Coral Towers Observatory

Cairns, Australia

Coral Towers Observatory

Cairns, Australia
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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.


PubMed | Mt Vernon Observatory, The Virtual Telescope Project, Las Campanas Observatory, Harvard - Smithsonian Center for Astrophysics and 14 more.
Type: Journal Article | Journal: Science (New York, N.Y.) | Year: 2016

We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached an absolute magnitude of Mu ,AB = -23.5 0.1 and bolometric luminosity Lbol = (2.2 0.2) 10(45) ergs s(-1), which is more than twice as luminous as any previously known supernova. It has several major features characteristic of the hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources and progenitors are currently poorly understood. In contrast to most previously known SLSNe-I that reside in star-forming dwarf galaxies, ASASSN-15lh appears to be hosted by a luminous galaxy (MK -25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1 0.2) 10(52) ergs, challenging the magnetar model for its engine.


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..


Schmidt S.J.,Ohio State University | Prieto J.L.,Princeton University | Stanek K.Z.,Ohio State University | Shappee B.J.,Ohio State University | And 19 more authors.
Astrophysical Journal Letters | Year: 2014

We analyze a ΔV -9 magnitude flare on the newly identified M8 dwarf SDSS J022116.84+194020.4 (hereafter SDSSJ0221) detected as part of the All-Sky Automated Survey for Supernovae. Using infrared and optical spectra, we confirm that SDSSJ0221 is a relatively nearby (d 76 pc) M8 dwarf with strong quiescent Hα emission. Based on kinematics and the absence of features consistent with low-gravity (young) ultracool dwarfs, we place a lower limit of 200 Myr on the age of SDSSJ0221. When modeled with a simple, classical flare light curve, this flare is consistent with a total U-band flare energy EU 10 34 erg, confirming that the most dramatic flares are not limited to warmer, more massive stars. Scaled to include a rough estimate of the emission line contribution to the V band, we estimate a blackbody filling factor of10%-30% during the flare peak and0.5%-1.6% during the flare decay phase. These filling factors correspond to flare areas that are an order of magnitude larger than those measured for most mid-M dwarf flares. © 2014. The American Astronomical Society. All rights reserved.


Shappee B.J.,Ohio State University | Prieto J.L.,Princeton University | Grupe D.,Pennsylvania State University | Kochanek C.S.,Ohio State University | And 46 more authors.
Astrophysical Journal | Year: 2014

After the All-Sky Automated Survey for SuperNovae discovered a significant brightening of the inner region of NGC 2617, we began a ∼70 day photometric and spectroscopic monitoring campaign from the X-ray through near-infrared (NIR) wavelengths. We report that NGC 2617 went through a dramatic outburst, during which its X-ray flux increased by over an order of magnitude followed by an increase of its optical/ultraviolet (UV) continuum flux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8 galaxy in 2003, is now a Seyfert 1 due to the appearance of broad optical emission lines and a continuum blue bump. Such "changing look active galactic nuclei (AGNs)" are rare and provide us with important insights about AGN physics. Based on the Hβ line width and the radius-luminosity relation, we estimate the mass of central black hole (BH) to be (4 ± 1) × 107 M . When we cross-correlate the light curves, we find that the disk emission lags the X-rays, with the lag becoming longer as we move from the UV (2-3 days) to the NIR (6-9 days). Also, the NIR is more heavily temporally smoothed than the UV. This can largely be explained by a simple model of a thermally emitting thin disk around a BH of the estimated mass that is illuminated by the observed, variable X-ray fluxes. © 2014. The American Astronomical Society. All rights reserved..


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 17 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.


Pastorello A.,National institute for astrophysics | Cappellaro E.,National institute for astrophysics | Inserra C.,Queen's University of Belfast | Smartt S.J.,Queen's University of Belfast | And 42 more authors.
Astrophysical Journal | Year: 2013

We report the results of a three-year-long dedicated monitoring campaign of a restless luminous blue variable (LBV) in NGC 7259. The object, named SN 2009ip, was observed photometrically and spectroscopically in the optical and near-infrared domains. We monitored a number of erupting episodes in the past few years, and increased the density of our observations during eruptive episodes. In this paper, we present the full historical data set from 2009 to 2012 with multi-wavelength dense coverage of the two high-luminosity events between 2012 August and September. We construct bolometric light curves and measure the total luminosities of these eruptive or explosive events. We label them the 2012a event (lasting ∼50 days) with a peak of 3 × 10 41 erg s-1, and the 2012b event (14 day rise time, still ongoing) with a peak of 8 × 1042 erg s-1. The latter event reached an absolute R-band magnitude of about -18, comparable to that of a core-collapse supernova (SN). Our historical monitoring has detected high-velocity spectral features (∼13,000 km s-1) in 2011 September, one year before the current SN-like event. This implies that the detection of such high-velocity outflows cannot, conclusively, point to a core-collapse SN origin. We suggest that the initial peak in the 2012a event was unlikely to be due to a faint core-collapse SN. We propose that the high intrinsic luminosity of the latest peak, the variability history of SN 2009ip, and the detection of broad spectral lines indicative of high-velocity ejecta are consistent with a pulsational pair-instability event, and that the star may have survived the last outburst. The question of the survival of the LBV progenitor star and its future fate remain open issues, only to be answered with future monitoring of this historically unique explosion. © 2013. The American Astronomical Society. All rights reserved..


Valenti S.,Queen's University of Belfast | Valenti S.,National institute for astrophysics | Fraser M.,Queen's 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.


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.


Prieto J.L.,Princeton University | Brimacombe J.,James Cook University | Brimacombe J.,Coral Towers Observatory | Drake A.J.,California Institute of Technology | Howerton S.,1401 South A
Astrophysical Journal Letters | Year: 2013

Recent observations by Mauerhan et al. have shown the unprecedented transition of the previously identified luminous blue variable (LBV) and supernova (SN) impostor SN 2009ip to a real Type IIn SN explosion. We present 100 optical R- and I-band photometric measurements of SN 2009ip obtained between UT 2012 September 23.6 and October 9.6, using 0.3-0.4 m aperture telescopes from the Coral Towers Observatory in Cairns, Australia. The light curves show well-defined phases, including very rapid brightening early on (0.5 mag in 6 hr observed during the night of September 24), a transition to a much slower rise between September 25 and September 28, and a plateau/peak around October 7. These changes are coincident with the reported spectroscopic changes that most likely mark the start of a strong interaction between the fast SN ejecta and a dense circumstellar medium formed during the LBV eruptions observed in recent years. In the 16-day observing period, SN 2009ip brightened by 3.7 mag from I = 17.4 mag on September 23.6 (MI ≃ -14.2) to I = 13.7 mag (M I ≃ -17.9) on October 9.6, radiating 3 × 1049 erg in the optical wavelength range. As of 2012 October 9.6, SN 2009ip is more luminous than most Type IIP SN and comparable to other Type IIn SN. © 2013. The American Astronomical Society. All rights reserved..

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