Photometric monitoring of the young star Par 1724 in Orion

Neuhäuser, R.; Koeltzsch, A.; Raetz,; Schmidt, T. O. B.; Mugrauer, M.; Young, Neil J.; Bertoldi, F.; Roell, T.; Eisenbeiss, T.; Hohle, M. M.; Vaňko, M.; Ginski, C.; Rammo, W.; Moualla, M.; Broeg, C.

doi:10.1002/asna.200911196

Cited by 3 publications

(2 citation statements)

References 17 publications

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“…Very young stars can produce such large flares, because they rotate faster and, hence, have larger magnetic fields (e.g. Preibisch et al 1995Preibisch et al , 1998Neuhäuser et al 1998Neuhäuser et al , 2009. Furthermore, as argued by Shibata et al (2013), such spots which might be able to power such large superflares (up to 10 35 erg) would last for ∼ 10 years, which was clearly never observed for the last two millennia, but such large and long-lasting spots would have been observable (even though only through clouds and/or near the horizon and/or shortly after a volcano eruption, when sufficient dust blocks some sunlight).…”

Section: Solar Flaresmentioning

confidence: 99%

A solar super-flare as cause for the 14C variation in AD 774/5 ?

Neuhaeuser,

Hambaryan

2014

Preprint

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We present further considerations regarding the strong 14 C variation in AD 774/5. For its cause, either a solar super-flare or a short Gamma-Ray Burst were suggested. We show that all kinds of stellar or neutron star flares would be too weak for the observed energy input at Earth in AD 774/5. Even though Maehara et al. (2012) present two super-flares with ∼ 10 35 erg of presumably solar-type stars, we would like to caution: These two stars are poorly studied and may well be close binaries, and/or having a M-type dwarf companion, and/or may be much younger and/or much more magnetic than the Sun -in any such case, they might not be true solar analog stars. From the frequency of large stellar flares averaged over all stellar activity phases (maybe obtained only during grand activity maxima), one can derive (a limit of) the probability for a large solar flare at a random time of normal activity: We find the probability for one flare within 3000 years to be possibly as low as 0.3 to 0.008 considering the full 1 σ error range. Given the energy estimate in Miyake et al. ( 2012) for the AD 774/5 event, it would need to be ∼ 2000 stronger than the Carrington event as solar super-flare. If the AD 774/5 event as solar flare would be beamed (to an angle of only ∼ 24 • ), 100 times lower energy would be needed. A new AD 774/5 energy estimate by Usoskin et al. ( 2013) with a different carbon cycle model, yielding 4 or 6 time lower 14 C production, predicts 4-6 times less energy. If both reductions are applied, the AD 774/5 event would need to be only ∼ 4 times stronger than the Carrington event in 1859 (if both had similar spectra). However, neither 14 C nor 10 Be peaks were found around AD 1859. Hence, the AD 774/5 event (as solar flare) either was not beamed that strongly, and/or it would have been much more than 4-6 times stronger than Carrington, and/or the lower energy estimate (Usoskin et al. 2013) is not correct, and/or such solar flares cannot form (enough) 14 C and 10 Be. The 1956 solar energetic particle event was followed by a small decrease in directly observed cosmic rays. We conclude that large solar super-flares remain very unlikely as the cause for the 14 C increase in AD 774/5.

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Section: Solar Flaresmentioning

confidence: 99%

A solar super-flare as cause for the 14C variation in AD 774/5 ?

Neuhaeuser,

Hambaryan

2014

Preprint

View full text Add to dashboard Cite

show abstract

“…Very young stars can produce such large flares, because they rotate faster and, hence, have larger magnetic fields (e.g. Preibisch et al 1995Preibisch et al , 1998Neuhäuser et al 1998Neuhäuser et al , 2009. Furthermore, as argued by Shibata et al (2013), such spots which might be able to power such large super-flares (up to 10 35 erg) would last for ∼ 10 years, which was clearly never observed for the last two millennia, but such large and long-lasting spots would have been observable (even though only through clouds and/or near the horizon and/or shortly after a volcano eruption, when sufficient dust blocks some sunlight).…”

Section: Solar Flaresmentioning

confidence: 99%

A solar super‐flare as cause for the ¹⁴C variation in AD 774/5?

Neuhäuser

Hambaryan

2014

Astron Nachr

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We present further considerations regarding the strong 14C variation in AD 774/5. For its cause, either a solar super‐flare or a short gamma‐ray burst were suggested. We show that all kinds of stellar or neutron star flares would be too weak for the observed energy input at Earth in AD 774/5. Even though Maehara et al. (2012) present two super‐flares with ∼1035 erg of presumably solar‐type stars, we would like to caution: These two stars are poorly studied and may well be close binaries, and/or having a M‐type dwarf companion, and/or may be much younger and/or much more magnetic than the Sun – in any such case, they might not be true solar analog stars. From the frequency of large stellar flares averaged over all stellar activity phases (maybe obtained only during grand activity maxima), one can derive (a limit of) the probability for a large solar flare at a random time of normal activity: We find the probability for one flare within 3000 years to be possibly as low as 0.3 to 0.008 considering the full 1σ error range. Given the energy estimate in Miyake et al. (2012) for the AD 774/5 event, it would need to be ∼2000 stronger than the Carrington event as solar super‐flare. If the AD 774/5 event as solar flare would be beamed (to an angle of only ∼24°), 100 times lower energy would be needed. A new AD 774/5 energy estimate by Usoskin et al. (2013) with a different carbon cycle model, yielding 4 ot 6 time lower 14C production, predicts 4–6 times less energy. If both reductions are applied, the AD 774/5 event would need to be only ∼4 times stronger than the Carrington event in 1859 (if both had similar spectra). However, neither 14C nor 10Be peaks were found around AD 1859. Hence, the AD 774/5 event (as solar flare) either was not beamed that strongly, and/or it would have been much more than 4‐6 times stronger than Carrington, and/or the lower energy estimate (Usoskin et al. 2013) is not correct, and/or such solar flares cannot form (enough) 14C and 10Be. The 1956 solar energetic particle event was followed by a small decrease in directly observed cosmic rays. We conclude that large solar super‐flares remain very unlikely as the cause for the 14C increase in AD 774/5. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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