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Merging Eccentric Pairs of Black Holes
Posted: Tue Apr 02, 2019 4:06 pm
by bystander
Merging Eccentric Pairs of Black Holes
NOVA | American Astronomical Society | 2019 Mar 27
Susanna Kohler wrote:
The dense, chaotic centers of star clusters may be a birthplace for binary pairs of black holes like those observed by the Laser Interferometer Gravitational-Wave Observatory (LIGO). A new study now explores how eccentric binaries might arise and merge in these extreme environments. ...
Eccentric Black Hole Mergers in Dense Star Clusters:
The Role of Binary–Binary Encounters ~ Michael Zevin
et al
A Rare Double-Detonation Supernova Caught in the Act
Posted: Tue Apr 02, 2019 4:14 pm
by bystander
A Rare Double-Detonation Supernova Caught in the Act
NOVA | American Astronomical Society | 2019 Mar 29
Kerry Hensley wrote:
There’s more than just one way for a star to explode. Supernovae — perhaps the most dramatic form of star death — come in many flavors, and astronomers are still learning about the vast diversity of these stellar explosions. ...
ZTF 18aaqeasu (SN 2018byg): A Massive Helium-Shell Double
Detonation on a Sub-Chandrasekhar Mass White Dwarf ~ Kishalay De
et al
What’s with Asteroid Ryugu’s Weird Shape?
Posted: Tue Apr 02, 2019 4:22 pm
by bystander
What’s with Asteroid Ryugu’s Weird Shape?
NOVA | American Astronomical Society | 2019 Apr 01
Susanna Kohler wrote:
Recent space missions have served as solar-system paparazzi, stalking a number of near-Earth objects — and the images they’ve sent home give us plenty to ponder. Can we use these observations to determine how one of these photogenic asteroids obtained its shape? ...
The Western Bulge of 162173 Ryugu Formed as a Result
of a Rotationally Driven Deformation Process ~ Masatoshi Hirabayash
et al
Re: A Rare Double-Detonation Supernova Caught in the Act
Posted: Tue Apr 02, 2019 4:32 pm
by Ann
bystander wrote: ↑Tue Apr 02, 2019 4:14 pm
A Rare Double-Detonation Supernova Caught in the Act
NOVA | American Astronomical Society | 2019 Mar 29
Kerry Hensley wrote:
There’s more than just one way for a star to explode. Supernovae — perhaps the most dramatic form of star death — come in many flavors, and astronomers are still learning about the vast diversity of these stellar explosions. ...
ZTF 18aaqeasu (SN 2018byg): A Massive Helium-Shell Double
Detonation on a Sub-Chandrasekhar Mass White Dwarf ~ Kishalay De
et al
Interesting. This faint double-detonation supernova is unusually red.
Kerry Hensley wrote:
In May 2018, an unusual supernova was detected by the Zwicky Transient Facility, an optical survey that hunts for fleeting events like stellar flares, fast-rotating asteroids, and the visible-light counterparts of gravitational-wave events. Within days of its detection, a team led by Kishalay De (Caltech) began to collect photometric observations and spectra of the object.
The photometry revealed that the object, ZTF 18aaqeasu, was
unusually red and less luminous than a typical Type Ia supernova, making it a good candidate for the double-detonation scenario.
I'm quite sure that some superluminous supernovas have been unusually blue.
Subo Dong et al. wrote:
We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found.
...
We obtained an optical spectrum (3700 to 9200 Å) of ASASSN-15lh on 21 June 2015 with the du Pont 100-inch telescope. The steep spectral slope with
relatively high blue flux motivated Swift UltraViolet and Optical Telescope (UVOT)/X-Ray Telescope (XRT) (12) target-of-opportunity observations starting on 24 June 2015. The six-band Swift light curve spanning from the ultraviolet (UV) to the optical (1928 to 5468 Å) is shown in Fig. 1. The Swift spectral energy distribution (SED), peaking in the UV, indicates that the source has a high temperature. We derive a 3σ x-ray flux limit of <1.6 × 10−14 ergs s–1 cm–2 (0.3 to 10 keV) from a total XRT exposure of 81 ks taken between 24 June and 18 September 2015.
