David J. Sand
YOU?
Author Swipe
View article: Optimizing Kilonova Searches: A Case Study of the Type IIb SN 2025ulz in the Localization Volume of the Low-significance Gravitational Wave Event S250818k
Optimizing Kilonova Searches: A Case Study of the Type IIb SN 2025ulz in the Localization Volume of the Low-significance Gravitational Wave Event S250818k Open
Kilonovae, the ultraviolet/optical/infrared counterparts to binary neutron star mergers, are an exceptionally rare class of transients. Optical follow-up campaigns are plagued by contaminating transients, which may mimic kilonovae but do n…
View article: Mid-infrared Dust Evolution and Late-time Circumstellar Medium Interaction in SN 2017eaw
Mid-infrared Dust Evolution and Late-time Circumstellar Medium Interaction in SN 2017eaw Open
We present JWST/Mid-Infrared Instrument (MIRI) and complementary ground-based near-infrared observations of the Type II SN 2017eaw taken 6 yr postexplosion. SN 2017eaw is still detected out to 25 μ m and there is minimal evolution in the m…
View article: DELVE-ing into the Milky Way’s Globular Clusters: Assessing Extratidal Features in NGC 5897, NGC 7492, and Testing Detectability with Deeper Photometry
DELVE-ing into the Milky Way’s Globular Clusters: Assessing Extratidal Features in NGC 5897, NGC 7492, and Testing Detectability with Deeper Photometry Open
Extratidal features around globular clusters (GCs) are tracers of their disruption, stellar stream formation, and their host’s gravitational potential. However, these features remain challenging to detect due to their low surface brightnes…
View article: SN 2019hnl: A Type IIP Supernova with a Partially Stripped, Low-mass Progenitor
SN 2019hnl: A Type IIP Supernova with a Partially Stripped, Low-mass Progenitor Open
We present optical photometry and spectroscopy of SN 2019hnl. Discovered within ∼26 hr of explosion by the ATLAS survey, SN 2019hnl is a typical Type IIP supernova (SN) with a peak absolute V -band magnitude of −16.7 ± 0.1 mag, a plateau l…
View article: JWST Spectroscopy of SN Ia 2022aaiq and 2024gy: Evidence for Enhanced Central Stable Ni Abundance and a Deflagration-to-Detonation Transition
JWST Spectroscopy of SN Ia 2022aaiq and 2024gy: Evidence for Enhanced Central Stable Ni Abundance and a Deflagration-to-Detonation Transition Open
We present optical + near-infrared (NIR) + mid-infrared (MIR) observations of the normal Type Ia supernovae (SN Ia) 2022aaiq and 2024gy in the nebular phase, continuously spanning 0.35-28 microns. Medium-resolution JWST spectroscopy reveal…
View article: Hubble Space Telescope Imaging of Three Isolated Faint Dwarf Galaxies Beyond the Local Group: Pavo, Corvus A, and Kamino
Hubble Space Telescope Imaging of Three Isolated Faint Dwarf Galaxies Beyond the Local Group: Pavo, Corvus A, and Kamino Open
We present new Hubble Space Telescope (HST) imaging of three recently discovered star-forming dwarf galaxies beyond the Local Group: Pavo, Corvus A, and Kamino. The discovery of Kamino is reported here for the first time. They rank among t…
View article: The DECam MAGIC Survey: Spectroscopic Follow-up of the Most Metal-poor Stars in the Distant Milky Way Halo<sup>*</sup>
The DECam MAGIC Survey: Spectroscopic Follow-up of the Most Metal-poor Stars in the Distant Milky Way Halo<sup>*</sup> Open
In this work, we present high-resolution spectroscopic observations for six metal-poor stars with [Fe/H] < –3 (including one with [Fe/H] < –4), selected using narrowband Ca ii HK photometry from the DECam MAGIC Survey. The spectroscopic da…
View article: Dichotomy in Long-Lived Radio Emission from Tidal Disruption Events AT 2020zso and AT 2021sdu: Multi-Component Outflows vs. Host Contamination
Dichotomy in Long-Lived Radio Emission from Tidal Disruption Events AT 2020zso and AT 2021sdu: Multi-Component Outflows vs. Host Contamination Open
We present a detailed radio study of the tidal disruption events (TDEs) AT 2020zso and AT 2021sdu. Both exhibit transient radio emission beginning shortly after optical discovery and persisting for several years. For AT 2020zso, we identif…
View article: DELVE Milky Way Satellite Census I: Satellite Population and Survey Selection Function
DELVE Milky Way Satellite Census I: Satellite Population and Survey Selection Function Open
The properties of Milky Way satellite galaxies have important implications for galaxy formation, reionization, and the fundamental physics of dark matter. However, the population of Milky Way satellites includes the faintest known galaxies…
View article: Early Shock Cooling Observations and Progenitor Constraints of Type IIb Supernova SN 2024uwq
