Search

We present TESSELLATE, a dedicated pipeline for performing an untargeted search documenting all variable phenomena captured by the TESS space telescope. Building on the TESSreduce difference imaging pipeline, TESSELLATE extracts calibrated and reduced photometric data for every full frame image in the TESS archive. Using this data, we systematically identify transient, variable and non-sidereal signals across timescales ranging from minutes to weeks. The high cadence and wide field of view of TESS enables us to conduct a comprehensive search of the entire sky to a depth of ~17 $m_i$. Based on the volumetric rates for known fast transients, we expect there to be numerous Fast Blue Optical Transients and Gamma Ray Burst afterglows present in the existing TESS dataset. Beyond transients, TESSELLATE can also identify new variable stars and exoplanet candidates, and recover known asteroids. We classify events using machine learning techniques and the work of citizen scientists via the Zooniverse Cosmic Cataclysms project. Finally, we introduce the TESSELLATE Sky Survey: a complete, open catalog of the variable sky observed by TESS., Comment: 15 pages, 9 figures, 2 tables, submitted ApJ

In this work we estimate the explosion and progenitor properties of six Type II supernovae (SNe) at 0.675 <= z <= 3.61 discovered by the JWST Advanced Deep Extragalactic Survey (JADES) transient survey by modeling their light curves. This high-redshift Type II SN sample allows us to compare low-redshift Type II SNe to their high-redshift counterparts. Two Type II SNe are found to have high explosion energies of 3e51 erg, while the other four Type II SNe are estimated to have typical explosion energies found in the local Universe [(0.5-2)e51 erg]. The fraction of Type II SNe with high explosion energies might be higher at high redshifts because of, e.g., lower metallicity, but it is still difficult to draw a firm conclusion because of the small sample size and potential observational biases. We found it difficult to constrain the progenitor masses for Type II SNe in our sample because of the sparse light-curve data. We found two Type II SN light curves can be better reproduced by introducing confined, dense circumstellar matter. Thus, the confined, dense circumstellar matter frequently observed in nearby Type II SNe is likely to exist in Type II SNe at high redshifts as well. Two Type II SNe are estimated to have high host galaxy extinctions, showing the ability of JWST to discover dust-obscured SNe at high redshifts. More high-redshift Type II SNe are required to investigate the differences in the properties of Type II SNe near and far, but here we show the first glimpse into the high-redshift population of Type II SNe., Comment: 12 pages, 12 figures, 2 tables, submitted to Publications of the Astronomical Society of Japan

We present a new photometric pipeline for the detection of pre-supernova (pre-SN) emission in the Young Supernova Experiment (YSE) sky survey. The method described is applied to SN 2020tlf, a type II SN (SN II) with precursor emission in the last ~100 days before first light. We re-analyze the YSE griz-band light curves of SN 2020tlf and provide revised pre-explosion photometry that includes a robust list of confident detection and limiting magnitudes. Compared to the results of Jacobson-Galan et al. 2022a, this new analysis yields fewer total r/i/z-band pre-SN detections at phases > -100 days. Furthermore, we discourage the use of the blackbody modeling of the pre-explosion spectral energy distribution, the pre-SN bolometric light curve and the blackbody model parameters presented in Jacobson-Galan et al. 2022a. Nevertheless, binned photometry of SN 2020tlf confirms a consistent progenitor luminosity of ~10$^{40}$ erg s$^{-1}$ before explosion., Comment: 5 pages, 1 figure. Published in RNAAS

Dust from core-collapse supernovae (CCSNe), specifically Type IIP SNe, has been suggested to be a significant source of the dust observed in high-redshift galaxies. CCSNe eject large amounts of newly formed heavy elements, which can condense into dust grains in the cooling ejecta. However, infrared (IR) observations of typical CCSNe generally measure dust masses that are too small to account for the dust production needed at high redshifts. Type IIn SNe, classified by their dense circumstellar medium (CSM), are also known to exhibit strong IR emission from warm dust, but the dust origin and heating mechanism have generally remained unconstrained because of limited observational capabilities in the mid-IR. Here, we present a JWST/MIRI Medium Resolution Spectrograph (MRS) spectrum of the Type IIn SN 2005ip nearly 17 years post-explosion. The Type IIn SN 2005ip is one of the longest-lasting and most well-studied SNe observed to date. Combined with a Spitzer mid-IR spectrum of SN 2005ip obtained in 2008, this data set provides a rare 15-year baseline, allowing for a unique investigation of the evolution of dust. The JWST spectrum shows a new high-mass dust component ($\gtrsim0.08$ M$_{\odot}$) that is not present in the earlier Spitzer spectrum. Our analysis shows dust likely formed over the past 15 years in the cold, dense shell (CDS), between the forward and reverse shocks. There is also a smaller mass of carbonaceous dust ($\gtrsim0.005$ M$_{\odot}$) in the ejecta. These observations provide new insights into the role of SN dust production, particularly within the CDS, and its potential contribution to the rapid dust enrichment of the early Universe.