Ann
The Variable Jets of Gamma-Ray Bursts
Posted: Sun Apr 07, 2019 4:40 pm
by bystander
The Variable Jets of Gamma-Ray Bursts
NOVA | American Astronomical Society | 2019 Apr 03
Susanna Kohler wrote:
What drives rapid flickering in the jets that are produced in some powerful, high-energy explosions? Recent research explores the role of magnetic fields. ...
The MRI Imprint on the Short-GRB Jets ~ K. Sapountzis, A. Janiuk
Supernovae, Dark Energy, and the Fate of Our Universe
Posted: Sun Apr 07, 2019 5:09 pm
by bystander
Supernovae, Dark Energy, and the Fate of Our Universe
NOVA | American Astronomical Society | 2019 Apr 05
Susanna Kohler wrote:
What’s the eventual fate of our universe? Is spacetime destined to continue to expand forever? Will it fly apart, tearing even atoms into bits? Or will it crunch back in on itself? New results from Dark Energy Survey supernovae address these and other questions. ...
First Cosmology Results using Type Ia Supernovae from the Dark Energy Survey:
Constraints on Cosmological Parameters ~ DES Collaboration: T. M. C. Abbott
et al
First Images of a Black Hole from the Event Horizon Telescope
Posted: Sat Apr 13, 2019 5:24 pm
by bystander
First Images of a Black Hole from the Event Horizon Telescope
NOVA | American Astronomical Society | 2019 Apr 10
Susanna Kohler wrote:
Astronomers have used a telescope that spans the globe to capture the first detailed images of a black hole: the nearby supermassive black hole in the Messier 87 galaxy. The first results from the Event Horizon Telescope (
EHT) are detailed in six articles that make up a new
Focus Issue in
The Astrophysical Journal Letters. ...
viewtopic.php?t=39338
A Faster Way to Form Planets
Posted: Sat Apr 13, 2019 5:32 pm
by bystander
A Faster Way to Form Planets
NOVA | American Astronomical Society | 2019 Apr 12
Kerry Hensley wrote:
When interstellar asteroid
‘Oumuamua sped through our solar system in 2017, it revealed that small bodies might make a habit of visiting other planetary systems. Could such objects occasionally be responsible for jump-starting planet formation? ...
A Hypothesis for the Rapid Formation of Planets ~ Susanne Pfalzner, Michele T. Bannister
NuSTAR Explores the Aftermath of a Supernova
Posted: Tue Apr 16, 2019 8:53 pm
by bystander
NuSTAR Explores the Aftermath of a Supernova
NOVA | American Astronomical Society | 2019 Apr 15
Susanna Kohler wrote:
There’s plenty to learn from the skeletons left behind after supernova explosions tear through their surroundings. An X-ray view from space has revealed new details about a particularly extreme supernova remnant. ...
Evidence for Rapid Adiabatic Cooling as an Origin of the Recombining Plasma
in the Supernova Remnant W49B Revealed by NuSTAR Observations ~ Hiroya Yamaguchi
et al
viewtopic.php?t=30719
Exploring Filaments on the Sun
Posted: Sat Apr 20, 2019 2:06 pm
by bystander
Exploring Filaments on the Sun
NOVA | American Astronomical Society | 2019 Apr 17
Susanna Kohler wrote:
Images of the Sun’s chromosphere often reveal dark threads cutting across the Sun’s face. New research has now explored how these solar filaments are built from magnetic fields and plasma. ...
Double-Decker Filament Configuration Revealed by Mass Motions ~ Arun Kumar Awasthi
et al
Compact Objects Charging Toward Merger
Posted: Sat Apr 20, 2019 2:12 pm
by bystander
Compact Objects Charging Toward Merger
NOVA | American Astronomical Society | 2019 Apr 19
Susanna Kohler wrote:
When two compact objects — neutron stars or black holes — merge, will they emit light? A recent study looks at a neglected factor that could affect the answer: electric charge. ...
Charged Compact Binary Coalescence Signal and Electromagnetic
Counterpart of Plunging Black Hole–Neutron Star Mergers ~ Bing Zhang
Hubble Confirms Interstellar Buckyballs
Posted: Fri Apr 26, 2019 11:06 pm
by bystander
Hubble Confirms Interstellar Buckyballs
NOVA | American Astronomical Society | 2019 Apr 24
Susanna Kohler wrote:
From a jumble of confusing clues in Hubble observations of interstellar space, scientists have picked out evidence of a celebrity molecule: ionized Buckminsterfullerene, or buckyballs. ...
