Erratum: Effect of magnetic activity saturation in chromospheric flux-flux relationships

Martínez-Arnáiz, R.; López‐Santiago, J.; Crespo‐Chacón, I.; Montes, D.

doi:10.1111/j.1365-2966.2011.19468.x

Cited by 11 publications

(24 citation statements)

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“…Our measurements show that the Ca ii H and K flux excesses are strongly linearly correlated, consistent with previous results (see Martínez-Arnáiz et al 2011, and references therein). When comparing the Ca ii H&K with the Hα chromospheric line flux we find significantly more scatter, larger than the measurement uncertainties.…”

Section: Discussionsupporting

confidence: 80%

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HADES RV Programme with HARPS-N at TNG

Scandariato

Maldonado

Affer

et al. 2017

A&A

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Context. M dwarfs are prime targets for current and future planet search programs, particularly of those focused on the detection and characterization of rocky planets in the habitable zone. In this context, understanding their magnetic activity is important for two main reasons: it affects our ability to detect small planets, and it plays a key role in the characterization of the stellar environment.Aims. We aim to analyze observations of the Ca ii H&K and Hα lines as diagnostics of chromospheric activity for low-activity early-type M dwarfs. Methods. We analyze the time series of spectra of 71 early-type M dwarfs collected in the framework of the HADES project for planet search purposes. The HARPS-N spectra provide simultaneously the Ca ii H&K doublet and the Hα line. We develop a reduction scheme able to correct the HARPS-N spectra for instrumental and atmospheric effects, and to provide also flux-calibrated spectra in units of flux at the stellar surface. The Ca ii H&K and Hα fluxes are then compared with each other, and their time variability is analyzed. Results. We find that the Ca ii H and K flux excesses are strongly correlated with each other, while the Hα flux excess is generally less correlated with the Ca ii H&K doublet. We also find that Hα emission does not increase monotonically with the Ca ii H&K line flux, showing some absorption before being filled in by chromospheric emission when Ca ii H&K activity increases. Analyzing the time variability of the emission fluxes, we derive a tentative estimate of the rotation period (of the order of a few tens of days) for some of the program stars, and the typical lifetime of chromospheric active regions (of the order of a few stellar rotations). Conclusions. Our results are in good agreement with similar previous studies. In particular, we find evidence that the chromospheres of early-type M dwarfs could be characterized by different filaments coverage, affecting the formation mechanism of the Hα line. We also show that chromospheric structure is likely related to spectral type.

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Section: Discussionsupporting

confidence: 80%

“…which is consistent within 3σ with similar previous studies performed on samples of M dwarfs (Martínez-Arnáiz et al 2011;Stelzer et al 2012). From Eq.…”

Section: Ca II H Vs Ca Ii Ksupporting

confidence: 82%

HADES RV Programme with HARPS-N at TNG

Scandariato

Maldonado

Affer

et al. 2017

A&A

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“…5 and in Table 3 the results from the least squares bisector regression, a method that is adequate in cases where the intrinsic scatter in the data dominates over the measurement errors and that treats the X and Y variables symmetrically. The same technique was used by MA11 and Martínez- Arnáiz et al (2011b), making the results directly comparable. Our power-law slope of F Ca K vs. F Ca H agrees well with that derived by Martínez-Arnáiz et al (2011b), while that of F Hα vs. F Ca K and of F x vs. F Hα are slightly different from the results of Martínez-Arnáiz et al (2011b) considering the 1 σ uncertainties.…”

Section: Flux-flux Relationsmentioning

confidence: 99%

“…The same technique was used by MA11 and Martínez- Arnáiz et al (2011b), making the results directly comparable. Our power-law slope of F Ca K vs. F Ca H agrees well with that derived by Martínez-Arnáiz et al (2011b), while that of F Hα vs. F Ca K and of F x vs. F Hα are slightly different from the results of Martínez-Arnáiz et al (2011b) considering the 1 σ uncertainties. DENIS 1048-3956 is shown as a green triangle in all plots and is not included in the fitting process (nor are any of the other UCDs that are shown in some of the plots as described below).…”

Section: Flux-flux Relationsmentioning

confidence: 99%

“…We performed linear regression fits to this subsample of M dwarfs (dash-dotted lines in Fig. 5), which can be compared to the linear regressions derived by MA11 and corrected by Martínez-Arnáiz et al (2011b) for the whole sample of F-M dwarfs (dashed lines). In Table 3, we give the values obtained for our linear regressions, including Balmer lines that were not included in MA11 and for which data were measured but not published before.…”

Section: Flux-flux Relationsmentioning

confidence: 99%

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The ultracool dwarf DENIS-P J104814.7-395606

