. † †[Part of] the data are retrieved from the JVO portal (http://jvo.nao.ac.jp/portal) operated by the NAOJ.

We have performed detailed high-resolution spectroscopic analysis on seven metal-poor stars (BD+75 348, BD+09 3019, HD238020, HE0319–0215, HE0507–1653, HE0930–0018, HE1023–1504) and derived their atmospheric parameters T eff, log g, [Fe/H], and microturbulent velocity (ξ). The metallicity range is found to be –2.57 < [Fe/H] < –0.42. The elemental abundances of 17 light elements and 12 heavy elements are estimated. We have classified BD+75 348 and BD+09 3019 as strong Ba stars, HD238020 as a mild Ba star, and the remaining four objects as CEMP-s stars. We have estimated the masses of the stars from Hertzsprung–Russel (HR) diagram, and, compiling the data of 205 Ba stars from literature, estimated the mass distribution of Ba stars. We have also estimated the initial masses of the companion AGBs of the program stars as well as the masses of the companion AGBs of 159 Ba and 36 CEMP-s stars from literature, with the help of a parametric-model-based analysis using FRUITY models. While the primary mass distribution of mild Ba stars peaks at 3.7 M ⊙, for the strong Ba stars the peak appears at 2.5 M ⊙. We, therefore, propose that the initial masses of the progenitor AGBs dominantly control the formation of mild and strong Ba stars. However, a clear overlap, in the range 1.3–4.0 M ⊙, noticed between the progenitor masses of both the subclasses of Ba stars, may indicate that other factors, such as the metallicities and the orbital periods, may also have significant contributions. The progenitor AGBs’ mass distribution of CEMP-s stars is found to peak at 2.03 M ⊙.

A UV census of the environments of stripped-envelope supernovae

ABSTRACTThis paper reports an environmental analysis of 41 uniformly selected stripped-envelope supernovae (SESNe) based on deep ultraviolet–optical images acquired by the Hubble Space Telescope. Young stellar populations are detected in most SN environments and their ages are derived with a hierarchical Bayesian approach. The age distributions are indistinguishable between Type IIb and Type Ib, while that for Type Ic is systematically younger. This suggests that the Type Ic SN progenitors are more massive, while the Type IIb and Type Ib SNe have very similar progenitor masses. Our result supports a hybrid envelope-stripping mechanism, in which the hydrogen envelopes of the SESN progenitors are stripped via a mass-insensitive process (e.g. binary interaction), while the helium envelopes are stripped via a mass-sensitive process (e.g. stellar wind of the post-binary interaction progenitor). We also provide progenitor constraints for three Type Ibn SNe and two broad-lined Type Ic SNe. All these results demonstrate the importance of the very diverse mass-loss processes in the origins of SESNe.

On the gravitational lensing interpretation of three gravitational wave detections in the mass gap by LIGO and Virgo

ABSTRACT We search for gravitational wave (GW) events from LIGO-Virgo’s third run that may have been affected by gravitational lensing. Gravitational lensing delays the arrival of GWs, and alters their amplitude – thus biasing the inferred progenitor masses. This would provide a physically well-understood interpretation of GW detections in the ‘mass gap’ between neutron stars and black holes, as gravitationally lensed binary neutron star (BNS) mergers. We selected three GW detections in LIGO-Virgo’s third run for which the probability of at least one of the constituent compact objects being in the mass gap was reported as high with low latency – i.e. candidate lensed BNS mergers. Our observations of powerful strong lensing clusters located adjacent to the peak of their sky localization error maps reached a sensitivity $\rm AB\simeq 25.5$ in the z′ band with the GMOS instruments on the Gemini telescopes, and detected no candidate lensed optical counterparts. We combine recent kilonova light-curve models with recent predictions of the lensed BNS population and the properties of the objects that we followed up to show that realistic optical counterparts were detectable in our observations. Further detailed analysis of two of the candidates suggests that they are a plausible pair of images of the same low-mass binary black hole merger, lensed by a local galaxy or small group of galaxies. This further underlines that access to accurate mass information with low latency would improve the efficiency of candidate lensed BNS selection.

The Messy Nature of Fiber Spectra: Star–Quasar Pairs Masquerading as Dual Type 1 AGNs

Theoretical studies predict that the most significant growth of supermassive black holes (SMBHs) occurs in late-stage mergers, coinciding with the manifestation of dual active galactic nuclei (AGNs), and both major and minor mergers are expected to be important for dual AGN growth. In fact, dual AGNs in minor mergers should be signposts for efficient minor-merger-induced SMBH growth for both the more and less massive progenitor. We identified two candidate dual AGNs residing in apparent minor mergers with mass ratios of ∼1:7 and ∼1:30. Sloan Digital Sky Survey (SDSS) fiber spectra show broad and narrow emission lines in the primary nuclei of each merger while only a narrow [O iii] emission line and a broad and prominent Hα/[N ii] complex is observed in the secondary nuclei. The FWHMs of the broad Hα lines in the primary and secondary nuclei are inconsistent in each merger, suggesting that each nucleus in each merger hosts a Type 1 AGN. However, spatially resolved Large Binocular Telescope optical spectroscopy reveals rest-frame stellar absorption features, indicating the secondary sources are foreground stars and that the previously detected broad lines are likely the result of fiber spillover effects induced by the atmospheric seeing at the time of the SDSS observations. This study demonstrates for the first time that optical spectroscopic searches for Type 1/Type 1 pairs similarly suffer from fiber spillover effects as has been observed previously for Seyfert 2 dual AGN candidates. The presence of foreground stars may not have been clear if an instrument with more limited wavelength range or limited sensitivity had been used.

MUSE crowded field 3D spectroscopy in NGC 300

Aims. We perform a deep survey of planetary nebulae (PNe) in the spiral galaxy NGC 300 to construct its planetary nebula luminosity function (PNLF). We aim to derive the distance using the PNLF and to probe the characteristics of the most luminous PNe. Methods. We analysed 44 fields observed with MUSE at the VLT, covering a total area of ∼11 kpc2. We find [O III]λ5007 sources using the differential emission line filter (DELF) technique. We identified PNe through spectral classification with the aid of the BPT diagram. The PNLF distance was derived using the maximum likelihood estimation technique. For the more luminous PNe, we also measured their extinction using the Balmer decrement. We estimated the luminosity and effective temperature of the central stars of the luminous PNe based on estimates of the excitation class and the assumption of optically thick nebulae. Results. We identify 107 PNe and derive a most-likely distance modulus $ (m-M)_0 = 26.48^{+0.11}_{-0.26} $ ($ d = 1.98^{+0.10}_{-0.23} $ Mpc). We find that the PNe at the PNLF cutoff exhibit relatively low extinction, with some high-extinction cases caused by local dust lanes. We present the lower limit luminosities and effective temperatures of the central stars for some of the brighter PNe. We also identify a few Type I PNe that come from a young population with progenitor masses &gt; 2.5 M⊙ but do not populate the PNLF cutoff. Conclusions. The spatial resolution and spectral information of MUSE allow precise PN classification and photometry. These capabilities also enable us to resolve possible contamination by diffuse gas and dust, improving the accuracy of the PNLF distance to NGC 300.