Confirming Interstellar C60+ Using the Hubble Space Telescope ~ M.A. Cordiner
et al
Prepping for Even Bigger Data in the Era of Interferometry
Posted: Fri Apr 26, 2019 11:12 pm
by bystander
Prepping for Even Bigger Data in the Era of Interferometry
NOVA | American Astronomical Society | 2019 Apr 26
Kerry Hensley wrote:
Interferometric arrays collect massive amounts of information, leaving astronomers with a happy problem: too much data! How can we handle mountains of data in an efficient way? ...
Unsupervised Generation of High Dynamic Range Solar Images:
A Novel Algorithm for Self-calibration of Interferometry Data ~ Surajit Mondal
et al
Mapping Clouds on a Distant World
Posted: Fri May 03, 2019 2:56 pm
by bystander
Mapping Clouds on a Distant World
NOVA | American Astronomical Society | 2019 May 01
Susanna Kohler wrote:
Nearby, cool dwarfs offer us the unique opportunity to learn more about the atmospheres of planetary-mass bodies. In a new study, Hubble observations shed some light on the clouds of one such object. ...
Cloud Atlas: Rotational Spectral Modulations and Potential Sulfide Clouds
in the Planetary-mass, Late T-type Companion Ross 458C ~ Elena Manjavacas
et al
A Link Between Fast Radio Bursts, Magnetars, and Supernovae?
Posted: Sat May 04, 2019 3:17 pm
by bystander
A Link Between Fast Radio Bursts, Magnetars, and Supernovae?
NOVA | American Astronomical Society | 2019 May 03
Susanna Kohler wrote:
What causes the bizarre, extragalactic fast radio bursts we’ve detected over the last decade? A new study of an unusually bright supernova may have found the key to answering this question. ...
A Radio Source Coincident with the Superluminous Supernova PTF10hgi:
Evidence for a Central Engine and an Analogue of the Repeating FRB121102? ~ T. Eftekhari
et al
Two More Explanations for ‘Oumuamua
Posted: Thu May 09, 2019 7:12 pm
by bystander
Two More Explanations for Interstellar Asteroid ‘Oumuamua
NOVA | American Astronomical Society | 2019 May 08
Susanna Kohler wrote:
More than a year has passed since the discovery of 1I/2017 ’Oumuamua, a bizarre body that
burst onto the scene and then disappeared into the distance as quickly as it had arrived. During ‘Oumuamua’s visit, astronomers gathered some 800+ observations from telescopes around the world, which together reveal a strange light curve that raises more questions than answers.
A few things are agreed upon. ‘Oumuamua’s orbit indicates it originated outside of our solar system, making it the first visiting interstellar body we’ve witnessed. Its shape appears to be highly elongated, suggesting it’s more cigar-shaped than spherical. And its light curve reveals a periodicity of roughly 8 hours, potentially indicating the speed at which this odd body rotates.
But many unsolved questions remain. What are ‘Oumuamua’s structure, composition, and shape? Where did it come from? How was it launched onto its journey to our solar system? ...
Could 1I/'Oumuamua be an Icy Fractal Aggregate? ~ Amaya Moro-Martín
On the Anomalous Acceleration of 1I/2017 U1 'Oumuamua ~ Darryl Seligman, Gregory Laughlin, Konstantin Batygin
viewtopic.php?t=37698
Nine Years of Energetic Atoms from IBEX
Posted: Fri May 10, 2019 5:24 pm
by bystander
Nine Years of Energetic Atoms from IBEX
NOVA | American Astronomical Society | 2019 May 10
Kerry Hensley wrote:
The Interstellar Boundary Explorer (
IBEX) has been observing the ebb and flow of energetic neutral atoms within our solar system for the past decade. How has the flux of these particles changed in that time? ...
