PMS and ZAMS stars associated with the dark cloud LDN 1655

TL;DR

This study characterizes stars associated with the dark cloud LDN 1655 using optical spectroscopy and infrared photometry, revealing their types, excitation sources, and estimating the cloud's distance at 1.9 kpc.

Contribution

It provides the first detailed spectroscopic and photometric analysis of stars in LDN 1655, clarifying their nature and the cloud's properties.

Findings

LDN 1655 is approximately 1.9 kpc away.

Stars include T Tauri, Herbig Ae/Be, and lithium-rich stars.

The brightest IR source is comparable to a reddened O8 star.

Abstract

We give results of a low-resolution optical spectroscopic study of the bright nebulous stars conforming the tight stellar trapezium embedded in IRAS06548-0815, of the exciting star of IRAS06547-0810, and of the stars associated with reflection nebulae (R-or N-stars) NJ065703.0-081421, NJ065714.1-081016, IRAS06548-0815 D and IRAS06548-0815 G, all objects scarcely observed and apparently pertaining to the dark cloud LDN 1655. Our results given here combined with the corresponding 2MASS near infrared photometry enables us to estimate a photometric distance to LDN1655 of 1.9 kpc and to locate the trapezium stars on the (log Lstar/Lsun, logTeff) or HR diagram in an attempt to disclose about their true nature. The spectroscopy of IRAS06548-0815 revealed two classic T Tauri, two Herbig Ae/Be stars, four weak-line T Tauri stars, and two probable lithium-rich stars. Additionally, we found that the R-star IRAS06547-0810 is excited by a single B1(V) star, that IRAS06548-0815 D is excited by a SpT. B2/B3(V) star, NJ065703.0-081421 and NJ065714.1-081016 are excited by a B3/B4(V) emission star and an A6(V) star, respectively. The brightest near infrared source of the trapezium, IRS1, has an infrared luminosity comparable to a highly reddened O8(V) star (Av of 29m). The second brightest near infrared source of the trapezium, IRAS06548-0815 C is, optically, a single classical T Tauri star of spectral type K4/K5, but is a resolved binary in the 2MASSKs band, both components being of about the same brightness.