The SED Machine: A Robotic Spectrograph for Fast Transient Classification

Blagorodnova, N.; Neill, James D.; Walters, Richard; Kulkarni, S. R.; Fremling, C.; Ben-Ami, Sagi; Dekany, Richard; Fucik, Jason; Konidaris, Nick; Nash, Reston; Ngeow, Chow-Choong; Ofek, E. O.; O’Sullivan, Donal; Quimby, R.; Ritter, Andreas; Vyhmeister, Karl

doi:10.1088/1538-3873/aaa53f

Cited by 203 publications

(174 citation statements)

References 31 publications

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“…We found that the Balmer lines of ZTF18aahiqfi, ZTF18aaidlyq, and ZTF18aasuray had gotten dramatically stronger and broader compared to archival SDSS spectra of their hosts, obtained more than a decade prior (in April 2003, Dec 2002, and Feb 2001. ZTF18aasszwr and ZTF18aaabltn showed similar striking spectral changes when they were followed up on 2018 Dec 3 and 9 using the Spectral Energy Distribution Machine (SEDM; Blagorodnova et al 2018a) IFU spectrograph on the Palomar 60-inch (P60; Cenko et al 2006) operating as part of ZTF. Both displayed broader emission lines and bluer continuua compared to archival LINER spectra (from Feb 2007 andJun 2004, respectively).…”

Section: Optical Spectroscopymentioning

confidence: 90%

A New Class of Changing-look LINERs

Frederick

Gezari

Graham

et al. 2019

ApJ

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103

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We report the discovery of six active galactic nuclei (AGN) caught "turning on" during the first nine months of the Zwicky Transient Facility (ZTF) survey. The host galaxies were classified as LINERs by weak narrow forbidden line emission in their archival SDSS spectra, and detected by ZTF as nuclear transients. In five of the cases, we found via follow-up spectroscopy that they had transformed into broad-line AGN, reminiscent of the changing-look LINER iPTF16bco. In one case, ZTF18aajupnt/AT2018dyk, follow-up HST UV and groundbased optical spectra revealed the transformation into a narrow-line Seyfert 1 (NLS1) with strong [Fe VII, X, XIV] and He II λ4686 coronal lines. Swift monitoring observations of this source reveal bright UV emission that tracks the optical flare, accompanied by a luminous soft X-ray flare that peaks ∼60 days later. Spitzer follow-up observations also detect a luminous mid-infrared flare implying a large covering fraction of dust. Archival light curves of the entire sample from CRTS, ATLAS, and ASAS-SN constrain the onset of the optical nuclear flaring from a prolonged quiescent state. Here we present the systematic selection and follow-up of this new class of changing-look LINERs, compare their properties to previously reported changing-look Seyfert galaxies, and conclude that they are a unique class of transients well-suited to test the uncertain physical processes associated with the LINER accretion state.

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Section: Optical Spectroscopymentioning

confidence: 90%

A New Class of Changing-look LINERs

Frederick

Gezari

Graham

et al. 2019

ApJ

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103

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“…An important instrument for photometric follow-up observations during PTF/iPTF was the 1.52-m telescope (known as P60) at Palomar Observatory. The telescope was used for imaging with the GRBCam camera (Cenko et al 2006) or the Spectral Energy Distribution Machine (SEDM) integral field spectrograph (Blagorodnova et al 2018) using SDSS gri filters. A typical strategy with the P60 was to obtain SDSS gri images of a SN field with a cadence of 1 d or 3 d (for young SNe) and a cadence of 6 d for older SNe.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Type IIn supernova light-curve properties measured from an untargeted survey sample

