We carry out a project to independently measure the distances of supernova remnants (SNRs) in the first quadrant of the Galaxy. In this project, red clump (RC) stars are used as standard candles and extinction probes to build the optical extinction (A V ) -distance(D) relation in each direction of extinction-known SNRs. The distances of 15 SNRs are well determined. Among them, the distances of G65.8-0.5, G66.0-0.0 and G67.6+0.9 are given for the first time. We also obtain 32 upper/lower limits of distances, and the distances to G5.7-0.1, G15.1-1.6, G28.8+1.5 and G78.2+2.1 are constrained. Most of the distances measured by the RC method are consistent with previous results. The RC method provides an independent access to the distances of SNRs.

No abstract

A small cluster of massive stars residing in the Galactic center, collectively known as IRS 13E, is of special interest due to its close proximity to the central supermassive black hole Sgr A* and the possibility that an embedded intermediate-mass black hole (IMBH) binds its member stars. It has been suggested that colliding winds from two member stars, both classified as Wolf–Rayet type, are responsible for the observed X-ray, infrared, and radio emission from IRS 13E. We have conducted an in-depth study of the X-ray spatial, temporal, and spectral properties of IRS 13E, based on 5.6 Ms of ultradeep Chandra observations obtained over 20 years. These X-ray observations show no significant evidence for source variability. We have also explored the kinematics of the cluster members, using Keck near-infrared imaging and spectroscopic data on a 14 yr baseline that considerably improve the accuracy of the stars’ proper motions. The observations are interpreted using three-dimensional hydrodynamical simulations of colliding winds tailored to match the physical conditions of IRS 13E, leading us to conclude that the observed X-ray spectrum and morphology can be well explained by the colliding wind scenario, in the meantime offering no support for the presence of a putative IMBH. An IMBH more massive than a few 103 M⊙ is also strongly disfavored by the stellar kinematics.

No abstract

We take advantage of the red clump stars to build the relation of the optical extinction (A V ) and distance in each direction of supernova remnants (SNRs) with known extinction in the fourth Galactic quadrant. The distances of 9 SNRs are well determined by this method. Their uncertainties range from 10% to 30%, which is significantly improved for 8 SNRs, G279.0+1.1, G284.3-1.8, G296.1-0.5, G299.2-2.9, G308.4-1.4, G309.2-0.6, G309.8-2.6, G332.4-0.4. In addition, SNR G284.3-1.8 with the new distance of 5.5 kpc is not likely associated with the PSR J1016-5857 at 3 kpc.