The most precise local measurements of H0 rely on observations of Type Ia supernovae (SNe Ia) coupled with Cepheid distances to SN Ia host galaxies. Recent results have shown tension comparing H0 to ...the value inferred from CMB observations assuming ΛCDM, making it important to check for potential systematic uncertainties in either approach. To date, precise local H0 measurements have used SN Ia distances based on optical photometry, with corrections for light curve shape and colour. Here, we analyse SNe Ia as standard candles in the near-infrared (NIR), where luminosity variations in the supernovae and extinction by dust are both reduced relative to the optical. From a combined fit to 9 nearby calibrator SNe with host Cepheid distances from Riess et al. (2016) and 27 SNe in the Hubble flow, we estimate the absolute peak J magnitude MJ = −18.524 ± 0.041 mag and H0 = 72.8 ± 1.6 (statistical) ±2.7 (systematic) km s-1 Mpc-1. The 2.2% statistical uncertainty demonstrates that the NIR provides a compelling avenue to measuring SN Ia distances, and for our sample the intrinsic (unmodeled) peak J magnitude scatter is just ~0.10 mag, even without light curve shape or colour corrections. Our results do not vary significantly with different sample selection criteria, though photometric calibration in the NIR may be a dominant systematic uncertainty. Our findings suggest that tension in the competing H0 distance ladders is likely not a result of supernova systematics that could be expected to vary between optical and NIR wavelengths, like dust extinction. We anticipate further improvements in H0 with a larger calibrator sample of SNe Ia with Cepheid distances, more Hubble flow SNe Ia with NIR light curves, and better use of the full NIR photometric data set beyond simply the peak J-band magnitude.
During the second observing run of the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo Interferometer, a gravitational-wave signal consistent with a binary neutron star ...coalescence was detected on 2017 August 17th (GW170817), quickly followed by a coincident short gamma-ray burst trigger detected by the Fermi satellite. The Distance Less Than 40 (DLT40) Mpc supernova search performed pointed follow-up observations of a sample of galaxies regularly monitored by the survey that fell within the combined LIGO+Virgo localization region and the larger Fermi gamma-ray burst error box. Here we report the discovery of a new optical transient (DLT17ck, also known as SSS17a; it has also been registered as AT 2017gfo) spatially and temporally coincident with GW170817. The photometric and spectroscopic evolution of DLT17ck is unique, with an absolute peak magnitude of Mr = −15.8 0.1 and an r-band decline rate of 1.1 mag day−1. This fast evolution is generically consistent with kilonova models, which have been predicted as the optical counterpart to binary neutron star coalescences. Analysis of archival DLT40 data does not show any sign of transient activity at the location of DLT17ck down to r ∼ 19 mag in the time period between 8 months and 21 days prior to GW170817. This discovery represents the beginning of a new era for multi-messenger astronomy, opening a new path by which to study and understand binary neutron star coalescences, short gamma-ray bursts, and their optical counterparts.
Abstract
We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from
z
= 0.001 to 2.26. ...This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω
M
= 0.334 ± 0.018 from SNe Ia alone. For a flat
w
0
CDM model, we measure
w
0
= −0.90 ± 0.14 from SNe Ia alone,
H
0
= 73.5 ± 1.1 km s
−1
Mpc
−1
when including the Cepheid host distances and covariance (SH0ES), and
w
0
=
−
0.978
−
0.031
+
0.024
when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both
w
0
values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat
w
0
w
a
CDM universe, and measure
w
a
=
−
0.1
−
2.0
+
0.9
from Pantheon+ SNe Ia alone,
H
0
= 73.3 ± 1.1 km s
−1
Mpc
−1
when including SH0ES Cepheid distances, and
w
a
=
−
0.65
−
0.32
+
0.28
when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of
H
0
and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.
