Dependence of coronal X-ray emission on spot-induced brightness variations in cool main sequence stars

Messina, S.; Pizzolato, Nicola; Guinan, E. F.; Rodono, M.

doi:10.1051/0004-6361:20031203

Cited by 66 publications

(71 citation statements)

References 46 publications

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“…The Rossby number is defined as the ratio of the rotation period to the convective turnover time c , i.e., Ro P rot / c . For MS stars, the theoretical expectations are well confirmed: it is well 2003) and Messina et al (2003) (open squares) and the Sun. 15 We note that the stars with known periods have systematically higher masses [Á log(M ) $ 0:06 dex, P KS (0) ¼ 0:006] than the stars without periods.…”

Section: The Activity-rotation Relation For the Ttssmentioning

confidence: 60%

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

Preibisch

Kim

Favata

et al. 2005

ASTROPHYS J SUPPL S

474

673

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The Chandra Orion Ultradeep Project (COUP) provides the most comprehensive data set ever acquired on the X-ray emission of pre-main-sequence stars. In this paper, we study the nearly 600 X-ray sources that can be reliably identified with optically well-characterized T Tauri stars (TTSs) in the Orion Nebula Cluster. With a detection limit of L X; min $ 10 27:3 ergs s À1 for lightly absorbed sources, we detect X-ray emission from more than 97% of the optically visible late-type (spectral types F-M) cluster stars. This proves that there is no ''X-ray-quiet'' population of late-type stars with suppressed magnetic activity. We use this exceptional optical, infrared, and X-ray data set to study the dependencies of the X-ray properties on other stellar parameters. All TTSs with known rotation periods lie in the saturated or supersaturated regime of the relation between activity and Rossby numbers seen for mainsequence ( MS) stars, but the TTSs show a much larger scatter in X-ray activity than that seen for the MS stars. Strong near-linear relations between X-ray luminosities, bolometric luminosities, and mass are present. We also find that the fractional X-ray luminosity L X /L bol rises slowly with mass over the 0:1 2 M range. The plasma temperatures determined from the X-ray spectra of the TTSs are much hotter than in MS stars but seem to follow a general solar-stellar correlation between plasma temperature and activity level. The scatter about the relations between X-ray activity and stellar parameters is larger than the expected effects of X-ray variability, uncertainties in the variables, and unresolved binaries. This large scatter seems to be related to the influence of accretion on the X-ray emission. While the X-ray activity of the nonaccreting TTSs is consistent with that of rapidly rotating MS stars, the accreting stars are less X-ray active (by a factor of $2-3 on average) and produce much less well-defined correlations than the nonaccretors. We discuss possible reasons for the suppression of X-ray emission by accretion and the implications of our findings on long-standing questions related to the origin of the X-ray emission from young stars, considering in particular the location of the X-ray-emitting structures and inferences for pre-main-sequence magnetic dynamos.

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Section: The Activity-rotation Relation For the Ttssmentioning

confidence: 60%

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

Preibisch

Kim

Favata

et al. 2005

ASTROPHYS J SUPPL S

474

673

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“…This is consistent with the expected dependence on rotation rate of the efficiency of magnetic field generation and intensification by an αΩ dynamo. The solid line represents the fit to the upper envelope of the light curve amplitude distribution of slowly rotating Pleiades G stars (110 Myr) taken from Messina et al (2001Messina et al ( , 2003. With the data at our disposal, we do not see any significant difference between the 110-Myr and the 230-Myr distribution upper envelopes.…”

Section: Photospheric Activitymentioning

confidence: 82%

RACE-OC project: rotation and variability in the open cluster M 11 (NGC 6705)

