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We present sensitive ALMA observations of TWA 3, a nearby, young (∼10 Myr) hierarchical system composed of three pre-main-sequence M3–M4.5 stars. For the first time, we detected 12CO and 13CO J = 2–1 emissions from the circumbinary protoplanetary disk around TWA 3A. We jointly fit the protoplanetary disk velocity field, stellar astrometric positions, and stellar radial velocities to infer the architecture of the system. The Aa and Ab stars (0.29 ± 0.01 M⊙ and 0.24 ± 0.01 M⊙, respectively) comprising the tight (P = 35 days) eccentric (e = 0.63 ± 0.01) spectroscopic binary are coplanar with their circumbinary disk (misalignment <6° with 68% confidence), similar to other short-period binary systems. From models of the spectral energy distribution, we found the inner radius of the circumbinary disk (rinner = 0.50–0.75 au) to be consistent with theoretical predictions of dynamical truncation rcav/ainner ≈ 3. The outer orbit of the tertiary star B (0.40 ± 0.28 M⊙, a ∼ 65 ± 18 au, e = 0.3 ± 0.2) is not as well constrained as the inner orbit; however, orbits coplanar with the A system are still preferred (misalignment < 20°). To better understand the influence of the B orbit on the TWA 3A circumbinary disk, we performed SPH simulations of the system and found that the outer edge of the gas disk (router = 8.5 ± 0.2 au) is most consistent with truncation from a coplanar, circular, or moderately eccentric orbit, supporting the preference from the joint orbital fit. [ABSTRACT FROM AUTHOR]

In this era of Gaia and ALMA, dynamical stellar mass measurements, derived from spatially and spectrally resolved observations of the Keplerian rotation of circumstellar disks, provide benchmarks that are independent of observations of stellar characteristics and their uncertainties. These benchmarks can then be used to validate and improve stellar evolutionary models, the latter of which can lead to both imprecise and inaccurate mass predictions for pre-main-sequence, low-mass (≤0.5 M⊙) stars. We present the dynamical stellar masses derived from disks around three M stars (FP Tau, J0432+1827, and J1100–7619) using ALMA observations of 12CO (J = 2–1) and 13CO (J = 2–1) emission. These are the first dynamical stellar mass measurements for J0432+1827 and J1100–7619 (0.192 ± 0.005 M⊙ and 0.461 ± 0.057 M⊙, respectively) and the most precise measurement for FP Tau (0.395 ± 0.012 M⊙). Fiducial stellar evolutionary model tracks, which do not include any treatment of magnetic activity, agree with the dynamical stellar mass measurement of J0432+1827 but underpredict the mass by ∼60% for FP Tau and by ∼80% for J1100–7619. Possible explanations for the underpredictions include inaccurate assumptions of stellar effective temperature, undetected binarity for J1100–7619, and that fiducial stellar evolutionary models are not complex enough to represent these stars. In the former case, the stellar effective temperatures would need to be increased by amounts ranging from ∼40 to ∼340 K to reconcile the fiducial stellar evolutionary model predictions with the dynamically measured masses. In the latter case, we show that the dynamical masses can be reproduced using results from stellar evolutionary models with starspots, which incorporate fractional starspot coverage to represent the manifestation of magnetic activity. Folding in low-mass M stars from the literature and assuming that the stellar effective temperatures are imprecise but accurate, we find tentative evidence of a relationship between fractional starspot coverage and observed effective temperature for these young, cool stars. [ABSTRACT FROM AUTHOR]

The volatile contents of protoplanetary disks both set the potential for planetary chemistry and provide valuable probes of defining disk system characteristics such as stellar mass, gas mass, ionization, and temperature structure. Current disk molecular inventories are fragmented, however, giving an incomplete picture: unbiased spectral line surveys are needed to assess the volatile content. We present here an overview of such a survey of the protoplanetary disks around the Herbig Ae star MWC 480 and the T Tauri star LkCa 15 in ALMA Band 7, spanning ∼36 GHz from 275 to 317 GHz and representing an order of magnitude increase in sensitivity over previous single-dish surveys. We detect 14 molecular species (including isotopologues), with five species (C34S, 13CS, H2CS, DNC, and C2D) detected for the first time in protoplanetary disks. Significant differences are observed in the molecular inventories of MWC 480 and LkCa 15, and we discuss how these results may be interpreted in light of the different physical conditions of these two disk systems. [ABSTRACT FROM AUTHOR]

