Related papers: X-ray response to disk evolution in two gamma-Cas …
We report the detection of both soft and hard excess X-ray emission in the cluster of galaxies A 2199, based upon spatially resolved spectroscopy with data from the BeppoSAX, EUVE and ROSAT missions. The excess emission is visible at radii…
We present deep Halpha images of three nearby late-type spiral galaxies (NGC628, NGC1058 and NGC6946), which reveal the presence of HII regions out to, and beyond, two optical radii (defined by the 25th B-band isophote). The outermost HII…
We have observed variations in the optical emission lines from the X-ray binary Circinus X-1. These variations may be attributed both to orbital variations and to long term secular changes in line strength. We have detected double-peaked…
We report on the results of a three-year program of coordinated X-ray and optical monitoring of the narrow-line Seyfert 1 galaxy NGC 4051. The rapid continuum variations observed in the X-ray spectra are not detected in the optical,…
We present XMM-Newton, NuSTAR, Swift and Hubble Space Telescope observations of the Narrow-line Seyfert 1 galaxy Mrk 335 in a protracted low state in 2018 and 2019. The X-ray flux is at the lowest level so far observed, and the extremely…
We present spectroscopic observations of two halo M subdwarfs which have H alpha emission lines. We show that in both cases close companions are the most likely cause of the chromospheric activity in these old, metal-poor stars. We argue…
We made mid-infrared observations of the 10Msun Herbig Be star HD200775 with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2m Subaru Telescope. We discovered diffuse emission of an elliptical shape extended in the…
Recent NuSTAR and XMM-Newton observations of the molecular cloud around the Arches stellar cluster demonstrate a dramatic change both in morphology and intensity of its non-thermal X-ray emission, similar to that observed in many molecular…
The Halpha and optical broadband images of 25 nearby Wolf-Rayet (WR) galaxies are presented. The WR galaxies are known to have the presence of a recent ($\le$10 Myr) and massive star formation episode. The photometric Halpha fluxes are…
Interferometric observations of two well-known Be stars, gamma Cas and phi Per, were collected and analyzed to determine the spatial characteristics of their circumstellar regions. The observations were obtained using the Navy Prototype…
GSN 069 is an optically identified very low-mass AGN which shows supersoft X-ray emission. The source is known to exhibit huge X-ray outburst, with flux increased by more than a factor of ~240 compared to the quiescence state. We report its…
We report on the coronal activity cycles of our stellar neighbors alpha Centauri A/B. The binary has been monitored with XMM-Newton since 2002 to study the long-term evolution of coronal activity evolution in X-rays. The solar analog alpha…
We present the analysis of Halpha3, an Halpha imaging survey of galaxies selected from the HI ALFALFA Survey in the Coma Supercluster. By using the Halpha line as a tracer of the "instantaneous" star formation, complemented with optical…
Halpha+[NII] imaging observations of 369 late-type galaxies in the Virgo cluster and in the Coma/A1367 supercluster are analyzed. They constitute an optically selected sample (m_p<16.0) observed with 60% c.a. completeness.These observations…
The solar disk is among the brightest gamma-ray sources in the sky. It is also among the most mysterious. No existing model fully explains the luminosity, spectrum, time variability, and morphology of its emission. We perform the first…
We make a search for Halpha emitting galaxies at z=0.24 in the Subaru Deep Field (SDF) using the archival data set obtained with the Subaru Telescope. We carefully select Halpha emitters in the narrowband filter NB816, using B, V, Rc, i',…
Neutral hydrogen represents the major observable baryonic constituent of galaxies that fuels the formation of stars through the transformation in molecular hydrogen. The emission of the hydrogen recombination line Halpha is the most direct…
We report results of a nine-year monitoring effort on the unusual classical Be with a robotic ground-based (APT) B,V-filtered telescope as well as simultaneous observations in 2004 November with this instrument and the RXTE (X-ray)…
gamma Cas has long been famous for its unique hard X-ray characteristics. We report herein on a 53 ks Chandra HETGS observation of this target. An inspection of our spectrum shows that it is quite atypical for a massive star, with…
From H alpha images of a carefully selected sample of 57 relatively large, Northern spiral galaxies with low inclination, we study the distribution of the H alpha emission in the circumnuclear and nuclear regions. At a resolution of around…