High-Redshift SDSS Quasars with Weak Emission Lines (2009)
Diamond-Stanic, Aleksandar M., Fan, Xiaohui, Brandt, W. N., Shemmer, Ohad, Strauss, Michael A., Anderson, Scott F., ...
We identify a sample of 74 high-redshift quasars (z>3) with weak emission lines from the Fifth Data Release of the Sloan Digital Sky Survey and present infrared, optical, and radio observations of a...
X-ray Insights into the Nature of Weak Emission-Line Quasars at High Redshift (2009)
Shemmer, Ohad, Brandt, W. N., Anderson, Scott F., Diamond-Stanic, Aleksandar M., Fan, Xiaohui, Richards, Gordon T., ...
We present Chandra observations of nine high-redshift quasars (z=2.7-5.9) discovered by the Sloan Digital Sky Survey with weak or undetectable high-ionization emission lines in their UV spectra...
Shemmer, Ohad, Brandt, W. N., Netzer, Hagai, Maiolino, Roberto, Kaspi, Shai
We study the hard-X-ray spectral properties of ten highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z=1.3-3.2, including new XMM-Newton observations of four of these sources. We find...
Black-Hole Mass and Growth Rate at High Redshift (2007)
Netzer, Hagai, Lira, Paulina, Trakhtenbrot, Benny, Shemmer, Ohad, Cury, Iara
We present new H and K bands spectroscopy of 15 high luminosity active galactic nuclei (AGNs) at redshifts 2.3-3.4 obtained on Gemini South. We combined the data with spectra of additional 29...
Reverberation Mapping of High-Luminosity Quasars: First Results (2006)
Kaspi, Shai, Brandt, W. N., Maoz, Dan, Netzer, Hagai, Schneider, Donald P., Shemmer, Ohad
Reverberation mapping of nearby active galactic nuclei has led to estimates of broad-line-region (BLR) sizes and central-object masses for some 37 objects to date. However, successful reverberation...
Shemmer, Ohad, Brandt, W. N., Netzer, Hagai, Maiolino, Roberto, Kaspi, Shai
We present new XMM-Newton observations of two luminous and high accretion-rate radio-quiet active galactic nuclei (AGNs) at z~2. Together with archival X-ray and rest-frame optical spectra of three...
Chandra Observations of the Highest Redshift Quasars from the Sloan Digital Sky Survey (2006)
Shemmer, Ohad, Brandt, W. N., Schneider, Donald P., Fan, Xiaohui, Strauss, Michael A., Diamond-Stanic, Aleksandar M., ...
We present new Chandra observations of 21 z>4 quasars, including 11 sources at z>5. These observations double the number of X-ray detected quasars at z>5, allowing investigation of the X-ray spectral...
New XMM-Newton Spectroscopy of the Most Luminous and Distant Quasars (2005)
In the two parts of this contribution we describe two related XMM-Newton programs. The first part summarizes our study of the X-ray spectral properties and variability of z>4 quasars (Shemmer et al....
Reverberation Mapping of High-Redshift, High-Luminosity Quasars (2002)
Kaspi, Shai, Netzer, Hagai, Maoz, Dan, Shemmer, Ohad, Brandt, W. N., Schneider, Donald P.
We present preliminary results from a reverberation mapping program to measure the Broad Line Region size in high-redshift, high-luminosity quasars. The observations are carried out at the...
Supernova 2002ap - The First Month (2002)
Gal-Yam, Avishay, Ofek, Eran O., Shemmer, Ohad
Supernova (SN) 2002ap in M74 was discovered on January 29, 2002. Being one of the nearest (10 Mpc) SN events in the last decades, and spectroscopically similar to the so-called ``hypernovae'' 1997ef...
The well known relationship between metallicity and luminosity in AGN is addressed by introducing new metallicity measurements (based on the method of Hamann & Ferland 1993; HF93) for a sample of...
Optical Monitoring of NLS1s at the Wise Observatory (2000)
We report the preliminary results of a spectrophotometric monitoring program of Narrow-Line Seyfert 1 galaxies conducted at the Wise Observatory in 1999. The data we collected will be used to...
Periodic Microvariation of B416, a New LBV in M33 (1999)
Shemmer, Ohad, Leibowitz, Elia M., Szkody, Paula
We report optical photometric and spectroscopic observations of the M33 star B416, establishing it as the fifth identified LBV in that galaxy. The B magnitude of the star varies with a period of 8.26...
The Discovery of a Nearby M Dwarf (1998)
We report the discovery of a nearby M dwarf star, found accidentally while observing the old nova DN Gem at the Wise Observatory. The star is designated 1200-05296925 in the PMM USNO-A1.0 catalogue...