Towards Real-time Classification of Astronomical Transients

Mahabal, A.; Djorgovski, S. G.; Williams, R. D.; Drake, A. J.; Donalek, C.; Graham, M. J.; Moghaddam, B.; Turmon, M.; Jewell, Jeffrey; Khosla, Atul; Hensley, Brandon

doi:10.1063/1.3059064

Cited by 21 publications

(12 citation statements)

References 12 publications

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“…Thus, despite the sparse sampling over the first ∼200 d, this large luminosity suggests that the early detections are not related to a pre-SN outburst, as was observed for SN 2006jc (Foley et al 2007;Pastorello et al 2007). CRTS images indicate that the SN was rising over the first ∼400 d (Mahabal et al 2009), which provides further evidence against a pre-SN outburst. Fig.…”

Section: Photometric Analysismentioning

confidence: 70%

“…The SN was later given the IAU designation SN 2008iy (Catelan et al 2009). Mahabal et al (2009) noted that the transient was present on CRTS images dating back to 2007 September 13; however, it went undetected by the CRTS automated transient detection software until 2008 because it was blended with a non-saturated, nearby (∼11-arcsec separation) star.…”

Section: Introductionmentioning

confidence: 99%

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SN 2008iy: an unusual Type IIn Supernova with an enduring 400-d rise time

Miller

Silverman

Butler

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We present spectroscopic and photometric observations of the Type IIn supernova (SN) 2008iy. SN 2008iy showed an unprecedentedly long rise time of ∼400 d, making it the first known SN to take significantly longer than 100 d to reach peak optical luminosity. The peak absolute magnitude of SN 2008iy was Mr≈−19.1 mag, and the total radiated energy over the first ∼700 d was ∼2 × 1050 erg. Spectroscopically, SN 2008iy is very similar to the Type IIn SN 1988Z at late times and, like SN 1988Z, it is a luminous X‐ray source (both SNe had an X‐ray luminosity LX > 1041 erg s−1). SN 2008iy has a growing near‐infrared excess at late times similar to several other SNe IIn. The Hα emission‐line profile of SN 2008iy shows a narrow P Cygni absorption component, implying a pre‐SN wind speed of ∼100 km s−1. We argue that the luminosity of SN 2008iy is powered via the interaction of the SN ejecta with a dense, clumpy circumstellar medium. The ∼400‐d rise time can be understood if the number density of clumps increases with distance over a radius ∼1.7 × 1016 cm from the progenitor. This scenario is possible if the progenitor experienced an episodic phase of enhanced mass loss <1 century prior to explosion or if the progenitor wind speed increased during the decades before core collapse. We favour the former scenario, which is reminiscent of the eruptive mass‐loss episodes observed for luminous blue variable (LBV) stars. The progenitor wind speed and increased mass‐loss rates serve as further evidence that at least some, and perhaps all, Type IIn SNe experience LBV‐like eruptions shortly before core collapse. We also discuss the host galaxy of SN 2008iy, a subluminous dwarf galaxy, and offer a few reasons why the recent suggestion that unusual, luminous SNe preferentially occur in dwarf galaxies may be the result of observational biases.

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Section: Photometric Analysismentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

SN 2008iy: an unusual Type IIn Supernova with an enduring 400-d rise time

Miller

Silverman

Butler

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…With a data set covering nearly 40% of the entire sky, with multiple passes reaching ∼ 21 mag each, and time baselines ranging from minutes (between different CCDs) to hours (repeated scans in the same night), days (within the same lunation), months, and years, and (using the cross-matches to DPOSS and SDSS catalogs) up to decades, PQ is in a unique position to explore time-variable sky in a systematic fashion. For some early reports, see Graham et al (2004), Mahabal et al (2004Mahabal et al ( , 2005, or Djorgovski et al (2006).…”

