18 citations · 44 across the 21 of their papers we have counts for
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Calibration of the Next Generation Palomar Spectrograph as a Stellar Speedometer
Pranav Nagarajan, Kareem El-Badry
We calibrate the Next Generation Palomar Spectrograph (NGPS) for precision stellar radial-velocity (RV) measurements using repeated observations of 24 Gaia-ESO RV standards spannin…
Spectroscopic follow-up of compact object binary candidates from Gaia DR3: White dwarfs, neutron stars, black holes, and the parallax zeropoint
Kareem El-Badry, David W. Latham, Hans-Walter Rix +12
Astrometry and radial velocities (RVs) from Gaia DR3 yielded orbits for hundreds of thousands of binary systems, including several samples proposed to contain black holes (BHs), ne…
A Galactic intermediate-mass stripped star with a Wolf-Rayet-like wind
Johanna Müller-Horn, Kareem El-Badry, Andreas A. C. Sander +17
Binary interaction in massive stars is expected to produce a large population of intermediate-mass (- M) envelope-stripped stars, yet such objects have remained elusi…
A systematic survey for hypervelocity runaways from thermonuclear supernovae
Kareem El-Badry, Klaus Werner, Ken J. Shen +16
The explosion of a white dwarf (WD) in a close binary can launch a surviving runaway star at velocities of . Such runaways provide a direct probe of…
Ongoing and Post-Mass-Transfer Binaries: A Living Catalog and Unified Review of Binary Mass Transfer Products
Lieke A. C. van Son, Natsuko Yamaguchi, Pranav Nagarajan +6
Mass transfer is arguably the most defining interaction in binary stellar systems, yet many aspects of its physics remain poorly understood, from stability to endpoints and observa…
Searching for the Third Wheel: High-Contrast Imaging Constraints on Tertiaries to Black Hole and Neutron Star Binaries
Pranav Nagarajan, Kareem El-Badry, Aniket Sanghi
Black holes (BHs) and neutron stars (NSs) with low-mass stellar companions challenge traditional isolated binary evolution models, motivating hierarchical triple evolution as a pro…
Deep Adaptive Optics Imaging Rules Out a Helium Star Companion to PSR J1928+1815
Pranav Nagarajan, Kareem El-Badry, Jim Fuller +2
PSR J1928+1815 is a 10.55 ms millisecond pulsar in a 3.6 hr orbit with a massive (-) companion that produces extended radio eclipses. The companion, proposed t…
Hide and Seek with Gaia. Detectability of Predicted Thin-Disc Metal-Rich RR Lyrae Binaries in Gaia DR3 and DR4
Giuliano Iorio, Pranav Nagarajan, Alexey Bobrick +8
RR Lyrae stars (RRLs) are classical tracers of old stellar populations, yet growing evidence suggests the presence of a metal-rich ([Fe/H]>-0.5), intermediate-age (2-7 Gyr) sub-pop…
Testing models for fully and partially stripped low-mass stars with Gaia: Implications for hot subdwarfs, binary RR Lyrae, and black hole impostors
Pranav Nagarajan, Kareem El-Badry, Alexey Bobrick +4
When low-mass ( ) red giants lose their envelopes to a companion just before the helium flash, the resulting mass transfer can produce binaries hosting hot s…
BE Lyncis is not a Black Hole Binary: Lessons From Gaia and Hipparcos Astrometry
Pranav Nagarajan, Kareem El-Badry, Thomas J. Maccarone +3
BE Lyncis (BE Lyn) is a well-studied high-amplitude Scuti variable star (HADS). Recently, Niu et al. (2026) analyzed a 39-year baseline of times of maximum light of BE Lyn, rep…
Optical Spectroscopy of the Most Compact Accreting Binary Harboring a Magnetic White Dwarf and a Hydrogen-rich Donor
Ilkham Galiullin, Antonio C. Rodriguez, Kareem El-Badry +4
Accreting white dwarfs in close binary systems, commonly known as cataclysmic variables (CVs), with orbital periods below the canonical period minimum ( 80 minutes) are ra…
A Spectroscopic Search for Dormant Black Holes in Low-Metallicity Binaries
Pranav Nagarajan, Kareem El-Badry, Henrique Reggiani +9
The discovery of the massive black hole (BH) system Gaia BH3 in pre-release Gaia DR4 data suggests that wide BH binaries with luminous companions may be significantly overrepresent…
Binary Parameters for the Recurrent Nova T Coronae Borealis
Kenneth H. Hinkle, Pranav Nagarajan, Francis C. Fekel +3
T CrB is among the brightest novae. It is recurrent with outbursts happening approximately every 80 years. The next outburst is imminent, expected in 2025. The T CrB binary consist…
The companion mass distribution of post common envelope hot subdwarf binaries: evidence for boosted and disrupted magnetic braking?
Lisa Blomberg, Kareem El-Badry, Katelyn Breivik +6
We measure the mass distribution of main-sequence (MS) companions to hot subdwarf B stars (sdBs) in post-common envelope binaries (PCEBs). We carried out a spectroscopic survey of…
The Symbiotic X-ray Binary IGR J16194-2810: A Window on the Future Evolution of Wide Neutron Star Binaries From Gaia
Pranav Nagarajan, Kareem El-Badry, Casey Lam +1
We present optical follow-up of IGR J16194-2810, a hard X-ray source discovered by the INTEGRAL mission. The optical counterpart is a red giant at a distance of…
Validation of Gaia DR3 orbital and acceleration solutions with hierarchical triples
Pranav Nagarajan, Kareem El-Badry
Using data from Gaia DR3, we construct a sample of 14,791 gravitationally bound wide pairs in which one of the components is an unresolved binary with an astrometric orbital or acc…
ESPRESSO observations of Gaia BH1: high-precision orbital constraints and no evidence for an inner binary
Pranav Nagarajan, Kareem El-Badry, Amaury H. M. J. Triaud +9
We present high-precision radial velocity (RV) observations of Gaia BH1, the nearest known black hole (BH). The system contains a solar-type G star orbiting a massive dark companio…