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Light echoes occur when light from a luminous transient is scattered by dust back into our line of sight with a time delay due to the extra propagation distance. We introduce a novel approach to estimating the distance to a source by combining light echoes with recent three-dimensional dust maps. We identify light echoes from the historical supernovae Cassiopeia A and SN 1572 (Tycho) in nearly a decade of imaging from the All-Sky Automated Survey for Supernovae (ASAS-SN). Using these light echoes, we find distances of $3.6\pm 0.1$kpc and ${3.2}_{-0.2}^{+0.1}$kpc to Cas A and Tycho, respectively, which are generally consistent with previous estimates but are more precise. These distance uncertainties are primarily dominated by the low distance resolution of the 3D dust maps, which will likely improve in the future. The candidate single degenerate explosion donor stars B and G in Tycho are clearly foreground stars. Finally, the inferred reddening towards each SN agrees well with the intervening column density estimates from X-ray analyses of the remnants. 

ABSTRACT The scaling of the specific Type Ia supernova (SN Ia) rate with host galaxy stellar mass $$\dot{\text{N}}_\text{Ia} / \text{M}_\star \sim \text{M}_\star ^{-0.3}$$ as measured in ASAS-SN and DES strongly suggests that the number of SNe Ia produced by a stellar population depends inversely on its metallicity. We estimate the strength of the required metallicity dependence by combining the average star formation histories (SFHs) of galaxies as a function of their stellar mass with the mass–metallicity relation (MZR) for galaxies and common parametrizations for the SN Ia delay-time distribution. The differences in SFHs can account for only ∼30 per cent of the increase in the specific SN Ia rate between stellar masses of M⋆ = 1010 and 107.2 M⊙. We find that an additional metallicity dependence of approximately ∼Z−0.5 is required to explain the observed scaling. This scaling matches the metallicity dependence of the close binary fraction observed in APOGEE, suggesting that the enhanced SN Ia rate in low-mass galaxies can be explained by a combination of their more extended SFHs and a higher binary fraction due to their lower metallicities. Due to the shape of the MZR, only galaxies below M⋆ ≈ 3 × 109 M⊙ are significantly affected by the metallicity-dependent SN Ia rates. The $$\dot{\text{N}}_\text{Ia} / \text{M}_\star \sim \text{M}_\star ^{-0.3}$$ scaling becomes shallower with increasing redshift, dropping by factor of ∼2 at 107.2 M⊙ between z = 0 and 1 with our ∼Z−0.5 scaling. With metallicity-independent rates, this decrease is a factor of ∼3. We discuss the implications of metallicity-dependent SN Ia rates for one-zone models of galactic chemical evolution. 

ABSTRACT We present the volumetric rates and luminosity functions (LFs) of Type Ia supernovae (SNe Ia) from the V-band All-Sky Automated Survey for Supernovae (ASAS-SN) catalogues spanning discovery dates from UTC 2014 January 26 to UTC 2017 December 29. Our standard sample consists of 404 SNe Ia with $$m_{\mathrm{{\it V},peak}} \lt 17\, \mathrm{mag}$$ and Galactic latitude |b| > 15°. Our results are both statistically more precise and systematically more robust than previous studies due to the large sample size and high spectroscopic completeness. We make completeness corrections based on both the apparent and absolute magnitudes by simulating the detection of SNe Ia in ASAS-SN light curves. We find a total volumetric rate for all subtypes of $$R_{\mathrm{tot}} = 2.28^{+0.20}_{-0.20} \times 10^{4}\, \mathrm{yr}^{-1}\, \mathrm{Gpc}^{-3}\, h^{3}_{70}$$ for $$M_{\mathrm{{\it V},peak}} \lt -16.5\, \mathrm{mag}$$ ($$R_{\mathrm{tot}} = 1.91^{+0.12}_{-0.12} \times 10^{4}\, \mathrm{yr}^{-1}\, \mathrm{Gpc}^{-3}\, h^{3}_{70}$$ for $$M_{\mathrm{{\it V},peak}} \lt -17.5\, \mathrm{mag}$$) at the median redshift of our sample, zmed = 0.024. This is in agreement (1σ) with the local volumetric rates found by previous studies. We also compile LFs for the entire sample as well as for subtypes of SNe Ia for the first time. The major subtypes with more than one SN include Ia-91bg, Ia-91T, Ia-CSM, and Ia-03fg with total rates of $$R_{\mathrm{Ia-91bg}} = 1.4^{+0.5}_{-0.5} \times 10^{3}\, \mathrm{yr}^{-1}\, \mathrm{Gpc}^{-3}\, h^{3}_{70}$$, $$R_{\mathrm{Ia-91T}} = 8.5^{+1.6}_{-1.7} \times 10^{2}\, \mathrm{yr}^{-1}\, \mathrm{Gpc}^{-3}\, h^{3}_{70}$$, $$R_{\mathrm{Ia-CSM}} = 10^{+7}_{-7}\, \mathrm{yr}^{-1}\, \mathrm{Gpc}^{-3}\, h^{3}_{70}$$, and $$R_{\mathrm{Ia-03fg}} = 30^{+20}_{-20}\, \mathrm{yr}^{-1}\, \mathrm{Gpc}^{-3}\, h^{3}_{70}$$, respectively. We estimate a mean host extinction of $$E(V-r) \approx 0.2\, \mathrm{mag}$$ based on the shift between our V band and the Zwicky Transient Facility r-band LFs. 

