10 research outputs found

    Galaxy Alignments with Surrounding Structure in the Sloan Digital Sky Survey

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    Using data from the Sloan Digital Sky Survey (SDSS) Legacy Survey, we study the alignment of relatively luminous galaxies with spectroscopic data with the surrounding larger-scale structure as defined by galaxies with only photometric data. We find that galaxies from the red sequence have a statistically significant tendency for their images to align parallel to the projected surrounding structure. Red galaxies brighter than the median of our sample (Mr<−21.05M_r < -21.05) have a mean alignment angle ⟚Ί⟩<45∘\langle \Phi \rangle < 45^\circ, indicating preferred parallel alignment, at a significance level >7.8σ > 7.8 \sigma on projected scales 1 Mpc<rp<30 Mpc1\,\textrm{Mpc} < r_p < 30\,\textrm{Mpc}. Fainter red galaxies have ⟚Ί⟩3.4σ\langle \Phi \rangle 3.4 \sigma only at scales rp>18 Mpcr_p > 18\,\textrm{Mpc}. Galaxies from the blue sequence show no statistically significant (3σ3\sigma) tendency for their images to align with larger-scale structure. No dependence of alignment angle is seen as a function of local overdensity or of offset from the local distribution of surrounding galaxies.Comment: 9 pages, 5 figures, 2 tables, submitted to Ap

    ASAS-SN follow-up of IceCube high-energy neutrino alerts

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    We report on the search for optical counterparts to IceCube neutrino alerts released between April 2016 and August 2021 with the All-Sky Automated Survey for SuperNovae (ASAS-SN). Despite the discovery of a diffuse astrophysical high-energy neutrino flux in 2013, the source of those neutrinos remains largely unknown. Since 2016, IceCube has published likely-astrophysical neutrinos as public realtime alerts. Through a combination of normal survey and triggered target-of-opportunity observations, ASAS-SN obtained images within 1 hour of the neutrino detection for 20% (11) of all observable IceCube alerts and within one day for another 57% (32). For all observable alerts, we obtained images within at least two weeks from the neutrino alert. ASAS-SN provides the only optical follow-up for about 17% of IceCube's neutrino alerts. We recover the two previously claimed counterparts to neutrino alerts, the flaring-blazar TXS 0506+056 and the tidal disruption event AT2019dsg. We investigate the light curves of previously-detected transients in the alert footprints, but do not identify any further candidate neutrino sources. We also analysed the optical light curves of Fermi 4FGL sources coincident with high-energy neutrino alerts, but do not identify any contemporaneous flaring activity. Finally, we derive constraints on the luminosity functions of neutrino sources for a range of assumed evolution models

    Fast and Not-so-Furious: Case Study of the Fast and Faint Type IIb SN 2021bxu

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    We present photometric and spectroscopic observations and analysis of SN~2021bxu (ATLAS21dov), a low-luminosity, fast-evolving Type IIb supernova (SN). SN~2021bxu is unique, showing a large initial decline in brightness followed by a short plateau phase. With Mr=−15.93±0.16 magM_r = -15.93 \pm 0.16\, \mathrm{mag} during the plateau, it is at the lower end of the luminosity distribution of stripped-envelope supernovae (SE-SNe) and shows a distinct ∌\sim10 day plateau not caused by H- or He-recombination. SN~2021bxu shows line velocities which are at least ∌1500 km s−1\sim1500\,\mathrm{km\,s^{-1}} slower than typical SE-SNe. It is photometrically and spectroscopically similar to Type IIb SNe during the photospheric phases of evolution, with similarities to Ca-rich IIb SNe. We find that the bolometric light curve is best described by a composite model of shock interaction between the ejecta and an envelope of extended material, combined with a typical SN~IIb powered by the radioactive decay of 56^{56}Ni. The best-fit parameters for SN~2021bxu include a 56^{56}Ni mass of MNi=0.029−0.005+0.004 M⊙M_{\mathrm{Ni}} = 0.029^{+0.004}_{-0.005}\,\mathrm{M_{\odot}}, an ejecta mass of Mej=0.57−0.03+0.04 M⊙M_{\mathrm{ej}} = 0.57^{+0.04}_{-0.03}\,\mathrm{M_{\odot}}, and an ejecta kinetic energy of Kej=9.3−0.6+0.7×1049 ergK_{\mathrm{ej}} = 9.3^{+0.7}_{-0.6} \times 10^{49}\, \mathrm{erg}. From the fits to the properties of the extended material of Ca-rich IIb SNe we find a trend of decreasing envelope radius with increasing envelope mass. SN~2021bxu has MNiM_{\mathrm{Ni}} on the low end compared to SE-SNe and Ca-rich SNe in the literature, demonstrating that SN~2021bxu-like events are rare explosions in extreme areas of parameter space. The progenitor of SN~2021bxu is likely a low mass He star with an extended envelope.Comment: 18 pages, 15 figures, submitted to MNRA

