J/ApJ/871/193 A combined Chandra & LAMOST study of stellar activity (He+, 2019)
A combined Chandra and LAMOST study of stellar activity.
He L., Wang S., Liu J., Soria R., Bai Z., Yang H., Bai Yu, Guo J.
<Astrophys. J., 871, 193 (2019)>
=2019ApJ...871..193H 2019ApJ...871..193H
ADC_Keywords: X-ray sources; Stars, ages; Stars, masses; Spectral types;
Abundances, [Fe/H]; Stars, masses; Stars, distances;
Photometry, UBV; Equivalent widths
Keywords: stars: activity ; stars: late-type ; X-rays: stars
Abstract:
We probed stellar X-ray activity over a wide range of stellar
parameters, using Chandra and Large Sky Area Multi-Object Fiber
Spectroscopic Telescope (LAMOST) data. We measured the
X-ray-to-bolometric luminosity ratio (RX=LX/Lbol) for 484
main-sequence stars and found a bimodal distribution for G and K
types. We interpret this bimodality as evidence of two subpopulations
with different coronal temperatures, which are caused by different
coronal heating rates. Using the metallicity and velocity information,
we find that both of the subpopulations are mostly located in the thin
disk. We find no trend of RX with stellar age for stars older than
∼4Gyr; there is a trough in the RX versus age distribution, with the
lowest range of RX appearing at ages around 2Gyr. We then examined
the correlation between RX and RHα (proxy of chromospheric
activity): we find that the two quantities are well correlated, as
found in many earlier studies. Finally, we selected a sample of 12
stars with X-ray flares and studied the light-curve morphology of the
flares. The variety of flare profiles and timescales observed in our
sample suggests the contribution of different processes of energy
release.
Description:
To estimate the X-ray-to-bolometric luminosity ratio (RX=LX/Lbol)
of different stellar types, we first cross-matched the Chandra
point-source catalog (Wang+ 2016, J/ApJS/224/40) and the LAMOST
database (DR4, V/153), using a radius of 3". This led to 2638 unique
Chandra sources with 3502 LAMOST spectral observations.
In order to have a reliable estimation of stellar parameters, we only
used spectra with signal-to-noise ratio (S/N) higher than 7 in the
r-band. After further exclusions of sources based on their SIMBAD
classification (see Section 2.1), we obtain 1086 unique X-ray sources
with 1479 LAMOST spectral observations (R∼1800; 3690-9100Å).
We also collected the V-band magnitude from the UCAC4 catalog (I/322).
For objects without a UCAC4 V-band magnitude, we calculated it using
the g- and r-band magnitudes from Pan-STARRS (see II/349).
Finally our sample is composed of 484 sources for which the optical
magnitude and complete stellar parameters (Teff, logg, E(B-V),
distance) can be obtained, and therefore a RX value was estimated.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 89 1084 X-ray information for the 484 stars in our sample
table2.dat 99 484 LAMOST information for the stars in our sample
table3.dat 91 484 Key results for the stars in our sample
table4.dat 42 24 Stars with Hα emission lines in our sample
table5.dat 35 12 Stars with X-ray flares in our sample
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
