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arXiv:2308.12991v3 Announce Type: replace Abstract: We present the photometric and spectroscopic evolution of SN 2022oqm, a nearby multi-peaked hydrogen- and helium-weak calcium-rich transient (CaRT). SN 2022oqm was detected 13.1 kpc from its host galaxy, the face-on spiral galaxy NGC 5875. Extensive spectroscopic coverage reveals an early hot (T >= 40,000 K) continuum and carbon features observed $\sim$1~day after discovery, SN Ic-like photospheric-phase spectra, and strong forbidden calcium emission starting 38 days after discovery. SN 2022oqm has a relatively high peak luminosity (MB = -17 mag) for (CaRTs), making it an outlier in the population. We determine that three power sources are necessary to explain the light curve (LC), with each corresponding to a distinct peak. The first peak is powered by an expanding blackbody with a power law luminosity, suggesting shock cooling by circumstellar material (CSM). Subsequent LC evolution is powered by a double radioactive decay model, consistent with two sources of photons diffusing through optically thick ejecta. From the LC, we derive an ejecta mass and 56Ni mass of ~0.6 solar masses and ~0.09 solar masses. Spectroscopic modeling suggests 0.6 solar masses of ejecta, and with well-mixed Fe-peak elements throughout. We discuss several physical origins for SN 2022oqm and find either a surprisingly massive white dwarf progenitor or a peculiar stripped envelope model could explain SN 2022oqm. A stripped envelope explosion inside a dense, hydrogen- and helium-poor CSM, akin to SNe Icn, but with a large 56Ni mass and small CSM mass could explain SN 2022oqm. Alternatively, helium detonation on an unexpectedly massive white dwarf could also explain SN 2022oqm.

TBD

Abstract not available

• Speaker: Tsevi Mazeh (Tel Aviv)
• Tuesday 07 May 2024, 11:30-12:30
• Venue: Hoyle Lecture Theatre + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2404.02958v1 Announce Type: new Abstract: Protostellar discs are mostly modelled as circular structures of gas and dust orbiting a protostar. However, a number of physical mechanisms, e.g. the presence of a (sub)stellar companion or initial axial asymmetry, can cause the gas and dust orbital motion to become eccentric. Theoretical studies have revealed that, when present, disc eccentricity is expected to occur with predictable profiles that can be long-lasting and potentially observable in protostellar systems. We construct an analytical model predicting the typical features of the kinematics and morphology of eccentric protostellar discs, with the final goal of characterising the observational appearance of eccentricity in discs. We validate the model using a numerical simulation of a circumbinary disc (where the binary makes the disc eccentric). We finally post-process the simulation with Monte Carlo Radiative Transfer to study how eccentric features would appear through the "eyes" of ALMA. Besides the motion of the material on eccentric Keplerian orbits in the disc orbital plane, the most characteristic eccentric feature emerging from the analytical model is strong vertical motion with a typical anti-symmetric pattern (with respect to the disc line of pericentres). A circumbinary disc with a $\approx 40$ au eccentric cavity ($e_{\rm cav}=0.2$), carved by an $a_{\rm bin}=15$ au binary, placed at a distance $d=130$ pc, is expected to host in its upper emission surface vertical oscillations up to $v_{z}\sim 400\, {\rm ms}^{-1}$ close to the cavity edge, i.e. well within ALMA spectral and spatial resolution capabilities. A residual spiral pattern in the vertical velocity $\Delta v_{z}\sim 150\, {\rm ms}^{-1}$ of the simulation cannot be captured by the theoretical model, we speculate it to be possibly linked to the presence of a companion in the system.

