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) × 10{sup 7} M {sub ☉}. 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 bymore » 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.« less

https://iopscience.iop.org/article/10.1088/0004-637X/788/1/48/pdf

The man behind the curtain: x-rays drive the uv through nir variability in the 2013 active galactic nucleus 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.

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

We combine high redshift Type Ia supernovae from the first 3 years of the Supernova Legacy Survey (SNLS) with other supernova (SN) samples, primarily at lower redshifts, to form a high-quality joint sample of 472 SNe (123 low-$z$, 93 SDSS, 242 SNLS, and 14 {\it Hubble Space Telescope}). SN data alone require cosmic acceleration at >99.9% confidence, including systematic effects. For the dark energy equation of state parameter (assumed constant out to at least $z=1.4$) in a flat universe, we find $w = -0.91^{+0.16}_{-0.20}(\mathrm{stat}) ^{+0.07}_{-0.14} (\mathrm{sys})$ from SNe only, consistent with a cosmological constant. Our fits include a correction for the recently discovered relationship between host-galaxy mass and SN absolute brightness. We pay particular attention to systematic uncertainties, characterizing them using a systematics covariance matrix that incorporates the redshift dependence of these effects, as well as the shape-luminosity and color-luminosity relationships. Unlike previous work, we include the effects of systematic terms on the empirical light-curve models. The total systematic uncertainty is dominated by calibration terms. We describe how the systematic uncertainties can be reduced with soon to be available improved nearby and intermediate-redshift samples, particularly those calibrated onto USNO/SDSS-like systems.

/pdf/supernova-constraints-and-systematic-uncertainties-from-the-5g85mmrsyc.pdf

Supernova constraints and systematic uncertainties from the first three years of the supernova legacy survey

Type Ia supernovae (SNe Ia) are important distance indicators, element factories, cosmic-ray accelerators, kinetic-energy sources in galaxy evolution, and end points of stellar binary evolution. It has long been clear that a SN Ia must be the runaway thermonuclear explosion of a degenerate carbon-oxygen stellar core, most likely a white dwarf (WD). However, the specific progenitor systems of SNe Ia, and the processes that lead to their ignition, have not been identified. Two broad classes of progenitor binary systems have long been considered: single-degenerate (SD), in which a WD gains mass from a nondegenerate star; and double-degenerate (DD), involving the merger of two WDs. New theoretical work has enriched these possibilities with some interesting updates and variants. We review the significant recent observational progress in addressing the progenitor problem. We consider clues that have emerged from the observed properties of the various proposed progenitor populations, from studies of SN Ia sites—...

Observational Clues to the Progenitors of Type Ia Supernovae

Precise and accurate parameters for late-type (late K and M) dwarf stars are important for characterization of any orbiting planets, but such determinations have been hampered by these stars' compl ...

/pdf/how-to-constrain-your-m-dwarf-measuring-effective-2d8sxzh4ve.pdf

How to constrain your m dwarf: measuring effective temperature, bolometric luminosity, mass, and radius

Revision 2.6, 2006/06/01 00:20:07 Nearby Supernova Factory Observations of SN 2005gj: Another Type Ia Supernova in a Massive Circumstellar Envelope. The Nearby Supernova Factory G. Aldering, P. Antilogus, S. Bailey, 1 C. Baltay, 8 A. Bauer, 8 N. Blanc, 2 S. Bongard, 1,5 Y. Copin, 2 E. Gangler, 2 S. Gilles, 3 R. Kessler, 7 D. Kocevski, 1,6 B. C. Lee, 1 S. Loken, 1 P. Nugent, 1 R. Pain, 3 E. P´ contal, 4 R. Pereira, 3 S. Perlmutter, 1,6 D. Rabinowitz, 8 e G. Rigaudier, R. Scalzo, G. Smadja, 2 R. C. Thomas, 1 L. Wang, 1 B. A. Weaver 1,5 ABSTRACT We report the independent discovery and follow-up observations of supernova 2005gj by the Nearby Supernova Factory. This is the second conﬁrmed case of a “hybrid” Type Ia/IIn supernova, which like the prototype SN 2002ic, we inter- pret as the explosion of a white dwarf interacting with a circumstellar medium. Our early-phase photometry of SN 2005gj shows that the strength of the inter- action between the supernova ejecta and circumstellar material is much stronger than for SN 2002ic. Our ﬁrst spectrum shows a hot continuum with broad and narrow Hα emission. Later spectra, spanning over 4 months from outburst, show clear Type Ia features combined with broad and narrow Hγ, Hβ, Hα and He I λλ5876,7065 in emission. At higher resolution, P Cygni proﬁles are appar- ent. Surprisingly, we also observe an inverted P Cygni proﬁle for [O III ] λ5007. Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720 Institut de Physique Nucl´ aire de Lyon, UMR5822, CNRS-IN2P3; Universit´ Claude Bernard Lyon 1, e e F-69622 Villeurbanne France Laboratoire de Physique Nucl´ aire et des Hautes Energies IN2P3 - CNRS - Universit´ s Paris VI et Paris e e VII, 4 place Jussieu Tour 33 - Rez de chauss´ e 75252 Paris Cedex 05 e Centre de Recherche Astronomique de Lyon, 9, av. Charles Andr´ , 69561 Saint Genis Laval Cedex e University of California, Space Sciences Laboratory, Berkeley, CA 94720-7450 Department of Physics, University of California, Berkeley, CA 94720 Kavli Institute for Cosmological Physics, The University of Chicago, Chicago, IL 60637 Department of Physics, Yale University, New Haven, CT 06250-8121

https://iopscience.iop.org/article/10.1086/507020/pdf

Nearby Supernova Factory Observations of SN 2005gj: Another Type Ia Supernova in a Massive Circumstellar Envelope.

We present four spectra of the Type Ia supernova SN Ia 2006Dextending from -7 to +13 days with respect to B-band maximum. The spectrainclude the strongest signature of unburned material at photosphericvelocities observed in a SN Ia to date. The earliest spectrum exhibits CII absorption features below 14,000 km/s, including a distinctive C IIlambda 6580 absorption feature. The carbon signatures dissipate as the SNapproaches peak brightness. In addition to discussing implications ofphotospheric-velocity carbon for white dwarf explosion models, we outlinesome factors that may influence the frequency of its detection before andaround peak brightness. Two effects are explored in this regard,including depopulation of the C II optical levels by non-LTE effects, andline-of-sight effects resulting from a clumpy distribution of unburnedmaterial with low volume-filling factor.

/pdf/nearby-supernova-factory-observations-of-sn-2006d-on-181vcb6y4e.pdf

Nearby Supernova Factory Observations of SN 2006D: On Sporadic Carbon Signatures in Early Type Ia Supernova Spectra

We present the results of applying new object classification techniques to the supernova search of the Nearby Supernova Factory. In comparison to simple threshold cuts, more sophisticated methods such as boosted decision trees, random forests, and support vector machines provide dramatically better object discrimination: we reduced the number of nonsupernova candidates by a factor of 10 while increasing our supernova identification efficiency. Methods such as these will be crucial for maintaining a reasonable false positive rate in the automated transient alert pipelines of upcoming large optical surveys.

/pdf/object-classification-at-the-nearby-supernova-factory-boyu37h6wo.pdf

B.A. Weaver

Papers

Nearby Supernova Factory Observations of SN 2005gj: Another Type Ia Supernova in a Massive Circumstellar Envelope.

Nearby Supernova Factory Observations of SN 2006D: On Sporadic Carbon Signatures in Early Type Ia Supernova Spectra

Object Classification at the Nearby Supernova Factory