Abstract We present 307 type Ia supernova (SN) light curves from the first 4 yr of the Transiting Exoplanet Survey Satellite mission. We use this sample to characterize the shapes of the early-time light curves, measure the rise times from first light to peak, and search for companion star interactions. Using simulations, we show that light curves must have noise <10% of the peak flux to avoid biases in the early-time light-curve shape, restricting our quantitative analysis to 74 light curves. We find that the mean power-law index $t^{{\beta }_1}$of the early-time light curves isβ₁= 1.93 ± 0.57, and the mean rise time to peak is 15.7 ± 3.5 days. The underlying population distribution forβ₁may instead consist of a Gaussian component with mean 2.29, width 0.34, and a long tail extending to values less than 1.0. We find that the data can rarely distinguish between models with and without companion interaction models. Nevertheless, we find three high-quality light curves that tentatively prefer the addition of a companion interaction model, but the statistical evidence for the companion interactions is not robust. We also find two SNe that disfavor the addition of a companion interaction model to a curved power-law model. Taking the 74 SNe together, we calculate 3σupper limits on the presence of companion signatures to control for orientation effects that can hide companions in individual light curves. Our results rule out common progenitor systems with companions having Roche lobe radii >31R_⊙(separations >5.7 × 10¹²cm, 99.9% confidence level) and disfavor companions having Roche lobe radii >10R_⊙(separations >1.9 × 10¹²cm, 95% confidence level). Lastly, we discuss the implications of our results for the intrinsic fraction of single degenerate progenitor systems. 

ABSTRACT Using blazar light curves from the optical All-Sky Automated Survey for Supernovae (ASAS-SN) and the γ-ray Fermi-LAT telescope, we performed the most extensive statistical correlation study between both bands, using a sample of 1180 blazars. This is almost an order of magnitude larger than other recent studies. Blazars represent more than 98 per cent of the AGNs detected by Fermi-LAT and are the brightest γ-ray sources in the extragalactic sky. They are essential for studying the physical properties of astrophysical jets from central black holes. However, their γ-ray flare mechanism is not fully understood. Multiwavelength correlations help constrain the dominant mechanisms of blazar variability. We search for temporal relationships between optical and γ-ray bands. Using a Bayesian Block Decomposition, we detect 1414 optical and 510 γ-ray flares, we find a strong correlation between both bands. Among all the flares, we find 321 correlated flares from 133 blazars, and derive an average rest-frame time delay of only 1.1$$_{-8.5}^{+7.1}$$ d, with no difference between the flat-spectrum radio quasars, BL Lacertae-like objects or low, intermediate, and high-synchrotron peaked blazar classes. Our time-delay limit rules out the hadronic proton-synchrotron model as the driver for non-orphan flares and suggests a leptonic single-zone model. Limiting our search to well-defined light curves and removing 976 potential but unclear ‘orphan’ flares, we find 191 (13 per cent) and 115 (22 per cent) clear ‘orphan’ optical and γ-ray flares. The presence of ‘orphan’ flares in both bands challenges the standard one-zone blazar flare leptonic model and suggests multizone synchrotron sites or a hadronic model for some blazars. 

ABSTRACT The All-Sky Automated Survey for Supernovae (ASAS-SN) is the first optical survey to monitor the entire sky, currently with a cadence of ≲ 24 h down to g ≲ 18.5 mag. ASAS-SN has routinely operated since 2013, collecting ∼ 2 000 to over 7 500 epochs of V- and g-band observations per field to date. This work illustrates the first analysis of ASAS-SN’s newer, deeper, and higher cadence g-band data. From an input source list of ∼55 million isolated sources with g < 18 mag, we identified 1.5 × 106 variable star candidates using a random forest (RF) classifier trained on features derived from Gaia, 2MASS, and AllWISE. Using ASAS-SN g-band light curves, and an updated RF classifier augmented with data from Citizen ASAS-SN, we classified the candidate variables into eight broad variability types. We present a catalogue of ∼116 000 new variable stars with high-classification probabilities, including ∼111 000 periodic variables and ∼5 000 irregular variables. We also recovered ∼263 000 known variable stars. 

