Mission Overview

A Panchromatic Spectrum Of LHS 3844 ("MSTARPANSPEC")

 

Primary Investigator: Hannah Diamond-Lowe

HLSP Authors: Hannah Diamond-Lowe

Released: 2021-05-27

Updated: 2021-05-27

Primary Reference(s): Diamond-Lowe et al. 2021

DOI: 10.17909/t9-fqky-7k61

Citations: See ADS Statistics

Read Me

 
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Quiescent spectrum of LHS 3844 from 1 Angstrom to 10 microns. This spectrum includes 1) an upper limit on the soft X-ray flux from Swift-XRT, 2) a spectrum of the FUV and NUV from HST/COS, 3) an estimate of the Ly-alpha flux using UV-UV line correlations, 4) an estimate of the unmeasured high-energy portions of the spectrum using a differential emission measure, 5) a PHOENIX model, and 6) a blackbody curve.

Overview

The team presents a panchromatic spectrum, from 1 Angstrom to 10 microns, of the nearby, planet-hosting M dwarf LHS 3844. This data product is motivated by high-energy measurements of LHS 3844 in the ultraviolet with the Cosmic Origins Spectrograph on board the Hubble Space Telescope (HST/COS), and an upper limit on the soft X-ray flux from Swift's X-ray Telescope (Swift-XRT). Ten orbits of HST and 31.8ks of Swift-XRT were used to obtain these data. The HST/COS data cover the far and near ultraviolet (FUV and NUV) with the G130M, G160M, and G230L gratings. During one of the FUV (G130M) observations the team observed a flare with an absolute energy of 8.96 +/- 0.77 x 1028 erg in the FUV and an equivalent duration of 355 +/- 31 seconds. The team excises this flare from the UV spectral data and produce panchromatic spectra for both the quiescent and flare cases of the star. Due to the large aperture of COS the prominent Lyman-alpha line is obscured by geocoronal emission. The team employs the UV-UV line correlations developed by the MUSCLES program to estimate the Lyman-α flux using measured UV emission lines in the rest of the COS data. For the rest of the high-energy spectrum, which is not measured directly, the team employs a differential emission measure (DEM) to fill in the gaps. Redward of the NUV the team uses a PHOENIX model and a blackbody curve to fill out the spectrum. 

To summarize, in constructing the quiescent LHS 3844 panchromatic spectrum the team uses:

The flare spectrum is constructed in a similar manner with the following exceptions:

  • X-ray: Estimated from the quiescent soft X-ray upper limit using a multiplicative factor
  • Unmeasured regions of UV (spectral data only exists for the G130M FUV grating): Differential emission measure (Duvvuri et al, arXiv:2102.08493)

The data products presented here are designed to be similar to those provided by the MUSCLES survey, such that users of MUSCLES data can easily access the spectrum of LHS 3844 and vice versa. 

Data Products

The HST spectra have the following file naming convention:

hlsp_mstarpanspec_hst_cos_lhs3844_<filter>_v01_component-<sedtype>.fits

where:

  • <filter> = One of "g130m", "g160m", or "g230l"
  • <sedtype> = One of "-sed-flare" (g130m only), "-sed-quiescent" (g130m only), or "-sed".

The panchromatic spectra have the following file naming convention:

hlsp_mstarpanspec_multi_multi_lhs3844_broadband_v01_<sedtype>.fits

where:

  • <sedtype> = The type of panchromatic spectrum, described in the table below.

Data file types:

_component-sed.fits HST quiescent spectrum for G160M or G230L filters.
_component-sed-flare.fits HST spectral data pertaining to the flare in the G130M filter.
_component-sed-quiescent.fits HST quiescent spectrum for G130M with the flare removed.

_adapt-const-res-sed-{flare,quiescent}.fits

Variable resolution to preserve the native COS resolution, for flare or quiescent cases.

_adapt-var-res-sed-{flare,quiescent}.fits

Variable resolution with adaptive binning (conserves overall flux but removes negative flux values), for flare or quiescent cases.

_const-res-sed-{flare,quiescent}.fits

Constant resolution binned to 1 Angstrom, for flare or quiescent cases.

_var-res-sed-{flare,quiescent}.fits

Constant resolution binned to 1 Angstrom with adaptive binning, for flare or quiescent cases.

Data Access

Citations

Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work. 

Note: These HLSP data products are licensed for use under CC BY 4.0.

References