Herbig Ae/Be stars towards the dark cloud LDN 1667

TL;DR

This study reports the discovery and characterization of a new Herbig Ae/Be star, SPH4-South, in the dark cloud LDN 1667, using spectroscopy, photometry, and color analysis, and discusses its possible membership in the cloud.

Contribution

It introduces the identification of SPH4-South as a Herbig Ae/Be star and applies multi-wavelength analysis to determine its properties and potential association with LDN 1667.

Findings

SPH4-South is classified as a Herbig Ae/Be star.

SPH4 is confirmed as a member of LDN 1667.

SPH4-South is likely associated with the nebula and possibly with LDN 1667.

Abstract

We report the discovery of a new emission-line object, named SPH4-South = (GAIA EDR3 5616553300192230272), towards the dark cloud LDN 1667. This object came to our attention after inspecting public images that show a faint diffuse nebula a few arcsec southern from SPH4, an emission-line object previously classified as a T Tauri star. We present high-resolution spectra and analyzed JHK photometry of SPH4 and SPH4-South, and new narrow-band and archival broad-band images of these objects. A comparison of the spectra of SPH4 and SPH4-South with high-resolution ones of DG Cir and R Mon, strongly suggests that SPH 4 and SPH4-South are Herbig Ae/Be stars. The classification of SPH4-South is further supported by using a k-NN algorithm to its position in H-K versus J-H color-color diagram. Both stars are detected in the four WISE bands and the WISE colors allow us to classify SPH4 as a Class I and SPH4-South as a Class II source. We also show that the faint nebula is most probably associated with SPH4-South. Using published results on LDN 1667 and the Gaia Early Data Release 3, we conclude that SPH4 is a member of LDN 1667. The case of SPH4-South is not clear because the determination of its distance and proper motion could be affected by the nebulosity around the star, although membership of SPH4-South to LDN 1667 cannot be ruled out.