Daniel Gruen

A census of Dark Energy Survey Year 3 redMaPPer galaxy clusters in a high exposure eROSITA All Sky Survey region

P. A. Giles, A. K. Romer, J. Pilling +64

We present the cross-match of galaxy clusters detected by redMaPPer using the first three years of Dark Energy Survey (DESY3RM) operations, and the first release of the eROSITA-All…

Data-driven Galaxy Population Prior for Photometric Redshifts

Nikolas Frediani, Daniel Gruen, Luca Tortorelli +1

Stage-IV cosmological surveys rely on well-characterised photometric redshift distributions for constraining cosmological models, yet the projected weak lensing requirements are ab…

On the Clustering Bias of Unresolved Gamma-Ray Sources

Bhashin A. Thakore, Marco Regis, Michela Negro +4

The Unresolved $γ$ -Ray Background (UGRB) encodes the collective emission of source populations that are too faint to be detected individually, and its cross-correlation with tracer…

GRB 260310A/SN 2026fgk: Photometric and Spectroscopic Evolution of a Nearby GRB-Supernova and an Exceptionally Bright Afterglow at z=0.153

Brendan O'Connor, Malte Busmann, Xander J. Hall +24

The association of broad-lined Type Ic supernovae with long-duration gamma-ray bursts (GRBs) has been known for 28 years. However, only about seventy gamma-ray burst supernovae (GR…

EP260321a/SN 2026gzf: The Faintest Shock Breakout Associated with a Broad-Lined Supernova

Brendan O'Connor, Xander J. Hall, Malte Busmann +33

The explosion of a star is first marked by the shock wave breaking out of the stellar surface, producing a burst of ultraviolet and X-ray radiation. These events are observationall…

Hard X-ray Sources in Fermi UFOs

Alessandro Paggi, Ioannis Liodakis, John Antoniadis +7

Identification and/or association of unidentified $γ$ -ray sources with lower-energy counterparts represents a key challenge in modern astronomy, due to the relatively large positio…

A Natural $≳ 100 \times$ Telescope: Discovery of the Strongly Lensed Type II SN 2025mkn at $z = 1.37$

Cameron Lemon, Ariel Goobar, Joel Johansson +90

We present the discovery of SN 2025mkn, a gravitationally lensed Type II supernova. First detected as a blue transient in ZTF, 0.83 $^{''}$ from a $z = 0.42$ elliptical gala…

Long GRB 250916A: an Off-axis Powerlaw Jet with Thermal Cocoon

Utkarsh Pathak, Sameer K. Patil, Hitesh Tanenia +22

Some gamma-ray bursts (GRBs) exhibit precursor emission episodes preceding the main emission, with a quiescent period in between. The properties of the precursor emission and the d…

astro-ph.HE2026★ 1 cited

TDE 2025abcr: A Tidal Disruption Event in the Outskirts of a Massive Galaxy

Robert Stein, Jonathan Carney, Charlotte Ward +27

Tidal disruption events (TDEs) have traditionally been discovered in optical sky surveys through targeted searches of nuclear transients. However, it is expected that some TDEs wil…

Multi-Tracer Cross-Correlations of the Unresolved $γ$ -Ray Sky

B. Thakore, M. Regis, M. Negro +4

Our understanding of the $γ$ -ray sky has greatly advanced, yet studying the unresolved $γ$ -ray background (UGRB) can unveil the nature of the faintest $γ$ -ray source populations in…

ZTF25abjmnps (AT2025ulz) and S250818k: A Candidate Superkilonova from a Sub-threshold Sub-Solar Gravitational Wave Trigger

Mansi M. Kasliwal, Tomas Ahumada, Robert Stein +61

On August 18, 2025, the LIGO-Virgo-KAGRA collaboration reported gravitational waves from a sub-threshold binary neutron star merger. If astrophysical, this event would have a surpr…

AT2025ulz and S250818k: Investigating early time observations of a subsolar mass gravitational-wave binary neutron star merger candidate

Xander J. Hall, Malte Busmann, Hauke Koehn +32

Over the past LIGO--Virgo--KAGRA (LVK) observing runs, it has become increasingly clear that identifying the next electromagnetic counterparts to gravitational-wave (GW) neutron st…

AT2025ulz and S250818k: Leveraging DESI spectroscopy in the hunt for a kilonova associated with a sub-solar mass gravitational wave candidate

Xander J. Hall, Antonella Palmese, Brendan O'Connor +47

On August 18th, 2025, the LIGO--Virgo--KAGRA collaboration reported a sub-threshold gravitational wave candidate detection consistent with a sub-solar-mass neutron star merger, den…

astro-ph.CO2025★ 1 cited

Discovery of SN 2025wny: a Strongly Gravitationally Lensed Superluminous Supernova at z = 2.01

Joel Johansson, Daniel A. Perley, Ariel Goobar +31

We present the discovery of SN 2025wny (ZTF25abnjznp/GOTO25gtq) and spectroscopic classification of this event as the first gravitationally lensed Type I superluminous supernovae (…

Comprehensive X-ray Observations of the Exceptional Ultra-long X-ray and Gamma-ray Transient GRB 250702B with Swift, NuSTAR, and Chandra: Insights from the X-ray Afterglow Properties

Brendan O'Connor, Ramandeep Gill, James DeLaunay +22

GRB 250702B is an exceptional transient that produced multiple episodes of luminous gamma-ray radiation lasting for $> 25$ ks, placing it among the class of ultra-long gamma-ray bur…

astro-ph.HE2025★ 1 cited

GRB 250704B: An Off-axis Short GRB with a Long-Lived Afterglow Plateau

Vishwajeet Swain, Tomás Ahumada, Sameer K. Patil +27

We present a detailed multi-wavelength afterglow study of the short GRB 250704B, extensively monitored in optical and near-infrared bands. Its afterglow displays an unusually long-…

Optical/infrared observations of the extraordinary GRB 250702B: a highly obscured afterglow in a massive galaxy consistent with multiple possible progenitors

Jonathan Carney, Igor Andreoni, Brendan O'Connor +31

GRB 250702B was the longest gamma-ray burst ever detected, with a duration that challenges standard collapsar models and suggests an exotic progenitor. We collected a rich set of o…