ABSTRACT We present new Large Binocular Telescope, Hubble Space Telescope, and Spitzer Space Telescope data for the failed supernova candidate N6946-BH1. We also report an unsuccessful attempt to detect the candidate with Chandra. The ∼300 000 $$\, \mathrm{L}_\odot$$ red supergiant progenitor underwent an outburst in 2009 and has since disappeared in the optical. In the LBT data from 2008 May through 2019 October, the upper limit on any increase in the R-band luminosity of the source is $$2000 \, \mathrm{L}_\odot$$. HST and Spitzer observations show that the source continued to fade in the near-IR and mid-IR, fading by approximately a factor of 2 between 2015 October and 2017 September to 2900 $$\, \mathrm{L}_\odot$$ at Hband (F160W). Models of the spectral energy distribution are inconsistent with a surviving star obscured either by an ongoing wind or dust formed in the transient. The disappearance of N6946-BH1 remains consistent with a failed supernova, but the post-failure phenomenology requires further theoretical study. 

ABSTRACT We report the All-Sky Automated Survey for SuperNovae discovery of the tidal disruption event (TDE) ASASSN-23bd (AT 2023clx) in NGC 3799, a LINER galaxy with no evidence of strong active galactic nucleus (AGN) activity over the past decade. With a redshift of z = 0.01107 and a peak ultraviolet (UV)/optical luminosity of (5.4 ± 0.4) × 1042 erg s−1, ASASSN-23bd is the lowest-redshift and least-luminous TDE discovered to date. Spectroscopically, ASASSN-23bd shows H α and He i emission throughout its spectral time series, there are no coronal lines in its near-infrared spectrum, and the UV spectrum shows nitrogen lines without the strong carbon and magnesium lines typically seen for AGN. Fits to the rising ASAS-SN light curve show that ASASSN-23bd started to brighten on MJD 59988$$^{+1}_{-1}$$, ∼9 d before discovery, with a nearly linear rise in flux, peaking in the g band on MJD $$60 \, 000^{+3}_{-3}$$. Scaling relations and TDE light curve modelling find a black hole mass of ∼106 M⊙, which is on the lower end of supermassive black hole masses. ASASSN-23bd is a dim X-ray source, with an upper limit of $$L_{0.3-10\, \mathrm{keV}} \lt 1.0\times 10^{40}$$ erg s−1 from stacking all Swift observations prior to MJD 60061, but with soft (∼0.1 keV) thermal emission with a luminosity of $$L_{0.3-2 \, \mathrm{keV}}\sim 4\times 10^{39}$$ erg s−1 in XMM-Newton observations on MJD 60095. The rapid (t < 15 d) light curve rise, low UV/optical luminosity, and a luminosity decline over 40 d of ΔL40 ≈ −0.7 dex make ASASSN-23bd one of the dimmest TDEs to date and a member of the growing ‘Low Luminosity and Fast’ class of TDEs. 

We present V -band photometry of the 20 000 brightest asteroids using data from the All-Sky Automated Survey for Supernovae (ASAS-SN) between 2012 and 2018. We were able to apply the convex inversion method to more than 5000 asteroids with more than 60 good measurements in order to derive their sidereal rotation periods, spin axis orientations, and shape models. We derive unique spin state and shape solutions for 760 asteroids, including 163 new determinations. This corresponds to a success rate of about 15%, which is significantly higher than the success rate previously achieved using photometry from surveys. We derive the first sidereal rotation periods for additional 69 asteroids. We find good agreement in spin periods and pole orientations for objects with prior solutions. We obtain a statistical sample of asteroid physical properties that is sufficient for the detection of several previously known trends, such as the underrepresentation of slow rotators in current databases, and the anisotropic distribution of spin orientations driven by the nongravitational forces. We also investigate the dependence of spin orientations on the rotation period. Since 2018, ASAS-SN has been observing the sky with higher cadence and a deeper limiting magnitude, which will lead to many more new solutions in just a few years. 

Abstract We present three new spectra of the nearby Type Ia supernova (SN Ia) 2011fe covering ≈480–850 days after maximum light and show that the ejecta undergoes a rapid ionization shift at ∼500 days after explosion. The prominent Feiiiemission lines at ≈4600 Å are replaced with Fei+Feiiblends at ∼4400 Å and ∼5400 Å. The ≈7300 Å feature, which is produced by [Feii]+[Niii] at ≲400 days after explosion, is replaced by broad (≈±15,000 km s⁻¹) symmetric [Caii] emission. Models predict this ionization transition occurring ∼100 days later than what is observed, which we attribute to clumping in the ejecta. Finally, we use the nebular-phase spectra to test several proposed progenitor scenarios for SN 2011fe. Nondetections of H and He exclude nearby nondegenerate companions, [Oi] nondetections disfavor the violent merger of two white dwarfs, and the symmetric emission-line profiles favor a symmetric explosion.