    Strong Carbon Features and a Red Early Color in the Underluminous Type Ia SN 2022xkq

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    We present optical, infrared, ultraviolet, and radio observations of SN 2022xkq, an underluminous fast-declining type Ia supernova (SN Ia) in NGC 1784 (D≈31\mathrm{D}\approx31 Mpc), from <1<1 to 180 days after explosion. The high-cadence observations of SN 2022xkq, a photometrically transitional and spectroscopically 91bg-like SN Ia, cover the first days and weeks following explosion which are critical to distinguishing between explosion scenarios. The early light curve of SN 2022xkq has a red early color and exhibits a flux excess which is more prominent in redder bands; this is the first time such a feature has been seen in a transitional/91bg-like SN Ia. We also present 92 optical and 19 near-infrared (NIR) spectra, beginning 0.4 days after explosion in the optical and 2.6 days after explosion in the NIR. SN 2022xkq exhibits a long-lived C I 1.0693 ÎŒ\mum feature which persists until 5 days post-maximum. We also detect C II λ\lambda6580 in the pre-maximum optical spectra. These lines are evidence for unburnt carbon that is difficult to reconcile with the double detonation of a sub-Chandrasekhar mass white dwarf. No existing explosion model can fully explain the photometric and spectroscopic dataset of SN 2022xkq, but the considerable breadth of the observations is ideal for furthering our understanding of the processes which produce faint SNe Ia.Comment: 38 pages, 16 figures, accepted for publication in ApJ, the figure 15 input models and synthetic spectra are now available at https://zenodo.org/record/837925

    SCAT Uncovers ATLAS's First Tidal Disruption Event ATLAS18mlw: A Faint and Fast TDE in a Quiescent Balmer Strong Galaxy

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    We present the discovery that ATLAS18mlw was a tidal disruption event (TDE) in the galaxy WISEA J073544.83+663717.3, at a distance of 334 Mpc. Initially discovered by the Asteroid Terrestrial Impact Last Alert System (ATLAS) on 2018 March 17.3, the TDE nature of the transient was uncovered only recently with the re-reduction of a SuperNova Integral Field Spectrograph (SNIFS) spectrum. This spectrum, taken by the Spectral Classification of Astronomical Transients (SCAT) survey, shows a strong blue continuum and a broad Hα\alpha emission line. Here we present roughly six years of optical survey photometry beginning before the TDE to constrain AGN activity, optical spectroscopy of the transient, and a detailed study of the host galaxy properties through analysis of archival photometry and a host spectrum. ATLAS18mlw was detected in ground-based light curves for roughly two months. From a blackbody fit to the transient spectrum and bolometric correction of the optical light curve, we conclude that ATLAS18mlw is likely a low-luminosity TDE with a peak luminosity of log(L [erg s−1^{-1}]) = 43.5±0.243.5 \pm 0.2. The TDE classification is further supported by the quiescent Balmer strong nature of the host galaxy. We also calculated the TDE decline rate from the bolometric light curve and find ΔL40=−0.7±0.2\Delta L_{40} = -0.7 \pm 0.2 dex, making ATLAS18mlw a member of the growing class of "faint and fast" TDEs with low peak luminosities and fast decline rates.Comment: 14 pages, 6 figures, 1 table. Will be submitted to AAS journals. Comments welcom

    ASAS-SN follow-up of IceCube high-energy neutrino alerts

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    We report on the search for optical counterparts to IceCube neutrino alerts released between April 2016 and August 2021 with the All-Sky Automated Survey for SuperNovae (ASAS-SN). Despite the discovery of a diffuse astrophysical high-energy neutrino flux in 2013, the source of those neutrinos remains largely unknown. Since 2016, IceCube has published likely-astrophysical neutrinos as public realtime alerts. Through a combination of normal survey and triggered target-of-opportunity observations, ASAS-SN obtained images within 1 hour of the neutrino detection for 20% (11) of all observable IceCube alerts and within one day for another 57% (32). For all observable alerts, we obtained images within at least two weeks from the neutrino alert. ASAS-SN provides the only optical follow-up for about 17% of IceCube's neutrino alerts. We recover the two previously claimed counterparts to neutrino alerts, the flaring-blazar TXS 0506+056 and the tidal disruption event AT2019dsg. We investigate the light curves of previously-detected transients in the alert footprints, but do not identify any further candidate neutrino sources. We also analysed the optical light curves of Fermi 4FGL sources coincident with high-energy neutrino alerts, but do not identify any contemporaneous flaring activity. Finally, we derive constraints on the luminosity functions of neutrino sources for a range of assumed evolution models