Early Shock Cooling Observations and Progenitor Constraints of Type IIb Supernova SN 2024uwq Open
We present early multiwavelength photometric and spectroscopic observations of the Type IIb supernova SN 2024uwq, capturing its shock-cooling emission phase and double-peaked light-curve evolution. Early spectra reveal broad H α ( v ∼ 15,5…
View article: Pavo: Stellar Feedback in Action in a Low-mass Dwarf Galaxy
Pavo: Stellar Feedback in Action in a Low-mass Dwarf Galaxy Open
MeerKAT observations of the recently discovered, extremely low mass galaxy Pavo have revealed a neutral gas (H i ) reservoir that was undetected in archival H i single dish data. We measure Pavo’s H i mass as , making it the l…
View article: One Year of SN 2023ixf: Breaking through the Degenerate Parameter Space in Light-curve Models with Pulsating Progenitors
One Year of SN 2023ixf: Breaking through the Degenerate Parameter Space in Light-curve Models with Pulsating Progenitors Open
We present and analyze the extensive optical broadband photometry of the Type II SN 2023ixf up to 1 yr after explosion. We find that, when compared to two preexisting model grids, the bolometric light curve is consistent with drastically d…
View article: The Dark Energy Camera All Data Everywhere cosmic shear project V: Constraints on cosmology and astrophysics from 270 million galaxies across 13,000 deg$^2$ of the sky
The Dark Energy Camera All Data Everywhere cosmic shear project V: Constraints on cosmology and astrophysics from 270 million galaxies across 13,000 deg$^2$ of the sky Open
We present constraints on models of cosmology and astrophysics using cosmic shear data vectors from three datasets: the northern and southern Galactic cap of the Dark Energy Camera All Data Everywhere (DECADE) project, and the Dark Energy …
View article: Late-time Hubble Space Telescope Ultraviolet Spectra of SN 2023ixf and SN 2024ggi Show Ongoing Interaction with Circumstellar Material
Late-time Hubble Space Telescope Ultraviolet Spectra of SN 2023ixf and SN 2024ggi Show Ongoing Interaction with Circumstellar Material Open
We present far- and near-ultraviolet (UV) spectra of the Type II supernovae (SNe) SN~2023ixf from days 199 to 722 and SN~2024ggi at days 41 and 232. Both supernovae show broad, blueshifted, and asymmetric UV emission lines with an initial …
View article: Departures from standard disc predictions in intensive ground-based monitoring of three AGNs
Departures from standard disc predictions in intensive ground-based monitoring of three AGNs Open
We present ground-based multiband light curves of the AGN Mrk 509, NGC 4151, and NGC 4593 obtained contemporaneously with Swift monitoring. We measure cross-correlation lags relative to Swift UVW2 (1928 Å) and test the standard prediction …
View article: Identifying Dwarfs of MC Analog GalaxiEs (ID-MAGE): The Search for Satellites around Low-mass Hosts
Identifying Dwarfs of MC Analog GalaxiEs (ID-MAGE): The Search for Satellites around Low-mass Hosts Open
We present results from Identifying Dwarfs of MC Analog GalaxiEs (ID-MAGE), a survey aimed at identifying and characterizing unresolved satellite galaxies around 35 nearby LMC- and SMC-mass hosts ( D = 4−10 Mpc). We use archival DESI Legac…
View article: Spectroscopic Analysis of Pictor II: a very low metallicity ultra-faint dwarf galaxy bound to the Large Magellanic Cloud
Spectroscopic Analysis of Pictor II: a very low metallicity ultra-faint dwarf galaxy bound to the Large Magellanic Cloud Open
We present Magellan/IMACS and Magellan/MIKE spectroscopy of the ultra-faint dwarf (UFD) galaxy Pictor~II (Pic~II) that is located only 12 kpc from the Large Magellanic Cloud (LMC). From the IMACS spectroscopy, we identify 13 member stars a…
View article: The NGC 3109 Satellite System: The First Systematic Resolved Search for Dwarf Galaxies Around an SMC-mass Host
The NGC 3109 Satellite System: The First Systematic Resolved Search for Dwarf Galaxies Around an SMC-mass Host Open
We report the results of the deepest search to date for dwarf galaxies around NGC 3109, a barred spiral galaxy with a mass similar to that of the Small Magellanic Cloud (SMC), using a semiautomated search method. Using the Dark Energy Came…
View article: Limits on the ejecta mass during the search for kilonovae associated with neutron star-black hole mergers: A case study of S230518h, GW230529, S230627c and the low-significance candidate S240422ed
Limits on the ejecta mass during the search for kilonovae associated with neutron star-black hole mergers: A case study of S230518h, GW230529, S230627c and the low-significance candidate S240422ed Open
