The origin of dust in galaxies is still a mystery (1, 2, 3, 4). The majority of the refractory elements are produced in supernova explosions but it is unclear how and where dust grains condense and grow, and how they avoid destruction in the harsh environments of star-forming 3 Figure 3 shows the resulting confidence interval for the two parameters a max and α around the best fit values of a min = 0.001 µm, a max = 4.2 µm and α = 3.6. It is evident that only size distributions extending to grain radii that are significantly larger than that of MW interstellar medium (21, 22) dust ( 0.25 µm) can reproduce the supernova extinction curve (Figure 2). The 2 σ lower limit on the maximum grain size is a max > 0.7 µm. We cannot perform a similar analysis of the late epoch because the intrinsic line profile at this epoch is unknown and likely highly affected by extinction (13). However, we note that the blueshift velocities change only marginally with wavelength (Extended Data Figure 6), suggestive of large grains also at this epoch. Figure 4 illustrates the continuous build-up of dust as a function of time. The increasing attenuation of the lines is accompanied by increasing emission in the near-infrared (NIR) spectra, from a slight excess over a supernova blackbody fit at early times to total dominance at the late epoch. We fitted the spectra with black bodies which for the NIR excess yield a constant blackbody radius of (1.0 ± 0.2) × 10 16 cm at the early epochs, and a temperature that declines from ∼ 2,300 K to ∼ 1,600 K from day 26 onwards. At the late epoch, we obtain a black-body radius of (5.7 ± 0.2) × 10 16 cm and a temperature of ∼ 1,100 K. The high temperatures detected at the early epochs suggest that the NIR excess is due to thermal emission from carbonaceous dust, rather than silicate dust, which has a lower condensation temperature of ∼ 1, 500 K (1). The high temperatures rule out suggestions that the NIR emission is due to pre-existing dust or a dust echo (11) (Figure 1), the accelerated dust formation occurring at later times ( Figure 4) and at larger radius is possibly facilitated by the bulk ejecta material, which travels on average at a velocity of ∼ 7, 500 km s −1 at early epochs (Extended Data Figure 4).Our detection of large grains soon after the supernova explosion suggests a remarkably rapid and efficient mechanism for dust nucleation and growth. The underlying physics is poorly understood but may involve a two-stage process governed by early dust formation in a cool, dense shell, 5 followed by accelerated dust formation involving ejecta material. For Type IIP supernovae, the growth of dust grains can be sustained up to 5 years past explosion (25). The dense CSM around Type IIn supernovae may provide conditions to facilitate dust growth beyond that. The process appears generic, in that other Type IIn supernovae like SN 1995N, SN 1998S, SN 2005ip, and SN 2006jd exhibited similar observed NIR properties (8, 10, 26, 27) and growing dust masses, consistent with the trend revealed here for SN 2010...

We report the discovery of a very cool, isolated brown dwarf, UGPS 0722???05, with the United Kingdom Infrared Telescope Deep Sky Survey (UKIDSS) Galactic Plane Survey. The near-infrared spectrum displays deeper H2O and CH4 troughs than the coolest known T dwarfs and an unidentified absorption feature at 1.275 ??m. We provisionally classify the object as a T10 dwarf but note that it may in future come to be regarded as the first example of a new spectral type. The distance is measured by trigonometric parallax as d= 4.1+0.6???0.5 pc, making it the closest known isolated brown dwarf. With the aid of Spitzer/Infrared Array Camera (IRAC) we measure H???[4.5]= 4.71. It is the coolest brown dwarf presently known ??? the only known T dwarf that is redder in H???[4.5] is the peculiar T7.5 dwarf SDSS J1416+13B, which is thought to be warmer and more luminous than UGPS 0722???05. Our measurement of the luminosity, aided by Gemini/T-ReCS N-band photometry, is L= 9.2 ?? 3.1 ?? 10???7 L???. Using a comparison with well-studied T8.5 and T9 dwarfs we deduce Teff= 520 ?? 40 K. This is supported by predictions of the Saumon & Marley models. With apparent magnitude J= 16.52, UGPS 0722???05 is the brightest of the ???90 T dwarfs discovered by UKIDSS so far. It offers opportunities for future study via high-resolution near-infrared spectroscopy and spectroscopy in the thermal infrared

