Pranav Nagarajan
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View article: Optical Spectroscopy of the Most Compact Accreting Binary Harboring a Magnetic White Dwarf and a Hydrogen-rich Donor
Optical Spectroscopy of the Most Compact Accreting Binary Harboring a Magnetic White Dwarf and a Hydrogen-rich Donor Open
Accreting white dwarfs (WDs) in close binary systems, commonly known as cataclysmic variables (CVs), with orbital periods below the canonical period minimum (≈80 minutes) are rare. Such short periods can only be reached if the donor star i…
View article: A Spectroscopic Search for Dormant Black Holes in Low-metallicity Binaries
A Spectroscopic Search for Dormant Black Holes in Low-metallicity Binaries Open
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 overrepresented at low metallicities. Motivated by this finding, we have…
View article: Spectra of Low-Metallicity Binaries with Elevated RUWE in Gaia DR3
Spectra of Low-Metallicity Binaries with Elevated RUWE in Gaia DR3 Open
We present FEROS and APF spectra of low-metallicity sources with elevated RUWE values or acceleration solutions in Gaia DR3. We also provide a follow-up MIKE spectrum of a promising dormant black hole candidate.
View article: Binary Parameters for the Recurrent Nova T Coronae Borealis
Binary Parameters for the Recurrent Nova T Coronae Borealis Open
T CrB is among the brightest novae. It is recurrent with outbursts happening approximately every 80 yr. The next outburst is imminent, expected in 2025. The T CrB binary consists of an M4 III red giant (RG) secondary and a white dwarf (WD)…
View article: Realistic Predictions for Gaia Black Hole Discoveries: Comparison of Isolated Binary and Dynamical Formation Models
Realistic Predictions for Gaia Black Hole Discoveries: Comparison of Isolated Binary and Dynamical Formation Models Open
Astrometry from Gaia has enabled discovery of three dormant black holes (BHs) in au-scale binaries. Numerous models have been proposed to explain their formation, including several that have forecasted Gaia detections. However, previous wo…
View article: Mixed Origins: Strong Natal Kicks for Some Black Holes and None for Others
Mixed Origins: Strong Natal Kicks for Some Black Holes and None for Others Open
Using stellar kinematic data from Gaia DR3, we revisit constraints on black hole (BH) natal kicks from observed accreting and detached BH binaries. We compare the space velocities and Galactic orbits of a sample of 12 BHs in the Galactic d…
View article: Realistic predictions for Gaia black hole discoveries: comparison of isolated binary and dynamical formation models
Realistic predictions for Gaia black hole discoveries: comparison of isolated binary and dynamical formation models Open
Astrometry from Gaia has enabled discovery of three dormant black holes (BHs) in au-scale binaries. Numerous models have been proposed to explain their formation, including several that have forecasted Gaia detections. However, previous wo…
View article: The Companion Mass Distribution of Post Common Envelope Hot Subdwarf Binaries: Evidence for Boosted and Disrupted Magnetic Braking?
