Search Publications
A Study of Two Dwarf Irregular Galaxies with Asymmetrical Star Formation Distributions
Gouliermis, Dimitrios A.; Grebel, Eva K.; Calzetti, Daniela +23 more
Two dwarf irregular galaxies, DDO 187 and NGC 3738, exhibit a striking pattern of star formation: intense star formation is taking place in a large region occupying roughly half of the inner part of the optical galaxy. We use data on the H I distribution and kinematics and stellar images and colors to examine the properties of the environment in t…
Discovery of X-Rays from the Old and Faint Pulsar J1154-6250
Mereghetti, Sandro; Igoshev, Andrei P.; Popov, Sergei B. +4 more
We report on the first X-ray observation of the 0.28 s isolated radio pulsar PSR J1154-6250 obtained with the XMM-Newton observatory in 2018 February. A point-like source is firmly detected at a position consistent with that of PSR J1154-6250. The two closest stars are outside the 3σ confidence limits of the source position and thus unlikely to be…
Revealing the Host Galaxy of a Quasar 2175 Å Dust Absorber at z = 2.12
Ge, Jian; Prochaska, J. Xavier; Brammer, Gabriel +2 more
We report the first detection of the host galaxy of a strong 2175 Å dust absorber at z = 2.12 toward the background quasar SDSS J121143.42+083349.7 using Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3) IR F140W direct imaging and G141 grism spectroscopy. The spectroscopically confirmed host galaxy is located at a small impact parameter of ∼5…
HST STIS UV Spectroscopic Observations of the Protoplanetary Nebula Hen3-1475
Gómez de Castro, Ana I.; Toalá, Jesús A.; Fang, Xuan +1 more
We present UV spectra of the protoplanetary nebula (pPN) Hen 3-1475 obtained with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). Our deep, low-dispersion spectroscopy enables monochromatic imaging of Hen 3-1475 in ultraviolet (UV) nebular emission lines, the first of such attempt ever made for a pPN. The…
NGC 6744: A Nearby Milky Way Twin with a Very Low-luminosity AGN
Steiner, J. E.; Menezes, R. B.; da Silva, Patrícia
NGC 6744 is the nearest and brightest south-hemisphere galaxy with a morphological type similar to that of the Milky Way. Using data obtained with the Integral Field Unit of the Gemini South Multi-Object Spectrograph, we found that this galaxy has a nucleus with LINER (Low Ionization Nuclear Emission Line Region) surrounded by three line emitting …
X-Ray Spectral Properties of Seyfert I Galaxy LEDA 168563
Fabian, Andrew C.; Tsuruta, Sachiko; Liebmann, Andrew C. +2 more
Interesting among possible mechanisms responsible for X-ray emission from active galactic nuclei (AGNs) is ionized relativistic reflection (IRR). Since it arises close to the central black hole it can test strong gravity. Its characteristic features include a high energy Compton hump, a broad Fe Kα line, and a soft excess. Therefore, using the Swi…
Dating the Tidal Disruption of Globular Clusters with GAIA Data on Their Stellar Streams
Loeb, Abraham; Bose, Sownak; Ginsburg, Idan
The Gaia mission promises to deliver precision astrometry at an unprecedented level, heralding a new era for discerning the kinematic and spatial coordinates of stars in our Galaxy. Here, we present a new technique for estimating the age of tidally disrupted globular cluster streams using the proper motions and parallaxes of tracer stars. We evolv…
Investigating the Relation between Sunspots and Umbral Dots
Mathew, Shibu K.; Louis, Rohan E.; Yadav, Rahul
Umbral dots (UDs) are transient, bright features observed in the umbral region of a sunspot. We study the physical properties of UDs observed in sunspots of different sizes. The aim of our study is to relate the physical properties of UDs with the large-scale properties of sunspots. For this purpose, we analyze high-resolution G-band images of 42 …
Investigation of the High-energy Emission from the Magnetar-like Pulsar PSR J1119-6127 after the 2016 Outburst
Hu, Chin-Ping; Kong, A. K. H.; Hui, C. Y. +7 more
PSR J1119-6127 is a radio pulsar that behaved with magnetar-like bursts, and we performed a comprehensive investigation of this pulsar using the archival high-energy observations obtained after its outburst in 2016 July. After the 2016 outburst, specific regions on the neutron star (NS) surface were heated up to >0.3 and >1 keV from ∼0.2 keV…
Reconciling the Predictions of Microlensing Analysis with Radial Velocity Measurements for OGLE-2011-BLG-0417
Boisse, I.; Bachelet, E.; Street, R. A. +2 more
Microlensing is able to reveal multiple body systems located several kilo-parsec away from the Earth. Since it does not require the measurement of light from the lens, microlensing is sensitive to a range of objects, from free-floating planets to stellar black holes. But, if the lens emits enough light, the microlensing model predictions can be te…