Double detonations in double white dwarf (WD) binaries undergoing unstable mass transfer have emerged in recent years as one of the most promising Type Ia supernova (SN Ia) progenitor scenarios. One ...potential outcome of this "dynamically driven double-degenerate double-detonation" (D6) scenario is that the companion WD survives the explosion and is flung away with a velocity equal to its >1000 km s−1 pre-SN orbital velocity. We perform a search for these hypervelocity runaway WDs using Gaia's second data release. In this paper, we discuss seven candidates followed up with ground-based instruments. Three sources are likely to be some of the fastest known stars in the Milky Way, with total Galactocentric velocities between 1000 and 3000 km s−1, and are consistent with having previously been companion WDs in pre-SN Ia systems. However, although the radial velocity of one of the stars is >1000 km s−1, the radial velocities of the other two stars are puzzlingly consistent with 0. The combined five-parameter astrometric solutions from Gaia and radial velocities from follow-up spectra yield tentative 6D confirmation of the D6 scenario. The past position of one of these stars places it within a faint, old SN remnant, further strengthening the interpretation of these candidates as hypervelocity runaways from binary systems that underwent SNe Ia.
Abstract
We present an analysis of 102 Type Ia supernovae (SNe Ia) in nearby (
z
< 0.1), x-ray-selected galaxy clusters. This is the largest such sample to date and is based on archival data ...primarily from ZTF and ATLAS. We divide our SNe Ia into an inner cluster sample projected within
r
500
of the cluster center and an outer cluster sample projected between
r
500
and 2
r
500
. We compare these to field samples of SNe Ia at similar redshifts in both quiescent and star-forming host galaxies. Based on SALT3 fits to the light curves, we find that the inner cluster SNe Ia have a higher fraction of fast-evolving objects (SALT3
x
1
< −1) than the outer cluster or field quiescent samples. This implies an intrinsically different population of SNe Ia occurs in inner cluster environments, beyond known correlations based on host galaxy alone. Our cluster samples show a strongly bimodal
x
1
distribution with a fast-evolving component that dominates the inner cluster objects (≳75%) but is just a small fraction of SNe Ia in field star-forming galaxies (≲10%). We do not see strong evidence for variations in the color (SALT3
c
) distributions among the samples and find only minor differences in SN Ia standardization parameters and Hubble residuals. We suggest that the age of the stellar population drives the observed distributions, with the oldest populations nearly exclusively producing fast-evolving SNe Ia.
Abstract
The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) is forecast to collect a large sample of Type Ia supernovae (SNe Ia) expected to be instrumental in unveiling the ...nature of dark energy. The feat, however, requires accurately measuring the two components of the Hubble diagram, distance modulus and redshift. Distance is estimated from SN Ia parameters extracted from light-curve fits, where the average quality of light curves is primarily driven by survey parameters. An optimal observing strategy is thus critical for measuring cosmological parameters with high accuracy. We present in this paper a three-stage analysis to assess the impact of the deep drilling (DD) strategy parameters on three critical aspects of the survey: redshift completeness, the number of well-measured SNe Ia, and cosmological measurements. We demonstrate that the current DD survey plans (internal LSST simulations) are characterized by a low completeness (
z
∼ 0.55–0.65), and irregular and low cadences (several days), which dramatically decrease the size of the well-measured SN Ia sample. We propose a method providing the number of visits required to reach higher redshifts. We use the results to design a set of optimized DD surveys for SN Ia cosmology taking full advantage of spectroscopic resources for host galaxy redshift measurements. The most accurate cosmological measurements are achieved with deep rolling surveys characterized by a high cadence (1 day), a rolling strategy (at least two seasons of observation per field), and ultradeep (
z
≳ 0.8) and deep (
z
≳ 0.6) fields. A deterministic scheduler including a gap recovery mechanism is critical to achieving a high-quality DD survey.