Messina

Parihar

Koo

et al. 2010

A&A

Self Cite

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Context. Rotation and magnetic activity are intimately linked in main-sequence stars of G or later spectral types. The presence and level of magnetic activity depend on stellar rotation, and rotation itself is strongly influenced by the strength and topology of the magnetic fields. Open clusters represent especially useful targets for investigating the connection among rotation, activity, and age. Over time, stellar activity and rotation evolve, providing us with a promising diagnostic tool to determine the age of the field stars.Aims. The open cluster M11 has been studied as a part of the RACE-OC project (Rotation and ACtivity Evolution in Open Clusters), which aims to explore the evolution of rotation and magnetic activity in the late-type members of open clusters with different ages. Methods. Photometric observations of the open cluster M 11 were carried out in June 2004 using the LOAO 1 m telescope. The rotation periods of the cluster members were determined by Fourier analysis of photometric data time series. We investigated the relations between the surface activity, characterized by the light curve amplitude, and rotation. Results. We have discovered a total of 75 periodic variables in the M 11 FoV, of which 38 are candidate cluster members. Specifically, among cluster members we discovered 6 early-type periodic variables, 2 eclipsing binaries, and 30 bona-fide single periodic late-type variables. Considering the rotation periods of 16 G-type members of the almost coeval 200-Myr M 34 cluster, we could determine the rotation period distribution from a more numerous sample of 46 single G stars at an age of about 200-230 Myr and determine a median rotation period of P = 4.8 d. Conclusions. A comparison with the younger M 35 cluster (∼150 Myr) and with the older M37 cluster (∼550 Myr) shows that G stars rotate more slowly than younger M 35 stars and more rapidly than older M 37 stars. The measured variation in the median rotation period is consistent with the scenario of rotational braking of main-sequence spotted stars as they age. Finally, G-type M11 members have a level of photospheric magnetic activity, as measured by light curve amplitude, comparable to what is observed in the younger 110-Myr Pleiades stars of similar mass and rotation.

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“…Indeed, chromospheric age estimators often use stellar activity to infer the rotation period, which is then used to infer an age (MH08). The rotation period of GJ 504 has been directly measured to be 3.328 days (Messina et al 2003) and 3.33 days (Donahue et al 1996). We adopt the average of these measurements, 3.329 days, as the star's rotation period.…”

Section: Gyrochronological Agementioning

confidence: 99%

Direct Imaging of a Cold Jovian Exoplanet in Orbit Around the Sun-Like Star Gj 504

Kuzuhara

Tamura

Kudo

et al. 2013

ApJ

222

170

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Direct Imaging of a Cold Jovian Exoplanet in Orbit around the Sun-like Star GJ 504Kuzuhara, M.; et al., [Unknown]; Thalmann, C.D. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 13 May 2018The Astrophysical Journal, 774:11 (18pp) ABSTRACT Several exoplanets have recently been imaged at wide separations of >10 AU from their parent stars. These span a limited range of ages (<50 Myr) and atmospheric properties, with temperatures of 800-1800 K and very red colors (J − H > 0.5 mag), implying thick cloud covers. Furthermore, substantial model uncertainties exist at these young ages due to the unknown initial conditions at formation, which can lead to an order of magnitude of uncertainty in the modeled planet mass. Here, we report the direct-imaging discovery of a Jovian exoplanet around the Sun-like star GJ 504, detected as part of the SEEDS survey. The system is older than all other known directly imaged planets; as a result, its estimated mass remains in the planetary regime independent of uncertainties related to choices of initial conditions in the exoplanet modeling. Using the most common exoplanet cooling model, and given the system age of 160 +350 −60 Myr, GJ 504b has an estimated mass of 4 +4.5 −1.0 Jupiter masses, among the lowest of directly imaged planets. Its projected separation of 43.5 AU exceeds the typical outer boundary of ∼30 AU predicted for the core accretion mechanism. GJ 504b is also significantly cooler (510 +30 −20 K) and has a bluer color (J − H = −0.23 mag) than previously imaged exoplanets, suggesting a largely cloud-free atmosphere accessible to spectroscopic characterization. Thus, it has the potential of providing novel insights into the origins of giant planets as well as their atmospheric properties.

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Dependence of coronal X-ray emission on spot-induced brightness variations in cool main sequence stars

Cited by 66 publications

References 46 publications

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

RACE-OC project: rotation and variability in the open cluster M 11 (NGC 6705)

Direct Imaging of a Cold Jovian Exoplanet in Orbit Around the Sun-Like Star Gj 504

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