arXiv:2404.02953v1 Announce Type: new Abstract: In the cold dark matter paradigm, our Galaxy is predicted to contain >10000 dark matter subhaloes in the $10^5-10^8M_\odot$ range which should be completely devoid of stars. Stellar streams are sensitive to the presence of these subhaloes, which can create small-scale features in streams if they pass closely enough. Modelling these encounters can therefore, potentially recover the subhalo's properties. In this work, we demonstrate this for streams generated in numerical simulations, modelled on eccentric orbits in a realistic Milky Way potential, which includes the Large Magellanic Cloud and the subhalo itself. We focus on a mock model of the ATLAS-Aliqa Uma stream and inject a $10^7 M_\odot$ subhalo, creating a similar discontinuous morphology to current observations. We then explore how well subhalo properties are recovered using mock stream observations, consisting of no observational errors, as well as assuming realistic observational setups. These setups include present day style observations, and what will be possible with 4MOST and Gaia DR5 in the future. We show that we can recover all parameters describing the impact even with uncertainties matching existing data, including subhalo positions, velocities, mass and scale radius. Modelling the subhalo on an orbit instead of assuming an impulse approximation, we greatly reduce the degeneracy between subhalo mass and velocity seen in previous works. However, we find a slight bias in the subhalo mass (~0.1 dex). This demonstrates that we should be able to reliably extract the properties of subhaloes with stellar streams in the near future.

2 min read

Hubble Peers at Pair of Closely Interacting Galaxies This NASA/ESA Hubble Space Telescope image features Arp 72. ESA/Hubble & NASA, L. Galbany, J. Dalcanton, Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA

This image from the NASA/ESA Hubble Space Telescope features Arp 72, a very selective galaxy group that only includes two galaxies interacting due to gravity: NGC 5996 (the large spiral galaxy) and NGC 5994 (its smaller companion, in the lower left of the image). Both galaxies lie approximately 160 million light-years from Earth, and their cores are separated from each other by a distance of about 67,000 light-years. The distance between the galaxies at their closest points is even smaller, closer to 40,000 light-years. While this might sound vast, in galactic separation terms it is really quite close. For comparison, the distance between the Milky Way and its nearest independent galactic neighbor Andromeda is around 2.5 million light-years. Alternatively, the distance between the Milky Way and its largest and brightest satellite galaxy, the Large Magellanic Cloud (satellite galaxies orbit around another galaxy), is about 162,000 light-years.

Given this and the fact that NGC 5996 is roughly comparable in size to the Milky Way, it is not surprising that NGC 5996 and NGC 5994 — separated by only about 40,000 light-years — are interacting with one another. In fact, the interaction likely distorted NGC 5996’s spiral shape. It also prompted the formation of the very long and faint tail of stars and gas curving away from NGC 5996, up to the top right of the image. This ‘tidal tail’ is a common phenomenon that appears when galaxies closely interact and is visible in other Hubble images of interacting galaxies.

Text credit: European Space Agency (ESA)

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Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

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Details Last Updated Apr 05, 2024 Editor Andrea Gianopoulos Related Terms

• Astrophysics
• Astrophysics Division
• Galaxies
• Goddard Space Flight Center
• Hubble Space Telescope
• Missions
• The Universe

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NASA Astrophysics

Nature, Published online: 04 April 2024; doi:10.1038/d41586-024-00965-1

An unusual technique picks up the slow vibration of a faint star.

I have two degrees in astronomy, so you'd think I would know what I'm doing when it comes to looking at the sky. I don't, but I'm trying to change that, says Chanda Prescod-Weinstein

The standard model of cosmology says that the strength of dark energy should be constant, but tentative hints are emerging that it may have weakened recently

In brief For the first time, a team of astronomers (including IoA astronomer Nic Walton) have spotted potential signs of a rainbow-like ‘glory effect’ on a planet outside our Solar System. Glory are colourful concentric rings of light that occur only under peculiar conditions. Data from ESA’s sensitive Characterising...

TBD (have to move to May 7?)

