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ABSTRACT We present a model to estimate the average primary masses, companion mass ranges, the inclination limit for recognizing a rotational variable, and the primary mass spreads for populations of binary stars. The model fits a population’s binary mass function distribution and allows for a probability that some mass functions are incorrectly estimated. Using tests with synthetic data, we assess the model’s sensitivity to each parameter, finding that we are most sensitive to the average primary mass and the minimum companion mass, with less sensitivity to the inclination limit and little to no sensitivity to the primary mass spread. We apply the model to five populations of binary spotted rotational variables identified in ASAS-SN, computing their binary mass functions using RV data from APOGEE. Their average primary mass estimates are consistent with our expectations based on their CMD locations ($$\sim 0.75 \, {\rm M}_{\odot }$$ for lower main sequence primaries and $$\sim 0.9$$–$$1.2 \, {\rm M}_{\odot }$$ for RS CVn and sub-subgiants). Their companion mass range estimates allow companion masses down to $$M_2/M_1\simeq 0.1$$, although the main sequence population may have a higher minimum mass fraction ($$\sim 0.4$$). We see weak evidence of an inclination limit $$\gtrsim 50^{\circ }$$ for the main sequence and sub-subgiant groups and no evidence of an inclination limit in the other groups. No groups show strong evidence for a preferred primary mass spread. We conclude by demonstrating that the approach will provide significantly better estimates of the primary mass and the minimum mass ratio and reasonable sensitivity to the inclination limit with 10 times as many systems. 

ABSTRACT We search a sample of 9361 613 isolated sources with 13<g<14.5 mag for slowly varying sources. We select sources with brightness changes larger than $$\sim 0.03$$ mag yr−1 over 10 yr, removing false positives due to, for example, nearby bright stars or high proper motions. After a thorough visual inspection, we find 782 slowly varying systems. Of these systems, 433 are identified as variables for the first time, 349 are previously classified as variables, and there are roughly equal numbers of sources becoming brighter and fainter. Previously classified systems were mostly identified as semiregular variables (SR), slow irregular variables (L), spotted stars (ROT), or unknown (MISC or VAR), as long time-scale variability does not fit into a standard class. The sources are scattered across the CMD and can be placed into five groups that exhibit distinct behaviours. The largest groups are very red subgiants and lower main sequence stars. There are also eight AGNs. There are 551 candidates ($$\sim$$ 70 per cent) that also show shorter time-scale periodic variability, mostly with periods longer than 10 d. The variability of 191 of these candidates may be related to dust. 

ABSTRACT We investigate the progenitor of the Crab supernova by examining the remnant’s surrounding stellar population. The Crab is interesting because of the apparently low energy and mass of the supernova remnant. We also know it was not a binary at death and that the explosion formed a neutron star. Using Gaia EDR3 parallaxes and photometry, we analyse stars inside a cylinder with a projected radius of 100 pc and spanning distances from $$\sim 1600$$ to 2300 pc set by the $$2\sigma$$ uncertainties in the Crab’s parallax. We also individually model the most luminous stars local to the Crab. The two most luminous stars are blue, roughly main sequence stars with masses of $$\sim 11\, {\rm M}_{\odot }$$. We estimate the stellar population’s age distribution using solar metallicity PARSEC isochrones. The estimated age distribution of the 205 $$M_{\mathrm{ G}} < 0$$ stars modestly favour lower mass stars, consistent with an AGB star or a lower mass binary merger as the progenitor, but statistically we cannot rule out higher masses. This may be driven by contamination due to the $$\sim 700$$ pc span of the cylinder in distance. 

Heartbeat stars are a subclass of binary stars with short periods, high eccentricities, and phase-folded light curves that resemble an electrocardiogram. We start from the $\text{𝐺𝑎𝑖𝑎}$catalogs of spectroscopic binaries and use $\text{𝑇𝐸𝑆𝑆}$photometry to identify 112 new heartbeat star systems. We fit their phase-folded light curves with an analytic model to measure their orbital periods, eccentricities, inclinations, and arguments of periastron. We then compare these orbital parameters to the $\text{𝐺𝑎𝑖𝑎}$spectroscopic orbital solution. Our periods and eccentricities are consistent with the $\text{𝐺𝑎𝑖𝑎}$solutions for 85 $\%$of the single-line spectroscopic binaries but only 20 $\%$of the double-line spectroscopic binaries. For the two double-line spectroscopic binary heartbeat stars with consistent orbits, we combine the $\text{𝑇𝐸𝑆𝑆}$phase-folded light curve and the $\text{𝐺𝑎𝑖𝑎}$velocity semi-amplitudes to measure the stellar masses and radii with $\text{𝙿𝙷𝙾𝙴𝙱𝙴}$. In a statistical analysis of the HB population, we find that non-giant heartbeat stars have evolved off the main sequence and that their fractional abundance rises rapidly with effective temperature. 