We report the discovery of three very late T dwarfs in the UKIRT Infrared Deep Sky Survey (UKIDSS) Third Data Release: ULAS J101721.40+011817.9 (ULAS1017), ULAS J123828.51+095351.3 (ULAS1238) and ULAS J133553.45+113005.2 (ULAS1335). We detail optical and near‐infrared (NIR) photometry for all three sources, and mid‐IR photometry for ULAS1335. We use NIR spectra of each source to assign spectral types T8p (ULAS1017), T8.5 (ULAS1238) and T9 (ULAS1335) to these objects. ULAS1017 is classed as a peculiar T8 (T8p) due to appearing as a T8 dwarf in the J band, whilst exhibiting H‐ and K‐band flux ratios consistent with a T6 classification. Through comparison to BT‐Settl model spectra we estimate that ULAS1017 has 750 K ≲Teff≲ 850 K, and 5.0 ≲ log g(cm s−2) ≲ 5.5, assuming solar metallicity. This estimate for gravity is degenerate with varying metallicity. We estimate that ULAS1017 has an age of 1.6–15 Gyr, a mass of 33–70MJ and lies at a distance of 31–54 pc. We do not estimate atmospheric parameters for ULAS1238 due to a lack of K‐band photometry. We extend the unified scheme of Burgasser et al. to the type T9 and suggest the inclusion of the WJ index to replace the now saturated J‐band indices. We propose ULAS1335 as the T9 spectral type standard. ULAS1335 is the same spectral type as ULAS J003402.77−005206.7 and CFBDS J005910.90−011401.3. We argue that given the similarity of the currently known >T8 dwarfs to the rest of the T dwarf sequence, the suggestion of the Y0 spectral class for these objects is premature. Comparison of model spectra with that of ULAS1335 suggest a temperature below 600 K, possibly combined with low gravity and/or high metallicity. We find ULAS1335 to be extremely red in NIR to mid‐IR colours, with H−[4.49]= 4.34 ± 0.04. This is the reddest NIR to mid‐IR colour yet observed for a T dwarf. The NIR to mid‐IR spectral energy distribution of ULAS1335 further supports Teff < 600 K, and we estimate Teff∼ 550–600 K for ULAS1335. We estimate that ULAS1335 has an age of 0.6–5.3 Gyr, a mass of 15–31MJ and lies at a distance of 8–12 pc.

Stars are generally spherical, yet their gaseous envelopes often appear non-spherical when ejected near the end of their lives. This quirk is most notable during the planetary nebula phase when these envelopes become ionized. Interactions among stars in a binary system are suspected to cause the asymmetry. In particular, a precessing accretion disk around a companion is believed to launch point-symmetric jets, as seen in the prototype Fleming 1. Our discovery of a post common-envelope binary nucleus in Fleming 1 confirms that this scenario is highly favorable. Similar binary interactions are therefore likely to explain these kinds of outflows in a large variety of systems.Planetary nebulae (PNe) are thought to represent the transitory phase of the end of the lives of solar-like stars. The mass-loss mechanisms at play during the late stages of stellar evolution that produce the observed shapes of planetary nebulae have been a matter of debate in the last two decades (1). The leading paradigm to produce the most extreme nebular morphologies is evolution in an interacting binary system (2-4), in particular common-envelope (CE) evolution -the dramatic outcome of unstable mass transfer resulting in a binary system with a greatly reduced orbital period (P<~1 day for PNe). Despite recent detections of multiple post common-envelope binary central stars (5-7), there are as yet no clear-cut examples of binaries actively shaping their surrounding planetary nebulae. A handful of post-CE nebulae are known to be oriented in agreement with the orbital inclination of the binaries that ejected them (8) -as would be expected. However, we do not yet have any inkling how a particular binary configuration gives rise to a specific fundamental nebula shape. An alternative approach to tackle this difficult

Using a simulated disc brown dwarf (BD) population, we find that new large area infrared surveys are expected to identify enough BDs covering wide enough mass-age ranges to potentially measure the present day mass function down to ∼0.03 M , and the BD formation history out to 10 Gyr, at a level that will be capable of establishing if BD formation follows star formation. We suggest these capabilities are best realized by spectroscopic calibration of BD properties (T eff , g and [M/H]) which when combined with a measured luminosity and an evolutionary model can give BD mass and age relatively independent of BD atmosphere models. Such calibration requires an empirical understanding of how BD spectra are affected by variations in these properties, and thus the identification and study of 'benchmark BDs' whose age and composition can be established independently.We identify the best sources of benchmark BDs as young open cluster members, moving group members, and wide (>1000 au) BD companions to both subgiant stars and high-mass white dwarfs (WDs). To accurately asses the likely number of wide companion BDs available, we have constrained the wide L dwarf companion fraction using the 2-Micron All Sky Survey (2MASS), and find a companion fraction of 2.7 +0.7 −0.5 per cent for separations of ∼1000-5000 au. This equates to a BD companion fraction of 34 +9 −6 per cent if one assumes an α ∼ 1 companion mass function. Using this BD companion fraction, we simulate populations of wide BD binaries, and estimate that 80 +21 −14 subgiant-BD binaries, and 50 +13 −10 benchmark WD-BD binaries could be identified using current and new facilities. The WD-BD binaries should all be identifiable using the Large Area Survey component of the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey, combined with the Sloan Digital Sky Survey. Discovery of the subgiant-BD binaries will require a near-infrared imaging campaign around a large (∼900) sample of Hipparcos subgiants. If identified, spectral studies of these benchmark BD populations could reveal the spectral sensitivities across the T eff , g and [M/H] space probed by new surveys.

