Search Publications
Fermi Transient J1544-0649: A Flaring Radio-weak BL Lac
Ubertini, Pietro; Bazzano, Angela; Panessa, Francesca +6 more
On 2017 May 15, the FERMI/LAT gamma-ray telescope observed a transient source not present in any previous high-energy catalog: J1544-0649. It was visible for two consecutive weeks, with a flux peak on May 21. Subsequently observed by a Swift/XRT follow-up starting on May 26, the X-ray counterpart position was coincident with the optical transient …
The Second Nucleus of NGC 7727: Direct Evidence for the Formation and Evolution of an Ultracompact Dwarf Galaxy
Kelson, Daniel D.; Seitzer, Patrick; Whitmore, Bradley C. +2 more
We present new observations of the late-stage merger galaxy NGC 7727, including Hubble Space Telescope/WFPC2 images and long-slit spectra obtained with the Clay telescope. NGC 7727 is relatively luminous ({M}V = -21.7) and features two unequal tidal tails, various bluish arcs and star clusters, and two bright nuclei 480 pc apart in proj…
The Mass of the Cepheid V350 Sgr
Evans, Nancy Remage; Carpenter, Kenneth G.; Kober, Gladys V. +6 more
V350 Sgr is a classical Cepheid suitable for mass determination. It has a hot companion which is prominent in the ultraviolet (UV) and which is not itself a binary. We have obtained two high-resolution echelle spectra of the companion at orbital velocity maximum and minimum with the Space Telescope Imaging Spectrograph on the Hubble Space Telescop…
Statistical Investigation of Supersonic Downflows in the Transition Region above Sunspots
Tian, Hui; Prasad Choudhary, Debi; Samanta, Tanmoy
Downflows at supersonic speeds have been observed in the transition region (TR) above sunspots for more than three decades. These downflows are often seen in different TR spectral lines above sunspots. We have performed a statistical investigation of these downflows using a large sample that was missing previously. The Interface Region Imaging Spe…
A Globular Cluster Luminosity Function Distance to NGC 4993 Hosting a Binary Neutron Star Merger GW170817/GRB 170817A
Im, Myungshin; Lee, Myung Gyoon; Kang, Jisu
NGC 4993 hosts a binary neutron star merger, GW170817/GRB 170817A, emitting gravitational waves and electromagnetic waves. The distance to this galaxy is not well established. We select the globular cluster candidates from the Hubble Space Telescope (HST)/ACS F606W images of NGC 4993 in the archive, using the structural parameters of the detected …
The Planck Cold Clump G108.37-01.06: A Site of Complex Interplay between H II Regions, Young Clusters, and Filaments
Jose, Jessy; Samal, Manash R.; Dutta, Somnath +1 more
The Planck Galactic Cold Clumps (PGCCs) are possible representations of the initial conditions and very early stages of star formation. With the objective of understanding better the star and star cluster formation, we probe the molecular cloud associated with PGCC G108.37-01.06 (hereafter PG108.3), which can be traced in a velocity range of -57 t…
Neutral Helium Triplet Spectroscopy of Quiescent Coronal Rain with Sensitivity Estimates for Spectropolarimetric Magnetic Field Diagnostics
Schad, Thomas A.
On account of its polarizability and magnetic field sensitivity, as well as the role of neutral helium in partially ionized solar environments, the neutral helium triplet (orthohelium) system provides important, yet underutilized, diagnostics of solar coronal rain. This work describes off-limb observations of coronal rain in NOAA Active Region 124…
The Origin of High-velocity Stars from Gaia and LAMOST
Shi, Jianrong; Chen, Yuqin; Ma, Jun +4 more
Based on the second Gaia data release and spectroscopy from the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) Data Release 5, we define the high-velocity (HiVel) stars sample as those stars with v gc > 0.85v esc, and derived the final sample of 24 HiVel stars with stellar astrometric parameters and rad…
A Search for Black Hole Microlensing Signatures in Globular Cluster NGC 6656 (M22)
Anderson, J.; Casertano, S.; Kains, N. +3 more
We report the results of a study aiming to detect signs of astrometric microlensing caused by an intermediate-mass black hole (IMBH) in the center of globular cluster M22 (NGC 6656). We used archival data from the Hubble Space Telescope (HST) taken between 1995 and 2014 to derive long-baseline astrometric time series for stars near the center of t…
SETI with Gaia: The Observational Signatures of Nearly Complete Dyson Spheres
Zackrisson, Erik; Korn, Andreas J.; Wehrhahn, Ansgar +1 more
A star enshrouded in a Dyson sphere with a high covering fraction may manifest itself as an optically subluminous object with a spectrophotometric distance estimate significantly in excess of its parallax distance. Using this criterion, the Gaia mission will in coming years allow for Dyson sphere searches that are complementary to searches based o…