We present the most comprehensive catalog to date of Type I Superluminous Supernovae (SLSNe), a class of stripped envelope supernovae (SNe) characterized by exceptionally high luminosities. We have compiled a sample of 262 SLSNe reported through 2022 December 31. We verified the spectroscopic classification of each SLSN and collated an exhaustive data set of UV, optical and IR photometry from both publicly available data and our own FLEET observational follow-up program, totaling over 30,000 photometric detections. Using these data we derive observational parameters such as the peak absolute magnitudes, rise and decline timescales, as well as bolometric luminosities, temperature and photospheric radius evolution for all SLSNe. Additionally, we model all light curves using a hybrid model that includes contributions from both a magnetar central engine and the radioactive decay of $^{56}$Ni. We explore correlations among various physical and observational parameters, and recover the previously found relation between ejecta mass and magnetar spin, as well as the overall progenitor pre-explosion mass distribution with a peak at $\approx 6.5$ M$_\odot$. We find no significant redshift dependence for any parameter, and no evidence for distinct sub-types of SLSNe. We find that $< 3$\% of SLSNe are best fit with a significant contribution from radioactive decay $\gtrsim 50$\%, representing a set of relatively dim and slowly declining SNe. We provide several analytical tools designed to simulate typical SLSN light curves across a broad range of wavelengths and phases, enabling accurate K-corrections, bolometric scaling calculations, and inclusion of SLSNe in survey simulations or future comparison works. The complete catalog, including all of the photometry, models, and derived parameters, is made available as an open-source resource on GitHub., Comment: 59 pages, 22 Figures, Submitted to MNRAS

The JWST Advanced Deep Extragalactic Survey (JADES) is a multi-cycle JWST program that has taken among the deepest near-/mid-infrared images to date (down to $\sim$30 ABmag) over $\sim$25 arcmin$^2$ in the GOODS-S field in two sets of observations with one year of separation. This presented the first opportunity to systematically search for transients, mostly supernovae (SNe), out to $z$$>$2. We found 79 SNe: 38 at $z$$<$2, 23 at 2$<$$z$$<$3, 8 at 3$<$$z$$<$4, 7 at 4$<$$z$$<$5, and 3 with undetermined redshifts, where the redshifts are predominantly based on spectroscopic or highly reliable JADES photometric redshifts of the host galaxies. At this depth, the detection rate is $\sim$1-2 per arcmin$^2$ per year, demonstrating the power of JWST as a supernova discovery machine. We also conducted multi-band follow-up NIRCam observations of a subset of the SNe to better constrain their light curves and classify their types. Here, we present the survey, sample, search parameters, spectral energy distributions (SEDs), light curves, and classifications. Even at $z$$\geq$2, the NIRCam data quality is high enough to allow SN classification via multi-epoch light-curve fitting with confidence. The multi-epoch SN sample includes a Type Ia SN at $z_{\mathrm{spec}}$$=$2.90, Type IIP SN at $z_{\mathrm{spec}}$$=$3.61, and a Type Ic-BL SN at $z_{\mathrm{spec}}$$=$2.83. We also found that two $z$$\sim$16 galaxy candidates from the first imaging epoch were actually transients that faded in the second epoch, illustrating the possibility that moderate/high-redshift SNe could mimic high-redshift dropout galaxies., Comment: 46 pages, 16 figures, 16 tables. Accepted by ApJ. Appendix A (64 MB) is available at https://drive.google.com/file/d/1xs5jXUVOvdDPgdghK72KR1FMGvPcK7dv/view?usp=sharing . Appendix B (81 MB) is available at https://drive.google.com/file/d/18ImLT80pQdPzXCZA-KEy21DaE2CQiGz1/view?usp=sharing

