Daily Archives: March 18, 2022

Dr. Amruta Jaodand;Division of Physics, Mathematics and Astronomy,California Institute of Technology

Transitional millisecond pulsars (tMSPs) switch between a low-mass X-ray binary (LMXB) and a radio millisecond pulsar (RMSP) state, establishing a firm evolutionary link between the two source classes. tMSPs provide a great avenue to study the low-level accretion processes that spin-up pulsars to millisecond periods. Systematic, multi-wavelength observational campaigns over the last decade have resulted in surprising finds such as: i) persistent, multi-year-long, low-level (Lx <10^34 ergs/s) accretion state with coherent pulsations; ii) extremely stable, bi-modal X-ray light curves; iii) radio outflows, and iv) uninterrupted pulsar spin down in the X-rays. In this unique state, we have now found the first known UV millisecond pulsar with a dedicated multi-wavelength campaign involving the Hubble space telescope. In my talk I will review observational understanding of tMSPs while highlighting key finds which reveal how these systems have altered our understanding of low level accretion and pulsed emission in neutron stars.

Biography:Dr. Amruta Jaodand is a postdoctoral reseacher in the NuSTAR group at Caltech's Division of Physics, Mathematics and Astronomy. Previously, she did her PhD at University of Amsterdam. She works on observational investigations of various neutron stars such as millisecond pulsars, magnetars, gravitational wave engines and X-ray binaries with a deeper expertise in transitional millisecond pulsars and multi-wavelength gravitational wave follow up. As a PI, she has won observational time and funding for ~30 proposals spanning observatories such as XMM, NuStar, Swift, Green Bank Telescope, ZTF and VLA etc. Another interest of hers is astroinformatics in the era of large scale datasets. To that effect she has worked for the past five years in bringing together EU and American astronomers through multiple conferences to probe machine learning and visualisation approaches.

22 MAR 2022: Physics and Astronomy Colloquium3:30pm, Online via ZoomZoom Link:https://uiowa.zoom.us/j/94392147007Meeting ID: 943 9214 7007, No passcode

Read the original post:

Physics & Astronomy Colloquium - Dr. Amruta Jaodand | Physics and Astronomy | The University of Iowa - The University of Iowa

An IDAS LPS-D2 filter suitable for two-inch push-fit telescope camera accessories with an M48 0.75 connection thread. The filter has male and female threads on either side, hence it is stackable with other filters and M48 adaptors. The LPS-D2 is also available in 52mm and Canon APS-C clip-filter formats. All images: Ade Ashford.At a glance

Type: light-pollution suppression filter for low-/high-pressure sodium vapour and LED lightsCoating technology: Ion-Gun Assisted Deposition (IGAD)Suitability: DSLR and astro camerasConnection thread: M48 0.75 (male and female on either side, hence stackable)Substrate thickness: 2.5mmDiameter of filter glass: 49mmPrice: 175 (M48 and 52mm); 185 (Canon APS-C clip filter)Manufacturer: ICAS Enterprises, JapanSupplier: rothervalleyoptics.co.uk

Light pollution is a regrettable fact of life for most of us. By night, the sky over our cities and towns even villages is increasingly awash with the glare of unnecessary or misdirected artificial light. This is not only a tremendous waste of energy, but it upsets nocturnal ecosystems and harms human health, disturbed sleep patterns and the disruption of natural circadian rhythms.

For almost three decades, Tokyo-based ICAS Enterprises IDAS Division has been responsible for manufacturing some of the worlds most respected interference filters for suppressing light pollution for astronomers. Their LPS-D1 filter made its debut in 1991 at a time when the main sources of artificial illumination in our towns and cities were low- and high-pressure sodium vapour and mercury vapour lamps. Fortunately for astronomers, both sodium (Na) and mercury (Hg) vapour lamps share a common characteristic: they typically emit light in specific and largely narrow wavelength bands of the spectrum so-called emission lines that can be removed by an interference filter.

The LPS-D1 was designed for one-shot CCD/CMOS colour cameras and DSLRs to eliminate the glow from low-pressure sodium and high-pressure mercury street lights, while substantially reducing the peak intensities of high-pressure sodium light emissions. Both the IDAS D1 and P2 filters pass the desirable spectral lines of hydrogen-beta, oxygen-III, hydrogen-alpha light from nebulae, plus diatomic carbon (C2, the so-called Swan bands) from comets. The LPS-P2 is virtually identical to the D1 except for a slightly greater red sensitivity encompassing sulphur-II emissions.