We present griz P1 light curves of 146 spectroscopically confirmed Type Ia supernovae (SNe Ia; 0.03 < z < 0.65) discovered during the first 1.5 yr of the Pan-STARRS1 Medium Deep Survey. The Pan-STARRS1 natural photometric system is determined by a combination of on-site measurements of the instrument response function and observations of spectrophotometric standard stars. We find that the systematic uncertainties in the photometric system are currently 1.2% without accounting for the uncertainty in the Hubble Space Telescope Calspec definition of the AB system. A Hubble diagram is constructed with a subset of 113 out of 146 SNe Ia that pass our light curve quality cuts. The cosmological fit to 310 SNe Ia (113 PS1 SNe Ia + 222 light curves from 197 low-z SNe Ia), using only supernovae (SNe) and assuming a constant dark energy equation of state and flatness, yields $w=-1.120^{+0.360}_{-0.206}\hbox{(Stat)} ^{+0.269}_{-0.291}\hbox{(Sys)}$. When combined with BAO+CMB(Planck)+H 0, the analysis yields $\Omega _{\rm M}=0.280^{+0.013}_{-0.012}$ and $w=-1.166^{+0.072}_{-0.069}$ including all identified systematics. The value of w is inconsistent with the cosmological constant value of –1 at the 2.3σ level. Tension endures after removing either the baryon acoustic oscillation (BAO) or the H 0 constraint, though it is strongest when including the H 0 constraint. If we include WMAP9 cosmic microwave background (CMB) constraints instead of those from Planck, we find $w=-1.124^{+0.083}_{-0.065}$, which diminishes the discord to <2σ. We cannot conclude whether the tension with flat ΛCDM is a feature of dark energy, new physics, or a combination of chance and systematic errors. The full Pan-STARRS1 SN sample with ~three times as many SNe should provide more conclusive results., Astronomy

We present observations of the unusual optical transient SN 2010U, including spectra taken 1.03 days to 15.3 days after maximum light that identify it as a fast and luminous Fe II type nova. Our multi-band light curve traces the fast decline (t2 = 3.5 ± 0.3 days) from maximum light (MV = −10.2 ± 0.1 mag), placing SN 2010U in the top 0.5% of the most luminous novae ever observed. We find typical ejecta velocities of ≈ 1100 km s−1 and that SN 2010U shares many spectral and photometric characteristics with two other fast and luminous Fe II type novae, including Nova LMC 1991 and M31N-2007-11d. For the extreme luminosity of this nova, the maximum magnitude vs. rate of decline relationship indicates a massive white dwarf progenitor with a low pre-outburst accretion rate. However, this prediction is in conflict with emerging theories of nova populations, which predict that luminous novae from massive white dwarfs should preferentially exhibit an alternate spectral type (He/N) near maximum light., Astronomy

We present the Pan-STARRS1 discovery of the long-lived and blue transient PS1-11af, which was also detected by Galaxy Evolution Explorer with coordinated observations in the near-ultraviolet (NUV) band. PS1-11af is associated with the nucleus of an early type galaxy at redshift z = 0.4046 that exhibits no evidence for star formation or active galactic nucleus activity. Four epochs of spectroscopy reveal a pair of transient broad absorption features in the UV on otherwise featureless spectra. Despite the superficial similarity of these features to P-Cygni absorptions of supernovae (SNe), we conclude that PS1-11af is not consistent with the properties of known types of SNe. Blackbody fits to the spectral energy distribution are inconsistent with the cooling, expanding ejecta of a SN, and the velocities of the absorption features are too high to represent material in homologous expansion near a SN photosphere. However, the constant blue colors and slow evolution of the luminosity are similar to previous optically selected tidal disruption events (TDEs). The shape of the optical light curve is consistent with models for TDEs, but the minimum accreted mass necessary to power the observed luminosity is only ∼0.002 M , which points to a partial disruption model. A full disruption model predicts higher bolometric luminosities, which would require most of the radiation to be emitted in a separate component at high energies where we lack observations. In addition, the observed temperature is lower than that predicted by pure accretion disk models for TDEs and requires reprocessing to a constant, lower temperature. Three deep non-detections in the radio with the Very Large Array over the first two years after the event set strict limits on the production of any relativistic outflow comparable to Swift J1644+57, even if off-axis., Physics

