21 research outputs found
Luminous Radio Emission from the Superluminous Supernova 2017ens at 3.3 Yr After Explosion
We present the results from a multiyear radio campaign of the superluminous supernova (SLSN) SN 2017ens, which yielded the earliest radio detection of an SLSN to date at the age of âź3.3 yr after explosion. SN 2017ens was not detected at radio frequencies in the first âź300 days but reached Lν â 1028 erg sâ1 cmâ2 Hzâ1 at ν âź 6 GHz, âź1250 days post explosion. Interpreting the radio observations in the context of synchrotron radiation from the supernova shock interaction with the circumstellar medium (CSM), we infer an effective mass-loss rate áš â 10â4 Mâ yrâ1 at r âź 1017 cm from the explosion\u27s site, for a wind speed of vw = 50â60 km sâ1 as measured from optical spectra. These findings are consistent with the spectroscopic metamorphosis of SN 2017ens from hydrogen poor to hydrogen rich âź190 days after explosion reported by Chen et al. SN 2017ens is thus an addition to the sample of hydrogen-poor massive progenitors that explode shortly after having lost their hydrogen envelope. The inferred circumstellar densities, implying a CSM mass up to âź0.5 Mâ, and low velocity of the ejection suggest that binary interactions (in the form of common-envelope evolution and subsequent envelope ejection) play a role in shaping the evolution of the stellar progenitors of SLSNe in the Ⲡ500 yr preceding core collapse
YSE-PZ: A Transient Survey Management Platform that Empowers the Human-in-the-Loop
The modern study of astrophysical transients has been transformed by an
exponentially growing volume of data. Within the last decade, the transient
discovery rate has increased by a factor of ~20, with associated survey data,
archival data, and metadata also increasing with the number of discoveries. To
manage the data at this increased rate, we require new tools. Here we present
YSE-PZ, a transient survey management platform that ingests multiple live
streams of transient discovery alerts, identifies the host galaxies of those
transients, downloads coincident archival data, and retrieves photometry and
spectra from ongoing surveys. YSE-PZ also presents a user with a range of tools
to make and support timely and informed transient follow-up decisions. Those
subsequent observations enhance transient science and can reveal physics only
accessible with rapid follow-up observations. Rather than automating out human
interaction, YSE-PZ focuses on accelerating and enhancing human decision
making, a role we describe as empowering the human-in-the-loop. Finally, YSE-PZ
is built to be flexibly used and deployed; YSE-PZ can support multiple,
simultaneous, and independent transient collaborations through group-level data
permissions, allowing a user to view the data associated with the union of all
groups in which they are a member. YSE-PZ can be used as a local instance
installed via Docker or deployed as a service hosted in the cloud. We provide
YSE-PZ as an open-source tool for the community.Comment: 23 pages, 9 figures, submitted to PAS
Radio analysis of SN2004C reveals an unusual CSM density profile as a harbinger of core collapse
We present extensive multifrequency Karl G. Jansky Very Large Array (VLA) and Very Long Baseline Array (VLBA) observations of the radio-bright supernova (SN) IIb SN 2004C that span âź40â2793 days post-explosion. We interpret the temporal evolution of the radio spectral energy distribution in the context of synchrotron self-absorbed emission from the explosion's forward shock as it expands in the circumstellar medium (CSM) previously sculpted by the mass-loss history of the stellar progenitor. VLBA observations and modeling of the VLA data point to a blastwave with average velocity âź0.06 c that carries an energy of â1049 erg. Our modeling further reveals a flat CSM density profile ĎCSM â Râ0.03Âą0.22 up to a break radius Rbr â (1.96 Âą 0.10) Ă 1016 cm, with a steep density gradient following ĎCSM â Râ2.3Âą0.5 at larger radii. We infer that the flat part of the density profile corresponds to a CSM shell with mass âź0.021 Mâ, and that the progenitor's effective mass-loss rate varied with time over the range (50â500) Ă 10â5 Mâ yrâ1 for an adopted wind velocity vw = 1000 km sâ1 and shock microphysical parameters epsilone = 0.1, epsilonB = 0.01. These results add to the mounting observational evidence for departures from the traditional single-wind mass-loss scenarios in evolved, massive stars in the centuries leading up to core collapse. Potentially viable scenarios include mass loss powered by gravity waves and/or interaction with a binary companion
