MSTARPANSPEC

The team presents a panchromatic spectrum, from 1 Angstrom to 10 microns, of the planet-hosting M dwarfs LHS 3844, K2-3, LTT 1445A, and GJ 486. These data products are motivated by high-energy measurements 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 panchromatic spectra, the team uses:

• X-ray: Swift-XRT (upper limit) or XMM-Newton (upper limit)
• Unmeasured regions of X-ray and EUV: Differential emission measure (this method is described in detail in Duvvuri et al. 2021, ApJ, 913, 40)
• Ly-α: UV-UV correlations with measured emission lines (correlations from Youngblood et al. 2017, ApJ, 843, 31)
• UV: HST/COS and HST/STIS (HST Proposal 15110, HST Proposal 15704, HST Proposal 16722)
• Optical, infrared: PHOENIX models out to 5.5 microns (Husser et al. 2013, A&A, 553, 6) and a blackbody function out to 10 microns, or a BT-Settl model out to 10 microns (Allard, 2014, IAUS, 299, 271A)

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 2021, ApJ, 913, 40)

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. 

Updates

Update August 1, 2024: The team provides two new panchromatic spectra for the stars LTT 1445A and GJ 486 from 1 Angstrom to 20 microns. These are the two closest M dwarfs to host transiting rocky planets. The spectra are constructed from Chandra and XMM-Newton data in the X-ray, estimates using the differential emission measure (DEM) method in the extreme UV, HST/COS + STIS data in the NUV and FUV, a HST/STIS data to do a Ly-alpha reconstruction, and PHOENIX models in the optical to infrared. The team detects flares in the X-ray and UV for both stars; these flares are removed from the data to produce "quiescent" or "typical" panchromatic spectra. These new results are presented in Diamond-Lowe et al. 2024

MAST Portal and Astroquery

The MSTARPANSPEC data products are available in the MAST Search Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write).

• In the MAST Search Portal, set the Provenance Name filter to "MSTARPANSPEC" in an Advanced Search to find these data. The user guide for how to search and download products using the MAST Portal is available here.
• For Astroquery, the following example code demonstrates how to search for and download these products.

from astroquery.mast import Observations
# Search for all MSTARPANSPEC products
all_obs = Observations.query_criteria(provenance_name="mstarpanspec")
data_products = Observations.get_product_list(all_obs)
# Download data
Observations.download_products(data_products)

• MAST Portal

  

  A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory.

  Portal

• MAST Astroquery

  

  Search for and download MSTARPANSPEC data products programmatically in Python.

  MAST Astroquery

 Direct Download Links

The data products can also be downloaded directly using the links below: