The intermediate-mass star-forming region Lynds 1340. An optical view

TL;DR

This study provides a comprehensive optical analysis of Lynds 1340, revealing its structure, stellar content, and properties of young stellar objects, including new low-mass pre-main sequence stars and their accretion characteristics.

Contribution

It offers the first detailed optical spectroscopic and photometric survey of Lynds 1340, identifying new young stellar objects and refining the cloud's distance and structure.

Findings

Identified 75 candidate low-mass pre-main sequence stars, 58 of which are new.

Revised the distance to Lynds 1340 to approximately 825 parsecs.

Discovered the most massive star in L1340 is a B4 type, about 5 solar masses.

Abstract

We have performed an optical spectroscopic and photometric search for young stellar objects associated with the molecular cloud Lynds 1340, and examined the structure of the cloud by constructing an extinction map, based on SDSS data. The new extinction map suggests a shallow, strongly fragmented cloud, having a mass of some 3700~Msun. Longslit spectroscopic observations of the brightest stars over the area of L1340 revealed that the most massive star associated with L1340 is a B4 type, about 5 solar mass star. The new spectroscopic and photometric data of the intermediate mass members led to a revised distance of 825 (+110 /-80) pc, and revealed seven members of the young stellar population with M > 2 solar masses. Our search for H alpha emission line stars, conducted with the Wide Field Grism Spectrograph 2 on the 2.2-meter telescope of the University of Hawaii and covering a 30 arcmin x 40 arcmin area, resulted in the detection of 75 candidate low-mass pre-main sequence stars, 58 of which are new. We constructed spectral energy distributions of our target stars, based on SDSS, 2MASS, Spitzer, and WISE photometric data, derived their spectral types, extinctions, and luminosities from BVRIJ fluxes, estimated masses by means of pre-main sequence evolutionary models, and examined the disk properties utilizing the 2-24 micron interval of the spectral energy distribution. We measured the equivalent width of the H alpha lines and derived accretion rates. The optically selected sample of pre-main sequence stars has a median effective temperature of 3970 K, stellar mass 0.7 Msun, and accretion rate of 7.6 10^{-9} Msun/yr.