## Mission Overview

### Panchromatic Spectra Of LHS 3844 and K2-3 ("MSTARPANSPEC")

Primary Investigator: Hannah Diamond-Lowe

HLSP Authors: Hannah Diamond-Lowe

Released: 2021-05-27

Updated: 2022-08-01

Primary Reference(s): Diamond-Lowe et al. 2021, Diamond-Lowe et al. 2022

## Overview

The team presents a panchromatic spectrum, from 1 Angstrom to 10 microns, of the planet-hosting M dwarfs LHS 3844 and K2-3. These data products are motivated by high-energy measurements of LHS 3844 and K2-3 in the ultraviolet with the Cosmic Origins Spectrograph on board the Hubble Space Telescope (HST/COS), and an upper limit on the X-ray flux from Swift's X-ray Telescope (Swift-XRT) and XMM-Newton. The HST/COS data cover the far and near ultraviolet (FUV and NUV) with the G130M, G160M, and G230L gratings. Due to the large aperture of COS the prominent Lyman-α 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 we use either a PHOENIX model plus a blackbody curve or a BT-Settl model to fill out the spectrum.

To summarize, in constructing the LHS 3844 and K2-3 panchromatic spectra, the team uses:

In the case of LHS 3844, the team observed a flare with COS G130M. 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 K2-3, and vice versa.

## Data Products

The HST spectra have the following file naming convention:

hlsp_mstarpanspec_hst_cos_<target>_<filter>_v01_component-<sedtype>.fits

where:

• <target> = One of "lhs3844" or "k2-3".
• <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_<target>_broadband_v01_<sedtype>.fits

where:

• <target> = One of "lhs3844" or "k2-3".
• <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 (for LHS 3844 only). _component-sed-quiescent.fits HST quiescent spectrum for G130M with the flare removed (for LHS 3844 only). _adapt-const-res-sed-{flare,quiescent}.fits Variable resolution to preserve the native COS resolution. For LHS 3844, includes flare and quiescent cases. _adapt-var-res-sed-{flare,quiescent}.fits Variable resolution with adaptive binning (conserves overall flux but removes negative flux values). For LHS 3844, includes flare and quiescent cases. _const-res-sed-{flare,quiescent}.fits Constant resolution binned to 1 Angstrom. For LHS 3844, includes flare and quiescent cases. _var-res-sed-{flare,quiescent}.fits Constant resolution binned to 1 Angstrom with adaptive binning. For LHS 3844, includes flare or quiescent cases.

## 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.