VIII/85 : SPECFIND V2.0 Catalog of radio continuum spectra (Vollmer+, 2009)
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
V/153 : LAMOST DR4 catalogs (Luo+, 2018)
IX/57 : The Chandra Source Catalog (CSC), Release 2.0 (Evans+, 2019)
J/AJ/111/439 : Chromospheric emission in late-type stars. (Henry+ 1996)
J/A+A/311/211 : X-ray flare of CF Tuc (=HD 5303) (Kuerster+ 1996)
J/A+A/348/897 : Ages of main-sequence stars (Lachaume+, 1999)
J/AJ/126/2048 : NStars project: the Northern Sample. I. (Gray+, 2003)
J/A+A/397/147 : Activity-rotation relationship in stars (Pizzolato+ 2003)
J/AJ/130/873 : Properties of BQS objects in SDSS DR3 area (Jester+, 2005)
J/MNRAS/367/781 : XMM observations of NGC 2547 (Jeffries+, 2006)
J/MNRAS/372/163 : Activity indices for southern stars (Jenkins+, 2006)
J/A+A/469/309 : Chromospheric activity late-type stars (Cincunegui+, 2007)
J/A+A/475/677 : X-ray emission from A-type stars (Schroeder+, 2007)
J/A+A/485/571 : Metallicities & activities southern stars (Jenkins+, 2008)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/ApJS/181/444 : X-emitting stars identified from RASS/SDSS (Agueros+,2009)
J/ApJ/725/480 : Stellar X-ray sources in the COSMOS survey (Wright+, 2010)
J/A+A/531/A8 : Activity indices & velocities, 890 stars (Jenkins+, 2011)
J/ApJ/743/48 : Stars with rotation periods & X-ray lum. (Wright+, 2011)
J/other/RAA/11.924 : Atmospheric parameters for 771 stars (Wu+, 2011)
J/A+A/551/L8 : Chromospheric activity of field stars (Pace, 2013)
J/MNRAS/431/2063 : UV/X-ray activity of M dwarfs within 10pc (Stelzer+, 2013)
J/A+A/581/A28 : Stellar X-ray flares from the 2XMM catalog (Pye+, 2015)
J/A+A/596/A76 : Hα-activity in the SARG binary survey (Sissa+, 2016)
J/ApJS/224/40 : Catalog of Chandra ACIS point like sources (Wang+, 2016)
J/ApJ/829/20 : Chandra ACIS survey in nearby galaxies. II (Wang+, 2016)
J/ApJ/849/36 : Flaring activity of M dwarfs in Kepler field (Yang+, 2017)
J/ApJ/835/61 : Chromospherically active stars in RAVE. II. (Zerjal+,2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- CXOGSG Object identifier
from Wang+ 2016, J/ApJS/224/40
18- 22 I5 --- ObsID [13/16543] Chandra observation identifier
24- 25 A2 --- Det Chandra ACIS detector
27- 34 F8.1 s Exp [128/189850] Chandra exposure time after
deadtime correction
36- 40 I5 d MJD [51439/56755] Modified Julian Date at the
beginning of observation (JD-2400000.5)
42- 46 F5.3 --- VigF [0.008/1.1] Vignetting factor
48- 48 A1 --- l_CR Limit flag on CR (1)
50- 54 F5.2 10+3ct/s CR [0.02/177]? Net count rate, 0.5-7keV
56- 59 F4.2 10+3ct/s e_CR [0.02/9.7]? Lower uncertainty in CR
60 A1 --- ueCR Uncertainty flag on e_CR (2)
63- 66 F4.2 10+3ct/s E_CR [0.04/9.7]? Upper uncertainty in CR
68- 68 A1 --- l_Flux Limit flag on Flux (1)
70- 75 F6.2 10-15mW/m2 Flux [0.01/848]? Absorbed X-ray flux, 0.5-7keV
in 10-15erg/cm2/s units
77- 81 F5.2 10-15mW/m2 e_Flux [0.01/47]? Lower uncertainty in Flux
82 A1 --- ueFlux Uncertainty flag on e_Flux (2)
85- 89 F5.2 10-15mW/m2 E_Flux [0.02/47]? Upper uncertainty in Flux
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Note (1): The source is not detected in this observation, and an upper
limit is estimated (335 occurrences).