We present mid-infrared (mid-IR) imaging of the Type IIL supernova (SN) 1980K with the James Webb Space Telescope (JWST) more than 40 yr post-explosion. SN 1980K, located in the nearby ($D\approx7$ Mpc) "SN factory" galaxy NGC 6946, was serendipitously captured in JWST/MIRI images taken of the field of SN 2004et in the same galaxy. SN 1980K serves as a promising candidate for studying the transitional phase between young SNe and older SN remnants and also provides a great opportunity to investigate its the close environment. SN 1980K can be identified as a clear and bright point source in all eight MIRI filters from F560W up to F2550W. We fit analytical dust models to the mid-IR spectral energy distribution that reveal a large amount ($M_d \approx 0.002 {M}_{\odot}$) of Si-dominated dust at $T_{dust}\approx 150$ K (accompanied by a hotter dust/gas component), and also computed numerical SED dust models. Radiative transfer modeling of a late-time optical spectrum obtained recently with Keck discloses that an even larger ($\sim 0.24-0.58~{M}_{\odot}$) amount of dust is needed in order for selective extinction to explain the asymmetric line profile shapes observed in SN 1980K. As a conclusion, with JWST, we may see i) pre-existing circumstellar dust heated collisionally (or, partly radiatively), analogous to the equatorial ring of SN 1987A, or ii) the mid-IR component of the presumed newly-formed dust, accompanied by much more colder dust present in the ejecta (as suggested by the late-time the optical spectra)., Comment: 14 pages, 9 figures

Gamma-ray bursts produce afterglows that can be observed across the electromagnetic spectrum and can provide insight into the nature of their progenitors. While most telescopes that observe afterglows are designed to rapidly react to trigger information, the Transiting Exoplanet Survey Satellite (TESS) continuously monitors sections of the sky at cadences between 30 minutes and 200 seconds. This provides TESS with the capability of serendipitously observing the optical afterglow of GRBs. We conduct the first extensive search for afterglows of known GRBs in archival TESS data reduced with the TESSreduce package, and detect 11 candidate signals that are temporally coincident with reported burst times. We classify 3 of these as high-likelihood GRB afterglows previously unknown to have been detected by TESS, one of which has no other afterglow detection reported on the Gamma-ray Coordinates Network. We classify 5 candidates as tentative and the remainder as unlikely. Using the afterglowpy package, we model each of the candidate light curves with a Gaussian and a top hat model to estimate burst parameters; we find that a mean time delay of $740\pm690\,$s between the explosion and afterglow onset is required to perform these fits. The high cadence and large field of view make TESS a powerful instrument for localising GRBs, with the potential to observe afterglows in cases when no other backup photometry is possible., Comment: 17 pages, 7 figures, 5 tables

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 $\approx$1000 days and an amplitude of $\Delta m \approx 0.6$ 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 ($T_{\mathrm{eff}} = 3500_{-1400}^{+800}$ K) and luminosity ($\log L/L_{\odot} = 5.1\pm0.2$). 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 $M_{\mathrm{init}} = 17\pm4 M_{\odot}$. We estimate the pre-supernova mass-loss rate of the star between 3 and 19 yr before explosion from the SED modeling at $\dot M \approx 3\times10^{-5}$ to $3\times10^{-4} M_{\odot}$ 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., Comment: 13 pages, 5 figures, published in ApJL, replacement with revisions to match published version

A growing number of supernovae (SNe) are now known to exhibit evidence for significant interaction with a dense, pre-existing, circumstellar medium (CSM). SNe Ibn comprise one such class that can be characterised by both rapidly evolving light curves and persistent narrow He I lines. The origin of such a dense CSM in these systems remains a pressing question, specifically concerning the progenitor system and mass-loss mechanism. In this paper, we present multi-wavelength data of the Type Ibn SN 2020nxt, including $HST$/STIS ultraviolet spectra. We fit the data with recently updated CMFGEN models designed to handle configurations for SNe Ibn. The UV coverage yields strong constraints on the energetics and, when combined with the CMFGEN models, offer new insight on potential progenitor systems. We find the most successful model is a $\lesssim4 {\rm M}_\odot$ helium star that lost its $\sim 1\,{\rm M}_\odot$ He-rich envelope in the years preceding core collapse. We also consider viable alternatives, such as a He white dwarf merger. Ultimately, we conclude at least some SNe Ibn do not arise from single, massive ($>30 {\rm M}_\odot$) Wolf-Rayet-like stars., Comment: 17 pages, 13 figures, 1 table, submitted to MNRAS

