HST Focus Variations with Temperature (2008)
Daiana Di Nino, Russell B. Makidon, Matt Lallo, Kailash C. Sahu, Marco Sirianni
One of the main advantages of space observatories is the quality and stability of the point spread function that allows programs not feasible from the ground. However, when pushed to the limits, even...
Planets in the Galactic Bulge: Results from the SWEEPS Project (2007)
Sahu, Kailash C., Casertano, Stefano, Valenti, Jeff, Bond, Howard E., Brown, Thomas M., Smith, T. Ed, ...
The exoplanets discovered so far have been mostly around relatively nearby and bright stars. As a result, the host stars are mostly (i) in the Galactic disk, (ii) relatively massive, and (iii)...
Kailash C. Sahu, Richard Shaw, Mary Elizabeth Kaiser, Stefi A. Baum, Henry C, ...
The cluster RXJ 1347.5-1145, the most luminous cluster in the X-ray wavelengths, was imaged with the newly installed Space Telescope Imaging Spectrograph (STIS) on-board HST. Its relatively high...
Davies, Ben, Oudmaijer, René D., Sahu, Kailash C.
We present NAOMI/OASIS adaptive-optics assisted integral-field spectroscopy of the transitional massive hypergiant IRC +10420, an extreme mass-losing star apparently in the process of evolving from a...
ACS PSF variations with temperatures (2007)
Kailash C. Sahu, Matt Lallo, Russ Makidon
We have used the HST ACS/WFC observations of a Galactic bulge field taken over a continuous interval of 7 days (Prop 9750) to investigate the possible dependence of the ACS focus with the external...
Transiting extrasolar planetary candidates in the Galactic bulge (2006)
Sahu, Kailash C., Casertano, Stefano, Bond, Howard E., Valenti, Jeff, Smith, T. Ed, Minniti, Dante, ...
More than 200 extrasolar planets have been discovered around relatively nearby stars, primarily through the Doppler line shifts owing to the reflex motions of their host stars, and more recently...
(Abridged) A close scrutiny of the microlensing results towards the Magellanic clouds reveals that the stars within the Magellanic clouds are major contributors as lenses, and the contribution of...
Near-Field Microlensing and Its Effects on Stellar Transit Observations by Kepler (2002)
Sahu, Kailash C., Gilliland, Ronald L.
In this paper, we explore the astrophysical implications of near-field microlensing and its effects on stellar transit observations, with a special emphasis on the Kepler mission. Kepler is a...
Determination of Substellar Mass Function of Young Open Clusters Using 2MASS and GSC Data (2002)
Tej, Anandmayee, Sahu, Kailash C., Chandrasekhar, T., Ashok, N. M.
We present a statistical method to derive the mass functions of open clusters using sky survey data such as the 2 Micron All Sky Survey and the Guide Star Catalogue. We have used this method to...
The Spatially-Resolved Mass Function of the Globular Cluster M22 (2002)
Albrow, Michael D., De Marchi, Guido, Sahu, Kailash C.
HST imaging of M22 has allowed, for the first time, a detailed and uniform mapping of mass segregation in a globular cluster. Luminosity and mass functions from the turnoff down to the mid to lower...
Tej, Anandmayee, Sahu, Kailash C., Chandrasekhar, T., Ashok, N. M.
In this paper we present the mass functions in the substellar regime of three young open clusters, IC 348, $\sigma$ Orionis and Pleiades, as derived using the data from the 2 Micron All Sky Survey...
Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalogue (2002)
Bakos, Gaspar A., Sahu, Kailash C., Nemeth, Peter
We present refined coordinates and proper motion data for the high proper motion (HPM) stars in the Luyten Half-Second (LHS) catalogue. The positional uncertainty in the original Luyten catalogue is...
A Re-examination of the "Planetary" Lensing Events in M22 (2001)
Sahu, Kailash C., Anderson, Jay, King, Ivan R.
We have carried out further analysis of the tentative, short-term brightenings reported by Sahu et al. (2001), which were suggested to be possible lensings of Galactic-bulge stars by free-floating...
High-velocity white dwarfs: thick disk, not dark matter (2001)
Reid, I. Neill, Sahu, Kailash C., Hawley, Suzanne L.
We present an alternative interpretation of the nature of the extremely cool, high-velocity white dwarfs identified by Oppenheimer et al (2001) in a high-latitude astrometric survey. We argue that...
Studying the Galactic Bulge Through Spectroscopy of Microlensed Sources: II. Observations (2001)
Kane, Stephen R., Sahu, Kailash C.
The spectroscopy of microlensed sources towards the Galactic bulge provides a unique opportunity to study (i) the kinematics of the Galactic bulge, particularly its far-side, (ii) the effects of...
Kane, Stephen R., Sahu, Kailash C.
The observed spectra of the microlensed sources towards the Galactic bulge may be used as a tool for studying the kinematics and extinction effects in the Galactic bulge. In this paper, we first...
Discovery of the optical counterpart and early optical observations of GRB990712 (2000)
We present the discovery observations of the optical counterpart of the gamma-ray burster GRB990712 taken 4.16 hours after the outburst and discuss its light curve observed in the V, R and I bands...
Discovery of the optical counterpart and early optical observations of GRB 990712 (2000)
Sahu, Kailash C., Vreeswijk, P. M., Bakos, Gaspar A., Menzies, John W., Bragaglia, Angela, Frontera, Filippo, ...
