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The Massive Star Population in M101. III. Spectra and Photometry of the Luminous and Variable Stars
Humphreys, Roberta M.; Grammer, Skyler H.; Gerke, Jill
We discuss moderate-resolution spectra, multicolor photometry, and light curves of 31 of the most luminous stars and variables in the giant spiral M101. The majority are intermediate A- to F-type supergiants. We present new photometry and light curves for three known “irregular blue variables,” V2, V4, and V9, and identify a new candidate. Their s…
Binary Astrometric Microlensing with Gaia
Sajadian, Sedighe
We investigate whether or not Gaia can specify the binary fractions of massive stellar populations in the Galactic disk through astrometric microlensing. Furthermore, we study whether or not some information about their mass distributions can be inferred via this method. In this regard, we simulate the binary astrometric microlensing events due to…
A Search for Intergalactic Globular Clusters in the Local Group
di Tullio Zinn, Graziella; Zinn, Robert
The whole Sloan Digital Sky Survey (SDSS, 14,555 {{deg }2}) has been searched for intergalactic globular clusters (IGCs) in the Local Group (LG). Using optical, infrared, and ultraviolet photometric selection criteria and photometric redshifts, the 2.1× {{10}8} objects in the SDSS Galaxy Catalog were reduced to only 183,791 b…
AGN Activity and IGM Heating in the Fossil Cluster RX J1416.4+2315
Raychaudhury, S.; Sengupta, C.; Khosroshahi, H. G. +3 more
We study active galactic nucleus (AGN) activity in the fossil galaxy cluster RX J1416.4+2315. Radio observations were carried out using the Giant Metrewave Radio Telescope at two frequencies, 1420 and 610 MHz. A weak radio lobe that extends from the central nucleus is detected in the 610 MHz map. Assuming the radio lobe originated from the central…
High Angular Resolution Multi-line Study of HH 1 and 2
Bally, J.; Raga, A. C.; Reipurth, Bo +2 more
We present new Hubble Space Telescope (HST) narrow band images of the bright Herbig-Haro (HH) objects HH 1 and 2 in the light of the Hα, Hβ, [O i] 6300, [O ii] 3726+28, [O iii] 5007 and [S ii] 6716+30 emission lines. The resulting emission and line ratio maps give an improved picture of the physical structure of these HH objects, showing the prese…
New Precision Orbits of Bright Double-Lined Spectroscopic Binaries. IX. HD 54371, HR 2692, and 16 Ursa Majoris
Williamson, Michael H.; Fekel, Francis C.; Muterspaugh, Matthew W. +3 more
With extensive sets of new radial velocities we have determined orbital elements for three previously known spectroscopic binaries, HD 54371, HR 2692, and 16 UMa. All three systems have had the lines of their secondaries detected for the first time. The orbital periods range from 16.24 to 113.23 days, and the three binaries have modestly or modera…
UrHip Proper Motion Catalog
Frouard, J.; Dorland, B. N.; Makarov, V. V. +2 more
Proper motions are computed and collected in a catalog using the Hipparcos positions (epoch 1991.25) and URAT1 positions (epoch 2012.3-2014.6). The goal is to obtain a significant improvement on the proper motion accuracy of single stars in the northern hemisphere, and to identify new astrometric binaries perturbed by orbital motion. For binaries …
A Calibration of NICMOS Camera 2 for Low Count Rates
Gladders, M. D.; Lidman, C.; Amanullah, R. +19 more
NICMOS 2 observations are crucial for constraining distances to most of the existing sample of z\gt 1 SNe Ia. Unlike conventional calibration programs, these observations involve long exposure times and low count rates. Reciprocity failure is known to exist in HgCdTe devices and a correction for this effect has already been implemented for high an…
The Three-dimensional Orbit and Physical Parameters of 47 Oph
Wang, Xiaoli; Ren, Shulin; Fu, Yanning +1 more
Although 47 Oph has been shown to be a binary with a period of ∼27 days using both spectroscopic and interferometric techniques, only a preliminary orbit has been obtained in the previous work due to the shortage of high precision measurements. Since 1997, new spectroscopic and interferometric measurements have been obtained with much higher preci…
A Starburst in the Core of a Galaxy Cluster: the Dwarf Irregular NGC 1427A in Fornax
Puzia, Thomas H.; Chanamé, Julio; Mora, Marcelo D.
Gas-rich galaxies in dense environments such as galaxy clusters and massive groups are affected by a number of possible types of interactions with the cluster environment, which make their evolution radically different than that of field galaxies. The dwarf irregular galaxy NGC 1427A, presently infalling toward the core of the Fornax galaxy cluste…