Nyholm

Sollerman

Tartaglia

et al. 2020

A&A

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The evolution of a Type IIn supernova (SN IIn) is governed by the interaction between the SN ejecta and a hydrogen-rich circumstellar medium (CSM). SNe IIn thus allow us to probe the late-time mass-loss history of their progenitor stars. We present a sample of SNe IIn from the untargeted, magnitude-limited surveys of the Palomar Transient Factory (PTF) and its successor, the intermediate PTF (iPTF). To date, statistics on SN IIn optical light curve properties have generally been based on small ( 10 SNe) samples from targeted SN surveys. SNe IIn found and followed by the PTF/iPTF were used to select a sample of 42 events with useful constraints on the rise times as well as with available post-peak photometry. The SNe were discovered in 2009-2016 and have at least one low-resolution classification spectrum, as well as photometry from the P48 and P60 telescopes at Palomar Observatory. We study the light-curve properties of these SNe IIn using spline fits (for the peak and the declining portion) and template matching (for the rising portion). We study the peak-magnitude distribution, rise times, decline rates, colour evolution, host galaxies, and K-corrections of the SNe in our sample. We find that the typical rise times are divided into fast and slow risers as 20 ± 8 d and 50 ± 15 d, respectively. The decline rates could possibly be divided into two groups (with slopes 0.013 ± 0.008 mag d −1 and 0.040 ± 0.014 mag d −1 ), but this division has weak statistical significance. We find no significant correlation between the peak luminosity of SNe IIn and their rise times, but the more luminous SNe IIn are generally found to be more durable and the slowly rising SNe IIn are generally found to be slowly declining. The SNe in our sample were hosted by galaxies of absolute magnitude −22 Mg −13 mag. The K-corrections at light-curve peak of the SNe in our sample are found to be within 0.2 mag for the observer's frame r-band, for SNe IIn at redshifts z < 0.25. Applying K-corrections and including also ostensibly "superluminous" SNe IIn, we find that the peak magnitudes are M r peak = −19.18 ± 1.32 mag. We conclude that the occurrence of conspicuous light-curve bumps in SNe IIn, such as in iPTF13z, is limited to 1.4 +14.6 −1.0 % of the SNe IIn. We also investigate a possible subtype of SNe IIn with a fast rise to a 50 d plateau followed by a slow, linear decline. iPTF13agz, iPTF13aki, iPTF13asr, iPTF13cuf, iPTF14bcw, iPTF14bpa, iPTF15aym, iPTF15bky, iPTF15blp, iPTF15eqr, iPTF16fb. ⋆ Based in part on observations made with the Palomar Transient Factory and intermediate Palomar Transient Factory surveys.

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“…The advent of such large SN surveys has prompted the development of high throughput low to medium resolution spectrographs like the SED Machine [145] and FLOYDS [146] to classify SNe in large numbers. However, more such instruments on larger aperture telescopes are needed for the LSST era.…”

Section: The Future: Bright Fast and Abundantmentioning

confidence: 99%

New regimes in the observation of core-collapse supernovae

2019

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Core-collapse Supernovae (CCSNe) mark the deaths of stars more massive than about eight times the mass of the sun (M ) and are intrinsically the most common kind of catastrophic cosmic explosions. They can teach us about many important physical processes, such as nucleosynthesis and stellar evolution, and thus, they have been studied extensively for decades. However, many crucial questions remain unanswered, including the most basic ones regarding which kinds of massive stars achieve which kind of explosions and how. Observationally, this question is related to the open puzzles of whether CCSNe can be divided into distinct types or whether they are drawn from a population with a continuous set of properties, and of what progenitor characteristics drive the diversity of observed explosions. Recent developments in wide-field surveys and rapid-response followup facilities are helping us answer these questions by providing two new tools: (1) large statistical samples which enable population studies of the most common SNe, and reveal rare (but extremely informative) events that question our standard understanding of the explosion physics involved, and (2) observations of early SNe emission taken shortly after explosion which carries signatures of the progenitor structure and mass loss history. Future facilities will increase our capabilities and allow us to answer many open questions related to these extremely energetic phenomena of the Universe.We focus this short review on a few open questions which are being tackled by new facilities for quick discovery and rapidresponse followup, as well as for studying CCSNe in large numbers. For a more exhaustive review of the field see recent compilations such as the Handbook of Supernovae [1]. The CCSN Classification LandscapeSN classification has been a challenge since the 1940's [2], but especially recently, as innovative surveys have brought a large increase of new and debated types. Classification schemes are important as physically motivated ones can give crucial insight into the explosion physics and stellar evolution pathways that lead to the different kinds of important explosions.The classical classification scheme [e.g., 3, 4] relies mostly on spectra and has two main types: Type I SNe (SNe I) which do not show hydrogen lines, and Type II SNe (SNe II) which do.In Figure 1 (left panel), we present spectra around peak brightness of the main CCSN classes. Among them, SNe II are perhaps the most heterogeneous class with a large range of observed photometric and spectroscopic properties. Because of this diversity, they can be further divided into several subclasses. The first historical subclassification was based on the light curve shape: SNe showing a linear decline (in magnitudes) in their light curve were named SNe IIL, while SNe showing a quasiconstant luminosity or a plateau for several weeks were called SNe IIP [13]. Later it was discovered that Type IIP and IIL SNe can also be distinguished by a subtle difference in their spectra, with SNe IIP showing deeper absor...

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The SED Machine: A Robotic Spectrograph for Fast Transient Classification

Cited by 203 publications

References 31 publications

A New Class of Changing-look LINERs

A New Class of Changing-look LINERs

Type IIn supernova light-curve properties measured from an untargeted survey sample

New regimes in the observation of core-collapse supernovae

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