8 research outputs found
Proposed host galaxies of repeating fast radio burst sources detected by CHIME/FRB
We present a search for host galaxy associations for the third set of
repeating fast radio burst (FRB) sources discovered by the CHIME/FRB
Collaboration. Using the ~1 arcmin CHIME/FRB baseband localizations and
probabilistic methods. We identify potential host galaxies of two FRBs,
20200223B and 20190110C at redshifts of 0.06024(2) and 0.12244(6),
respectively. We also discuss the properties of a third marginal candidate host
galaxy association for FRB 20191106C with a host redshift of 0.10775(1). The
three putative host galaxies are all relatively massive, fall on the standard
mass-metallicity relationship for nearby galaxies, and show evidence of ongoing
star formation. They also all show signatures of being in a transitional
regime, falling in the "green valley" which is between the bulk of star-forming
and quiescent galaxies. The plausible host galaxies identified by our analysis
are consistent with the overall population of repeating and non-repeating FRB
hosts while increasing the fraction of massive and bright galaxies. Coupled
with these previous host associations, we identify a possible excess of FRB
repeaters whose host galaxies have M_u - M_r colors redder than the bulk of
star-forming galaxies. Additional precise localizations are required to confirm
this trend.Comment: 11 pages, submitted to AAS journal
SN2023ixf in Messier 101: the twilight years of the progenitor as seen by Pan-STARRS
The nearby type II supernova, SN2023ixf in M101 exhibits signatures of
early-time interaction with circumstellar material in the first week
post-explosion. This material may be the consequence of prior mass loss
suffered by the progenitor which possibly manifested in the form of a
detectable pre-supernova outburst. We present an analysis of the long-baseline
pre-explosion photometric data in , , , , and filters from
Pan-STARRS as part of the Young Supernova Experiment, spanning 5,000
days. We find no significant detections in the Pan-STARRS pre-explosion light
curve. We train a multilayer perceptron neural network to classify
pre-supernova outbursts. We find no evidence of eruptive pre-supernova activity
to a limiting absolute magnitude of . The limiting magnitudes from the full
set of (average absolute magnitude -8) data are consistent
with previous pre-explosion studies. We use deep photometry from the literature
to constrain the progenitor of SN2023ixf, finding that these data are
consistent with a dusty red supergiant (RSG) progenitor with luminosity
5.12 and temperature 3950K,
corresponding to a mass of 14-20 MComment: 19 pages, 8 figures, 1 tabl
A fast radio burst localized at detection to a galactic disk using very long baseline interferometry
Fast radio bursts (FRBs) are millisecond-duration, luminous radio transients
of extragalactic origin. These events have been used to trace the baryonic
structure of the Universe using their dispersion measure (DM) assuming that the
contribution from host galaxies can be reliably estimated. However,
contributions from the immediate environment of an FRB may dominate the
observed DM, thus making redshift estimates challenging without a robust host
galaxy association. Furthermore, while at least one Galactic burst has been
associated with a magnetar, other localized FRBs argue against magnetars as the
sole progenitor model. Precise localization within the host galaxy can
discriminate between progenitor models, a major goal of the field. Until now,
localizations on this spatial scale have only been carried out in follow-up
observations of repeating sources. Here we demonstrate the localization of FRB
20210603A with very long baseline interferometry (VLBI) on two baselines, using
data collected only at the time of detection. We localize the burst to SDSS
J004105.82+211331.9, an edge-on galaxy at , and detect recent
star formation in the kiloparsec-scale vicinity of the burst. The edge-on
inclination of the host galaxy allows for a unique comparison between the line
of sight towards the FRB and lines of sight towards known Galactic pulsars. The
DM, Faraday rotation measure (RM), and scattering suggest a progenitor
coincident with the host galactic plane, strengthening the link between the
environment of FRB 20210603A and the disk of its host galaxy. Single-pulse VLBI
localizations of FRBs to within their host galaxies, following the one
presented here, will further constrain the origins and host environments of
one-off FRBs.Comment: 40 pages, 13 figures, submitted. Fixed typo in abstrac
CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources
We present the discovery of 25 new repeating fast radio burst (FRB) sources
found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1.
