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Thread: AD Leonis, the flare star of flare stars, has a planet maybe?

  1. #1
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    AD Leonis, the flare star of flare stars, has a planet maybe?

    https://arxiv.org/pdf/1802.06064.pdf

    AD LEONIS: RADIAL VELOCITY SIGNAL OF STELLAR ROTATION OR SPIN-ORBIT RESONANCE?
    Mikko Tuomi, Hugh R. A. Jones, John R. Barnes, Guillem Anglada-Escude, R. Paul Butler, Marcin Kiraga, Steven S. Vogt
    May 2018
    "AD Leonis is a nearby magnetically active M dwarf. We find Doppler variability with a period of 2.23 days as well as photometric signals: (1) a short period signal which is similar to the radial velocity signal albeit with considerable variability; and (2) a long term activity cycle of 4070±120 days. We examine the short-term photometric signal in the available ASAS and MOST photometry and find that the signal is not consistently present and varies considerably as a function of time. This signal undergoes a phase change of roughly 0.8 rad when considering the first and second halves of the MOST data set which are separated in median time by 3.38 days. In contrast, the Doppler signal is stable in the combined HARPS and HIRES radial velocities for over 4700 days and does not appear to vary in time in amplitude, phase, period or as a function of extracted wavelength. We consider a variety of star-spot scenarios and find it challenging to simultaneously explain the rapidly varying photometric signal and the stable radial velocity signal as being caused by starspots co-rotating on the stellar surface. This suggests that the origin of the Doppler periodicity might be the gravitational tug of a planet orbiting the star in spin-orbit resonance. For such a scenario and no spin-orbit misalignment, the measured v sin i indicates an inclination angle of 15.5±2.5 deg and a planetary companion mass of 0.237±0.047 MJup."

    A Saturn-sized planet tidally locked to a flare star's rotation, blasted by radiation? Poor baby, but.. wow!
    Do good work. —Virgil Ivan "Gus" Grissom

  2. #2
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    Imagine a spacecraft on the other side of the planet from the star during a flare. Enough light for a planet wide "x-ray" image of sorts?

  3. #3
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    Paper on the stellar eruptions of AD Leo, but without mention of its possible planet. Details on the effects of such eruptions on habitable planets.

    https://arxiv.org/abs/2003.06163

    High-resolution spectroscopy of flares and CMES on AD Leo*
    Priscilla Muheki, Eike.W.Guenther, Tom Mutabazi, Edward Jurua
    (Submitted on 13 Mar 2020)

    Flares and coronal mass ejections (CMEs) are important for the evolution of the atmospheres of planets and their potential habitability, particularly for planets orbiting M stars at a distance < 0.4 AU. Detections of CMEs on these stars have been sparse and thus previous studies have modeled their occurrence frequency by scaling up solar relations. However, since the topology and strength of the magnetic fields on M stars is different from that of the Sun, it is not obvious that this approach works well. Our aim was to study, using a large amount of high resolution spectra, flares, CMEs and their dynamics of an active M dwarf star AD Leo. The results can then be used as reference for other M dwarfs. We obtained more than 2000 high-resolution spectra (R (35000)) of the highly active M dwarf AD Leo which is viewed nearly pole on. Using this data, we studied the behaviour of the spectral lines H(alpha) , H(beta) , and HeI 5876 in detail and investigated asymmetric features that could be Doppler signatures of CMEs. We detected numerous flares. The largest one emitted 8.32E31 erg in H(beta) and 2.12E32 erg in H(alpha) . Although the spectral lines in this and other events showed a significant blue asymmetry, the velocities associated with it are far below the escape velocity. Although AD Leo shows a high level of flare activity, the number of CMEs is relatively low. It is thus not appropriate to use the same flare to CME relation for M dwarfs as for the Sun.
    Do good work. —Virgil Ivan "Gus" Grissom

  4. #4
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    Lots and lots of flares, but few coronal mass ejections from this active red dwarf.

    https://arxiv.org/abs/2003.06163

    High-resolution spectroscopy of flares and CMES on AD Leo*

    Priscilla Muheki, Eike.W.Guenther, Tom Mutabazi, Edward Jurua
    (Submitted on 13 Mar 2020 (v1), last revised 3 Apr 2020 (this version, v2))
    Flares and coronal mass ejections (CMEs) are important for the evolution of the atmospheres of planets and their potential habitability, particularly for planets orbiting M stars at a distance < 0.4 AU. Detections of CMEs on these stars have been sparse, and previous studies have therefore modelled their occurrence frequency by scaling up solar relations. However, because the topology and strength of the magnetic fields on M stars is different from that of the Sun, it is not obvious that this approach works well. We used a large number of high-resolution spectra to study flares, CMEs, and their dynamics of the active M dwarf star AD Leo. The results can then be used as reference for other M dwarfs. We obtained more than 2000 high-resolution spectra (R~35000) of the highly active M dwarf AD Leo, which is viewed nearly pole on. Using these data, we studied the behaviour of the spectral lines H-alpha , H-beta , and He-I 5876 in detail and investigated asymmetric features that might be Doppler signatures of CMEs. We detected numerous flares. The largest flare emitted 8.32 x 10^31 erg in H-beta and 2.12 x 10^32 erg in H-alpha. Although the spectral lines in this and other events showed a significant blue asymmetry, the velocities associated with it are far below the escape velocity. Although AD Leo shows a high level of flare activity, the number of CMEs is relatively low. It is thus not appropriate to use the same flare-to-CME relation for M dwarfs as for the Sun.
    Do good work. —Virgil Ivan "Gus" Grissom