Abstract not available

• Speaker: Tsevi Mazeh (Tel Aviv)
• Friday 03 May 2024, 11:30-12:30
• Venue: Ryle seminar room + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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Chemo-dynamical evolution of disks over cosmic time

Abstract not available

• Speaker: Emily Wisnioski (ANU)
• Friday 12 April 2024, 11:30-12:30
• Venue: Ryle seminar room + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2404.02139v2 Announce Type: replace Abstract: A bright ($m_{\rm F150W,AB}$=24 mag), $z=1.95$ supernova (SN) candidate was discovered in JWST/NIRCam imaging acquired on 2023 November 17. The SN is quintuply-imaged as a result of strong gravitational lensing by a foreground galaxy cluster, detected in three locations, and remarkably is the second lensed SN found in the same host galaxy. The previous lensed SN was called "Requiem", and therefore the new SN is named "Encore". This makes the MACS J0138.0$-$2155 cluster the first known system to produce more than one multiply-imaged SN. Moreover, both SN Requiem and SN Encore are Type Ia SNe (SNe Ia), making this the most distant case of a galaxy hosting two SNe Ia. Using parametric host fitting, we determine the probability of detecting two SNe Ia in this host galaxy over a $\sim10$ year window to be $\approx3\%$. These observations have the potential to yield a Hubble Constant ($H_0$) measurement with $\sim10\%$ precision, only the third lensed SN capable of such a result, using the three visible images of the SN. Both SN Requiem and SN Encore have a fourth image that is expected to appear within a few years of $\sim2030$, providing an unprecedented baseline for time-delay cosmography.

arXiv:2404.02303v1 Announce Type: new Abstract: In this third paper of a series, we study the kinematics of the ionised gas and stars, calculating the dynamical masses of the circumnuclear star-forming regions in the ring of of the face-on spiral NGC 7742. We have used high spectral resolution data from the MEGARA instrument attached to the Gran Telescopio Canarias (GTC) to measure the kinematical components of the nebular emission lines of selected HII regions and the stellar velocity dispersions from the CaT absorption lines that allow the derivation of the associated cluster virialized masses. The emission line profiles show two different kinematical components: a narrow one with velocity dispersion $\sim$ 10 km/s and a broad one with velocity dispersion similar to those found for the stellar absorption lines. The derived star cluster dynamical masses range from 2.5 $\times$ 10$^6$ to 10.0 $\times$ 10$^7$ M$_\odot$. The comparison of gas and stellar velocity dispersions suggests a scenario where the clusters have formed simultaneously in a first star formation episode with a fraction of the stellar evolution feedback remaining trapped in the cluster, subject to the same gravitational potential as the cluster stars. Between 0.15 and 7.07 % of the total dynamical mass of the cluster would have cooled down and formed a new, younger, population of stars, responsible for the ionisation of the gas currently observed.

Nature, Published online: 03 April 2024; doi:10.1038/d41586-024-00973-1

The Sun’s mysterious outer atmosphere, the corona, will become easier to view from Earth on 8 April.

arXiv:2404.01235v1 Announce Type: new Abstract: We present LAISS (Lightcurve Anomaly Identification and Similarity Search), an automated pipeline to detect anomalous astrophysical transients in real-time data streams. We deploy our anomaly detection model on the nightly ZTF Alert Stream via the ANTARES broker, identifying a manageable $\sim$1-5 candidates per night for expert vetting and coordinating follow-up observations. Our method leverages statistical light-curve and contextual host-galaxy features within a random forest classifier, tagging transients of rare classes (spectroscopic anomalies), of uncommon host-galaxy environments (contextual anomalies), and of peculiar or interaction-powered phenomena (behavioral anomalies). Moreover, we demonstrate the power of a low-latency ($\sim$ms) approximate similarity search method to find transient analogs with similar light-curve evolution and host-galaxy environments. We use analogs for data-driven discovery, characterization, (re-)classification, and imputation in retrospective and real-time searches. To date we have identified $\sim$50 previously known and previously missed rare transients from real-time and retrospective searches, including but not limited to: SLSNe, TDEs, SNe IIn, SNe IIb, SNe Ia-CSM, SNe Ia-91bg-like, SNe Ib, SNe Ic, SNe Ic-BL, and M31 novae. Lastly, we report the discovery of 325 total transients, all observed between 2018-2021 and absent from public catalogs ($\sim$1% of all ZTF Astronomical Transient reports to the Transient Name Server through 2021). These methods enable a systematic approach to finding the "needle in the haystack" in large-volume data streams. Because of its integration with the ANTARES broker, LAISS is built to detect exciting transients in Rubin data.