Temporal Evolution of the Latitude and Energy Dependence of the Energetic Neutral Atom Spectral
Indices Measured by the Interstellar Boundary Explorer (IBEX) Over the First Nine Years ~ M. I. Desai
et al
viewtopic.php?t=18120
Focus on SOPHIA
Posted: Sat May 18, 2019 3:39 pm
by bystander
My GREAT Experience with SOFIA: Part 1 & Part 2
NOVA | American Astronomical Society | 2019 May 13-14
Susanna Kohler wrote:
What’s more exciting than jetting through the stratosphere over the Pacific Ocean? Doing so with an opening the size of a garage door gaping in the side of your airplane — while observing the universe! Such is the bizarre experience of flying aboard the Stratospheric Observatory for Infrared Astronomy, or
SOFIA. ...
Focus on SOFIA: FIFI-LS, EXES, & HAWC+
NOVA | American Astronomical Society | 2019 May 15-17
Susanna Kohler wrote:
One of SOFIA’s great strengths is that the instruments mounted on this flying telescope can be easily swapped out, allowing for a broad range of infrared observations. Three of SOFIA’s instruments are featured in science recently published in the ApJ Letters Focus Issue: the Far Infrared Field-Imaging Line Spectrometer (
FIFI-LS), the High-Resolution Airborne Wideband Camera Plus (
HAWC+), and the Echelon-Cross-Echelle Spectrograph (
EXES). ...
- FIFI-LS
FIFI-LS is a German-built instrument that can record spectra for each pixel of its field of view simultaneously, exploring objects in two far-infrared channels: 51–120 µm and 115–203 µm. Many astronomically interesting emission lines fall into these ranges — particularly those that trace the formation of massive stars and the properties of the interstellar medium.
By simultaneously capturing both images and spectra, FIFI-LS is able to deeply probe the composition and physical properties (like pressure and temperature) of heavily dust-obscured, star-forming regions in our own galaxy, as well as those in nearby external galaxies and galactic nuclei. ...
- EXES
EXES is used for high-resolution spectroscopy at mid-infrared wavelengths — from 4.5 to 28.3 µm — to study molecular gas in dense, quiescent clouds and protostellar disks. EXES uses a special coarsely-ruled aluminum reflection grating to spread light into a spectrum, allowing scientists to identify specific spectral lines associated with emission from different molecules.
The instrument’s high spectral resolution enables the study of molecular hydrogen, water vapor, and methane from sources like molecular clouds, protoplanetary disks, interstellar shocks, circumstellar shells, and planetary atmospheres. For many sources, EXES is able to achieve comparable sensitivity even to space-based observatories like Spitzer. ...
- HAWC+
HAWC+ is a one-of-a-kind instrument: it’s the only currently operating astronomical camera that takes images in far-infrared light. HAWC+ observes in the 50-μm to 240-μm range at high angular resolution, affording us a detailed look at low-temperature phenomena, like the early stages of star and planet formation.
In addition to the camera, HAWC+ also includes a polarimeter, which allows the instrument to measure the alignment of incoming light waves produced by dust emission. By observing this far-infrared polarization, HAWC+ can produce detailed maps of otherwise invisible celestial magnetic fields. The insight gained with HAWC+ spans an incredible range of astronomical sources, from nearby star-forming regions to the large-scale environments surrounding other galaxies. ...
Focus on New Results from SOFIA
Astrophysical Journal Letters | Jan 2019
William Reach wrote:
Half of the universe's stellar energy, including diagnostic far-infrared emission from interstellar ions and molecules at temperatures 10-1000 K, appears at far-infrared wavelengths that are unobservable from the Earth's surface due to atmospheric absorption. The US, European, and Japanese space agencies pioneered far-infrared astronomy, with the expansion of the field to nearly all areas of astrophysics by the Infrared Astronomical Satellite (IRAS) in 1983. Between ground and space, NASA developed the Kuiper Airborne Observatory to rise above the tropopause (below which lies the vast majority of the water vapor that causes most of the far-infrared telluric absorption). This airborne platform allows for scientific instrument upgrades, and investigators are able to participate in experiments hands-on. Kuiper was retired in order to initiate the development of its successor, the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA), whose 20-year mission was a recommendation of the 1990 astrophysics decadal survey. SOFIA has now become the world's premier far-infrared observatory, with over 1,200 guest observers. This Focus Issue highlights the first results from SOFIA's latest scientific instruments, which were designed to take advantage of access to completely different properties of far-infrared photons: their spectra and polarization. ...
