Skynet Algorithm for Single-dish Radio Mapping. I. Contaminant-cleaning, Mapping, and Photometering Small-scale Structures

Martin, J. R.; Reichart, D.; Dutton, D. A.; Maples, M.; Berger, Travis A.; Ghigo, F. D.; Haislip, J.; Shaban, O. H.; Trotter, A.; Barnes, LukeA .; Paggen, M. L.; Gao, R. L.; Salemi, C.; Langston, G. I.; Bussa, Srikanth; Duncan, James; White, S.; Heatherly, Sue Ann; Joseph, Karlik,; Johnson, Ellen M.; Reichart, J. E.; Foster, Antonina; Kouprianov, V. V.; Mazlin, S.; Harvey, J. A.

doi:10.3847/1538-4365/aad7c1

Cited by 7 publications

(4 citation statements)

References 115 publications

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“…J234402 was monitored with the 0.4m PROMPT6 telescope, operated as part of Skynet (an introduction to this network is provided in Martin et al 2019), using Johnson B and R filters. These observations provided nine additional epochs to the light curve.…”

Section: New Optical Follow-upmentioning

confidence: 99%

Discovery of the luminous X-ray ignition eRASSt J234402.9−352640

Homan¹,

Krumpe²,

A.³

et al. 2023

A&A

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In November 2020, a new, bright object, eRASSt J234402.9−352640, was discovered in the second all-sky survey of SRG/eROSITA. The object brightened by a factor of at least 150 in 0.2–2.0 keV flux compared to an upper limit found six months previous, reaching an observed peak of 1.76−0.24+0.03 × 10−11 erg cm−2 s−1. The X-ray ignition is associated with a galaxy at z = 0.10, making the peak luminosity log10(L0.2−2 keV/[erg s−1]) = 44.7 ± 0.1. Around the time of the rise in X-ray flux, the nucleus of the galaxy brightened by approximately 3 mag. in optical photometry, after correcting for the host contribution. We present X-ray follow-up data from Swift, XMM-Newton, and NICER, which reveal a very soft spectrum as well as strong 0.2–2.0 keV flux variability on multiple timescales. Optical spectra taken in the weeks after the ignition event show a blue continuum with broad, asymmetric Balmer emission lines, and high-ionisation ([OIII]λλ4959,5007) and low-ionisation ([NII]λ6585, [SII]λλ6716,6731) narrow emission lines. Following the peak in the optical light curve, the X-ray, UV, and optical photometry all show a rapid decline. The X-ray light curve shows a decrease in luminosity of ∼0.45 over 33 days and the UV shows a drop of ∼0.35 over the same period. eRASSt J234402.9−352640 also shows a brightening in the mid-infrared, likely powered by a dust echo of the luminous ignition. We find no evidence in Fermi-LAT γ-ray data for jet-like emission. The event displays characteristics of a tidal disruption event (TDE) as well as of an active galactic nucleus (AGN), complicating the classification of this transient. Based on the softness of the X-ray spectrum, the presence of high-ionisation optical emission lines, and the likely infrared echo, we find that a TDE within a turned-off AGN best matches our observations.

show abstract

Section: New Optical Follow-upmentioning

confidence: 99%

Discovery of the luminous X-ray ignition eRASSt J234402.9−352640

Homan¹,

Krumpe²,

A.³

et al. 2023

A&A

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show abstract

“…We conducted multiband photometric observations of EX Lupi with an FLI camera on the Prompt6 telescope at Cerro Tololo Inter-American Observatory (CTIO), Chile. The telescope operates under the Skynet Robotic Telescope Network (Martin et al 2019). Prompt6 is a 0.4 m aperture telescope with a field of view of 15.1 15.1 ¢ ´¢ .…”

Section: Cerro Tololo Inter-american Observatorymentioning

confidence: 99%

Accretion Funnel Reconfiguration during an Outburst in a Young Stellar Object: EX Lupi