Keck Infrared Transient Survey I: Survey Description and Data Release 1
We present the Keck Infrared Transient Survey (KITS), a NASA Key Strategic
Mission Support program to obtain near-infrared (NIR) spectra of astrophysical
transients of all types, and its first data release, consisting of 105 NIR
spectra of 50 transients. Such a data set is essential as we enter a new era of
IR astronomy with the James Webb Space Telescope (JWST) and the upcoming Nancy
Grace Roman Space Telescope (Roman). NIR spectral templates will be essential
to search JWST images for stellar explosions of the first stars and to plan an
effective Roma} SN Ia cosmology survey, both key science objectives for mission
success. Between 2022 February and 2023 July, we systematically obtained 274
NIR spectra of 146 astronomical transients, representing a significant increase
in the number of available NIR spectra in the literature. The first data
release includes data from the 2022A semester. We systematically observed three
samples: a flux-limited sample that includes all transients 17 mag in a red
optical band (usually ZTF r or ATLAS o bands); a volume-limited sample
including all transients within redshift ( Mpc); and
an SN Ia sample targeting objects at phases and light-curve parameters that had
scant existing NIR data in the literature. The flux-limited sample is 39%
complete (60% excluding SNe Ia), while the volume-limited sample is 54%
complete and is 79% complete to . All completeness numbers will rise
with the inclusion of data from other telescopes in future data releases.
Transient classes observed include common Type Ia and core-collapse supernovae,
tidal disruption events (TDEs), luminous red novae, and the newly categorized
hydrogen-free/helium-poor interacting Type Icn supernovae. We describe our
observing procedures and data reduction using Pypeit, which requires minimal
human interaction to ensure reproducibility
The Young Supernova Experiment: Survey Goals, Overview, and Operations
Time domain science has undergone a revolution over the past decade, with
tens of thousands of new supernovae (SNe) discovered each year. However,
several observational domains, including SNe within days or hours of explosion
and faint, red transients, are just beginning to be explored. Here, we present
the Young Supernova Experiment (YSE), a novel optical time-domain survey on the
Pan-STARRS telescopes. Our survey is designed to obtain well-sampled
light curves for thousands of transient events up to . This
large sample of transients with 4-band light curves will lay the foundation for
the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope,
providing a critical training set in similar filters and a well-calibrated
low-redshift anchor of cosmologically useful SNe Ia to benefit dark energy
science. As the name suggests, YSE complements and extends other ongoing
time-domain surveys by discovering fast-rising SNe within a few hours to days
of explosion. YSE is the only current four-band time-domain survey and is able
to discover transients as faint 21.5 mag in and 20.5 mag in
, depths that allow us to probe the earliest epochs of stellar explosions.
YSE is currently observing approximately 750 square degrees of sky every three
days and we plan to increase the area to 1500 square degrees in the near
future. When operating at full capacity, survey simulations show that YSE will
find 5000 new SNe per year and at least two SNe within three days of
explosion per month. To date, YSE has discovered or observed 8.3% of the
transient candidates reported to the International Astronomical Union in 2020.