  5. #5
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    AD Leonis remains an extremely active flare star.

    https://arxiv.org/abs/2005.04336
    Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with Seimei Telescope, SCAT, NICER and OISTER
    Kosuke Namekata, Hiroyuki Maehara, Ryo Sasaki, Hiroki Kawai, Yuta Notsu, Adam F. Kowalski, Joel C. Allred, Wataru Iwakiri, Yoko Tsuboi, Katsuhiro L. Murata, Masafumi Niwano, Kazuki Shiraishi, Ryo Adachi, Kota Iida, Motoki Oeda, Satoshi Honda, Miyako Tozuka, Noriyuki Katoh, Hiroki Onozato, Soshi Okamoto, Keisuke Isogai, Mariko Kimura, Naoto Kojiguchi, Yasuyuki Wakamatsu, Yusuke Tampo, Daisaku Nogami, Kazunari Shibata
    [Submitted on 9 May 2020]
    We report multi-wavelength monitoring observations of an M-dwarf flare star AD Leonis with Seimei Telescope (6150--7930 Ĺ), SCAT (Spectroscopic Chuo-university Astronomical Telescope; 3700--7500 Ĺ), NICER (Neutron Star Interior Composition Explorer; 0.2--12.0 keV), and collaborations of OISTER (Optical and Infrared Synergetic Telescopes for Education and Research) program. Twelve flares are detected in total which include ten Hα, four X-ray, and four optical-continuum flares; one of them is a superflare....
    Do good work. —Virgil Ivan "Gus" Grissom

  6. #6
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    Alas, it appears that AD Leo does NOT have a close-in planet; it was a misdetection.

    https://arxiv.org/abs/2005.09657
    Persistent starspot signals on M dwarfs: multi-wavelength Doppler observations with the Habitable-zone Planet Finder and Keck/HIRES
    Paul Robertson, Gudmundur Stefansson, Suvrath Mahadevan, Michael Endl, William D. Cochran, Corey Beard, Chad F. Bender, Scott A. Diddams, Nicholas Duong, Eric B. Ford, Connor Fredrick, Samuel Halverson, Fred Hearty, Rae Holcomb, Lydia Juan, Shubham Kanodia, Jack Lubin, Andrew J. Metcalf, Andrew Monson, Joe P. Ninan, Jonathan Palafoutas, Lawrence W. Ramsey, Arpita Roy, Christian Schwab, Ryan C. Terrien, Jason T. Wright
    [Submitted on 19 May 2020]
    Young, rapidly-rotating M dwarfs exhibit prominent starspots, which create quasiperiodic signals in their photometric and Doppler spectroscopic measurements. The periodic Doppler signals can mimic radial velocity (RV) changes expected from orbiting exoplanets. Exoplanets can be distinguished from activity-induced false positives by the chromaticity and long-term incoherence of starspot signals, but these qualities are poorly constrained for fully-convective M stars. Coherent photometric starspot signals on M dwarfs may persist for hundreds of rotations, and the wavelength dependence of starspot RV signals may not be consistent between stars due to differences in their magnetic fields and active regions. We obtained precise multi-wavelength RVs of four rapidly-rotating M dwarfs (AD Leo, G 227-22, GJ 1245B, GJ 3959) using the near-infrared (NIR) Habitable-zone Planet Finder, and the optical Keck/HIRES spectrometer. Our RVs are complemented by photometry from Kepler, TESS, and the Las Cumbres Observatory (LCO) network of telescopes. We found that all four stars exhibit large spot-induced Doppler signals at their rotation periods, and investigated the longevity and optical-to-NIR chromaticity for these signals. The phase curves remain coherent much longer than is typical for Sunlike stars. Their chromaticity varies, and one star (GJ 3959) exhibits optical and NIR RV modulation consistent in both phase and amplitude. In general, though, we find that the NIR amplitudes are lower than their optical counterparts. We conclude that starspot modulation for rapidly-rotating M stars frequently remains coherent for hundreds of stellar rotations, and gives rise to Doppler signals that, due to this coherence, may be mistaken for exoplanets.
    Do good work. —Virgil Ivan "Gus" Grissom

  7. #7
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    I was particularly sad to hear about this non-planet as I had been following papers since my childhood on AD Leonis and a possible planet there.

    http://articles.adsabs.harvard.edu/f...J.....74..224L
    Do good work. —Virgil Ivan "Gus" Grissom

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