We present broad-band observations of the afterglow and environment of the short GRB 111020A. An extensive X-ray light curve from Swift/XRT, XMM-Newton and Chandra, spanning ∼ 100 seconds to 10 days after the burst, reveals a significant break at δt ≈2 days with pre- and post-break decline rates of αX,1 ≈ −0.78 and αX,2 . −1.7, respectively. Interpreted as a jet break, we infer a collimated outflow with an opening angle of θj ≈ 3 − 8◦. The resulting beaming-corrected γ-ray (10 − 1000 keV band) and blastwave kinetic energies are (2−3)×1048 erg and (0.3−2)×1049 erg, respectively, with the range depending on the unknown redshift of the burst. We report a radio afterglow limit of <39 µJy (3σ) from EVLA observations which, along with our finding that νc < νX , constrains the circumburst density to n0 ∼ 0.01 − 0.1 cm−3. Optical observations provide an afterglow limit of i & 24.4 mag at 18 hours after the burst, and reveal a potential host galaxy with i ≈ 24.3 mag. The sub-arcsecond localization from Chandra provides a precise offset of 0.80′′ ±0.11′′ (1σ) from this galaxy corresponding to an offset of 5−7 kpc for z = 0.5−1.5. We find a high excess neutral Hydrogen column density of (7.5 ± 2.0) × 1021 cm−2 (z = 0). Our observations demonstrate that a growing fraction of short GRBs are collimated which may lead to a true event rate of & 100 − 1000 Gpc−3 yr−1, in good agreement with the NS-NS merger rate of ≈ 200 − 3000 Gpc−3 yr−1. This consistency is promising for coincident short GRB-gravitational wave searches in the forthcoming era of Advanced LIGO/VIRGO., Astronomy

We present the first spectroscopic study of the host environments of Type Ibc supernovae (SN Ibc) discovered exclusively by untargeted SN searches. Past studies of SN Ibc host environments have been biased towards high-mass, high-metallicity galaxies by focusing on SNe discovered in galaxytargeted SN searches. Our new observations more than double the total number of spectroscopic stellar population age and metallicity measurements published for untargeted SN Ibc host environments. For the 12 SNe Ib and 21 SNe Ic in our metallicity sample, we find median metallicities of 0.62 Z⊙ and 0.83 Z⊙, respectively, but determine that the discrepancy in the full distribution of metallicities is not statistically significant. This median difference would correspond to only a small difference in the mass loss via metal-line driven winds (. 30%), suggesting this does not play the dominant role in distinguishing SN Ib and Ic progenitors. However, the median metallicity of the 7 broad-lined SN Ic (SN Ic-BL) in our sample is significantly lower, 0.45 Z⊙. The age of the young stellar population of SN Ic-BL host environments also seems to be lower than for SN Ib and Ic, but our age sample is small. Combining all SN Ibc host environment spectroscopy from the literature to date does not reveal a significant difference in SN Ib and Ic metallicities, but reinforces the significance of the lower metallicities for SN Ic-BL. This combined sample demonstrates that galaxy-targeted SN searches introduce a significant bias for studies seeking to infer the metallicity distribution of SN progenitors, and we identify and discuss other systematic effects that play smaller roles. We discuss the path forward for making progress on SN Ibc progenitor studies in the LSST era. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile., Astronomy

