To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Stellar coronal mass ejections (CMEs) may play an important role in stellar and planetary evolution, therefore the knowledge on parameter distributions of this energetic activity phenomenon is highly relevant. During the last years several attempts have been made to detect stellar CMEs of late-type main-sequence and pre main-sequence stars from dedicated optical spectroscopic observations. Up to now only a handful of distinct stellar CME detections are known which contradicts the results from stellar CME modelling, which predict higher CME rates. We report on dedicated ongoing and future observational attempts to detect stellar CMEs and discuss the observational results with respect to the results from stellar CME modelling.
The Isaac Newton Photometric H-Alpha Survey (IPHAS) provides (r′-Hα)-(r′-i′) colors, which can be used to select AV0-5 Main Sequence star candidates (age~20-200 Myr). By combining a sample of 23050 IPHAS-selected A-type stars with 2MASS, GLIMPSE and MIPSGAL photometry we searched for mid-infrared excesses attributable to dusty circumstellar disks. Positional cross-correlation yielded a sample of 2692 A-type stars, of which 0.6% were found to have 8-μm excesses above the expected photospheric values. The low fraction of main sequence stars with mid-IR excesses found in this work indicates that dust disks in the terrestrial planet zone of Main Sequence intermediate mass stars are rare. Dissipation mechanisms such as photo-evaporation, grain growth, collisional grinding or planet formation could possibly explain the depletion of dust detected in the inner regions of these disks.
About one core-collapse supernova (CCSN) is expected to explode every 5–10 years in the nuclear regions of M 82 and other nearby starburst galaxies. In luminous infrared galaxies (LIRGs) such as the interacting system Arp 299 (NGC 3690 + IC 0694) at least one CCSN can be expected every year. Due to the high dust extinction most of these SNe have remained undetected. Here we show results from two near-IR searches we have recently carried out to detect obscured SNe in nearby starburst galaxies and LIRGs.
There is now considerable interest in how stellar streams in the Milky Way can be used to probe how the earlier merger history of our galaxy, which in turn can be related to hierarchical models of galaxy evolution.
We have begun a census of various stellar groups in Local Group Galaxies, using the wide field camera on the Isaac Newton Telescope on La Palma. Here we present a preliminary color-magnitude diagram for the dwarf irregular galaxy IC-10. At present time, metallicity of IC-10 is measured to be Z = 0.005 (Garnett 1990). Comparison with recent literature values of reddening and distance suggest that IC-10's distance is ~ 1 Mpc. Our comprehensive wide-field survey encompasses both broad (g′, r′, i′) and narrow-band (O iii, He ii, Hα, S ii, Strömgren y) observations to look for emission-line objects, including Wolf-Rayet stars and Luminous Blue Variables. The analysis also yields the coordinates of massive stars to an accuracy sufficient for follow-up multi-object spectroscopic observations.
Although the use of telluric lines as wavelength fiducials to measure radial velocities does not achieve as high a precision as other fiducial-imposition techniques, this very convenient technique can be used concurrently with other observing programs to increase the temporal sampling of target stars. We have been carrying out a program to monitor the line-profile variations of early-type non-radial pulsators at the Hα and He I 667.8-nm region. With the rather modest reciprocal dispersion of 1nm/mm and the use of a 4096-element CCD, the telluric lines in the 630-nm region are also available in the observed spectra. We decided to use these telluric lines as wavelength fiducials to monitor bright, latetype stars for radial-velocity variations. As an experiment, we have also decided to reduce the spectra using available simple IRAF tasks to see how high a velocity precision can be achieved with only minor tweaking. The precision certainly would not rival other precise techniques, but the convenience in both the observing and reduction procedure may enable more target stars to be monitored by more observers. Moreover, interesting results can still be obtained with a mere 100 m/s precision. The result for a few late-type stars which also have prior HF velocities will be presented.
Email your librarian or administrator to recommend adding this to your organisation's collection.