We present high-cadence ultraviolet through near-infrared observations of the Type Ia supernova (SN Ia) 2023bee in NGC~2708 ($D = 32 \pm 3$ Mpc), finding excess flux in the first days after explosion relative to the expected power-law rise from an expanding fireball. This deviation from typical behavior for SNe Ia is particularly obvious in our 10-minute cadence $TESS$ light curve and $Swift$ UV data. Compared to a few other normal SNe Ia with detected early excess flux, the excess flux in SN 2023bee is redder in the UV and less luminous. We present optical spectra of SN 2023bee, including two spectra during the period where the flux excess is dominant. At this time, the spectra are similar to those of other SNe Ia but with weaker Si II, C II and Ca II absorption lines, perhaps because the excess flux creates a stronger continuum. We compare the data to several theoretical models that have been proposed to explain the early flux excess in SNe Ia. Interaction with either a nearby companion star or close-in circumstellar material is expected to produce a faster evolution than seen in the data. Radioactive material in the outer layers of the ejecta, either from a double detonation explosion or simply an explosion with a $^{56}$Ni clump near the surface, can not fully reproduce the evolution either, likely due to the sensitivity of early UV observable to the treatment of the outer part of ejecta in simulation. We conclude that no current model can adequately explain the full set of observations. We find that a relatively large fraction of nearby, bright SNe Ia with high-cadence observations have some amount of excess flux within a few days of explosion. Considering potential asymmetric emission, the physical cause of this excess flux may be ubiquitous in normal SNe Ia., Comment: 21 pages, 12 figures. Accepted by the astrophysical journal

We present a photometric and spectroscopic analysis of the ultra-luminous and slowly evolving 03fg-like Type Ia SN 2021zny. Our observational campaign starts from $\sim5.3$ hours after explosion (making SN 2021zny one of the earliest observed members of its class), with dense multi-wavelength coverage from a variety of ground- and space-based telescopes, and is concluded with a nebular spectrum $\sim10$ months after peak brightness. SN 2021zny displayed several characteristics of its class, such as the peak brightness ($M_{B}=-19.95$ mag), the slow decline ($\Delta m_{15}(B) = 0.62$ mag), the blue early-time colours, the low ejecta velocities and the presence of significant unburned material above the photosphere. However, a flux excess for the first $\sim1.5$ days after explosion is observed in four photometric bands, making SN 2021zny the third 03fg-like event with this distinct behavior, while its $+313$ d spectrum shows prominent [O I] lines, a very unusual characteristic of thermonuclear SNe. The early flux excess can be explained as the outcome of the interaction of the ejecta with $\sim0.04\:\mathrm{M_{\odot}}$ of H/He-poor circumstellar material at a distance of $\sim10^{12}$ cm, while the low ionization state of the late-time spectrum reveals low abundances of stable iron-peak elements. All our observations are in accordance with a progenitor system of two carbon/oxygen white dwarfs that undergo a merger event, with the disrupted white dwarf ejecting carbon-rich circumstellar material prior to the primary white dwarf detonation., Comment: 19 pages, 16 figures, accepted for publication in MNRAS

Supernova (SN) explosions have been sought for decades as a possible source of dust in the Universe, providing the seeds of galaxies, stars, and planetary systems. SN 1987A offers one of the most promising examples of significant SN dust formation, but until the James Webb Space Telescope (JWST), instruments have traditionally lacked the sensitivity at both late times (>1 yr post-explosion) and longer wavelengths (i.e., >10 um) to detect analogous dust reservoirs. Here we present JWST/MIRI observations of two historic Type IIP SNe, 2004et and SN 2017eaw, at nearly 18 and 5 yr post-explosion, respectively. We fit the spectral energy distributions as functions of dust mass and temperature, from which we are able to constrain the dust geometry, origin, and heating mechanism. We place a 90% confidence lower limit on the dust masses for SNe 2004et and 2017eaw of >0.014 and >4e-4 M_sun, respectively. More dust may exist at even colder temperatures or may be obscured by high optical depths. We conclude dust formation in the ejecta to be the most plausible and consistent scenario. The observed dust is radiatively heated to ~100-150 K by ongoing shock interaction with the circumstellar medium. Regardless of the best fit or heating mechanism adopted, the inferred dust mass for SN 2004et is the second highest (next to SN 1987A) inferred dust mass in extragalactic SNe thus far, promoting the prospect of SNe as potential significant sources of dust in the Universe., Comment: 12 pages, 7 figures, submitting to MNRAS