Stelzer

Alcalá

Biazzo

et al. 2012

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Context. Several diagnostics ranging from the radio to the X-ray band are suitable for investigating the magnetic activity of late-type stars. Empirical connections between the emission at different wavelengths place constraints on the nature and efficiency of the emission mechanism and the physical conditions in different atmospheric layers. The activity of ultracool dwarfs, at the low-mass end of the main-sequence, is poorly understood. Aims. We perform a multi-wavelength study of one of the nearest M9 dwarfs, DENIS-P J104814.7-395606 (4 pc), to examine its position within the group of magnetically active ultracool dwarfs, and, in general, advance our understanding of these objects by comparing them to early-M type dwarf stars and the Sun. Methods. We obtained an XMM-Newton observation of DENIS-P J104814.7-395606 and a broad-band spectrum from the ultraviolet to the near-infrared with X-Shooter. From this dataset, we derive the X-ray properties, stellar parameters, kinematics, and the emission-line spectrum tracing chromospheric activity. We integrate these data by compiling the activity parameters of ultracool dwarfs from the literature. Results. Our deep XMM-Newton observation provides the first X-ray detection of DENIS-P J104814.7-395606 (log L x = 25.1), as well as the first measurement of its V band brightness (V = 17.35 mag). The flux-flux relations between X-ray and chromospheric activity indicators are here for the first time extended into the regime of the ultracool dwarfs. The approximate agreement of DENIS-P J104814.7-395606 and other ultracool dwarfs with flux-flux relations for early-M dwarfs suggests that the same heating mechanisms work in the atmospheres of ultracool dwarfs, albeit weaker as judged from their lower fluxes. The observed Balmer decrements of DENIS 1048-3956 are compatible with optically thick plasma in local thermal equilibrium (LTE) at low, nearly photospheric temperature or optically thin LTE plasma at 20 000 K. Describing the decrements with case B recombination requires different emitting regions for Hα and the higher Balmer lines. The high observed Hα/Hβ flux ratio is also poorly fitted by the optically thin models. We derive a similarly high value for the Hα/Hβ ratio of vB 10 and LHS 2065 and conclude that this may be a characteristic of ultracool dwarfs. We add DENIS-P J104814.7-395606 to the list of ultracool dwarfs detected in both the radio and the X-ray band. The Benz-Güdel relation between radio and X-ray luminosity of late-type stars is well-known to be violated by ultracool dwarfs. We speculate on the presence of two types of ultracool dwarfs with distinct radio and X-ray behaviors.

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The corona – chromosphere connection studied with simultaneous eROSITA and TIGRE observations

Fuhrmeister

Czesla

Robrade

et al. 2022

A&A

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Stellar activity manifests itself in a variety of different phenomena, some of which we can measure as activity tracers from different atmospheric layers of the star, typically at different wavelengths. Stellar activity is furthermore inherently time variable, therefore simultaneous measurements are necessary to study the correlation between different activity indicators. In this study we compare X-ray fluxes measured within the first all-sky survey conducted by the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) instrument on board the Spectrum-Roentgen-Gamma observatory to Ca II H&K excess flux measurements RHK+, using observations made with the robotic TIGRE telescope. We created the largest sample of simultaneous X-ray and spectroscopic Ca II H&K observations of late-type stars obtained so far, and in addition, previous measurements of Ca II H&K for all sample stars were obtained. We find the expected correlation between our log(LX/Lbol) to log(RHK+) measurements, but when the whole stellar ensemble is considered, the correlation between coronal and chromospheric activity indicators does not improve when the simultaneously measured data are used. A more detailed analysis shows that the correlation of log(LX/Lbol) to log(RHK+) measurements of the pseudo-simultaneous data still has a high probability of being better than that of a random set of non-simultaneous measurements with a long time baseline between the observations. Cyclic variations on longer timescales are therefore far more important for the activity flux-flux relations than short-term variations in the form of rotational modulation or flares, regarding the addition of “noise” to the activity flux-flux correlations. Finally, regarding the question of predictability of necessarily space-based log (LX/Lbol) measurements by using ground-based chromospheric indices, we present a relation for estimating log (LX/Lbol) from RHK+ values and show that the expected error in the calculated minus observed (C-O) log (LX/Lbol) values is 0.35 dex.

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Erratum: Effect of magnetic activity saturation in chromospheric flux-flux relationships

Cited by 11 publications

References 1 publication

HADES RV Programme with HARPS-N at TNG

HADES RV Programme with HARPS-N at TNG

The ultracool dwarf DENIS-P J104814.7-395606

The corona – chromosphere connection studied with simultaneous eROSITA and TIGRE observations

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