    Extreme Nuclear Transients Resulting from the Tidal Disruption of Intermediate Mass Stars

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    International audienceModern transient surveys now routinely discover flares resulting from tidal disruption events (TDEs) which occur when stars, typically ∌0.5−2\sim0.5-2 M⊙_{\odot}, are ripped apart after passing too close to a supermassive black hole. We present three examples of a new class of extreme nuclear transients (ENTs) that we interpret as the tidal disruption of intermediate mass (∌3−10\sim3-10 M⊙_{\odot}) stars. Each is coincident with their host-galaxy nucleus and exhibits a smooth (150150 days) flare. ENTs are extremely rare (≄1×10−3\geq1\times10^{-3} Gpc−1^{-1} yr−1^{-1}) compared to any other known class of transients. They are at least twice as energetic (0.5−2.5×10530.5-2.5\times 10^{53} erg) as any other known transient and these extreme energetics rule out stellar origins

    Fast and not-so-furious: case study of the fast and faint Type IIb SN 2021bxu

    No full text
    We present photometric and spectroscopic observations and analysis of SN 2021bxu (ATLAS21dov), a low-luminosity, fast-evolving Type IIb supernova (SN). SN 2021bxu is unique, showing a large initial decline in brightness followed by a short plateau phase. With during the plateau, it is at the lower end of the luminosity distribution of stripped-envelope supernovae (SE-SNe) and shows a distinct ∌10 d plateau not caused by H- or He-recombination. SN 2021bxu shows line velocities which are at least slower than typical SE-SNe. It is photometrically and spectroscopically similar to Type IIb SNe during the photospheric phases of evolution, with similarities to Ca-rich IIb SNe. We find that the bolometric light curve is best described by a composite model of shock interaction between the ejecta and an envelope of extended material, combined with a typical SN IIb powered by the radioactive decay of 56Ni. The best-fitting parameters for SN 2021bxu include a 56Ni mass of, an ejecta mass of, and an ejecta kinetic energy of. From the fits to the properties of the extended material of Ca-rich IIb SNe we find a trend of decreasing envelope radius with increasing envelope mass. SN 2021bxu has MNi on the low end compared to SE-SNe and Ca-rich SNe in the literature, demonstrating that SN 2021bxu-like events are rare explosions in extreme areas of parameter space. The progenitor of SN 2021bxu is likely a low-mass He star with an extended envelope.Fil: Desai, Dhvanil D.. University of Hawai‘i at Manoa; Estados UnidosFil: Ashall, Chris. Virginia Tech University; Estados UnidosFil: Shappee, Benjamin J.. University of Hawai‘i at Manoa; Estados UnidosFil: Morrell, Nidia Irene. Las Campanas Observatory; ChileFil: Galbany, LluĂ­s. Instituto de Estudios Espaciales de Cataluña; EspañaFil: Burns, Christopher R.. Carnegie Observatories; ChileFil: Derkacy, James M.. Virginia Tech University; Estados UnidosFil: Hinkle, Jason T.. University of Hawai‘i at Manoa; Estados UnidosFil: Hsiao, Eric. Florida State University; Estados UnidosFil: Kumar, Sahana. Florida State University; Estados UnidosFil: Lu, Jing. Florida State University; Estados UnidosFil: Phillips, Mark. Las Campanas Observatory; ChileFil: Shahbandeh, Melissa. Space Telescope Science Institute; Estados UnidosFil: Stritzinger, Maximilian. University Aarhus; DinamarcaFil: Baron, Eddie. Universitat Hamburg; Alemania. Oklahoma State University; Estados UnidosFil: Bersten, Melina Cecilia. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂ­sica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂ­sicas. Instituto de AstrofĂ­sica La Plata; ArgentinaFil: Brown, Peter J.. Texas A&M University; Estados UnidosFil: De Jaeger, Thomas. University of Hawai‘i at Manoa; Estados UnidosFil: Elias Rosa, Nancy. CSIC. Instituto de Ciencias del Espacio; EspañaFil: Folatelli, Gaston. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂ­sica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂ­sicas. Instituto de AstrofĂ­sica La Plata; ArgentinaFil: Huber, Mark E.. University of Hawai‘i at Manoa; Estados UnidosFil: Mazzali, Paolo. Liverpool John Moores University; Reino UnidoFil: MĂŒller Bravo, TomĂĄs E.. Instituto de Estudios Espaciales de Cataluña; EspañaFil: Piro, Anthony. Carnegie Observatories; ChileFil: Polin, Abigail. Carnegie Observatories; ChileFil: Suntzeff, Nicholas B.. Texas A&M University; Estados UnidosFil: Anderson, Joseph. European Southern Observatory Santiago; Chile. Instituto Milenio de AstrofĂ­sica; ChileFil: Chambers, Kenneth C.. University of Hawai‘i at Manoa; Estados UnidosFil: Chen, Ting Wan. Gobierno de la RepĂșblica Federal de Alemania. Max Planck Institut fĂŒr Astrophysik; Alemania. Universitat Technical Zu Munich; AlemaniaFil: De Boer, Thomas. University of Hawai‘i at Manoa; Estados UnidosFil: Fulton, Michael D.. The Queens University of Belfast; IrlandaFil: Gao, Hua. University of Hawai‘i at Manoa; Estados UnidosFil: Gromadzki, Mariusz. University of Warsaw; PoloniaFil: Inserra, Cosimo. Cardiff University; Reino UnidoFil: Magnier, Eugene A.. University of Hawai‘i at Manoa; Estados UnidosFil: Nicholl, Matt. The Queens University of Belfast; IrlandaFil: Ragosta, Fabio. Istituto Nazionale di Astrofisica; ItaliaFil: Wainscoat, Richard. University of Hawai‘i at Manoa; Estados UnidosFil: Young, David R.. The Queens University of Belfast; Irland