Tidal disruption events (TDEs) are bursts of electromagnetic energy released when supermassive black holes (SMBHs) at the centers of galaxies violently disrupt a star that passes too close. TDEs provide a new window to study accretion onto SMBHs; in some rare cases, this accretion leads to launching of a relativistic jet, but the necessary conditions are not fully understood. The best studied jetted TDE to date is Swift J1644+57, which was discovered in gamma-rays, but was too obscured by dust to be seen at optical wavelengths. Here we report the optical discovery of AT2022cmc, a rapidly fading source at cosmological distance (redshift z=1.19325) whose unique lightcurve transitioned into a luminous plateau within days. Observations of a bright counterpart at other wavelengths, including X-rays, sub-millimeter, and radio, supports the interpretation of AT2022cmc as a jetted TDE containing a synchrotron "afterglow", likely launched by a SMBH with spin $a \gtrsim 0.3$. Using 4 years of Zwicky Transient Facility (ZTF) survey data, we calculate a rate of $0.02 ^{+ 0.04 }_{- 0.01 }$ Gpc$^{-3}$ yr$^{-1}$ for on-axis jetted TDEs based on the luminous, fast-fading red component, thus providing a measurement complementary to the rates derived from X-ray and radio observations. Correcting for the beaming angle effects, this rate confirms that about 1% of TDEs have relativistic jets. Optical surveys can use AT2022cmc as a prototype to unveil a population of jetted TDEs., Comment: Accepted for publication in Nature

We present early observations and analysis of the double-peaked Type IIb supernova (SN IIb) 2021zby. $TESS$ captured the prominent early shock cooling peak of SN 2021zby within the first $\sim$10 days after explosion with a 30-minute cadence. We present optical and near-infrared spectral series of SN 2021zby, including three spectra during the shock cooling phase. Using a multi-band model fit, we find that the inferred properties of its progenitor are consistent with a red supergiant or yellow supergiant, with an envelope mass of $\sim$0.3-3.0 M$_\odot$ and an envelope radius of $\sim$50-350$ R_\odot$. These inferred progenitor properties are similar to those of other SNe IIb with double-peak feature, such as SNe 1993J, 2011dh, 2016gkg and 2017jgh. This study further validates the importance of the high cadence and early coverage in resolving the shape of the shock cooling light curve, while the multi-band observations, especially UV, is also necessary to fully constrain the progenitor properties., Comment: 12 pages, 5 figures, 2 tables, submitted to ApJL

We present multi-band ATLAS photometry for SN 2019tsf, a stripped-envelope Type Ib supernova (SESN). The SN shows a triple-peaked light curve and a late (re-)brightening, making it unique among stripped-envelope systems. The re-brightening observations represent the latest photometric measurements of a multi-peaked Type Ib SN to date. As late-time photometry and spectroscopy suggest no hydrogen, the potential circumstellar material (CSM) must be H-poor. Moreover, late (>150 days) spectra show no signs of narrow emission lines, further disfavouring CSM interaction. On the contrary, an extended CSM structure is seen through a follow-up radio campaign with Karl G. Jansky Very Large Array (VLA), indicating a source of bright optically thick radio emission at late times, which is highly unusual among H-poor SESNe. We attribute this phenomenology to an interaction of the supernova ejecta with spherically-asymmetric CSM, potentially disk-like, and we present several models that can potentially explain the origin of this rare Type Ib supernova. The warped disc model paints a novel picture, where the tertiary companion perturbs the progenitors CSM, that can explain the multi-peaked light curves of SNe, and here we apply it to SN 2019tsf. This SN 2019tsf is likely a member of a new sub-class of Type Ib SNe and among the recently discovered class of SNe that undergo mass transfer at the moment of explosion, Comment: 23 pages, Comments are welcome, Submitted to ApJ

We present panchromatic observations and modeling of calcium-strong supernovae (SNe) 2021gno in the star-forming host galaxy NGC 4165 (D = 30.5 Mpc) and 2021inl in the outskirts of elliptical galaxy NGC 4923 (D = 80 Mpc), both monitored through the Young Supernova Experiment (YSE) transient survey. The multi-color light curves of both SNe show two peaks, the former peak being derived from shock cooling emission (SCE) and/or shock interaction with circumstellar material (CSM). The primary peak in SN 2021gno is coincident with luminous, rapidly decaying X-ray emission ($L_x = 5 \times 10^{41}$ erg s$^{-1}$) detected by Swift-XRT at $\delta t = 1$ day after explosion, this observation being the second ever detection of X-rays from a calcium-strong transient. We interpret the X-ray emission from SN 2021gno in the context of shock interaction with dense CSM that extends to $r < 3 \times 10^{14}$ cm. Based on modeling of the SN 2021gno X-ray spectrum, we calculate a CSM mass range of $M_{\rm CSM} = (0.3 - 1.6) \times 10^{-3}$ M$_{\odot}$ and particle densities of $n = (1-4) \times 10^{10}$ cm$^{-3}$. Radio non-detections of SN 2021gno indicate a low-density environment at larger radii ($r > 10^{16}$ cm) and a progenitor mass loss rate of $\dot{M} < 10^{-4}$ M$_{\odot}$ yr$^{-1}$, for $v_w = 500$ km s$^{-1}$. For radiation derived from SCE, modeling of the primary light curve peak in both SNe indicates an extended progenitor envelope mass and radius of $M_e = 0.02 - 0.05$ M$_{\odot}$ and $R_e = 30 - 230$ R$_{\odot}$. The explosion properties of SNe 2021gno and 2021inl suggest progenitor systems containing either a low-mass massive star or a white dwarf (WD), the former being unlikely for either object given the lack of star formation at both explosion sites. Furthermore, the progenitor environments of both SNe are consistent with explosion models for low-mass hybrid He/C/O WD + C/O WD binaries., Comment: 33 pages, 19 figures. Submitted to ApJ. Comments welcome!