Plasma Processes in Mars’s Shadow
Posted: Sat May 25, 2019 4:11 pm
by bystander
Plasma Processes in Mars’s Shadow
NOVA | American Astronomical Society | 2019 May 24
Kerry Hensley wrote:
When solar ultraviolet and X-ray photons collide with atoms and molecules in Mars’s atmosphere, they form a layer of plasma called an ionosphere. That’s what happens on the sunlit side, at least. What’s going on in Mars’s shadow? ...
Evaluating Local Ionization Balance in the Nightside Martian
Upper Atmosphere during MAVEN Deep Dip Campaigns ~ Jun Cui
et al
Do Active Galactic Nuclei Help or Hurt Life?
Posted: Fri May 31, 2019 3:14 pm
by bystander
Do Active Galactic Nuclei Help or Hurt Life?
NOVA | American Astronomical Society | 2019 May 29
Susanna Kohler wrote:
How does life arise on exoplanets? What environments are necessary for it to survive? What conditions pose threats to life? These are some of the many questions of astrobiology, the study of life beyond our solar system.
While much research explores how stellar radiation influences whether planets can form or sustain life, fewer studies examine other sources of radiation. Today’s study explores extreme sources: the violent and bright centers of active galaxies. ...
Active Galactic Nuclei: Boon or Bane for Biota? ~ Manasvi Lingam, Idan Ginsburg, Shmuel Bialy
Building a Pair of Blue Stragglers
Posted: Sat Jun 01, 2019 1:58 pm
by bystander
Building a Pair of Blue Stragglers
NOVA | American Astronomical Society | 2019 May 31
Susanna Kohler wrote:
Unusually blue and bright stars may not have only themselves to thank for their uniqueness. A new study looks at one way these unconventional objects might form in clusters … with a little help from a friend. …
A Triple Origin for Twin Blue Stragglers in Close Binaries ~ Simon Portegies Zwart, Nathan W. C. Leigh
Astro2020: The Current State of Astronomy Research
Posted: Wed Jun 05, 2019 5:01 pm
by bystander
The Current State of Astronomy Research, Summarized in 573 Papers
NOVA | American Astronomical Society | 2019 Jun 05
Susanna Kohler wrote:
What are the big topics in astronomy research that we’ll be working to address in the next decade? No need to pull out a crystal ball astronomers have a pretty good guess, and they’ve shared what they think in a
series of white papers that are part of the
2020 Decadal Survey.
Astro2020: Decadal Survey on Astronomy and Astrophysics, Science White Papers
- Bulletin of the American Astronomical Society 51(3) (2019 Jun 04)
Two Planets Straddling the Gap
Posted: Mon Jun 24, 2019 7:20 pm
by bystander
Two Planets Straddling the Gap
NOVA | American Astronomical Society | 2019 Jun 19
Susanna Kohler wrote:
As of last week, the count of confirmed exoplanets officially exceeds 4,000 — and while we’ve learned a lot about planet formation from this wealth of data, it’s also prompted new questions. Could the recent detection of two intriguing new planets shed light on one of these open puzzles? ...
The Transiting Multi-planet System HD15337: Two Nearly
Equal-mass Planets Straddling the Radius Gap ~ Davide Gandolfi
et al
Tough Times for Binaries Near Black Holes
Posted: Mon Jun 24, 2019 7:27 pm
by bystander
Tough Times for Binaries Near Black Holes
NOVA | American Astronomical Society | 2019 Jun 21
Kerry Hensley wrote:
What happens to binary stars under the influence of a nearby supermassive black hole? A new study shows that things can go one of two ways — being torn apart or becoming closer than ever. ...
The Fate of Binaries in the Galactic Center: The Mundane and the Exotic ~ Alexander P. Stephan
et al
Exomoon, or No Exomoon?
Posted: Sun Jul 14, 2019 9:49 pm
by bystander
Exomoon, or No Exomoon?
NOVA | American Astronomical Society | 2019 Jun 24
Susanna Kohler wrote:
Last October, the first discovery of a potential exomoon was announced. But is Kepler-1625b-i an actual moon in another solar system? Or just an artifact of data reduction? ...
No Evidence for Lunar Transit in New Analysis of Hubble Space Telescope
Observations of the Kepler-1625 System ~ Laura Kreidberg, Rodrigo Luger, Megan Bedell