Rotationally Driven Ultraviolet Emission of Red Giant Stars

Abstract

Main sequence stars exhibit a clear rotation-activity relationship, in which rapidly rotating stars drive strong chromospheric/coronal ultraviolet and X-ray emission. While the vast majority of red giant stars are inactive, a few percent exhibit strong ultraviolet emission. Here we use a sample of 133 red giant stars observed by SDSS APOGEE and GALEX to demonstrate an empirical relationship between NUV excess and rotational velocity (vsini). Beyond this simple relationship, we find that NUV excess also correlates with rotation period and with Rossby number in a manner that shares broadly similar trends to those found in M dwarfs, including activity saturation among rapid rotators. Our data also suggest that the most extremely rapidly rotating giants may exhibit so-called "super-saturation", which could be caused by centrifugal stripping of these stars rotating at a high fraction of breakup speed. As an example application of our empirical rotation-activity relation, we demonstrate that the NUV emission observed from a recently reported system comprising a red giant with a black hole companion is fully consistent with arising from the rapidly rotating red giant in that system. Most fundamentally, our findings suggest a common origin of chromospheric activity in rotation and convection for cool stars from main sequence to red giant stages of evolution.

arXiv comment14 pages, accepted for publication in AAS journals

References in corpus (30)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• ASPCAP: The Apogee Stellar Parameter and Chemical Abundances Pipeline
• Galactic Reddening in 3D from Stellar Photometry - An Improved Map
• The Data Reduction Pipeline for the Apache Point Observatory Galactic Evolution Experiment
• Empirical extinction coefficients for the GALEX, SDSS, 2MASS and WISE passbands
• Testing a Predictive Theoretical Model for the Mass Loss Rates of Cool Stars
• The Second APOKASC Catalog: The Empirical Approach
• APOGEE Data Releases 13 and 14: Data and Analysis
• Discovery of a Candidate Black Hole - Giant Star Binary System in the Galactic Field
• A giant planet undergoing extreme ultraviolet irradiation by its hot massive-star host
• Calibrations of Atmospheric Parameters Obtained from the First Year of SDSS-III APOGEE Observations
• Stellar Multiplicity Meets Stellar Evolution And Metallicity: The APOGEE View
• Close Binary Companions to APOGEE DR16 Stars: 20,000 Binary-star Systems Across the Color-Magnitude Diagram
• A path towards understanding the rotation-activity relation of M dwarfs with K2 mission, X-ray and UV data
• Surface rotation of Kepler red giant stars
• Stellar Activity in the Broad-Band Ultraviolet
• Tidal interactions between binary stars drives lithium production in low-mass red giants
• Far-Ultraviolet Activity Levels of F, G, K, and M dwarf Exoplanet Host Stars
• Investigating coronal saturation and super-saturation in fast-rotating M-dwarf stars
• Rapid Rotation of Low-Mass Red Giants Using APOKASC: A Measure of Interaction Rates on the Post-main-sequence
• The Frequency of Rapid Rotation Among K Giant Stars
• Ultraviolet-Selected Field and Pre-Main-Sequence Stars Towards Taurus and Upper Scorpius
• XUV Radiation from A-stars: Implications for Ultra-hot Jupiters
• Empirical Bolometric Fluxes and Angular Diameters of 1.6 Million Tycho-2 Stars and Radii of 350,000 Stars with \emph{Gaia} DR1 Parallaxes
• Understanding the Limitations of Gyrochronology for Old Field Stars
• The UV Emission of Stars in LAMOST Survey I. Catalogs

Cited by in corpus (17)

• The ASAS-SN Catalog of Variable Stars IX: The Spectroscopic Properties of Galactic Variable Stars
• Stellar Rotation in the Gaia Era: Revised Open Clusters Sequences
• The White Dwarf Binary Pathways Survey VI: two close post common envelope binaries with TESS light curves
• Many Roads Lead to Lithium: Formation Pathways For Lithium-Rich Red Giants
• The White Dwarf Binary Pathways Survey -- IX. Three long period white dwarf plus subgiant binaries
• Testing the Limits of Precise Subgiant Characterization with APOGEE and Gaia: Opening a Window to Unprecedented Astrophysical Studies
• The "Giraffe": Discovery of a stripped red giant in an interacting binary with a $\sim 2M_{\odot }$ lower giant
• Revealing the Field Sub-subgiant Population Using a Catalog of Active Giant Stars and Gaia EDR3
• Spinning up the Surface: Evidence for Planetary Engulfment or Unexpected Angular Momentum Transport?
• An extremely hot white dwarf with a rapidly rotating K-type subgiant companion: UCAC2 46706450
• UVIT Open Cluster Study. X. Rich Collection of Post Mass Transfer Systems in NGC 6791
• Magnetic activity of red giants: correlation between the amplitude of solar-like oscillations and chromospheric indicators
• Lithium in Kepler Red Giants: Defining Normal and Anomalous
• Statistics of Magrathea exoplanets beyond the Main Sequence. Simulating the long-term evolution of circumbinary giant planets with TRES
• An Eclipsing Binary Comprising Two Active Red Stragglers of Identical Mass and Synchronized Rotation: A Post-Mass-Transfer System or Just Born That Way?
• Rotationally Driven Ultraviolet Emission of Red Giant Stars II. Metallicity, Activity, Binarity and Sub-subgiants
• Stellar multiplicity and stellar rotation: Insights from APOGEE