As many of us up and down the United Kingdom and around the world are now acutely aware, the nature of street lighting is rapidly changing. The mellow yellow glow of low-pressure sodium light is being replaced with the energy-efficient yet brilliant white glare of light-emitting diodes (LEDs). I never thought that I would lament the passing of sodium street lights, but at least their light was relatively easy to mitigate. White LEDs, on the other hand, emit what is largely a continuous spectrum across a swathe of wavelengths (or colours, if you prefer) which is far harder to filter out.

If you consult the accompanying graph that shows the spectral profile of a typical white LED in blue, you will see immediately that it emits its greatest intensity of light almost 98 per cent transmittance in a well-defined peak at a wavelength close to 463 nanometres (nm), which is 4.63 107 metres, or 0.000463mm. Thus, the peak emission of a typical white LED is actually in the violet end of the blue region of the visible spectrum, at wavelengths that research has shown disrupts human circadian rhythms by keeping our brains in an awake state.

After the initial peak intensity, the white LEDs transmittance rapidly drops to around nine per cent at a wavelength of about 486nm in the bluegreen part of the spectrum. Thereafter, the transmittance rises steeply to a secondary, broader peak intensity of 53 per cent at about 560nm in the yellow part of the visible spectrum before gradually tailing off to zero in the far-infrared. If we were to use a conventional IDAS LPS-D1 or P2 filter on a white LED, then its peak intensity and much of its broader secondary intensity would not be filtered out. Clearly, we need another type of interference filter.

I was able to obtain data for the LPS-D2 filter based on a laboratory analysis rather than just rely on the design specification. The accompanying graph is a plot of the filters transmission versus wavelength in yellow, superimposed with that of a typical white LED in cyan. Where the white LEDs light intrudes into the D2 filters transmission curve is shown in green. Furthermore, the graphic shows the emission spectra of desirable nebula light (vertical dashed green lines), plus residual sources of light pollution that we wish to remove or mitigate (vertical red dashed lines). At the top and bottom of the graphic we see a continuous spectrum showing the approximate colour that corresponds to a specific wavelength; V = violet, B = blue, G = green, and so on.

The IDAS LPS-D2 is clearly very effective at removing the initial and most intense transmission spike from a typical white LED centred around 463 nanometres. However, when we come to capturing the desirable emission spectra of nebulae and comets in the blue green part of the spectrum hydrogen-beta, oxygen-III and diatomic carbon the intrusion of the LEDs light rises from a transmission of nine per cent at the hydrogen-beta line to around 30 per cent at the Swan bands of diatomic carbon. Note that some high-pressure mercury light pollution at 436nm and 546nm will also be passed by the LPS-D2 filter. Similarly, the second transmission peak of the LPS-D2 encompasses some of the white LEDs secondary peak light at around 52 per cent transmittance, so your white balance will have some strong green dominance. Fortunately, low-pressure sodium light pollution is fully suppressed and by the hydrogen-alpha and sulphur-II emission lines the white LEDs transmission is down to just 18 and 13 per cent, respectively.

More here:

Beating the LED streetlights: IDAS light-pollution suppression LPS-D2 filter Astronomy Now - Astronomy Now Online

A mysterious, repeating radio signal in the Milky Way that baffled astronomers could be an object so rare, only one other has ever been tentatively identified.

According to a paper by astrophysicist Jonathan Katz of Washington University at St. Louis, uploaded to preprint server arXiv, and yet to be peer-reviewed, the signal named GLEAM-X J162759.5523504.3 could be a white dwarf radio pulsar.

"Since the early days of pulsar astronomy there has been speculation that a rotating magnetic white dwarf might show pulsar-like activity," Katz wrote in his paper.

"The recently discovered periodic radio transient GLEAM-X J162759.5523504.3 is a candidate for the first true white dwarf pulsar. It has a period of 18.18 minutes (1091 s) and its pulses show low frequency (72215 MHz) emission with a brightness temperature 1016 K implying coherent emission. It has no binary companion with which to interact. It thus meets the criteria of a classical pulsar, although its period is hundreds of times longer than any of theirs."

