J/AJ/160/12 J, Ks, NUV emission of 133 red giant stars (Dixon+, 2020)
Rotationally driven ultraviolet emission of red giant stars.
Dixon D., Tayar J., Stassun K.G.
<Astron. J., 160, 12 (2020)>
=2020AJ....160...12D 2020AJ....160...12D
ADC_Keywords: Stars, giant; Spectra, ultraviolet; Photometry, infrared;
Keywords: Stellar rotation; Stellar activity; Giant branch; Red giant branch;
Evolved stars; Spectroscopy; Ultraviolet photometry
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 Sloan Digital
Sky Survey APOGEE and Galaxy Evolution Explorer to demonstrate an
empirical relationship between near-UV (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 supersaturation, 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.
Description:
To identify the red giant stars used in this analysis and to measure
their rotation velocities, we rely on spectroscopic observations from
Data Release 14 (Abolfathi+, 2018ApJS..235...42A 2018ApJS..235...42A) of the APOGEE
survey. APOGEE is a part of the Sloan Digital Sky Survey IV taking
H-band spectra on the 2.5m Sloan Digital Sky Survey (SDSS) telescope
for stars across the galaxy.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 81 133 Stellar parameters used to derive the NUV excess
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
J/A+AS/139/433 : RV and vsini of evolved stars (de Medeiros+ 1999)
J/A+A/397/147 : Activity-rotation relationship in stars (Pizzolato+ 2003)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/AJ/139/1338 : UV-selected stars in Tau and Upper Sco (Findeisen+, 2010)
J/ApJ/732/39 : Rotational velocities of K giant stars (Carlberg+, 2011)
J/MNRAS/411/2099 : Fast-rotating M-dwarf stars in NGC 2547 (Jeffries+, 2011)
J/ApJ/743/48 : Stars with rotation periods & X-ray lum. (Wright+, 2011)
J/AJ/146/133 : Stellar param. from SDSS-III APOGEE DR10 (Meszaros+, 2013)
J/ApJ/807/82 : Rotational velocities of APOKASC red giants (Tayar+, 2015)
J/AJ/151/144 : ASPCAP weights for 15 APOGEE chem. elements (Garcia+, 2016)
J/MNRAS/463/1844 : M dwarfs rotation-activity relation (Stelzer+, 2016)
J/A+A/605/A111 : Surface rotation of Kepler red giant stars (Ceillier+, 2017)
J/AJ/154/94 : APOGEE-2 data from DR16 (Majewski+, 2017)
J/AJ/154/259 : Fundamental param. of Tycho-2 & TGAS stars (Stevens+, 2017)
J/A+A/612/A48 : 4 oxygen-rich evolved stars NH3 spectra (Wong+, 2018)
J/ApJS/235/16 : UV emission of stars in LAMOST. I. Catalogs (Bai+, 2018)
J/ApJS/239/32 : APOKASC-2 catalog Kepler evolved stars (Pinsonneault+, 2018)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- APOGEE APOGEE 2MASS position based identifier
20- 23 I4 --- LOC [2001/5162] APOGEE field location number
25- 31 F7.2 K Teff [3929/5186] Effective temperature
33- 36 F4.2 [cm/s2] logg [2.31/3.29] Surface gravity
38- 42 F5.2 km/s vsini [1.4/94.07] Rotational velocity
44- 48 F5.2 km/s e_vsini [0.0/33.94] Uncertainty in vsini
50- 54 F5.2 mag Jmag [7.65/12.66] 2MASS J band magnitude
56- 59 F4.2 mag e_Jmag [0.02/0.04] Uncertainty in Jmag
61- 65 F5.2 mag Ksmag [7.01/12.0] 2MASS Ks band magnitude
67- 70 F4.2 mag e_Ksmag [0.02/0.04] Uncertainty in Ksmas
72- 76 F5.2 mag NUVmag [14.3/22.51] GALEX NUV magnitude
78- 81 F4.2 mag e_NUVmag [0.0/0.51] Uncertainty in NUVmag
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 02-Oct-2020