The Companion Mass Distribution of Post Common Envelope Hot Subdwarf Binaries: Evidence for Boosted and Disrupted Magnetic Braking? Open
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 14 eclipsing systems (“HW Vir binaries”) with orbital perio…
View article: Mixed origins: strong natal kicks for some black holes and none for others
Mixed origins: strong natal kicks for some black holes and none for others Open
Using stellar kinematic data from Gaia DR3, we revisit constraints on black hole (BH) natal kicks from observed accreting and detached BH binaries. We compare the space velocities and Galactic orbits of a sample of 12 BHs in the Galactic d…
View article: Validation of Gaia DR3 Orbital and Acceleration Solutions with Hierarchical Triples
Validation of Gaia DR3 Orbital and Acceleration Solutions with Hierarchical Triples Open
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 acceleration solution. These systems are hierarchical triples,…
View article: The Symbiotic X-Ray Binary IGR J16194-2810: A Window on the Future Evolution of Wide Neutron Star Binaries From Gaia
The Symbiotic X-Ray Binary IGR J16194-2810: A Window on the Future Evolution of Wide Neutron Star Binaries From Gaia Open
We present optical follow-up of IGR J16194-2810, a hard X-ray source discovered by the INTEGRAL mission. The optical counterpart is a ∼500 L ⊙ red giant at a distance of 2.1 kpc. We measured 17 radial velocities (RVs) of the giant over a p…
View article: ESPRESSO Observations of Gaia BH1: High-precision Orbital Constraints and no Evidence for an Inner Binary
ESPRESSO Observations of Gaia BH1: High-precision Orbital Constraints and no Evidence for an Inner Binary Open
We present high-precision radial velocity observations of Gaia BH1, the nearest known black hole (BH). The system contains a solar-type G star orbiting a massive dark companion, which could be either a single BH or an inner BH + BH binary.…
View article: ESPRESSO observations of Gaia BH1: high-precision orbital constraints and no evidence for an inner binary
ESPRESSO observations of Gaia BH1: high-precision orbital constraints and no evidence for an inner binary Open
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 companion, which could be either a single BH or an inner BH + BH bi…
View article: Correction to: Spectroscopic follow-up of black hole and neutron star candidates in ellipsoidal variables from <i>Gaia</i> DR3
Correction to: Spectroscopic follow-up of black hole and neutron star candidates in ellipsoidal variables from <i>Gaia</i> DR3 Open
Figure 1.Colour-magnitude diagrams (CMDs) visualizing our sample selection.The upper left-hand panel displays the original sample of ellipsoidal variables (i.e.objects in the Gomel et al. 2023 catalogue that ha ve a vailable extinctions) p…
View article: The fastest stars in the Galaxy
The fastest stars in the Galaxy Open
We report a spectroscopic search for hypervelocity white dwarfs (WDs) that are runaways from Type Ia supernovae (SNe Ia) and related thermonuclear explosions. Candidates are selected from Gaia data with high tangential velocities and blue …
View article: The fastest stars in the Galaxy
The fastest stars in the Galaxy Open
We report a spectroscopic search for hypervelocity white dwarfs (WDs) that are runaways from Type Ia supernovae (SNe Ia) and related thermonuclear explosions. Candidates are selected from Gaia data with high tangential velocities and blue …
View article: A 4–8 GHz Galactic Center Search for Periodic Technosignatures
A 4–8 GHz Galactic Center Search for Periodic Technosignatures Open
Radio searches for extraterrestrial intelligence have mainly targeted the discovery of narrowband continuous-wave beacons and artificially dispersed broadband bursts. Periodic pulse trains, in comparison to the above technosignature morpho…
View article: Spectroscopic follow-up of black hole and neutron star candidates in ellipsoidal variables from Gaia DR3
Spectroscopic follow-up of black hole and neutron star candidates in ellipsoidal variables from Gaia DR3 Open
We present multi-epoch spectroscopic follow-up of a sample of ellipsoidal variables selected from Gaia DR3 as candidates for hosting quiescent black holes (BHs) and neutron stars (NSs). Our targets were identified as BH/NS candidates becau…
View article: RR Lyrae-based Distances for 39 Nearby Dwarf Galaxies Calibrated to Gaia eDR3
RR Lyrae-based Distances for 39 Nearby Dwarf Galaxies Calibrated to Gaia eDR3 Open
We provide uniform RR Lyrae-based distances to 39 dwarf galaxies in and around the Local Group. We determine distances based on a Bayesian hierarchical model that uses periods and magnitudes of published RR Lyrae in dwarf galaxies and is a…
View article: RR Lyrae-based Distances for 39 Nearby Dwarf Galaxies Calibrated to Gaia eDR3
RR Lyrae-based Distances for 39 Nearby Dwarf Galaxies Calibrated to Gaia eDR3 Open
We provide uniform RR Lyrae-based distances to 39 dwarf galaxies in and around the Local Group. We determine distances based on a Bayesian hierarchical model that uses periods and magnitudes of published RR Lyrae in dwarf galaxies and is a…
View article: A Lean and Highly-automated Model-Based Software Development Process Based on DO-178C/DO-331
A Lean and Highly-automated Model-Based Software Development Process Based on DO-178C/DO-331 Open
The emergence of a global market for urban air mobility and unmanned aerial systems has attracted many startups across the world. These organizations have little training or experience in the traditional processes used in civil aviation fo…