The ASAS-SN Catalog of Variable Stars II: <i>Uniform Classification of 412,000 Known Variables</i>

Jayasinghe, T.; Stanek, K. Z.; Kochanek, C. S.; Shappee, B. J.; Holoien, T. W. S.; Thompson, Todd A.; Prieto, J. L.; Dong, Subo; Pawlak, M.; Pejcha, Ondřej; Shields, J.; Pojmański, G.; Otero, S.; Britt, Chris; Will, D.

doi:10.1093/mnras/stz844

Cited by 162 publications

(135 citation statements)

References 62 publications

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“…We used the astropy implementation of the Generalized Lomb- Scargle (GLS;Zechmeister & Kürster 2009;Scargle 1982) periodogram and the astrobase implementation (Bhatti et al 2018) of the Box Least Squares (BLS; Kovács et al 2002) periodogram to search for periodicity over the range 0.05 ≤ P ≤ 100 days. Periodic sources were classified using a random forest classifier and quality checks as described in Jayasinghe et al (2019). In order to minimize false positives due to spurious variability signals in the data, we implemented cuts in classification probability Prob > 0.9 and the Lafler-Kinmann string length statistic (Lafler & Kinman 1965;Clarke 2002;Jayasinghe et al 2019) calculated for the magnitudes sorted by phase T (φ|P ) < 0.65.…”

Section: Variability Analysismentioning

confidence: 99%

A Catalog of M-dwarf Flares with ASAS-SN

Martínez

Lopez

Shappee

et al. 2020

ApJ

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We analyzed the light curves of 1376 early-to-late, nearby M dwarfs to search for white-light flares using photometry from the All-Sky Automated Survey for Supernovae (ASAS-SN). We identified 480 M dwarfs with at least one potential flare employing a simple statistical algorithm that searches for sudden increases in V -band flux. After more detailed evaluation, we identified 62 individual flares on 62 stars. The event amplitudes range from 0.12 < ∆V < 2.04 mag. Using classical-flare models, we place lower limits on the flare energies and obtain V -band energies spanning 2.0 × 10 30 E V 6.9 × 10 35 erg. The fraction of flaring stars increases with spectral type, and most flaring stars show moderate to strong Hα emission. Additionally, we find that 14 of the 62 flaring stars are rotational variables, and they have shorter rotation periods and stronger Hα emission than non-flaring rotational variable M dwarfs.

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Section: Variability Analysismentioning

confidence: 99%

A Catalog of M-dwarf Flares with ASAS-SN

Martínez

Lopez

Shappee

et al. 2020

ApJ

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“…The RF algorithm has been successfully applied to a variety of tasks in astronomy (e.g., Carliles et al 2010;Dubath et al 2011;Richards et al 2012;Carrasco Kind & Brunner 2013;Wyrzykowski et al 2014;Jayasinghe et al 2019;Chen et al 2019), including AGN classification and photometric redshift estimation (e.g., Pichara et al 2012;Carrasco et al 2015;Schindler et al 2017;Nakoneczny et al 2019;Jin et al 2019). We note that our work is the first RF-assisted AGN classification across the whole sky.…”

Section: Random Forest Algorithmmentioning

confidence: 99%

Catalogues of active galactic nuclei from Gaia and unWISE data

Shu

Koposov

Evans

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present two catalogues of active galactic nucleus (AGN) candidates selected from the latest data of two all-sky surveys -Data Release 2 (DR2) of the Gaia mission and the unWISE catalogue of the Wide-field Infrared Survey Explorer (WISE ). We train a random forest classifier to predict the probability of each source in the Gaia-unWISE joint sample being an AGN, P RF , based on Gaia astrometric and photometric measurements and unWISE photometry. The two catalogues, which we designate C75 and R85, are constructed by applying different P RF threshold cuts to achieve an overall completeness of 75% (≈90% at Gaia G ≤ 20 mag) and reliability of 85% respectively. The C75 (R85) catalogue contains 2, 734,464 (2,182,193) AGN candidates across the effective 36,000 deg 2 sky, of which ≈0.91 (0.52) million are new discoveries. Photometric redshifts of the AGN candidates are derived by a random forest regressor using Gaia and WISE magnitudes and colours. The estimated overall photometric redshift accuracy is 0.11. Cross-matching the AGN candidates with a sample of known bright cluster galaxies, we identify a high-probability strongly-lensed AGN candidate system, SDSS J1326+4806, with a large image separation of 21. 06. All the AGN candidates in our catalogues will have ∼5-year long light curves from Gaia by the end of the mission, and thus will be a great resource for AGN variability studies. Our AGN catalogues will also be helpful in AGN target selections for future spectroscopic surveys, especially ones in the southern hemisphere. The C75 catalogue can be downloaded at https://www.ast.cam.ac.uk/~ypshu/AGN_Catalogues.html

