DOI: 10.5281/zenodo.13884607
title: ENTROPY DR1. High-resolution near-UV/optical spectra of 2MASS J11151597+1937266

description: ENTROPY Data Release 1

Summary

The files in this data release consist of the flux-calibrated, stacked 1D spectum of the isolated, free-floating accreting planetary-mass object 2MASS J11151597+1937266 (2M1115). The data results from the high-resolution (R~50,000) observations by the Ultraviolet and Visual Echelle Spectrograph (UVES) at ESO's Very Large Telescope (VLT) in Chile, between 10-11 June 2023, taken as part of the ESO programme 0111.C-0166(A). This is the underlying data used for the analysis in the publication Viswanath et al. (2024)

Details of Observations

The observations of 2M1115 with UVES were carried out between 10-11 June 2023 (MJD 60105, 60106) as part of the ExoplaNeT accretion mOnitoring sPectroscopic surveY (ENTROPY) in #Dichroic 1 mode with both the blue (390 nm) and red (580 nm) arms using a 0.8 arcsec wide slit without AO or chopping.

A total of four frames at 740 s exposure (NDIT=1) each were obtained across the two nights, giving a total integration time of 0.82 hr at an average seeing of 1.43 arcsec and an average airmass 1.416. The total wavelength range covered by the spectrum is 320–680 nm.

Target

Identifier: 2MASS J11151597+1937266

ICRS RA (ep=2016.0): 168.816234 deg

ICRA DEC (ep=2016.0): +19.623939 deg

Distance: 45.21 +- 2.20 pc

Age: 5-45 Myr

Mass: 6(+8, -4) Mjup

Radius: 1.5 +- 0.1 Rjup

Effective Temperature: 1816 +- 63 K

Data reduction

Each of the 4 raw data frames from the original set of exposures from the 2 nights were bias subtracted and flat-field corrected using the calibration files from ESO. Inter-order background was also subtracted. Cosmic rays were accounted for by using a horizontal median filtering and masking out pixels higher than 10 times the local variance. The flux was extracted order by order using standard aperture photometry, which included the subtraction of sky background and telluric lines.

The flux was calibrated based on the observations of a standard star taken contemporaneously with the same observing setup as the target, and was corrected for the relative slit loss (~4%) from seeing. Wavelength calibration was performed using the arc lamp spectrum and a Th–Ar line list. The wavelengths listed in the spectrum are in air. A barycentric velocity correction was applied to the wavelength calibration to transform the spectral reference system to that of the source. The stacked 1D spectrum available in this data release is obtained by taking the weighted average of the 4 individual spectra, with the weights determined from the respective photon noise.

Description of files

The data release consists of:

a) 1 merged spectrum 2M1115.Merged-spectrum-UVES-2023.06.10-11.txt covering the entire UVES range of these observations (320–680 nm). The flux for the overlapping wavelengths in adjacent orders of each arm were averaged to get a single flux value per wavelength. This allows for easy access of the entire spectral range of all arms together. The ascii file has 4 columns;

Column1 : Wavelength, in ångstrøm

Column2 : Flux, in units of 1E-17 ergs/s/cm2/ångstrøm

Column3 : Flux_std, the weighted standard deviation of the flux across the 4 individual spectra, in units of 1E-17 ergs/s/cm2/ångstrøm

Column4 : Flux_err, Average of the photometric uncertainties in flux across the 4 spectra, in units of 1E-17 ergs/s/cm2/ångstrøm

b) 3 unmerged spectra of the name UVES-2023.06.10-11.2M1115.<arm>.Unmerged.1Dspec.npz, one for each UVES arm (BLUE, REDL, REDU). These are provided for the purpose of preserving the signal-to-noise ratio (S/N) of the individual orders of each arm. Some important emission lines like H𝛽 occur in both adjacent orders but at different signal strengths. Merging the orders by averaging the flux as in file (a) will suppress the S/N of such emission lines. The order numbers of the respective arms containing detected emission lines from 2M1115 can be found in Tables 2 and G.1 in Viswanath et al. (2024). Each npz files contain as many data blocks as the number of orders in the respective arm, and each data block has 4 columns with same description as in file (a). The spectra of the individual orders can be accesses from the .npz ascii files using the following python code:

 

import numpy as np
loaded_data = np.load(<path>+'/UVES-2023.06.10-11.2M1115.<arm>.Unmerged.1Dspec.npz')  # <arm> is BLUE/REDL/REDU, <path> is  the path to the folder containing these files
# To extract all orders
wave = []
flux = []
for i in np.arange(1, len(loaded_data)):
    data = loaded_data[f'array{i+1}']
    wave.append(data[:, 0])
    flux.append(data[:, 1])
    flux_err.append(data[:, 2])

# To plot the whole spectrum
import matplotlib.pyplot as plt
    for i in range(len(wave)):
        plt.plot(wave[i], flux[i])

 

c) 2M1115-Photometry.txt, an ascii file containing the exisig photometry for the target