This Letter presents the detection of a source at the position of the Type Ib/c supernova (SN) 2013ge more than four years after the radioactive component is expected to have faded. This source could mark the first post-SN direct detection of a surviving companion to a stripped-envelope Type Ib/c explosion. We test this hypothesis and find the shape of the source's spectral energy distribution is most consistent with that of a B5 I supergiant. While binary models tend to predict OB-type stars for stripped-envelope companions, the location of the source on a color-magnitude diagram (CMD) places it redward of its more likely position on the main sequence (MS). The source may be temporarily out of thermal equilibrium, or a cool and inflated non-MS companion, which is similar to the suggested companion of Type Ib SN 2019yvr that was constrained from pre-SN imaging. We also consider other possible physical scenarios for the source, including a fading SN, circumstellar shock interaction, line of site coincidence, and an unresolved host star cluster, all of which will require future observations to more definitively rule out. Ultimately, the fraction of surviving companions ("binary fraction") will provide necessary constraints on binary evolution models and the underlying physics., Comment: Accepted to ApJL. 9 pages, 4 figures, 1 table

We present observations of SN 2020fqv, a Virgo-cluster Type II core-collapse supernova (CCSN) with a high temporal resolution light curve from the Transiting Exoplanet Survey Satellite (TESS) covering the time of explosion; ultraviolet (UV) spectroscopy from the Hubble Space Telescope (HST) starting 3.3 days post-explosion; ground-based spectroscopic observations starting 1.1~days post-explosion; along with extensive photometric observations. Massive stars have complicated mass-loss histories leading up to their death as CCSNe, creating circumstellar medium (CSM) with which the SNe interact. Observations during the first few days post-explosion can provide important information about the mass-loss rate during the late stages of stellar evolution. Model fits to the quasi-bolometric light curve of SN 2020fqv reveal ~0.23 $M_{\odot}$ of CSM confined within ~1450 $R_{\odot}$ ($10^{14}$ cm) from its progenitor star. Early spectra (<4 days post-explosion), both from HST and ground-based observatories, show emission features from high-ionization metal species from the outer, optically thin part of this CSM. We find that the CSM is consistent with an eruption caused by the injection of $\sim$$5\times 10^{46}$ erg into the stellar envelope $\sim$300 days pre-explosion, potentially from a nuclear burning instability at the onset of oxygen burning. Light-curve fitting, nebular spectroscopy, and pre-explosion \textit{HST} imaging consistently point to a red supergiant (RSG) progenitor with $M_{\rm ZAMS}$$\approx$$13.5$--$15 \, M_{\odot}$, typical for SN~II progenitor stars. This finding demonstrates that a typical RSG, like the progenitor of SN 2020fqv, has a complicated mass-loss history immediately before core collapse., Comment: Published in MNRAS

We 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 with the Pan-STARRS1 telescope. Pre-explosion emission was detected in $riz-$bands at 130 days prior to SN 2020tlf and persisted at relatively constant flux until first light. Soon after discovery, "flash" spectroscopy of SN 2020tlf revealed prominent narrow symmetric emission lines ($v_w < 300$ km s$^{-1}$) that resulted from the photo-ionization of unshocked circumstellar material (CSM) shedded in progenitor mass loss episodes in the final weeks to months before explosion. Surprisingly, this novel display of pre-SN emission and associated mass loss occurred in a RSG progenitor with ZAMS mass of only 10-12 M$_{\odot}$, 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 (RHD) code HERACLES suggests a dense CSM limited to $r \approx 10^{15}$ cm, and mass loss rate of $10^{-2}$ M$_{\odot}$ yr$^{-1}$. The subsequent luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with a RSG model with $R_{\star} = 1100$ R$_{\odot}$. Inferences from the limits on the shock-powered X-ray and radio luminosity are consistent with these conclusions and suggest a CSM density of $\rho < 2 \times 10^{-16}$ g cm$^{-3}$ for distances of $r \approx 5 \times 10^{15}$ cm, as well as a mass loss rate of $\dot M<1.3 \times 10^{-5}\,\rm{M_{\odot}\,yr^{-1}}$ 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., Comment: 36 pages, 20 figures. Accepted for publication in ApJ