When a star dies, there are a range of outcomes, once it has ejected its outer material and core, no longer supported by the outward pressure of fusion, it collapses under its own gravity.

If the precursor star is over around 30 times the mass of the Sun, the core collapses into a black hole.

A precursor star between eight and 30 times the mass of the Sun results in a neutron star, around 20 kilometers (12 miles) across and up to around 1.4 times the mass of the Sun.

The core of a precursor star less than eight times the mass of the Sun will collapse into a white dwarf, packing mass up to 1.5 times that of the Sun into a ball between the sizes of Earth and the Moon.

Pulsars are a subset of neutron stars. They're neutron stars that rotate insanely fast, and angled in such a way that beams of bright radio waves shooting from the magnetic poles sweep past Earth on every rotation on the scale of seconds down to milliseconds. (Here's what that sounds like transcribed into audio.)

Scientists have wondered if similar behavior might be observed in white dwarf stars, and in 2016, they seem to have come close,with a star called AR Scorpii. Locked in a binary system with a red dwarf star, AR Scorpii flashes on a timescale of minutes.

However, as Katz notes, its binary orbit is closer than those of neutron star pulsars in binary systems, and the periodic signal lacks coherence. This means that the physical processes that produces the signal might be very different from traditional radio pulsars.

This brings us back to GLEAM-X J162759.5523504.3, located roughly 4,000 light-years away from Earth. From January to March of 2018, data collected by the Murchison Widefield Array in the Australian desert showed it pulsing brightly for roughly 30 to 60 seconds, every 18.18 minutes one of the most luminous objects in the low-frequency radio sky.

It matched the profile of no known astronomical object, but the research team that discovered it thought it might be a hypothetical object known as an ultra-long-period magnetar. That's a neutron star with an extraordinarily powerful magnetic field, but the explanation still didn't quite fit.

"Nobody expected to directly detect one like this because we didn't expect them to be so bright," astrophysicist Natasha Hurley-Walker of the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) in Australia explained at the time. "Somehow it's converting magnetic energy to radio waves much more effectively than anything we've seen before."

A pulsar was considered as a possibility, but there are two major problems: the first is that long rotation period, and the second is that the pulses were too bright for a neutron star pulsar. Both these problems, Katz lays out, are resolved if the object is a white dwarf.

If this is the case, it would be the first white dwarf discovered that shares the physics and radiation mechanism of traditional radio pulsars. This means that GLEAM-X J162759.5523504.3 could be a promising target for optical observations; although white dwarfs are very dim, and we might not be able to pick up any visible light at its distance. Nevertheless, given the possibility, it's worth a shot.

And astronomers could also examine other white dwarfs, to see if they match any of the properties of GLEAM-X J162759.5523504.3.

"If it were bright enough, optical observations could also determine its magnetic field, spectroscopically or polarimetrically," Katz explained.

"The fast-rotating, strongly magnetized, white dwarves would be promising targets for low frequency radio observations to determine if any of them are white dwarf pulsars."

The paper has been uploaded to preprint server arXiv.

See original here:

Mysterious Signal Coming From Our Galaxy Could Be One of The Rarest Known Objects - ScienceAlert

The Emirates Astronomical Society said on Friday that Ramadan is set to begin on April 2.

Eid Al Fitr and the first of Shawwal will be on May 2.

Ibrahim Al Jarwan, chairman of the board of directors of the society, said that the holy month is expected to last 30 days, according to state news agency Wam.

Residents of Khorfakkan will be the first to start fasting due to the city's location. Abu Dhabi residents will begin eight minutes later.

At the start of Ramadan, the dawn call to prayer in Khorfakkan will be at 4:48am. In the capital it is 4:56am, and in Sila and Ghuwaifat it is 5:08am.

Mr Al Jarwan said each day will call for around 13 hours and 46 minutes of fasting.

The precise start of Ramadan will be confirmed closer to the time through the moon-sighting committee.