Singh,

Ninan,

Romanova

et al. 2024

ApJ

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EX Lupi, a low-mass young stellar object, went into an accretion-driven outburst in 2022 March. The outburst caused a sudden phase change of ∼112° ± 5° in periodically oscillating multiband lightcurves. Our high-resolution spectra obtained with the High Resolution Spectrograph (HRS) on board the Southern African Large Telescope also revealed a consistent phase change in the periodically varying radial velocities (RVs), along with an increase in the RV amplitude of various emission lines. The phase change and increase in RV amplitude morphologically translates to a change in the azimuthal and latitudinal location of the accretion hotspot over the stellar surface, which indicates a reconfiguration of the accretion funnel geometry. Our three-dimensional magnetohydrodynamic simulations reproduce the phase change for EX Lupi. To explain the observations, we explored the possibility of forward shifting of the dipolar accretion funnel as well as the possibility of the emergence of a new accretion funnel. During the outburst, we also found evidence of the hotspot’s morphology extending azimuthally asymmetrically with a leading hot edge and cold tail along the stellar rotation. Further, our high-cadence photometry showed that the accretion flow has clumps. We also detected possible clumpy accretion events in the HRS spectra that showed episodically highly blueshifted wings in the Ca ii IR triplet and Balmer H lines.

show abstract

“…J234402 was monitored with the 0.4m PROMPT6 telescope, operated as part of Skynet (an introduction to this network is provided in Martin et al 2019), using Johnson B and R filters.…”

Section: New Optical Follow-upmentioning

confidence: 99%

Discovery of the luminous X-ray ignition eRASSt J234402.9$-$352640; I. Tidal disruption event or a rapid increase in accretion in an active galactic nucleus?

Homan¹,

Krumpe²,

A.³

et al. 2023

Preprint

View full text Add to dashboard Cite

In November 2020, a new, bright object, eRASSt J234402.9−352640, was discovered in the second all-sky survey of SRG/eROSITA. The object brightened by a factor of at least 150 in 0.2-2.0 keV flux compared to an upper limit found six months previous, reaching an observed peak of 1.76 +0.03 −0.24 × 10 −11 erg cm −2 s −1 . The X-ray ignition is associated with a galaxy at z = 0.10, making the peak luminosity log 10 (L 0.2−2keV /[erg s −1 ])=44.7 ± 0.1. Around the time of the rise in X-ray flux, the nucleus of the galaxy brightened by approximately 3 mag. in optical photometry, after correcting for the host contribution. We present X-ray follow-up data from Swift, XMM-Newton, and NICER, which reveal a very soft spectrum as well as strong 0.2-2.0 keV flux variability on multiple timescales. Optical spectra taken in the weeks after the ignition event show a blue continuum with broad, asymmetric Balmer emission lines, and high-ionisation ([OIII]λλ4959,5007) and low-ionisation ([NII]λ6585, [SII]λλ6716,6731) narrow emission lines. Following the peak in the optical light curve, the X-ray, UV, and optical photometry all show a rapid decline. The X-ray light curve shows a decrease in luminosity of ∼0.45 over 33 days and the UV shows a drop of ∼0.35 over the same period. eRASSt J234402.9−352640 also shows a brightening in the mid-infrared, likely powered by a dust echo of the luminous ignition. We find no evidence in Fermi-LAT γ-ray data for jet-like emission. The event displays characteristics of a tidal disruption event (TDE) as well as of an active galactic nucleus (AGN), complicating the classification of this transient. Based on the softness of the X-ray spectrum, the presence of high-ionisation optical emission lines, and the likely infrared echo, we find that a TDE within a turned-off AGN best matches our observations.

show abstract

Skynet Algorithm for Single-dish Radio Mapping. I. Contaminant-cleaning, Mapping, and Photometering Small-scale Structures

Cited by 7 publications

References 115 publications

Discovery of the luminous X-ray ignition eRASSt J234402.9−352640

Discovery of the luminous X-ray ignition eRASSt J234402.9−352640

Accretion Funnel Reconfiguration during an Outburst in a Young Stellar Object: EX Lupi

Discovery of the luminous X-ray ignition eRASSt J234402.9$-$352640; I. Tidal disruption event or a rapid increase in accretion in an active galactic nucleus?

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