The sources were found using a new clustering algorithm that looks for multiple
events co-located on the sky having similar dispersion measures (DMs). The new
repeaters have DMs ranging from 220 pc cm to 1700 pc
cm, and include sources having exhibited as few as two bursts to as many
as twelve. We report a statistically significant difference in both the DM and
extragalactic DM (eDM) distributions between repeating and apparently
nonrepeating sources, with repeaters having lower mean DM and eDM, and we
discuss the implications. We find no clear bimodality between the repetition
rates of repeaters and upper limits on repetition from apparently nonrepeating
sources after correcting for sensitivity and exposure effects, although some
active repeating sources stand out as anomalous. We measure the repeater
fraction and find that it tends to an equilibrium of % over
our exposure thus far. We also report on 14 more sources which are promising
repeating FRB candidates and which merit follow-up observations for
confirmation.Comment: Submitted to ApJ. Comments are welcome and follow-up observations are
encouraged
The Pan-African School for Emerging Astronomers
International audienceThe Pan-African School for Emerging Astronomers (PASEA) is an innovative short course for African university students, held by an African-led international collaboration. PASEA aims to build a critical mass of astronomers in Africa and exchange ideas about teaching across continents
Proposed Host Galaxies of Repeating Fast Radio Burst Sources Detected by CHIME/FRB
We present a search for host galaxy associations for the third set of repeating fast radio burst (FRB) sources discovered by the CHIME/FRB Collaboration. Using the ∼1′ CHIME/FRB baseband localizations and probabilistic methods, we identify potential host galaxies of two FRBs, 20200223B and 20190110C at redshifts of 0.06024(2) and 0.12244(6), respectively. We also discuss the properties of a third marginal candidate host galaxy association for FRB 20191106C with a host redshift of 0.10775(1). The three putative host galaxies are all relatively massive, fall on the standard mass–metallicity relationship for nearby galaxies, and show evidence of ongoing star formation. They also all show signatures of being in a transitional regime, falling in the green valley , which is between the bulk of star-forming and quiescent galaxies. The plausible host galaxies identified by our analysis are consistent with the overall population of repeating and nonrepeating FRB hosts while increasing the fraction of massive and bright galaxies. Coupled with these previous host associations, we identify a possible excess of FRB repeaters whose host galaxies have M _u − M _r colors redder than the bulk of star-forming galaxies. Additional precise localizations are required to confirm this trend
SN2023ixf in Messier 101: the twilight years of the progenitor as seen by Pan-STARRS
The nearby type II supernova, SN2023ixf in M101 exhibits signatures of early-time interaction with circumstellar material in the first week post-explosion. This material may be the consequence of prior mass loss suffered by the progenitor which possibly manifested in the form of a detectable pre-supernova outburst. We present an analysis of the long-baseline pre-explosion photometric data in , , , , and filters from Pan-STARRS as part of the Young Supernova Experiment, spanning 5,000 days. We find no significant detections in the Pan-STARRS pre-explosion light curve. We train a multilayer perceptron neural network to classify pre-supernova outbursts. We find no evidence of eruptive pre-supernova activity to a limiting absolute magnitude of . The limiting magnitudes from the full set of (average absolute magnitude -8) data are consistent with previous pre-explosion studies. We use deep photometry from the literature to constrain the progenitor of SN2023ixf, finding that these data are consistent with a dusty red supergiant (RSG) progenitor with luminosity 5.12 and temperature 3950K, corresponding to a mass of 14-20 M$_\odot
Final Moments. I. Precursor Emission, Envelope Inflation, and Enhanced Mass Loss Preceding the Luminous Type II Supernova 2020tlf
International audienceWe present panchromatic observations and modeling of supernova (SN) 2020tlf, the first normal Type II-P/L SN with confirmed precursor emission, as detected by the Young Supernova Experiment transient survey. Pre-SN activity was detected in riz-bands at −130 days and persisted at relatively constant flux until first light. Soon after discovery, “flash” spectroscopy of SN 2020tlf revealed narrow, symmetric emission lines that resulted from the photoionization of circumstellar material (CSM) shed in progenitor mass-loss episodes before explosion. Surprisingly, this novel display of pre-SN emission and associated mass loss occurred in a red supergiant (RSG) progenitor with zero-age main-sequence mass of only 10–12 M , as inferred from nebular spectra. Modeling of the light curve and multi-epoch spectra with the non-LTE radiative-transfer code CMFGEN and radiation-hydrodynamical code HERACLES suggests a dense CSM limited to r ≈ 10 cm, and mass-loss rate of 10 M yr. The luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with an RSG model with R = 1100 R . Limits on the shock-powered X-ray and radio luminosity are consistent with model conclusions and suggest a CSM density of ρ < 2 × 10 g cm for distances from the progenitor star of r ≈ 5 × 10 cm, as well as a mass-loss rate of at larger distances. A promising power source for the observed precursor emission is the ejection of stellar material following energy disposition into the stellar envelope as a result of gravity waves emitted during either neon/oxygen burning or a nuclear flash from silicon combustion