We present the 30-min cadence Kepler/K2 light curve of the Type Ia supernova (SN Ia) SN 2018agk, covering approximately one week before explosion, the full rise phase and the decline until 40 days after peak. We additionally present ground-based observations in multiple bands within the same time range, including the 1-day cadence DECam observations within the first $\sim$5 days after the first light. The Kepler early light curve is fully consistent with a single power-law rise, without evidence of any bump feature. We compare SN 2018agk with a sample of other SNe~Ia without early excess flux from the literature. We find that SNe Ia without excess flux have slowly-evolving early colors in a narrow range ($g-i\approx -0.20\pm0.20$ mag) within the first $\sim 10$ days. On the other hand, among SNe Ia detected with excess, SN 2017cbv and SN 2018oh tend to be bluer, while iPTF16abc's evolution is similar to normal SNe Ia without excess in $g-i$. We further compare the Kepler light curve of SN 2018agk with companion-interaction models, and rule out the existence of a typical non-degenerate companion undergoing Roche-lobe overflow at viewing angles smaller than $45^{\circ}$., Comment: 20 pages, 14 figures, 5 tables. Published in ApJ

Since two people came down a county of north Seattle with positive COVID-19 (coronavirus-19) in 2019, the current total cases in the United States (U.S.) are over 12 million. Predicting the pandemic trend under effective variables is crucial to help find a way to control the epidemic. Based on available literature, we propose a validated Vector Autoregression (VAR) time series model to predict the positive COVID-19 cases. A real data prediction for U.S. is provided based on the U.S. coronavirus data. The key message from our study is that the situation of the pandemic will getting worse if there is no effective control., Comment: 14 pages, 4 figures

The Cosmology Large Angular Scale Surveyor consists of four instruments performing a CMB polarization survey. Currently, the 40 GHz and first 90 GHz instruments are deployed and observing, with the second 90 GHz and a multichroic 150/220 GHz instrument to follow. The receiver is a central component of each instrument's design and functionality. This paper describes the CLASS receiver design, using the first 90 GHz receiver as a primary reference. Cryogenic cooling and filters maintain a cold, low-noise environment for the detectors. We have achieved receiver detector temperatures below 50 mK in the 40 GHz instrument for 85% of the initial 1.5 years of operation, and observed in-band efficiency that is consistent with pre-deployment estimates. At 90 GHz, less than 26% of in-band power is lost to the filters and lenses in the receiver, allowing for high optical efficiency. We discuss the mounting scheme for the filters and lenses, the alignment of the cold optics and detectors, stray light control, and magnetic shielding., Comment: Fixed formatting of abstract; 20 Pages, 11 Figures, SPIE Conference Proceedings

The Cosmology Large Angular Scale Surveyor (CLASS) aims to detect and characterize the primordial B-mode signal and make a sample-variance-limited measurement of the optical depth to reionization. CLASS is a ground-based, multi-frequency microwave polarimeter that surveys 70% of the microwave sky every day from the Atacama Desert. The focal plane detector arrays of all CLASS telescopes contain smooth-walled feedhorns that couple to transition-edge sensor (TES) bolometers through symmetric planar orthomode transducer (OMT) antennas. These low noise polarization-sensitive detector arrays are fabricated on mono-crystalline silicon wafers to maintain TES uniformity and optimize optical efficiency throughout the wafer. In this paper, we discuss the design and characterization of the first CLASS 93 GHz detector array. We measure the dark parameters, bandpass, and noise spectra of the detectors and report that the detectors are photon-noise limited. With current array yield of 82%, we estimate the total array noise-equivalent power (NEP) to be 2.1 aW$\sqrt[]{\mathrm{s}}$., Comment: 16 pages, 9 figures