We present an overview of YSE, including science goals, survey characteristics
and a summary of our transient discoveries to date.Comment: ApJ, in press; more information at https://yse.ucsc.edu
Radio and X-ray observations of the luminous fast blue optical transient AT 2020xnd
We present deep X-ray and radio observations of the fast blue optical transient (FBOT) AT 2020xnd/ZTF 20acigmel at z = 0.2433 from 13 days to 269 days after explosion. AT 2020xnd belongs to the category of optically luminous FBOTs with similarities to the archetypal event AT 2018cow. AT 2020xnd shows luminous radio emission reaching L ν â 8 Ă 1029 erg sâ1 Hzâ1 at 20 GHz and 75 days post-explosion, accompanied by luminous and rapidly fading soft X-ray emission peaking at L X â 6 Ă 1042 erg sâ1. Interpreting the radio emission in the context of synchrotron radiation from the explosionâs shock interaction with the environment, we find that AT 2020xnd launched a high-velocity outflow (v âź 0.1câ0.2c) propagating into a dense circumstellar medium (effective MĚâ10â3Mâ yrâ1 for an assumed wind velocity of v w = 1000 km sâ1). Similar to AT 2018cow, the detected X-ray emission is in excess compared to the extrapolated synchrotron spectrum and constitutes a different emission component, possibly powered by accretion onto a newly formed black hole or neutron star. These properties make AT 2020xnd a high-redshift analog to AT 2018cow, and establish AT 2020xnd as the fourth member of the class of optically luminous FBOTs with luminous multiwavelength counterparts
Quantum Spacetime Phenomenology
I review the current status of phenomenological programs inspired by
quantum-spacetime research. I stress in particular the significance of results
establishing that certain data analyses provide sensitivity to effects
introduced genuinely at the Planck scale. And my main focus is on
phenomenological programs that managed to affect the directions taken by
studies of quantum-spacetime theories.Comment: 125 pages, LaTex. This V2 is updated and more detailed than the V1,
particularly for quantum-spacetime phenomenology. The main text of this V2 is
about 25% more than the main text of the V1. Reference list roughly double
The Early Phases of Supernova 2020pni:Shock Ionization of the Nitrogen-enriched Circumstellar Material
We present multiwavelength observations of the Type II SN 2020pni. Classified
at days after explosion, the object showed narrow (FWHM
) recombination lines of ionized helium,
nitrogen, and carbon, as typically seen in flash-spectroscopy events. Using the
non-LTE radiative transfer code CMFGEN to model our first high resolution
spectrum, we infer a progenitor mass-loss rate of
M yr (assuming a wind
velocity of ), estimated at a radius of
. In addition, we find that the
progenitor of SN 2020pni was enriched in helium and nitrogen (relative
abundances in mass fractions of 0.300.40, and ,
respectively). Radio upper limits are also consistent with a dense CSM, and a
mass-loss rate of . During
the first 4 days after first light, we also observe an increase in velocity of
the hydrogen lines (from to ), which suggests a complex CSM. The
presence of dense and confined CSM, as well as its inhomogeneous structure,
suggest a phase of enhanced mass loss of the progenitor of SN 2020pni during
the last year before explosion. Finally, we compare SN 2020pni to a sample of
other shock-photoionization events. We find no evidence of correlations among
the physical parameters of the explosions and the characteristics of the CSM
surrounding the progenitors of these events. This favors the idea that the
mass-loss experienced by massive stars during their final years could be
governed by stochastic phenomena, and that, at the same time, the physical
mechanisms responsible for this mass-loss must be common to a variety of
different progenitors.Comment: 19 pages, 14 figure
Luminous Radio Emission from the Superluminous Supernova 2017ens at 3.3 yr after Explosion
We present the results from a multiyear radio campaign of the superluminous supernova (SLSN) SN 2017ens, which yielded the earliest radio detection of an SLSN to date at the age of âź3.3 yr after explosion. SN 2017ens was not detected at radio frequencies in the first âź300 days but reached L _ν â 10 ^28 erg s ^â1 cm ^â2 Hz ^â1 at ν âź 6 GHz, âź1250 days post explosion. Interpreting the radio observations in the context of synchrotron radiation from the supernova shock interaction with the circumstellar medium (CSM), we infer an effective mass-loss rate at r âź 10 ^17 cm from the explosionâs site, for a wind speed of v _w = 50â60 km s ^â1 as measured from optical spectra. These findings are consistent with the spectroscopic metamorphosis of SN 2017ens from hydrogen poor to hydrogen rich âź190 days after explosion reported by Chen et al. SN 2017ens is thus an addition to the sample of hydrogen-poor massive progenitors that explode shortly after having lost their hydrogen envelope. The inferred circumstellar densities, implying a CSM mass up to âź0.5 M _â , and low velocity of the ejection suggest that binary interactions (in the form of common-envelope evolution and subsequent envelope ejection) play a role in shaping the evolution of the stellar progenitors of SLSNe in the â˛500 yr preceding core collapse