arXiv:2404.00465v1 Announce Type: new Abstract: We present a speculative exploration of the properties of a proposed new Dark Matter (DM) candidate in a heretofore under-explored region of parameter space. Our proposed ultra-cold candidatae has been a matter of speculation for some time,and has recently been tentatively identified via direct-detection. While unconventional, demonstrated existence of this DM candidate would have wide-ranging implications for a range of fields, from particle cosmology to exobiology and the Search for Extraterrestrial Life (SETI).

Title to be confirmed

Abstract not available

• Speaker: Georges Meynet (Geneva)
• Friday 14 June 2024, 11:30-12:30
• Venue: Ryle seminar room + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2404.02139v1 Announce Type: new Abstract: A bright ($m_{\rm F150W,AB}$=24 mag), $z=1.95$ supernova (SN) candidate was discovered in JWST/NIRCam imaging acquired on 2023 November 17. The SN is quintuply-imaged as a result of strong gravitational lensing by a foreground galaxy cluster, detected in three locations, and remarkably is the second lensed SN found in the same host galaxy. The previous lensed SN was called "Requiem", and therefore the new SN is named "Encore". This makes the MACS J0138.0$-$2155 cluster the first known system to produce more than one multiply-imaged SN. Moreover, both SN Requiem and SN Encore are Type Ia SNe (SNe Ia), making this the most distant case of a galaxy hosting two SNe Ia. Using parametric host fitting, we determine the probability of detecting two SNe Ia in this host galaxy over a $\sim10$ year window to be $\approx3\%$. These observations have the potential to yield a Hubble Constant ($H_0$) measurement with $\sim10\%$ precision, only the third lensed SN capable of such a result, using the three visible images of the SN. Both SN Requiem and SN Encore have a fourth image that is expected to appear within a few years of $\sim2030$, providing unprecedented baseline for time-delay cosmography.

5 min read

That Starry Night Sky? It’s Full of Eclipses An artist’s concept shows the TRAPPIST-1 planets as they might be seen from Earth using an extremely powerful – and fictional – telescope. NASA/JPL-Caltech

Our star, the Sun, on occasion joins forces with the Moon to offer us Earthlings a spectacular solar eclipse – like the one that will be visible to parts of the United States, Mexico, and Canada on April 8.

But out there, among the other stars, how often can we see similar eclipses? The answer depends on your point of view. Literally.

On Earth, a total solar eclipse occurs when the Moon blocks the Sun’s disk as seen from part of Earth’s surface. In this case, the “path of totality” will be a strip cutting across the country, from Texas to Maine.

We also can see “eclipses” involving Mercury and Venus, the two planets in our solar system that orbit the Sun more closely than Earth, as they pass between our telescopes and the Sun (though only by using telescopes with protective filters to avoid eye damage). In these rare events, the planets are tiny dots crossing the Sun’s much larger disk.

A composite of images of the Venus transit taken by NASA’s Solar Dynamics Observatory on June 5, 2012. The image shows a timelapse of Venus’ path across the Sun. NASA/Goddard/SDO

And astronomers can, in a sense, “see” eclipses among other systems of planets orbiting their parent stars. In this case, the eclipse is a tiny drop in starlight as a planet, from our point of view, crosses the face of its star. That crossing, called a transit, can register on sensitive light sensors attached to telescopes on Earth and those in space, such as NASA’s Hubble Space Telescope, James Webb Space Telescope, or TESS (the Transiting Exoplanet Survey Satellite). It’s how the bulk of the more than 5,500 confirmed exoplanets – planets around other stars – have been detected so far, although other methods also are used to detect exoplanets.

