We present multiband photometry of 185 type-Ia supernovae (SNe Ia), with over 11,500 observations. These were acquired between 2001 and 2008 at the F. L. Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA). This sample contains the largest number of homogeneously observed and reduced nearby SNe Ia (z 0.08) published to date. It more than doubles the nearby sample, bringing SN Ia cosmology to the point where systematic uncertainties dominate. Our natural system photometry has a precision of 0.02 mag in BV RI r i and 0.04 mag in U for points brighter than 17.5 mag. We also estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system BV RI r i photometry and 0.07 mag for U. Comparisons of our standard system photometry with published SN Ia light curves and comparison stars, where available for the same SN, reveal agreement at the level of a few hundredths mag in most cases. We find that 1991bg-like SNe Ia are sufficiently distinct from other SNe Ia in their color and light-curve-shape/ luminosity relation that they should be treated separately in light-curve/distance fitter training samples. The CfA3 sample will contribute to the development of better light-curve/distance fitters, particularly in the few dozen cases where near-infrared photometry has been obtained and, together, can help disentangle host-galaxy reddening from intrinsic supernova color, reducing the systematic uncertainty in SN Ia distances due to dust.

Using the large multiwavelength data set in the Chandra/SWIRE Survey (0.6 deg 2 in the Lockman Hole), we show evidence for the existence of highly obscured (Compton-thick) AGNs, estimate a lower limit to their surface density, and characterize their multiwavelength properties. Two independent selection methods based on the X-ray and infrared spectral properties are presented. The two selected samples contain (1) five X-ray sources with hard X-ray spectra and column densities k10 24 cm À2 and (2) 120 infrared sources with red and AGN-dominated infrared SEDs. We estimate a surface density of at least 25 Compton-thick AGNs deg À2 detected in the infrared in the Chandra/ SWIRE field, of which $40% show distinct AGN signatures in their optical/near-infrared SEDs, the remaining being dominated by the host galaxy emission. Only $33% of all Compton-thick AGNs are detected in the X-rays at our depth [F(0:3 8 keV) > 10 À15 ergs cm À2 s À1 ]. We report the discovery of two sources in our sample of Comptonthick AGNs, SWIRE J104409.95+585224.8 (z ¼ 2:54) and SWIRE J104406.30+583954.1 (z ¼ 2:43), which are the most luminous Compton-thick AGNs at high z currently known. The properties of these two sources are discussed in detail with an analysis of their spectra, SEDs, luminosities, and black hole masses.

We analyse Chandra High Resolution Camera observations of the starburst galaxy M82, concentrating on the most luminous X‐ray source. We find a position for the source of (J2000) with a 1σ radial error of 0.7 arcsec. The accurate X‐ray position shows that the luminous source is neither at the dynamical centre of M82 nor coincident with any suggested radio AGN candidate. The source is highly variable between observations, which suggests that it is a compact object and not a supernova or remnant. There is no significant short‐term variability within the observations. Dynamical friction and the off‐centre position place an upper bound of 105–106 M⊙ on the mass of the object, depending on its age. The X‐ray luminosity suggests a compact object mass of at least 500 M⊙. Thus the luminous source in M82 may represent a new class of compact object with a mass intermediate between those of stellar‐mass black hole candidates and supermassive black holes.

We present a comparison of X-ray point source luminosity functions of 3 starburst galaxies (the Antennae, M82, and NGC 253) and 4 non-starburst spiral galaxies (NGC 3184, NGC 1291, M83, and IC 5332). We find that the luminosity functions of the starbursts are flatter than those of the spiral galaxies; the starbursts have relatively more sources at high luminosities. This trend extends to early-type galaxies which have steeper luminosity functions than spirals. We show that the luminosity function slope is correlated with 60µm luminosity, a measure of star formation. We suggest that the difference in luminosity functions is related to the age of the X-ray binary populations and present a simple model which highlights how the shape of the luminosity distribution is affected by the age of the underlying X-ray binary population.

. (2007) 'The orbital period of the Wolf-Rayet binary IC 10 X-1 : dynamic evidence that the compact ob ject is a black hole.', Astrophysical journal letters., 669 (1). L21-L24.Further information on publisher's website: Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACT IC 10 X-1 is a bright (L X p 10 38 ergs s Ϫ1 ) variable X-ray source in the Local Group starburst galaxy IC 10. The most plausible optical counterpart is a luminous Wolf-Rayet star, making IC 10 X-1 a rare example of a Wolf-Rayet X-ray binary. In this Letter, we report on the detection of an X-ray orbital period for IC 10 X-1 of 34.4 hr. This result, combined with a reexamination of optical spectra, allows us to determine a mass function for the system of M , and a probable mass for the compact object of 24-33 M , . If this analysis is f (M) p 7.8 correct, the compact object is the most massive stellar-mass black hole known. We further show that the observed period is inconsistent with Roche lobe overflow, suggesting that the binary is detached and that the black hole is accreting the wind of the Wolf-Rayet star. The observed mass-loss rate of [MAC92] 17A is sufficient to power the X-ray luminosity of IC 10 X-1.