Section: Pq Exploration Of the Time Domain: Some Preliminary Resultsmentioning

confidence: 99%

The Palomar‐Quest digital synoptic sky survey

Djorgovski¹,

Baltay

Mahabal

et al. 2008

Astron Nachr

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We describe briefly the Palomar-Quest (PQ) digital synoptic sky survey, including its parameters, data processing, status, and plans. Exploration of the time domain is now the central scientific and technological focus of the survey. To this end, we have developed a real-time pipeline for detection of transient sources. We describe some of the early results, and lessons learned which may be useful for other, similar projects, and time-domain astronomy in general. Finally, we discuss some issues and challenges posed by the real-time analysis and scientific exploitation of massive data streams from modern synoptic sky surveys. In the first phase of the survey, data were obtained in the drift scan mode in 4.6• wide strips of a constant Dec, in the range −25• < δ < +25• , excluding the Galactic plane. The total area coverage is ∼ 15 000 deg 2 , with multiple passes, ranging from a few to about 25, and typically 5-10 times, with time baselines ranging from hours to years. There are some thin-strip gaps in the coverage, due to a combination of inter-CCD gaps, bad CCDs, and a suboptimal dithering strategy. Typical area coverage rate is up to ∼ 500 deg 2 /night in 4 filters. The raw data rate is on average ∼ 70 GB per clear night. To date, about 25 TB of usable data have been collected in the drift scan mode. Data were obtained with two filter sets, Johnson UBRI and Gunn/SDSS rizz, recently changed to griz. Effective In the second phase of the survey, which started in the spring of 2007, data are obtained in the traditional pointand-track mode, in a single, wide-band red filter (RG610), with ∼ 10% of the time in the drift scan mode. The coverage and the cadence are optimized for the nearby supernova search, in collaboration with the LBNL NSNF group, and a search for dwarf planets, in collaboration with M. Brown. Data are processed with several different pipelines, optimized for different scientific goals. This includes the Yale pipeline (Andrews et al. 2008), which does the PSF fitting and was designed for a search for gravitationally lensed quasars; the Caltech data cleaning pipeline, used to remove numerous instrumental artifacts present in the data; the Caltech real-time pipeline, used for real-time detections of transient events, as described below; the LBNL NSNF pipeline, based on image subtraction and designed for detection of nearby SNe; and a pipeline for an optimal coadding of images and detection of sources in them, now developed at Caltech. Images and resulting catalogs are stored in multiple locations, using a variety of databases.PQ is the first major digital sky survey fully designed and implemented in the Virtual Observatory (VO) era, and it uses VO standards and protocols throughout. Public data releases will be also done through VO-type interfaces. The first public data release is imminent, pending the completion of various data quality control and assessment tests.

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“…A holistic method will have to take cognizance of the multiple ways in which probabilities are assigned (Mahabal et al. ). For fusing the varied classification schemes, a Bayesian fusion network is ideal given the often sparse information and possible interdependencies.…”

Section: Discussionmentioning

confidence: 99%

Skysurveys, Light Curves and Statistical Challenges

Babu

Mahabal

2015

Int Statistical Rev

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Research in astronomy is undergoing a profound transformation from the study of small samples to the analysis of large-scale digital surveys of the sky. Ever larger amounts of data and better statistical techniques are being used to address a vast range of astronomical problems, from nearby asteroids to universe-wide cosmology. There is a huge need for new methodology development to address petabyte-sized datasets of images, atlases with millions of spectra, multivariate catalogues and time series with billions of objects. The focus of this article is on the analysis of light-curves (i.e. the variation of source brightness as a function of time). A description of the importance of the problem and the techniques already being used is given. The field is ripe with many statistical and computational challenges.

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Towards Real-time Classification of Astronomical Transients

Cited by 21 publications

References 12 publications

SN 2008iy: an unusual Type IIn Supernova with an enduring 400-d rise time

SN 2008iy: an unusual Type IIn Supernova with an enduring 400-d rise time

The Palomar‐Quest digital synoptic sky survey

Skysurveys, Light Curves and Statistical Challenges

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