We present the Pan-STARRS1 discovery and light curves, and follow-up MMT and Gemini spectroscopy of an ultra-luminous supernova (ULSN; dubbed PS1-11bam) at a redshift of z = 1.566 with a peak brightness of MUV ≈ −22.3 mag. PS1-11bam is one of the highest redshift spectroscopically-confirmed SNe known to date. The spectrum is characterized by broad absorption features typical of previous ULSNe (e.g., C II, Si III), and by strong and narrow Mg II and Fe II absorption lines from the interstellar medium (ISM) of the host galaxy, confirmed by an [O II]λ3727 emission line at the same redshift. The equivalent widths of the Fe IIλ2600 and Mg IIλ2803 lines are in the top quartile of the quasar intervening absorption system distribution, but are weaker than those of gamma-ray burst intrinsic absorbers (i.e., GRB host galaxies). We also detect the host galaxy in pre-explosion Pan-STARRS1 data and find that its UV spectral energy distribution is best fit with a young stellar population age of τ∗ ≈ 15 − 45 Myr and a stellar mass of M∗ ≈ (1.1 − 2.6) × 109 M⊙ (for Z = 0.05 − 1 Z⊙). The star formation rate inferred from the UV continuum and [O II]λ3727 emission line is ≈ 10 M⊙ yr−1, higher than in any previous ULSN host. PS1-11bam provides the first direct demonstration that ULSNe can serve as probes of the interstellar medium in distant galaxies. At the present, the depth and red sensitivity of PS1 are uniquely suited to finding such events at cosmologically interesting redshifts (z ∼ 1 − 2); the future combination of LSST and 30-m class telescopes promises to extend this technique to z ∼ 4., Astronomy

We present the discovery of two ultraluminous supernovae (SNe) at z ≈ 0.9 with the Pan-STARRS1 Medium Deep Survey. These SNe, PS1-10ky and PS1-10awh, are among the most luminous SNe ever discovered, comparable to the unusual transients SN 2005ap and SCP 06F6. Like SN 2005ap and SCP 06F6, they show characteristic high luminosities (M bol ≈ –22.5 mag), blue spectra with a few broad absorption lines, and no evidence for H or He. We have constructed a full multi-color light curve sensitive to the peak of the spectral energy distribution in the rest-frame ultraviolet, and we have obtained time series spectroscopy for these SNe. Given the similarities between the SNe, we combine their light curves to estimate a total radiated energy over the course of explosion of (0.9-1.4) × 1051 erg. We find photospheric velocities of 12,000-19,000 km s–1 with no evidence for deceleration measured across ~3 rest-frame weeks around light curve peak, consistent with the expansion of an optically thick massive shell of material. We show that, consistent with findings for other ultraluminous SNe in this class, radioactive decay is not sufficient to power PS1-10ky, and we discuss two plausible origins for these events: the initial spin-down of a newborn magnetar in a core-collapse SN, or SN shock breakout from the dense circumstellar wind surrounding a Wolf-Rayet star., Astronomy, Physics

Hubble Space Telescope and ground-based observations of the Type IIn supernova (SN) 2010jl are analyzed, including photometry and spectroscopy in the ultraviolet, optical, and near-IR bands, 26-1128 days after first detection. At maximum, the bolometric luminosity was ∼3 × 1043 erg s–1 and even at 850 days exceeds 1042 erg s–1. A near-IR excess, dominating after 400 days, probably originates in dust in the circumstellar medium (CSM). The total radiated energy is ≳ 6.5 × 1050 erg, excluding the dust component. The spectral lines can be separated into one broad component that is due to electron scattering and one narrow with expansion velocity ∼100 km s–1 from the CSM. The broad component is initially symmetric around zero velocity but becomes blueshifted after ∼50 days, while remaining symmetric about a shifted centroid velocity. Dust absorption in the ejecta is unlikely to explain the line shifts, and we attribute the shift instead to acceleration by the SN radiation. From the optical lines and the X-ray and dust properties, there is strong evidence for large-scale asymmetries in the CSM. The ultraviolet lines indicate CNO processing in the progenitor, while the optical shows a number of narrow coronal lines excited by the X-rays. The bolometric light curve is consistent with a radiative shock in an r–2 CSM with a mass-loss rate of . The total mass lost is ≳ 3 M☼. These properties are consistent with the SN expanding into a CSM characteristic of a luminous blue variable progenitor with a bipolar geometry. The apparent absence of nuclear processing is attributed to a CSM that is still opaque to electron scattering. [ABSTRACT FROM AUTHOR]