“A solar eclipse is a huge transit,” said Allison Youngblood, the deputy project scientist for TESS at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

And both types of “transits” – whether they involve solar eclipses or exoplanets – can yield world-changing science. Solar eclipse observations in 1919 helped prove Einstein’s theory of general relativity, when the bending of a star’s light by the Sun’s gravity caused the star’s apparent position to shift – showing that gravity causes space and time to curve around it.

Exoplanet transits also provide far more than just detections of distant planets, Youngblood said.

“The planet passes in front of the star, and blocks a certain amount of the star’s light,” she said. “The dip [in starlight] tells us about the size of the planet. It gives us a measurement of the radius of the planet.”

Careful measurements of multiple transits also can reveal how long a year is on an exoplanet, and provide insights into its formation and history. Careful measurements of multiple transits also can provide insights into exoplanet formation and history.

And the starlight shining through the exoplanet’s atmosphere during its transit, if measured using an instrument called a spectrograph, can reveal deeper characteristics of the planet itself. The light is split into a rainbow-like spectrum, and slices missing from the spectrum can indicate gases in the planet’s atmosphere that absorbed that “color” – or wavelength.

“Measuring the planet at many wavelengths tells us what chemicals and what molecules are in that planet’s atmosphere,” Youngblood said.

Eclipses are such a handy way to capture information about distant worlds that scientists have learned how to create their own. Instead of waiting for eclipses to occur in nature, they can engineer them right inside their telescopes. Instruments called coronagraphs, first used on Earth to study the Sun’s outer atmosphere (the corona), are now carried aboard several space telescopes. And when NASA’s next flagship space telescope, the Nancy Grace Roman Space Telescope, launches by May 2027, it will demonstrate new coronagraph technologies that have never been flown in space before. Coronagraphs use a system of masks and filters to block the light from a central star, revealing the far fainter light of planets in orbit around it.

Of course, that isn’t quite as easy as it sounds. Whether searching for transits, or for direct images of exoplanets using a coronagraph, astronomers must contend with the overwhelming light from stars – an immense technological challenge.

“An Earth-like transit in front of stars is equivalent to a mosquito walking in front of a headlight,” said David Ciardi, chief scientist at the NASA Exoplanet Science Institute at Caltech. “That’s how little light is blocked.”

We don’t have this problem when viewing solar eclipses – “our very first coronagraphs,” Ciardi says. By pure happenstance, the Moon covers the Sun completely during an eclipse.

“A solar eclipse is like a human walking in front of a headlight,” he said.

We would have no such luck on other planets in our solar system.

Mars’ oddly shaped moons are too small to fully block the Sun during their transits; and while eclipses might be spectacular among the outer planets – for instance, Jupiter and its many moons – they wouldn’t match the total coverage of a solar eclipse.

We happen to be living at a fortunate time for eclipse viewing. Billions of years ago, the Moon was far closer to Earth, and would have appeared to dwarf the Sun during an eclipse. And in about 700 million years, the Moon will be so much farther away that it will no longer be able to make total solar eclipses.

“A solar eclipse is the pinnacle of being lucky,” Tripathi said. “The Moon’s size and distance allow it to completely block out the Sun’s light. We’re at this perfect time and place in the universe to be able to witness such a perfect phenomenon.”

A Long Year for a Cold Saturn

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Details Last Updated Apr 02, 2024 Related Terms

• Earth-like Exoplanets
• Eclipses
• Exoplanets
• Gas Giant Exoplanets
• James Webb Space Telescope (JWST)
• TESS (Transiting Exoplanet Survey Satellite)
• The Universe

Keep Exploring Discover More Topics From NASA

Exoplanets

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Solar System

A tiny clump of stars orbiting our galaxy should have been ripped apart by the Milky Way, but its continued existence hints it may be held together by a massive amount of dark matter