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“…Intermediate luminosity optical transients (ILOTs) are exotic outbursts with luminosities which fall between those of novae and supernovae (SN). Many new ILOTs are being discovered by modern surveys and dedicated campaigns (e.g., [1,[7][8][9][10][11][12][28][29][30][36][37][38][39][40][41][42][43][43][44][45][46][47][48][49]51,52,57,58,64,66,70,73]. The group consists of many different astronomical eruptions which are diverse, but are found to have shared properties [32,33,59].…”

Section: Introductionmentioning

confidence: 99%

“…Differently from V838 Mon which is much more energetic, the mass of the destructed planet is too low to cause the YSO to have an inflated envelope, and hence the merger remnant stays hot, and therefore does not redden as the LRNe.In addition to [32] further suggested that another transient, , may also be a related object. The variable low-mass star ASASSN-13db was identified by the All Sky Automated Survey for SuperNovae (ASAS-SN; e.g., [30]), after brightening in the visual by ≈ 4 mag in September 2013 ([27,50,55]). The outburst occurred in an M5 young star surrounded with a proto-planetary disk.…”

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confidence: 99%

ASASSN-13db 2014–2017 Eruption as an Intermediate Luminosity Optical Transient

2019

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The low mass star ASASSN-13db experienced an EXor outburst in 2013, which identified it as a Young Stellar Object (YSO). Then, from 2014 to 2017 it had another outburst, longer and more luminous than the earlier. We analyze the observations of the second outburst, and compare it to eruptions of Intermediate Luminosity Optical Transients (ILOTs). We show that the decline of the light curve is almost identical to that of the V838 Mon, a prototype of a type of ILOT known as Luminous Red Nova (LRN). This similarity becomes conspicuous when oscillations that are associated with rotation are filtered out from the light curve of ASASSN-13db. We suggest that the eruption was the result of accretion of a proto-planet of a few Earth masses. The proto-planet was shredded by tidal forces before it was accreted onto the YSO, releasing gravitational energy that powered the outburst for ≈ 800 days, and ended in a ≈ 55 days decline phase. When the accretion material started depleting the accretion rate lowered and the eruption light curve declined for almost two months. Then it exhausted completely, creating a sharp break in the light curve. Another possibility is that the mass was a result of an instability in the proto-planetary disk that lead to a large episode of accretion from an inner viscous disk. We find that the variation of the temperature of the outburst is consistent with the surface temperature expected from a depleted viscous accretion disk. The 2014-2017 outburst of ASASSN-13db may be the least energetic ILOT to have been discovered to date, with an energy budget of only ≈ 10 42 erg.Galaxies 2020, xx, 5 2 of 16The Energy-Time Diagram (ETD; [33], [32]) is used for classifying transients in terms of their characteristic time of decline and their total energy (The ETD webpage: phsites.technion.ac.il/soker/ilotclub/.). In the ETD many of the transients form a slated stripe more energetic, for a given time scale, than novae yet less energetic than SNe. We refer to this stripe as the Optical Transient Stripe. In [33] it was suggested that most objects that populate the stripe share a similar powering mechanism, that they suggest to be accretion energy. The different time scale are related to the accretion rate or the mass supply rate, that in some cases can be limited by the time it takes to dissipate the angular momentum of the accreted mass through viscosity.One well studied transient is the 2002 outburst of V838 Mon [11]. It is considered a prototype of a sub-type of ILOTs, known as Luminous Red Novae (LRN). Both classical nova and He-shell flash were suggested as explanations for the unusual eruption, but later ruled out [67]. The star involved in the V838 Mon eruption was a massive star, possibly even on the main-sequence (MS). Perhaps the most unusual observation was that as time passed V838 Mon became redder [16,63], which is exactly opposite to the evolution of classical novae.A model for the eruption of V838 Mon that involves a stellar merger event followed by an accretion process, in which the surviving star a...

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The ASAS-SN Catalog of Variable Stars II: Uniform Classification of 412,000 Known Variables

Cited by 162 publications

References 62 publications

A Catalog of M-dwarf Flares with ASAS-SN

A Catalog of M-dwarf Flares with ASAS-SN

Catalogues of active galactic nuclei from Gaia and unWISE data

ASASSN-13db 2014–2017 Eruption as an Intermediate Luminosity Optical Transient

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