Neutron star-black hole (NSBH) mergers, detectable via their gravitational-wave (GW) emission, are expected to produce kilonovae (KNe). Four NSBH candidates have been identified and followed-up by more than fifty instruments since the star…
View article: Double-offset Cassegrain telescopes for the Ultraviolet Type Ia mission concept
Double-offset Cassegrain telescopes for the Ultraviolet Type Ia mission concept Open
Our understanding of cosmology is shaped by Type Ia supernovae (SNe Ia), the runaway thermonuclear detonations of white dwarfs via accretion from a companion star. The nature of this companion star is highly debated, with disparate models …
View article: Near-Infrared Spectroscopy and Detection of Carbon Monoxide in the Type II Supernova SN 2023ixf
Near-Infrared Spectroscopy and Detection of Carbon Monoxide in the Type II Supernova SN 2023ixf Open
Core-collapse supernovae (CCSNe) may contribute a significant amount of dust in the early universe. Freshly formed coolant molecules (e.g., CO) and warm dust can be found in CCSNe as early as ~100 d after the explosion, allowing the study …
View article: DELVE-ing into the Milky Way's Globular Clusters: Assessing extra-tidal features in NGC 5897, NGC 7492, and testing detectability with deeper photometry
DELVE-ing into the Milky Way's Globular Clusters: Assessing extra-tidal features in NGC 5897, NGC 7492, and testing detectability with deeper photometry Open
Extra-tidal features around globular clusters (GCs) are tracers of their disruption, stellar stream formation, and their host's gravitational potential. However, these features remain challenging to detect due to their low surface brightne…
View article: The DECam MAGIC Survey: Spectroscopic Follow-up of the Most Metal-Poor Stars in the Distant Milky Way Halo
The DECam MAGIC Survey: Spectroscopic Follow-up of the Most Metal-Poor Stars in the Distant Milky Way Halo Open
In this work, we present high-resolution spectroscopic observations for six metal-poor stars with [Fe/H]<-3 (including one with [Fe/H]<-4), selected using narrow-band Ca II HK photometry from the DECam MAGIC Survey. The spectroscopic data …
View article: NGC3109 detection limits
NGC3109 detection limits Open
This directory contains the completeness results obtained in Doliva-Dolinsky et al. 2025. We present the detection limits obtain for a dwarf with a V-band magnitude between mv and mv+0.5 , and log(rh/pc) between log_rh and log_rh+0.2.
View article: SN 2021hpr: A Normal Type Ia Supernova Showing Excess Emission in the Early Rising Phase
SN 2021hpr: A Normal Type Ia Supernova Showing Excess Emission in the Early Rising Phase Open
We present extensive optical observations of a nearby Type Ia supernova (SN Ia), SN 2021hpr, located in the spiral galaxy NGC 3147 at a distance of ∼45 Mpc. Our observations cover a phase within ∼1–2 days to ∼290 days after the explosion. …
View article: Deep Photometric Observations of Ultrafaint Milky Way Satellites Centaurus I and Eridanus IV*
Deep Photometric Observations of Ultrafaint Milky Way Satellites Centaurus I and Eridanus IV* Open
We present deep Magellan+Megacam imaging of Centaurus I (Cen I) and Eridanus IV (Eri IV), two recently discovered Milky Way ultrafaint satellites. Our data reach ∼2–3 mag deeper than the discovery data from the DECam Local Volume Explorati…
View article: X-Ray Constraints on Wandering Black Holes in Stripped Galaxy Nuclei in the Halo of NGC 5128
X-Ray Constraints on Wandering Black Holes in Stripped Galaxy Nuclei in the Halo of NGC 5128 Open
A subset of galaxies have dense nuclei, and when these galaxies are accreted and tidally stripped, the nuclei can masquerade as globular clusters in the halos of large galaxies. If these nuclei contain massive central black holes, some may…
View article: JWST and Ground-based Observations of the Type Iax Supernovae SN 2024pxl and SN 2024vjm: Evidence for Weak Deflagration Explosions
JWST and Ground-based Observations of the Type Iax Supernovae SN 2024pxl and SN 2024vjm: Evidence for Weak Deflagration Explosions Open
We present panchromatic optical $+$ near-infrared (NIR) $+$ mid-infrared (MIR) observations of the intermediate-luminosity Type Iax supernova (SN Iax) 2024pxl and the extremely low-luminosity SN Iax 2024vjm. JWST observations provide unpre…
View article: Early Shock-Cooling Observations and Progenitor Constraints of Type IIb SN 2024uwq
Early Shock-Cooling Observations and Progenitor Constraints of Type IIb SN 2024uwq Open
We present early multi-wavelength photometric and spectroscopic observations of the Type IIb supernova SN 2024uwq, capturing its shock-cooling emission phase and double-peaked light curve evolution. Early spectra reveal broad H-alpha (v ~ …