First day of Ramadan at the Sheikh Zayed Grand Mosque. A canon is fired to mark the beginning of iftar. Victor Besa/The National

Updated: March 18, 2022, 12:27 PM

Go here to read the rest:

Ramadan 2022 set to begin on April 2, UAE astronomy society says - The National

COLUMBIA, Md., March 18, 2022 /PRNewswire/ --The Stratospheric Observatory for Infrared Astronomy, SOFIA, landed at the Santiago International Airport on March 18, 2022. Like other deployments to the Southern Hemisphere, SOFIA is a partnership between NASA and German Aerospace Agency (DLR) and temporarily changing its base of operations from Palmdale, California, to Santiago, Chile, to observe celestial objects that can only be seen from Southern Hemisphere latitudes.

This is SOFIA's first visit to South America, and its first short-term deployment that will last two weeks. The team will operate from the Santiago International Airport to accomplish eight science flights. SOFIA will primarily observe the Large and Small Magellanic Clouds during the deployment, which are two close neighboring galaxies to our Milky Way. Both are gravitationally bound to each other and are passing by our galaxy for the first time in a hyperbolic orbit.

"Scientific collaboration, particularly in astronomy, has been a cornerstone of the U.S.-Chile relationship dating back to the establishment of the Observatorio de Cerro Santa Lucia in Santiago more than 170 years ago," said Richard Glenn, the U.S. Embassy Chile Charg d'Affaires. "NASA's SOFIA deployment to Chile is the next exciting milestone in that relationship, bringing us closer to the stars than ever before."

This is called a short deployment because of the shorter stay in Chile compared to SOFIA's long deployments, where more than 25 flights are typically planned using multiple instruments. The SOFIA team is taking a single instrument for this deployment, the Far Infrared Field Imaging Line Spectrometer, or FIFI-LS, and will observe several critical Southern Hemisphere celestial targets.

"We are thrilled to deploy to Chile so we can provide more access to the Southern Hemisphere skies for our scientific community," said Naseem Rangwala, SOFIA's project scientist. "We are increasing our deployment tempo with a focus on efficiency and prioritized targets, and we are grateful for the opportunity to do that from Santiago."

Since the Large Magellanic Cloud, or LMC, is so close to our galaxy, SOFIA can observe it in great detail, on relatively small astronomical scales,to help scientists better understand how stars formed in the early universe. Having the context of the physical areas in which stars form is why these LMC observations are so powerful. Scientists cannot see detailed physical structures in distant, ancient galaxies, so, instead, galaxies like the LMC are observed as local stand-ins. The planned observations are to create the first SOFIA map of ionized carbon in the LMC. These observations pair well with NASA's upcoming Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory, or GUSTO a high altitude balloon-based mission, and they extend the legacy of the Herschel Space Observatory.

In addition to the observations of the Large Magellanic Cloud, SOFIA will observe supernova remnants to investigate how certain types of supernovas might have contributed to the abundance of dust in the early universe. SOFIA will also attempt its first observation to measure the primordial abundance of lithium by looking into the halo of our galaxy where clouds of neutral hydrogen can be found. These clouds have been relatively undisturbed and thus directly probe the properties of pristine gas that existed in the early universe. A successful observation of lithium could have implications for our understanding of fundamental physics and the early universe because there is a significant discrepancy in lithium abundance between the big-bang theory of the evolution of the universe and the observed abundance from astronomical measurements. These observations obtained by SOFIA during this Southern Hemisphere are in line with some of the scientific questions and priorities identified in recently published Astro2020 Decadal Survey.

About SOFIA

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. NASA's Ames Research Center in California's Silicon Valley manages the SOFIA program, science, and mission operations in cooperation with the Universities Space Research Association, headquartered in Columbia, Maryland, and the German SOFIA Institute at the University of Stuttgart. The aircraft is maintained and operated by NASA's Armstrong Flight Research Center Building 703, in Palmdale, California.

About USRA

Foundedin 1969, under the auspices of the National Academy of Sciences at the request of the U.S. Government, the Universities Space Research Association (USRA), is a nonprofit corporation chartered to advance space-related science, technology and engineering. USRA operates scientific institutes and facilities, and conducts other major research and educational programs. USRA engages the university community and employs in-house scientific leadership, innovative research and development, and project management expertise.More information about USRA is available at http://www.usra.edu.

PR Contact:

Suraiya Farukhi, Ph.D.[emailprotected]443-812-6945 (cell)

SOURCE Universities Space Research Association

See the original post here:

Science in the Southern Hemisphere: SOFIA Deploys to Chile - PR Newswire