The original article can be found at: http://www3.interscience.wiley.com Copyright Blackwell Publishing / Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.14620.xWe report the discovery of a T8.5 dwarf, which is a companion to the M4 dwarf Wolf 940. [Please see original online abstract for complete version with correct notation

Aims. In this work we present chromospheric activity indices, kinematics, radial-velocities, and rotational velocities for more than 850 FGK-type dwarfs and subgiant stars in the southern hemisphere and test how best to calibrate and measure S -indices from echelle spectra. Methods. We measured our parameters using the high-resolution and high-S /N FEROS echelle spectra acquired for this purpose. Results. We confirm the bimodal distribution of chromospheric activities for such stars and highlight the role that the more active K-dwarfs play in biasing the number of active stars. We show that the age-activity relationship does appear to continue to ages older than the Sun if we simply compare main sequence stars and subgiant stars with an offset of around 2.5 Gyr between the peaks of both distributions. Also we show evidence of an increased spin-down timescale for cool K dwarfs compared with earlier F and G type stars. We highlight that activities drawn from low-resolution spectra (R < 2500) significantly increase the rms scatter when calibrating onto common systems of measurements like the Mt. Wilson system. Also we show that older and widely used catalogues of activities in the south appear to be offset compared to more recent works at the ∼0.1 dex level in log R HK through calibrator drift. In addition, we show how kinematics can be used to preselect inactive stars for future planet search projects. We see the well known trend between projected rotational velocity and activity, however we also find a correlation between kinematic space velocity and chromospheric activity. It appears that after the Vaughan-Preston gap there is a quick step function in the kinematic space motion towards a significantly broader spread in velocities. We speculate on reasons for this correlation and provide some model scenarios to describe the bimodal activity distribution through magnetic saturation, residual low level gas accretion, or accretion by the star of planets or planetesimals. Finally, we provide a new empirical measurement for the disk-heating law, using the latest age-activity relationships to reconstruct the age-velocity distribution for local disk stars. We find a value of 0.337 ± 0.045 for the exponent of this power law (i.e. σ tot ∝ t 0.337 ), in excellent agreement with those found using isochrone fitting methods and with theoretical disk-heating models.

We report the discovery of a peculiar L dwarf from the UKIDSS Large Area Survey (LAS), ULAS J222711−004547. The very red infrared photometry (MKO J − K = 2.79±0.06, WISE W 1−W 2 = 0.65±0.05) of ULAS J222711−004547 makes it one of the reddest brown dwarfs discovered so far. We obtained a moderate resolution spectrum of this target using VLT/XSHOOTER, and classify it as L7pec, confirming its very red nature. Comparison to theoretical models suggests that the object could be a low-gravity L dwarf with a solar or higher than solar metallicity. Nonetheless, the match of such fits to the spectral energy distribution is rather poor and this and other less red peculiar red L dwarfs pose new challenges for the modeling of ultracool atmospheres, especially to the understanding of the effects of condensates and their sensitivity to gravity and metallicity. We determined the proper motion of ULAS J222711−004547 using the data available in the literature, and we find that its kinematics do not suggest membership of any of the known young associations. We show that applying a simple de-reddening curve to its spectrum allows it to resemble the spectra of the L7 spectroscopic standards without any spectral features that distinguish it as low metallicity or low gravity. Given the negligible interstellar reddening of the field containing our target, we conclude that the reddening of the spectrum is mostly due to an excess of dust in the photosphere of the target. De-reddening the spectrum using extinction curves for different dust species gives surprisingly good results and suggests a characteristic grain size of ∼0.5 µm. We show that by increasing the optical depth, the same extinction curves allow the spectrum of ULAS J222711−004547 to resemble the spectra of unusually blue L dwarfs and even slightly metal-poor L dwarfs. Grains of similar size also yield very good fits when dereddening other unusually red L dwarfs in the L5 to L7.5 range. These results suggest that the diversity in near infrared colours and spectra seen in late-L dwarfs could be due to differences in the optical thickness of the dust cloud deck.