arXiv subjects

J. Brimacombe

Publications and source records attributed to J. Brimacombe.

31 records · Page 2Linked to original sources

arXiv2016

The ASAS-SN Bright Supernova Catalog $-$ I. 2013$-$2014

We present basic statistics for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) during its first year-and-a-half of operations, spanning 2013 and 2014. We also present the same information for all other bright ($m_V\leq17$), spectroscopically confirmed supernovae discovered from 2014 May 1 through the end of 2014, providing a comparison to the ASAS-SN sample starting from the point where ASAS-SN became operational in both hemispheres. In addition, we present collected redshifts and near-UV through IR magnitudes, where available, for all host galaxies of the bright supernovae in both samples. This work represents a comprehensive catalog of bright supernovae and their hosts from multiple professional and amateur sources, allowing for population studies that were not previously possible because the all-sky emphasis of ASAS-SN redresses many previously existing biases. In particular, ASAS-SN systematically finds bright supernovae closer to the centers of host galaxies than either other professional surveys or amateurs, a remarkable result given ASAS-SN's poorer angular resolution. This is the first of a series of yearly papers on bright supernovae and their hosts that will be released by the ASAS-SN team.

astro-ph.HE↗

arXiv2016

Discovery and Observations of the Unusually Luminous Type-Defying II-P/II-L Supernova ASASSN-13co

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 from Pejcha & Prieto (2015) 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.

astro-ph.HE↗

arXiv2016

The Young and Bright Type Ia Supernova ASASSN-14lp: Discovery, Early-Time Observations, First-Light Time, Distance to NGC 4666, and Progenitor Constraints

On 2014 Dec. 9.61, the All-Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin") discovered ASASSN-14lp just $\sim2$ days after first light using a global array of 14-cm diameter telescopes. ASASSN-14lp went on to become a bright supernova ($V = 11.94$ mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-14lp for more than 100 days. We find that ASASSN-14lp had a broad light curve ($Δm_{15}(B) = 0.80 \pm 0.05$), a $B$-band maximum at $2457015.82 \pm 0.03$, a rise time of $16.94^{+ 0.11 }_{- 0.10 }$ days, and moderate host--galaxy extinction ($E(B-V)_{\textrm{host}} = 0.33 \pm 0.06$). Using ASASSN-14lp we derive a distance modulus for NGC 4666 of $μ= 30.8 \pm 0.2$ corresponding to a distance of $14.7 \pm 1.5$ Mpc. However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any non-degenerate companion larger than $0.34 R_{\textrm{sun}}$.

astro-ph.CO↗

arXiv2016

Six Months of Multi-Wavelength Follow-up of the Tidal Disruption Candidate ASASSN-14li and Implied TDE Rates from ASAS-SN

We present ground-based and Swift photometric and spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at the center of PGC 043234 ($d\simeq90$ Mpc) by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity of $L\simeq10^{44}$ ergs s$^{-1}$ and a total integrated energy of $E\simeq7\times10^{50}$ ergs radiated over the $\sim6$ months of observations presented. The UV/optical emission of the source is well-fit by a blackbody with roughly constant temperature of $T\sim35,000$ 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, $L\propto e^{-t/t_0}$, with $t_0\simeq60$ days. 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 $r \simeq 4.1 \times 10^{-5}~{\rm yr}^{-1}$ per galaxy with a 90% confidence interval of $(2.2 - 17.0) \times 10^{-5}~{\rm yr}^{-1}$ 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.

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arXiv2016

ASASSN-15lh: A Highly Super-Luminous Supernova

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 M_{u,AB} = -23.5+/-0.1 and bolometric luminosity L_bol = (2.2+/-0.2)x 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 (M_K ~ -25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1+/- 0.2)x10^52 ergs, challenging the magnetar model for its engine.

astro-ph.HE↗

arXiv2015

Massive stars exploding in a He-rich circumstellar medium - VII. The metamorphosis of ASASSN-15ed from a narrow line Type Ibn to a normal Type Ib Supernova

We present the results of the spectroscopic and photometric monitoring campaign of ASASSN-15ed. The transient was discovered quite young by the All Sky Automated Survey for SuperNovae (ASAS-SN). Amateur astronomers allowed us to sample the photometric SN evolution around maximum light, which we estimate to have occurred on JD = 2457087.4 +- 0.6 in the r-band. Its apparent r-band magnitude at maximum was r = 16.91 +- 0.10, providing an absolute magnitude M(r) ~ -20.04 +- 0.20, which is slightly more luminous than the typical magnitudes estimated for Type Ibn SNe. The post-peak evolution was well monitored, and the decline rate (being in most bands around 0.1 mag/d during the first 25 d after maximum) is marginally slower than the average decline rates of SNe Ibn during the same time interval. The object was initially classified as a Type Ibn SN because early-time spectra were characterized by a blue continuum with superimposed narrow P-Cygni lines of He I, suggesting the presence of a slowly moving (1200-1500 km/s), He-rich circumstellar medium. Later on, broad P-Cygni He I lines became prominent. The inferred velocities, as measured from the minimum of the broad absorption components, were between 6000 and 7000 km/s. As we attribute these broad features to the SN ejecta, this is the first time we have observed the transition of a Type Ibn SN to a Type Ib SN.

