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Charters Towers, Australia

Holoien T.W.-S.,Ohio State University | Prieto J.L.,Princeton University | Stanek K.Z.,Ohio State University | Kochanek C.S.,Ohio State University | And 22 more authors.
Astrophysical Journal Letters | Year: 2014

We discuss ASASSN-13db, an EX Lupi-type ("EXor") accretion event on the young stellar object (YSO) SDSS J051011.01-032826.2 (hereafter SDSSJ0510) discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN). Using archival photometric data of SDSSJ0510 we construct a pre-outburst spectral energy distribution and find that it is consistent with a low-mass class II YSO near the Orion star forming region (d 420 pc). We present follow-up photometric and spectroscopic observations of the source after the ΔV -5.4 mag outburst that began in 2013 September and ended in early 2014. These data indicate an increase in temperature and luminosity consistent with an accretion rate of 10-7 M yr -1, three or more orders of magnitude greater than in quiescence. Spectroscopic observations show a forest of narrow emission lines dominated by neutral metallic lines from Fe I and some low-ionization lines. The properties of ASASSN-13db are similar to those of the EXor prototype EX Lupi during its strongest observed outburst in late 2008. © 2014. The American Astronomical Society. All rights reserved..


Holoien T.W.-S.,Ohio State University | Prieto J.L.,Princeton University | Prieto J.L.,Diego Portales University | Prieto J.L.,Millennium Institute of Astrophysics | And 15 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

ASASSN-14ae is a candidate tidal disruption event (TDE) found at the centre of SDSS J110840.11+340552.2 (d ≃ 200 Mpc) by the All-Sky Automated Survey for Supernovae (ASAS-SN).We present ground-based and Swift follow-up photometric and spectroscopic observations of the source, finding that the transient had a peak luminosity of L≃8×1043 erg s-1 and a total integrated energy of E ≃ 1.7 × 1050 erg radiated over the ~5 months of observations presented. The blackbody temperature of the transient remains roughly constant at T ~ 20 000 K while the luminosity declines by nearly 1.5 orders of magnitude during this time, a drop that is most consistent with an exponential, L ∝ e-t/t0 with t0 ≃ 39 d. The source has broad Balmer lines in emission at all epochs as well as a broad He II feature emerging in later epochs. We compare the colour and spectral evolution to both supernovae and normal AGN to show that ASASSN-14ae does not resemble either type of object and conclude that a TDE is the most likely explanation for our observations. At z = 0.0436, ASASSN-14ae is the lowest-redshift TDE candidate discovered at optical/UV wavelengths to date, and we estimate that ASAS-SN may discover 0.1-3 of these events every year in the future. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Holoien T.W.-S.,Ohio State University | Holoien T.W.-S.,U.S. Department of Energy | Prieto J.L.,Diego Portales University | Prieto J.L.,Millennium Institute of Astrophysics | And 16 more authors.
Acta Astronomica | Year: 2016

We present photometric and spectroscopic observations of ASASSN-13co, an unusually luminous Type II supernova and the first core-collapse supernova discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN). First detection of the supernova was on UT 2013 August 29 and the data presented span roughly 3.5 months after discovery. We use the recently developed model by Pejcha and Prieto to model the multi-band light curves of ASASSN-13co and derive the bolometric luminosity curve. We compare ASASSN-13co to other Type II supernovae to show that it was unusually luminous for a Type II supernova and that it exhibited an atypical light curve shape that does not cleanly match that of either a standard Type II-L or Type II-P supernova.


Holoien T.W.-S.,Ohio State University | Kochanek C.S.,Ohio State University | Prieto J.L.,Diego Portales University | Prieto J.L.,Millennium Institute of Astrophysics | And 24 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

We present ground-based and Swift photometric and spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at the centre of PGC 043234 (d ≃ 90 Mpc) by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity of L ≃ 1044 erg s-1 and a total integrated energy of E ≃ 7 × 1050 erg radiated over the ~6 months of observations presented. The UV/optical emission of the source is well fitted by a blackbody with roughly constant temperature of T ~ 35 000 K, while the luminosity declines by roughly a factor of 16 over this time. The optical/UV luminosity decline is broadly consistent with an exponential decline, L ∝ e-t/t0 , with t0 ≃ 60 d. ASASSN-14li also exhibits soft X-ray emission comparable in luminosity to the optical and UV emission but declining at a slower rate, and the X-ray emission now dominates. Spectra of the source show broad Balmer and helium lines in emission as well as strong blue continuum emission at all epochs.We use the discoveries of ASASSN-14li and ASASSN-14ae to estimate the TDE rate implied by ASAS-SN, finding an average rate of r ≃ 4.1 × 10-5 yr-1 per galaxy with a 90 per cent confidence interval of (2.2-17.0) × 10-5 yr-1 per galaxy. ASAS-SN found roughly 1 TDE for every 70 Type Ia supernovae in 2014, a rate that is much higher than that of other surveys. © 2015 The Author.


Valenti S.,Queens University of Belfast | Valenti S.,National institute for astrophysics | Fraser M.,Queens University of Belfast | Benetti S.,National institute for astrophysics | And 32 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

We present an extensive set of photometric and spectroscopic data for SN 2009jf, a nearby Type Ib supernova (SN), spanning from ∼20d before B-band maximum to 1 yr after maximum. We show that SN 2009jf is a slowly evolving and energetic stripped-envelope SN and is likely from a massive progenitor (25-30M⊙). The large progenitor's mass allows us to explain the complete hydrogen plus helium stripping without invoking the presence of a binary companion. The SN occurred close to a young cluster, in a crowded environment with ongoing star formation. The spectroscopic similarity with the He-poor Type Ic SN 2007gr suggests a common progenitor for some SNe Ib and Ic. The nebular spectra of SN 2009jf are consistent with an asymmetric explosion, with an off-centre dense core. We also find evidence that He-rich Ib SNe have a rise time longer than other stripped-envelope SNe, however confirmation of this result and further observations are needed. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

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