Access to Astronomical Catalogues

← Click to display the menu
J/ApJ/835/25        Calibrated solar S-index time series        (Egeland+, 2017)

The Mount Wilson Observatory S-index of the Sun. Egeland R., Soon W., Baliunas S., Hall J.C., Pevtsov A.A., Bertello L. <Astrophys. J., 835, 25-25 (2017)> =2017ApJ...835...25E (SIMBAD/NED BibCode)
ADC_Keywords: Sun Keywords: stars: activity; Sun: activity; Sun: chromosphere Abstract: The most commonly used index of stellar magnetic activity is the instrumental flux scale of singly ionized calcium H & K line core emission, S, developed by the Mount Wilson Observatory (MWO) HK Project, or the derivative index R'HK. Accurately placing the Sun on the S scale is important for comparing solar activity to that of the Sun-like stars. We present previously unpublished measurements of the reflected sunlight from the Moon using the second-generation MWO HK photometer during solar cycle 23 and determine cycle minimum S23,min=0.1634±0.0008, amplitude ΔS23=0.0143±0.0012, and mean <S23≥0.1701±0.0005. By establishing a proxy relationship with the closely related National Solar Observatory Sacramento Peak calcium K emission index, itself well correlated with the Kodaikanal Observatory plage index, we extend the MWO S time series to cover cycles 15-24 and find on average <Smin≥0.1621±0.0008, <ΔScyc≥0.0145±0.0012, <Scyc≥0.1694±0.0005. Our measurements represent an improvement over previous estimates that relied on stellar measurements or solar proxies with non-overlapping time series. We find good agreement from these results with measurements by the Solar-Stellar Spectrograph at Lowell Observatory, an independently calibrated instrument, which gives us additional confidence that we have accurately placed the Sun on the S-index flux scale. Description: The Mount Wilson HK Program observed the Moon with both the HKP-1 and HKP-2 instruments. After removing 11 obvious outliers, there are 162 HKP-1 observations taken from 1966 September 2 to 1977 June 4 with the Mount Wilson 100 inch reflector, covering the maximum of cycle 20 and the cycle 20-21 minimum. As mentioned in Baliunas+ (1995ApJ...438..269B), observations of the Moon resumed in 1993 with the HKP-2 instrument. After removing 10 obvious outliers, there are 75 HKP-2 observations taken from 1994 March 27 to 2002 November 23 with the Mount Wilson 60 inch reflector, covering the end of cycle 22 and the cycle 23 minimum, extending just past the cycle 23 maximum. The end of observations coincides with the unfortunate termination of the HK Project in 2003. We seek to extend our time series of solar variability beyond cycle 23 by establishing a proxy to the NSO Sacramento Peak (NSO/SP) observations taken from 1976 to 2016, covering cycles 21 to 24. The spectral intensity scale is set by integrating a 0.53Å band centered at 3934.869Å in the K-line wing and setting it to the fixed value of 0.162. We extend the S-index record back to cycle 20 using the composite K time series of Bertello+ (2016SoPh..291.2967B). See section 3 for further explanations. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table4.dat 37 6349 Calibrated solar S-index time series
See also: III/159 : Ca II H and K Measurements Made at MWO (Duncan+ 1991) J/ApJ/416/787 : Mount Wilson Crv Metallicity index (Soon+ 1993) J/ApJ/457/L99 : 25yr CaII-HK obs. of F-K nearby stars (Baliunas+, 1996) J/PASP/108/313 : Empirical stellar flux scales (Hall 1996) J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008) J/AJ/138/312 : Activity of bright solar analogs (Hall+, 2009) J/ApJ/812/12 : S-index and Stroemgren LC of HD30495 (Egeland+, 2015) Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 9 F9.3 d JD Julian Date; JD-2400000 11- 18 F8.6 --- OrgSK [0.08/0.2] Orignal S or K index 20- 27 F8.6 --- CalS [0.1/0.2] Calibrated S index 29- 37 A9 --- Inst Instrument used (1)
Note (1): Instrument as follows: MWO/HKP-1 = Mount Wilson Observatory (MWO) HKP-1 instrument (162 occurrences); see section 3.1. MWO/HKP-2 = Mount Wilson Observatory (MWO) HKP-2 instrument (75 occurrences) see section 3.1. NSO/SP = National Solar Observatory Sacramento Peak (4112 occurrences); see sections 3.2. and 3.3. SSS/CCD-1 = Solar-Stellar Spectrograph (SSS) at Lowell Observatory (1241 occurrences); see section 3.4. SSS/CCD-2 = Solar-Stellar Spectrograph (SSS) at Lowell Observatory (759 occurrences); see section 3.4
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Aug-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

catalogue service

© Unistra/CNRS