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arXiv2014

ASASSN-14ae: A Tidal Disruption Event at 200 Mpc

ASASSN-14ae is a candidate tidal disruption event (TDE) found at the center of SDSS J110840.11+340552.2 ($d\simeq200$~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 $L\simeq8\times10^{43}$~erg~s$^{-1}$ and a total integrated energy of $E\simeq1.7\times10^{50}$ ergs radiated over the $\sim5$ months of observations presented. The blackbody temperature of the transient remains roughly constant at $T\sim20,000$~K while the luminosity declines by nearly 1.5 orders of magnitude during this time, a drop that is most consistent with an exponential, $L\propto e^{-t/t_0}$ with $t_0\simeq39$~days. 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 color and spectral evolution to both supernovae and normal AGN to show that {\name} 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.

astro-ph.GA↗

arXiv2014

The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617

After the All-Sky Automated Survey for SuperNovae (ASAS-SN) 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 (AGN)" are rare and provide us with important insights about AGN physics. Based on the Hbeta line width and the radius-luminosity relation, we estimate the mass of central black hole to be (4 +/- 1) x 10^7 M_sun. 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 black hole of the estimated mass that is illuminated by the observed, variable X-ray fluxes.

astro-ph.HE↗

arXiv2014

Discovery and Observations of ASASSN-13db, an EX Lupi-Type Accretion Event on a Low-Mass T Tauri Star

We discuss ASASSN-13db, an EX Lupi-type ("EXor") accretion event on the young stellar object (YSO) SDSS J051011.01$-$032826.2 (hereafter SDSSJ0510) discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN). Using archival photometric data of SDSSJ0510 we construct a pre-outburst spectral energy distribution (SED) and find that it is consistent with a low-mass class II YSO near the Orion star forming region ($d \sim 420$ pc). We present follow-up photometric and spectroscopic observations of the source after the $ΔV \sim-$5.4 magnitude outburst that began in September 2013 and ended in early 2014. These data indicate an increase in temperature and luminosity consistent with an accretion rate of $\sim10^{-7}$ $\rm{M}_\odot$ 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.

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arXiv2013

Characterizing a Dramatic $ΔV\sim-9$ Flare on an Ultracool Dwarf Found by the ASAS-SN Survey

We analyze a $ΔV\sim-9$ 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 (ASAS-SN). Using infrared and optical spectra, we confirm that SDSSJ0221 is a relatively nearby (d$\sim$76 pc) M8 dwarf with strong quiescent H$α$ 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 $E_U\sim$ 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 of $\sim$$10-30\%$ during the flare peak and $\sim$$0.5-1.6\%$ 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.

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arXiv2013

Interacting Supernovae and Supernova Impostors. SN 2009ip, is this the end?

We report the results of a 3 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 2009-2012 with multi-wavelength dense coverage of the two high luminosity events between August - September 2012. 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 3x10^41 erg/s, and the 2012b event (14 day rise time, still ongoing) with a peak of 8x10^42 erg/s. 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 (~13000 km/s) in September 2011, 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.

astro-ph.SR↗

arXiv2012

The Rise of the Remarkable Type IIn Supernova SN 2009ip

Recent observations by Mauerhan et al. have shown the unprecedented transition of the previously identified luminous blue variable (and supernova impostor) SN 2009ip to a real Type IIn supernova (SN) explosion. We present high-cadence optical imaging of SN 2009ip obtained between 2012 UT Sep. 23.6 and Oct. 9.6, using 0.3-0.4 meter 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 Sep. 24), a transition to a much slower rise between Sep. 25 and Sep. 28, and a plateau/peak around Oct. 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 earlier LBV eruptions. In the 16-day observing period SN 2009ip brightened by 3.7 mag from I = 17.4 mag on Sep. 23.6 (MI = -14.2) to I = 13.7 mag (MI = -17.9) on Oct. 9.6, radiating ~2x10^49 erg in the optical wavelength range. Currently, SN 2009ip is more luminous than most Type IIP SNe and comparable to other Type IIn SNe.

astro-ph.SR↗

arXiv2011

SN 2009jf: a slow-evolving stripped-envelope core-collapse supernova

We present an extensive set of photometric and spectroscopic data for SN 2009jf, a nearby Type Ib supernova, spanning from ~20 days before B-band maximum to one year after maximum. We show that SN 2009jf is a slow evolving and energetic stripped-envelope SN and is likely from a massive progenitor (25-30 solar masses). The large progenitor's mass allows us to explain the complete hydrogen plus helium stripping without invoking the presence of a binary companion. The supernova occurred close to a young cluster, in a crowded environment with ongoing star-formation. The specroscopic similarity with the He-poor Type Ic SN 2007gr suggests a common progenitor for some supernovae Ib and Ic. The nebular spectra of SN 2009jf are consistent with an asymmetric explosion, with an off-center dense core. We also find evidence that He-rich Ib supernovae have a rise time longer than other stripped-envelope supernovae, however confirmation of this result and further observations are needed.

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