We present the discovery observations of the optical counterpart of the gamma-ray burst GRB 990712 taken 4.16 hr after the outburst and discuss its light curve observed in the V, R, and I bands...
Discovery of the optical counterpart and early optical observations of GRB 990712 (2000)
Sahu, Kailash C., Vreeswijk, P. M., Bakos, Gaspar A., Menzies, John W., Bragaglia, Angela, Frontera, Filippo, ...
We present the discovery observations of the optical counterpart of the gamma-ray burst GRB 990712 taken 4.16 hr after the outburst and discuss its light curve observed in the V, R, and I bands...
Fruchter, Andrew S., Thorsett, S. E., Metzger, Mark R., Sahu, Kailash C., Petro, Larry, Livio, Mario, ...
We report on HST and Palomar optical images of the field of GRB 990123, obtained on 8 and 9 February 1999. We find that the optical transient (OT) associated with GRB 990123 is located on an...
Spectroscopy of MACHO 97-SMC-1: self-lensing within the SMC (1998)
More than a dozen microlensing events have been detected so far towards the LMC and 2 towards the SMC. If all the lenses are in the Galactic halo, both the LMC and the SMC events are expected to have...
Astrometric Microlensing of Stars (1998)
Dominik, Martin, Sahu, Kailash C.
Due to dramatic improvements in the precision of astrometric measurements, the observation of light centroid shifts in observed stars due to intervening massive compact objects (`astrometric...
HST/STIS Observations of the Optical Counterpart to GRB 970228 (1998)
Fruchter, Andrew S., Pian, Elena, Thorsett, Stephen E., Gonzalez, Rosa, Sahu, Kailash C., Mutchler, Max, ...
We report on observations of the fading optical counterpart of the gamma-ray burst GRB 970228, made on 4~September~1997 using the STIS CCD on the Hubble Space Telescope. The unresolved counterpart is...
STIS Near Ultraviolet Time-Tagged Spectra of the Crab Pulsar (1997)
Gull, Theodore R., Lindler, Don J., Crenshaw, D. Michael, Dolan, Joseph F., Hulbert, Stephen J., Kraemer, Steven B., ...
We present the spectrum and pulse profile of the Crab Pulsar in the near ultraviolet (1600-3200 Angstroms) observed with the Space Telescope Imaging Spectrograph (STIS) during the Hubble Space...
The decay of optical emission from the Gamma-Ray Burst GRB 970228 (1997)
Galama, Titus J., Groot, Paul J., Van Paradijs, Jan, Kouveliotou, Chryssa, Sahu, Kailash C., Livio, Mario, ...
We present the R_c band light curve of the optical transient (OT) associated with GRB970228, based on re-evaluation of existing photometry. Data obtained until April 1997 suggested a slowing down of...
The Gamma Ray Bursts GRB970228 and GRB970508: What Have We Learnt? (1997)
Livio, Mario, Sahu, Kailash C., Petro, Larry, Fruchter, Andrew, Pian, Elena, Macchetto, F. Duccio, ...
We examine what we regard as key observational results on GRB 970228 and GRB 970508 and show that the accumulated evidence strongly suggests that gamma-ray bursts (GRBs) are cosmological fireballs....
Search for Extra-Solar Planets Through Monitoring Microlensing Events from Antarctica (1997)
During the months when the galactic bulge is visible from the southern hemisphere, there are typically about 8 to 10 on-going microlensing events at any given time. If the lensing stars have planets...
Imaging and spectroscopy of arcs around the most luminous X-ray cluster RX J1347.5-1145 (1997)
Sahu, Kailash C., Shaw, Richard A., Kaiser, Mary Elizabeth, Baum, Stefi A., Ferguson, Henry C., Hayes, Jeffrey J. E., ...
The cluster RX J1347.5-1145, the most luminous cluster in the X-ray wavelengths, was imaged with the newly installed Space Telescope Imaging Spectrograph (STIS) on-board HST. Its relatively high...
Observations of GRB 970228 and GRB 970508, and the Neutron-Star Merger Model (1997)
Sahu, Kailash C., Livio, Mario, Petro, Larry, Bond, Howard E., Macchetto, F. Duccio, Galama, Titus J., ...
We present the discovery observations for the optical counterpart of the $\gamma$-ray burster GRB 970508 and discuss its light curve in the context of the fireball model. We analyze the HST data for...
Sahu, Kailash C., Livio, Mario, Petro, Larry, Macchetto, F. Duccio, Van Paradijs, Jan, Kouveliotou, Chryssa, ...
Although more than 2,000 astronomical gamma-ray bursts (GRBs) have been detected, and numerous models proposed to explain their occurrence, they have remained enigmatic owing to the lack of an...
Detecting Planets Through Microlensing (1997)
More than 100 microlensing events have been detected during the last ~4 years, most of them towards the Galactic Bulge. Since the line of sight towards the Bulge passes through the disk and the Bulge...
Microlensing Events of the LMC are Better Explained by Stars within the LMC Than by Machos (1994)
The recently reported microlensing events of the LMC have caused much excitement, and have been interpreted as due to `dark objects' (MACHOs) in the halo of our Galaxy. It is shown here that the...
Stars within the Large Magellanic Cloud as Potential Lenses for Observed Microlensing Events (1994)
Massive Compact objects in the halo, known as MACHOs, have been postulated as the origin of a substantial fraction of `dark matter' known to exist in the haloes of galaxies$^{1,2}$. Paczy\'nski$^3$...