Aims.The volumetric rates and luminosity functions (LFs) of core-collapse supernovae (ccSN) and their subtypes are important for understanding the cosmic history of star formation and the buildup of ccSNe products. To estimate these rates, we used data of nearby ccSNe discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) from 2014 to 2017, when all observations were made in theVband. Methods.The sample is composed of 174 discovered or recovered events, with high spectroscopic completeness from follow-up observations. This allowed us to obtain a statistically precise and systematically robust estimate of nearby rates for ccSNe and their subtypes. The volumetric rates were estimated by correcting the observed number of events for survey completeness, which was estimated through injection recovery simulations using ccSN light curves. Results.We find a total volumetric rate for ccSNe of 7.0^+1.0_−0.9× 10⁻⁵yr⁻¹Mpc⁻³h³₇₀, at a median redshift of 0.0149, for absolute magnitudes at peakM_V, peak ≤ −14 mag. This result is in agreement with previous local volumetric rates. We obtain volumetric rates for the different ccSN subtypes (II, IIn, IIb, Ib, Ic, Ibn, and Ic-BL), and find that the relative fractions of Type II, stripped-envelope, and interacting ccSNe are 63.2%, 32.3%, and 4.4%, respectively. We also estimate a volumetric rate for superluminous SNe of 1.5^+4.4_−1.1yr⁻¹Gpc⁻³h³₇₀, corresponding to a fraction of 0.002% of the total ccSN rate. We produced intrinsicV-band LFs of ccSNe and their subtypes, and show that ccSN rates steadily decline for increasing luminosities. We further investigated the specific ccSN rate as a function of their host galaxy stellar mass and find that the rate decreases with increasing stellar mass, with significantly higher rates at lower mass galaxies (logM_* < 9.0 M_⊙). 

ABSTRACT Dust absorption is invoked in a number of contexts for hiding a star that has survived some sort of transient event from view. Dust formed in a transient is expanding away from the star and, in spherical models, the mass and energy budgets implied by a high optical depth at late times make such models untenable. Concentrating the dust in a disc or torus can in principle hide a source from an equatorial observer using less mass and so delay this problem. However, using axisymmetric dust radiation transfer models with a range of equatorial dust concentrations, we find that this is quite difficult to achieve in practice. The polar optical depth must be either low or high to avoid scattering optical photons to equatorial observers. Most of the emission remains at wavelengths easily observed by JWST. The equatorial brightness can be significantly suppressed for very discy configurations with little polar optical depth – but only by a factor of ∼2 for polar optical depths of τp = 1 and ∼5 for τp = 0.1 even for a very high optical depth disc (τe = 1000) viewed edge-on. It is particularly difficult to hide a source with silicate dusts because the absorption feature near 10 µm frequently leads to the emission being concentrated just bluewards of the feature, near 8 µm. 

Abstract In the absence of a parallax distance to a pulsar or a surviving binary in a supernova remnant (SNR), distances to Galactic SNRs are generally very uncertain. However, by combining Gaia data with wide-field, multifiber echelle spectroscopy, it is now possible to obtain accurate distances to many SNRs with limited extinction by searching for the appearance of high-velocity Caiior Naiabsorption lines in hot stars as a function of distance. We demonstrate this for the SNR S147 using the spectra of 259 luminous blue stars. We obtain a median distance of 1.37 kpc (1.30–1.47 kpc at 90% confidence), which is consistent with the median parallax distance to the pulsar of 1.46 kpc (1.12–2.10 kpc at 90% confidence) but with significantly smaller uncertainties. Our distance is also consistent with the distance to the candidate unbound binary companion in this SNR, HD 37424 at a photogeometric distance of 1.45 kpc (1.40–1.50 kpc at 1σ). The presence of high-velocity absorption lines is correlated with the Hα/O [iii] emission-line flux of the SNR but not with the radio flux. 