    Strong Carbon Features and a Red Early Color in the Underluminous Type Ia SN 2022xkq

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    International audienceWe present optical, infrared, ultraviolet, and radio observations of SN 2022xkq, an underluminous fast-declining type Ia supernova (SN Ia) in NGC 1784 (D≈31\mathrm{D}\approx31 Mpc), from <1<1 to 180 days after explosion. The high-cadence observations of SN 2022xkq, a photometrically transitional and spectroscopically 91bg-like SN Ia, cover the first days and weeks following explosion which are critical to distinguishing between explosion scenarios. The early light curve of SN 2022xkq has a red early color and exhibits a flux excess which is more prominent in redder bands; this is the first time such a feature has been seen in a transitional/91bg-like SN Ia. We also present 92 optical and 19 near-infrared (NIR) spectra, beginning 0.4 days after explosion in the optical and 2.6 days after explosion in the NIR. SN 2022xkq exhibits a long-lived C I 1.0693 ÎŒ\mum feature which persists until 5 days post-maximum. We also detect C II λ\lambda6580 in the pre-maximum optical spectra. These lines are evidence for unburnt carbon that is difficult to reconcile with the double detonation of a sub-Chandrasekhar mass white dwarf. No existing explosion model can fully explain the photometric and spectroscopic dataset of SN 2022xkq, but the considerable breadth of the observations is ideal for furthering our understanding of the processes which produce faint SNe Ia

    Strong Carbon Features and a Red Early Color in the Underluminous Type Ia SN 2022xkq

    No full text
    International audienceWe present optical, infrared, ultraviolet, and radio observations of SN 2022xkq, an underluminous fast-declining type Ia supernova (SN Ia) in NGC 1784 (D≈31\mathrm{D}\approx31 Mpc), from <1<1 to 180 days after explosion. The high-cadence observations of SN 2022xkq, a photometrically transitional and spectroscopically 91bg-like SN Ia, cover the first days and weeks following explosion which are critical to distinguishing between explosion scenarios. The early light curve of SN 2022xkq has a red early color and exhibits a flux excess which is more prominent in redder bands; this is the first time such a feature has been seen in a transitional/91bg-like SN Ia. We also present 92 optical and 19 near-infrared (NIR) spectra, beginning 0.4 days after explosion in the optical and 2.6 days after explosion in the NIR. SN 2022xkq exhibits a long-lived C I 1.0693 ÎŒ\mum feature which persists until 5 days post-maximum. We also detect C II λ\lambda6580 in the pre-maximum optical spectra. These lines are evidence for unburnt carbon that is difficult to reconcile with the double detonation of a sub-Chandrasekhar mass white dwarf. No existing explosion model can fully explain the photometric and spectroscopic dataset of SN 2022xkq, but the considerable breadth of the observations is ideal for furthering our understanding of the processes which produce faint SNe Ia
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