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to determine the Hubble constant from optical and infrared observations of over 600 Cepheid variables in the host galaxies of ...eight recent Type Ia supernovae (SNe Ia), providing the calibration for a magnitude-redshift relation based on 253 SNe Ia. Increased precision over past measurements of the Hubble constant comes from five improvements: (1) more than doubling the number of infrared observations of Cepheids in the nearby SN hosts; (2) increasing the sample size of ideal SN Ia calibrators from six to eight; (3) increasing by 20% the number of Cepheids with infrared observations in the megamaser host NGC 4258; (4) reducing the difference in the mean metallicity of the Cepheid comparison samples between NGC 4258 and the SN hosts from Delta *Dlog O/H = 0.08 to 0.05; and (5) calibrating all optical Cepheid colors with a single camera, WFC3, to remove cross-instrument zero-point errors. The result is a reduction in the uncertainty in H 0 due to steps beyond the first rung of the distance ladder from 3.5% to 2.3%. The measurement of H 0 via the geometric distance to NGC 4258 is 74.8 ? 3.1 km s--1 Mpc--1, a 4.1% measurement including systematic uncertainties. Better precision independent of the distance to NGC 4258 comes from the use of two alternative Cepheid absolute calibrations: (1) 13 Milky Way Cepheids with trigonometric parallaxes measured with HST/fine guidance sensor and Hipparcos and (2) 92 Cepheids in the Large Magellanic Cloud for which multiple accurate and precise eclipsing binary distances are available, yielding 74.4 ? 2.5 km s--1 Mpc--1, a 3.4% uncertainty including systematics. Our best estimate uses all three calibrations but a larger uncertainty afforded from any two: H 0 = 73.8 ? 2.4 km s--1 Mpc--1 including systematic errors, corresponding to a 3.3% uncertainty. The improved measurement of H 0, when combined with the Wilkinson Microwave Anisotropy Probe (WMAP) 7 year data, results in a tighter constraint on the equation-of-state parameter of dark energy of w = --1.08 ? 0.10. It also rules out the best-fitting gigaparsec-scale void models, posited as an alternative to dark energy. The combined H 0 + WMAP results yield N eff = 4.2 ? 0.7 for the number of relativistic particle species in the early universe, a low-significance excess for the value expected from the three known neutrino flavors.
Abstract
We analyze pre-explosion near- and mid-infrared (IR) imaging of the site of SN 2023ixf in the nearby spiral galaxy M101 and characterize the candidate progenitor star. The star displays ...compelling evidence of variability with a possible period of ≈1000 days and an amplitude of Δ
m
≈ 0.6 mag in extensive monitoring with the Spitzer Space Telescope since 2004, likely indicative of radial pulsations. Variability consistent with this period is also seen in the near-IR
J
and
K
s
bands between 2010 and 2023, up to just 10 days before the explosion. Beyond the periodic variability, we do not find evidence for any IR-bright pre-supernova outbursts in this time period. The IR brightness (
M
K
s
=
−
10.7
mag) and color (
J
−
K
s
= 1.6 mag) of the star suggest a luminous and dusty red supergiant. Modeling of the phase-averaged spectral energy distribution (SED) yields constraints on the stellar temperature (
T
eff
=
3500
−
1400
+
800
K) and luminosity (
log
L
/
L
⊙
=
5.1
±
0.2
). This places the candidate among the most luminous Type II supernova progenitors with direct imaging constraints, with the caveat that many of these rely only on optical measurements. Comparison with stellar evolution models gives an initial mass of
M
init
= 17 ± 4
M
⊙
. We estimate the pre-supernova mass-loss rate of the star between 3 and 19 yr before explosion from the SED modeling at
M
̇
≈
3
×
10
−
5
to 3 × 10
−4
M
⊙
yr
−1
for an assumed wind velocity of
v
w
= 10 km s
−1
, perhaps pointing to enhanced mass loss in a pulsation-driven wind.
Abstract
The nondetection of companion stars in SN Ia progenitor systems lends support to the notion of double-degenerate systems and explosions triggered by the merging of two white dwarfs. This ...very asymmetric process should lead to a conspicuous polarimetric signature. By contrast, observations consistently find very low continuum polarization as the signatures from the explosion process largely dominate over the pre-explosion configuration within several days. Critical information about the interaction of the ejecta with a companion and any circumstellar matter is encoded in the early polarization spectra. In this study, we obtain spectropolarimetry of SN 2018gv with the ESO Very Large Telescope at −13.6 days relative to the
B
-band maximum light, or ∼5 days after the estimated explosion—the earliest spectropolarimetric observations to date of any SN Ia. These early observations still show a low continuum polarization (≲0.2%) and moderate line polarization (0.30% ± 0.04% for the prominent Si
ii
λ
6355 feature and 0.85% ± 0.04% for the high-velocity Ca component). The high degree of spherical symmetry implied by the low-line and continuum polarization at this early epoch is consistent with explosion models of delayed detonations and is inconsistent with the merger-induced explosion scenario. The dense UV and optical photometry and optical spectroscopy within the first ∼100 days after the maximum light indicate that SN 2018gv is a normal SN Ia with similar spectrophotometric behavior to SN 2011fe.
PDF