The search for inflationary primordial gravitational waves and the measurement of the optical depth to reionization, both through their imprint on the large angular scale correlations in the polarization of the cosmic microwave background (CMB), has created the need for high sensitivity measurements of polarization across large fractions of the sky at millimeter wavelengths. These measurements are subject to instrumental and atmospheric $1/f$ noise, which has motivated the development of polarization modulators to facilitate the rejection of these large systematic effects. Variable-delay polarization modulators (VPMs) are used in the Cosmology Large Angular Scale Surveyor (CLASS) telescopes as the first element in the optical chain to rapidly modulate the incoming polarization. VPMs consist of a linearly polarizing wire grid in front of a movable flat mirror. Varying the distance between the grid and the mirror produces a changing phase shift between polarization states parallel and perpendicular to the grid which modulates Stokes U (linear polarization at $45^\circ$) and Stokes V (circular polarization). The CLASS telescopes have VPMs as the first optical element from the sky; this simultaneously allows a lock-in style polarization measurement and the separation of sky polarization from any instrumental polarization further along in the optical path. The Q-band CLASS VPM was the first VPM to begin observing the CMB full time, starting in the Spring of 2016. The first W-band CLASS VPM was installed in the Spring of 2018.

Measurement-device-independent (MDI) method is a way to solve all detector side-channel attacks in quantum key distribution (QKD). However, very little work has been done on experimentally feasible qudit-based MDI-QKD scheme although the famous (qudit-based) round-robin differential-phase-shift (RRDPS) scheme is vulnerable to attacks on uncharacterized detectors. Here we report a mother-of-all QKD protocol on which all provably secure qubit-based QKD schemes known to date including the RRDPS and the so-called Chau15 schemes are based. We also report an experimentally feasible MDI system via optical implementation of entanglement swapping based on a recent qudit teleportation proposal by Goyal et al. In this way, we show that all provably secure qudit-based QKD schemes discovered to date can be made MDI., Comment: 3 pages

Recently, Chau introduced an experimentally feasible qudit-based quantum-key-distribution (QKD) scheme. In that scheme, one bit of information is phase encoded in the prepared state in a $2^n$-dimensional Hilbert space in the form $(|i\rangle\pm|j\rangle)/\sqrt{2}$ with $n\ge 2$. For each qudit prepared and measured in the same two-dimensional Hilbert subspace, one bit of raw secret key is obtained in the absence of transmission error. Here we show that by modifying the basis announcement procedure, the same experimental setup can generate $n$ bits of raw key for each qudit prepared and measured in the same basis in the noiseless situation. The reason is that in addition to the phase information, each qudit also carries information on the Hilbert subspace used. The additional $(n-1)$ bits of raw key comes from a clever utilization of this extra piece of information. We prove the unconditional security of this modified protocol and compare its performance with other existing provably secure qubit- and qudit-based protocols on market in the one-way classical communication setting. Interestingly, we find that for the case of $n=2$, the secret key rate of this modified protocol using non-degenerate random quantum code to perform one-way entanglement distillation is equal to that of the six-state scheme., Comment: extensively revised, conclusions changed, 7 pages, 2 figures and 1 table, published in PRA

We report on 0.3-10 keV observations with the Chandra X-ray Observatory of eight hard X-ray sources discovered within 8 degrees of the Galactic plane by the INTEGRAL satellite. The short (5 ks) Chandra observations of the IGR source fields have yielded very likely identifications of X-ray counterparts for three of the IGR sources: IGR J14091-6108, IGR J18088-2741, and IGR J18381-0924. The first two have very hard spectra in the Chandra band that can be described by a power-law with photon indices of Gamma = 0.6+/-0.4 and -0.7(+0.4)(-0.3), respectively (90% confidence errors are given), and both have a unique near-IR counterpart consistent with the Chandra position. IGR J14091-6108 also displays a strong iron line and a relatively low X-ray luminosity, and we argue that the most likely source type is a Cataclysmic Variable (CV), although we do not completely rule out the possibility of a High Mass X-ray Binary. IGR J18088-2741 has an optical counterpart with a previously measured 6.84 hr periodicity, which may be the binary orbital period. We also detect five cycles of a possible 800-950 s period in the Chandra light curve, which may be the compact object spin period. We suggest that IGR J18088-2741 is also most likely a CV. For IGR J18381-0924, the spectrum is intrinsically softer with Gamma = 1.5(+0.5)(-0.4), and it is moderately absorbed, nH = (4+/-1)e22 cm-2. There are two near-IR sources consistent with the Chandra position, and they are both classified as galaxies, making it likely that IGR J18381-0924 is an Active Galactic Nucleus (AGN). For the other five IGR sources, we provide lists of nearby Chandra sources, which may be used along with further observations to identify the correct counterparts, and we discuss the implications of the low inferred Chandra count rates for these five sources., Comment: Accepted by ApJ, 14 pages