Note (2):
: = For J105645.2-033859, J203406.5+411829, and J203802.0+423459,
the lower uncertainty in CR or flux is not well constrained.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- CXOGSG Object identifier
from Wang+ 2016, J/ApJS/224/40
19- 22 A4 --- SpT Spectral type subclass (1)
24- 27 I4 K Teff [3586/8925] Stellar effective
temperature (2)
29- 31 I3 K e_Teff [58/493] Uncertainty in Teff
33- 36 F4.2 [cm/s2] logg [1.8/5.6] log of surface gravity (2)
38- 41 F4.2 [cm/s2] e_logg [0.06/0.33] Uncertainty in logg
43- 46 F4.2 mag E(B-V) [0/1] Extinction (2)
48- 52 F5.2 [-] [Fe/H] [-1.8/0.71]? Metallicity (2)
54- 57 F4.2 [-] e_[Fe/H] [0.06/0.41]? Uncertainty in [Fe/H]
59- 63 F5.2 [-] [alpha/Fe] [-0.39/0.5]? alpha element abundance
relative to Fe (2)
65- 68 F4.2 [-] e_[alpha/Fe] [0.03/0.15]? Uncertainty in [alpha/Fe]
70- 73 I4 pc Dist [21/5604] Distance (2)
75- 78 I4 pc e_Dist [2/1399] Uncertainty in Dist
80- 84 F5.2 Gyr Age [0.36/16]? Stellar Age (3)
86- 89 F4.2 Gyr e_Age [0.12/4.3]? Uncertainty in Age
91- 94 F4.2 Msun Mass [0.85/2.71]? Stellar Mass (3)
96- 99 F4.2 Msun e_Mass [0.04/0.41]? Uncertainty in Mass
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Note (1): The subclass is from LAMOST DR1 (Luo+ 2015, V/146)
Note (2): The Teff, logg, E(B-V), [Fe/H], [alpha/Fe], and Dist are
from Xiang+ 2017MNRAS.467.1890X 2017MNRAS.467.1890X
Note (3): The Age and Mass are from Xiang+ 2017ApJS..232....2X 2017ApJS..232....2X
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- CXOGSG Object identifier
from Wang+ 2016, J/ApJS/224/40
19- 23 F5.2 mag Vmag [8.6/17.3] Extinction-corrected V-band
magnitude
25- 28 F4.2 mag e_Vmag [0.09/1] Uncertainity on Vmag
30- 34 F5.2 mag Mbol [-3.1/11] Bolometric magnitude
36- 43 F8.2 10-15mW/m2 uFlux [0.02/10072] Unabsorbed 0.3-8keV X-ray flux
in 10-15erg/cm2/s units
45- 51 F7.2 10-15mW/m2 e_uFlux [0.02/1964] Uncertainty in uFlux
53- 59 E7.1 10-7W LumX [4.5e+25/7.5e+32] 0.3-8keV X-ray luminosity
in erg/s units
61- 67 E7.1 10-7W e_LumX [4.9e+25/4.7e+32] Uncertainty in LumX
69- 73 F5.2 [-] logRx [-6.6/-1.9] log, X-ray-to-bolometric
luminosity ratio
75- 78 F4.2 [-] e_logRx [0.09/1.2] Uncertainty in logRx
80- 84 F5.2 --- HR [-1.2/1.4] Hardness ratio (4)
86- 89 F4.2 --- e_HR [0.01/2.3] Uncertainty in HR
91- 91 A1 --- r_Vmag Source of V-band magnitude (5)
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Note (4): Hardness ratio, HR=(c2-c1)/(c1+c2) where c1 and c2
represent background-subtracted counts in soft (0.3-1keV) and hard
(1-8keV) band.
Note (5): Sources as follows:
u = UCAC4 (Fourth U.S. Naval Observatory CCD Astrograph Catalogue);
Zacharias+, 2012, I/322 (456 occurrences)
p = Pan-STARRS; Chambers+, 2016, II/349 (28 occurrences).
For objects without a UCAC4 V-band magnitude, we calculated it using
the g and r magnitudes from Pan-STARRS,
following Jester+ (2005AJ....130..873);
Equation (1): V=g-0.59x(g-r)-0.01
See section 2.4 for further details.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- CXOGSG Object identifier
18- 21 F4.2 0.1nm EW [0.35/9] Equivalent Width, Hα
23- 26 F4.2 0.1nm e_EW [0.02/0.33] Uncertainty in EW
28- 31 F4.2 0.1nm EWp [1.9/9.7] Excess Hα equivalent width
over chromospheric emission
33- 37 F5.2 --- logRHa [-4/-3.2] log, Hα emission index,
LHα/Lbol
39- 42 F4.2 --- e_logRHa [0.03/0.11] Uncertainty in logRHa
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- CXOGSG Object identifier from Wang+ 2016, J/ApJS/224/40
18- 21 A4 --- SpT Spectral type subclass
23- 27 I5 --- ObsID [1663/13656] Chandra Observation identifier
30- 30 A1 --- l_dT [>]? Limit flag on dT
31- 35 I5 s dT [4000/43000] Flare duration
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 07-Apr-2020