Abstract We report the results from a pilot study to search for black holes and other dark companions in binary systems using direct imaging with SHARK-VIS and the iLocater pathfinder “Lili” on the Large Binocular Telescope. Starting from known single-lined spectroscopic binaries, we select systems with high mass functions that could host dark companions and whose spectroscopic orbits indicate a projected orbital separation ≥30 mas. For this first exploration, we selected four systems (HD 137909, HD 104438, HD 117044, and HD 176695). In each case, we identify a luminous companion and measure the flux ratio and angular separation. However, two of the systems (HD 104438 and HD 176695) are not consistent with simple binary systems and are most likely hierarchical triples. The observed companions rule out a massive compact object for HD 137909, HD 117044, and HD 176695. HD 104438 requires further study because the identified star cannot be responsible for the RV orbit and is likely a dwarf tertiary companion. The SHARK-VIS observation was taken near pericenter, and a second image near apocenter is needed to discriminate between a closely separated luminous secondary and a compact object. When a luminous companion is found, the combination of the RVs and the single SHARK-VIS observation strongly constrains the orbital inclination and the companion mass. Since a single SHARK-VIS observation has a typical on-source observing time of only ∼10 minutes, this a promising method to efficiently identify non-interacting compact object candidates. 

ABSTRACT The progenitor of SN 2023ixf was an ∼104.8 to $$10^{5.0}\, \text{L}_\odot$$ star (∼9 to $$14\, \text{M}_\odot$$ at birth) obscured by a dusty $$\dot{M} \simeq 10^{-5}\, \text{M}_\odot \rm \, yr^{-1}$$ wind with a visual optical depth of τV ≃ 13. This is required by the progenitor spectral energy distribution, the post-SN X-ray and H α luminosities, and the X-ray column density estimates. In Large Binocular Telescope (LBT) data spanning 5600 to 400 d before the supernova (SN), there is no evidence for optical variability at the level of $$\sim 10^3\, \text{L}_\odot$$ in R band, roughly three times the predicted luminosity of the obscured progenitor. This constrains direct observation of any pre-SN optical outbursts where there are LBT observations. However, models of the effects of any pre-SN outburst on the dusty wind show that an outburst of essentially any duration exceeding ∼5 times the luminosity of the progenitor would have detectable effects on the dust optical depth for decades. While the dust obscuration here is high, all red supergiants have dusty winds, and the destruction (or formation) of dust by even short-lived transients will always have long-term effects on the observed brightness of the star because changes in the dust optical depths after a luminous transient occur very slowly. 

We present optical photometric and spectroscopic observations of the peculiar Type Ia supernovae (SNe Ia) ASASSN-20jq/SN 2020qxp. It is a low-luminosity object, with a peak absolute magnitude ofM_B = −17.1 ± 0.5 mag, while its post-peak light-curve decline rate of Δm₁₅(B) = 1.35 ± 0.09 mag and color-stretch parameter ofs_BV ⪆ 0.82 is similar to that of normal luminosity SNe Ia. That makes it a prevalent outlier in both the SN Ia luminosity-width and the luminosity-color-stretch relations. The analysis of the early light curves indicates a possible “bump” during the first ≈1.4 days of explosion. ASASSN-20jq synthesized a low radioactive⁵⁶Ni mass of 0.09 ± 0.01 M_⊙. The near-maximum light spectra of the supernova show strong Si IIabsorption lines, indicating a cooler photosphere than normal SNe Ia; however, it lacks Ti IIabsorption lines. Additionally, it shows unusually strong absorption features of O Iλ7773 and the Ca IInear-infrared triplet. The nebular spectra of ASASSN-20jq show a remarkably strong but narrow forbidden [Ca II]λλ7291, 7324 doublet emission that has not been seen in SNe Ia except for a handful of Type Iax events. There is also a marginal detection of the [O I]λλ6300, 6364 doublet emission in nebular spectra, which is extremely rare. Both the [Ca II] and [O I] lines are redshifted by roughly 2000 km s⁻¹. ASASSN-20jq also exhibits a strong [Fe II]λ7155 emission line with a tilted-top line profile, which is identical to the [Fe II]λ16433 line profile. The asymmetric [Fe II] line profiles, along with the redshifted [Ca II] and emission lines, suggest a high central density white dwarf progenitor that underwent an off-center delayed-detonation explosion mechanism, synthesizing roughly equal amounts of⁵⁶Ni during the deflagration and detonation burning phases. The equal production of⁵⁶Ni in both burning phases distinguishes ASASSN-20jq from normal bright and subluminous SNe Ia. Assuming this scenario, we simultaneously modeled the optical and near-infrared nebular spectra, achieving a good agreement with the observations. The light curve and spectroscopic features of ASASSN-20jq do not align with any single sub-class of SNe Ia. However, the significant deviation from the luminosity versus light-curve shape relations (along with several light-curve and spectroscopic features) exhibits similarities to some 2002es-like objects. Therefore, we have identified ASASSN-20jq as an extreme candidate within the broad and heterogeneous parameter space of 2002es-like SNe Ia.