12 research outputs found
Dilute ferrimagnetic semiconductors in Fe-substituted spinel ZnGaO
Solid solutions of nominal composition
[ZnGaO][FeO], of the semiconducting spinel
ZnGaO with the ferrimagnetic spinel FeO have been prepared with
= 0.05, 0.10, and 0.15. All samples show evidence for long-range magnetic
ordering with ferromagnetic hysteresis at low temperatures. Magnetization as a
function of field for the = 0.15 sample is S-shaped at temperatures as high
as 200 K. M\"ossbauer spectroscopy on the = 0.15 sample confirms the
presence of Fe, and spontaneous magnetization at 4.2 K. The magnetic
behavior is obtained without greatly affecting the semiconducting properties of
the host; diffuse reflectance optical spectroscopy indicates that Fe
substitution up to = 0.15 does not affect the position of the band edge
absorption. These promising results motivate the possibility of dilute
ferrimagnetic semiconductors which do not require carrier mediation of the
magnetic moment.Comment: 9 pages and 6 figure
The Carnegie Supernova Project I: photometry data release of low-redshift stripped-envelope supernovae
The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated
supernova follow-up program based at the Las Campanas Observatory that
collected science data of young, low-redshift supernovae between 2004 and 2009.
Presented in this paper is the CSP-I photometric data release of low-redshift
stripped-envelope core-collapse supernovae. The data consist of optical
(uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared
(YJH) photometry. Twenty objects have optical pre-maximum coverage with a
subset of 12 beginning at least five days prior to the epoch of B-band maximum
brightness. In the near-infrared, 17 objects have pre-maximum observations with
a subset of 14 beginning at least five days prior to the epoch of J-band
maximum brightness. Analysis of this photometric data release is presented in
companion papers focusing on techniques to estimate host-galaxy extinction
(Stritzinger et al., submitted) and the light-curve and progenitor star
properties of the sample (Taddia et al., submitted). The analysis of an
accompanying visual-wavelength spectroscopy sample of ~150 spectra will be the
subject of a future paper.Comment: Updated a couple of small error
Supernova 2008J: early time observations of a heavily reddened SN 2002ic-like transient
We provide additional observational evidence that some Type Ia supernovae
(SNe Ia) show signatures of circumstellar interaction (CSI) with hydrogen-rich
material. Early phase optical and near-infrared (NIR) light curves and
spectroscopy of SN 2008J obtained by the Carnegie Supernova Project are studied
and compared to those of SNe 2002ic and 2005gj. Our NIR spectrum is the first
obtained for a 2002ic-like object extending up to 2.2 m. A published
high-resolution spectrum is used to provide insight on the circumstellar
material (CSM). SN 2008J is found to be affected by 1.9 mag of
extinction and to closely resemble SN 2002ic. Spectral and color comparison to
SNe 2002ic and 2005gj suggests 3.1. Spectral decomposition reveals
the underlying SN emission matches a 1991T-like event and, since SN 2008J is as
luminous as SN 2005gj ( 20.3 mag), we conclude that their
CSI emissions are similarly robust. The high-resolution spectrum reveals narrow
emission lines produced from un-shocked gas characterized by a wind velocity of
50 km s. We conclude that SN 2008J best matches an explosion of a
SN Ia that interacts with its CSM.Comment: 8 pages, 4 figures, minor changes to match the published versio