arXiv subjects

Sasha Mintz

Publications and source records attributed to Sasha Mintz.

3 recordsLinked to original sources

arXiv2026

First Pre-peak Ultraviolet Spectrum of a Tidal Disruption Event: A Fast Outflow Revealed Prior to Maximum Light in TDE2025aarm

The tidal disruption and eventual accretion of a star by a massive black hole can lead to the launching of outflows and winds that encode important information about the tidal disruption and accretion processes. However, little is known about the existence and behavior of these outflows before optical light-curve peak, when processes such as stream-stream collisions and disk formation may be important. Here, we present the first pre-peak ultraviolet (UV) spectrum of a tidal disruption event (TDE), obtained $\sim 20$ days before optical maximum light of the nearby (redshift $z=0.0137$) TDE2025aarm, along with quasi-simultaneous infrared (IR) through X-ray observations. Our HST/STIS spectrum shows strong evidence for an early-time outflow through broad near-UV (NUV) and far-UV (FUV) absorption lines blueshifted by $\sim$10,000 km s$^{-1}$, including two new UV broad absorption features not yet identified in a TDE. We find that the FUV--IR continuum deviates significantly from a blackbody ($f_λ\propto λ^{-3.08}$), which we interpret as a signature of reprocessing through the outflow. This deviation implies that the bolometric luminosity in optical TDEs may be underestimated by a significant factor ($\sim$9 in this case) when inferred from single-temperature blackbody fits to NUV--optical photometry alone. This work further confirms that TDEs are capable of launching fast outflows at very early times and emphasizes the importance of prompt FUV spectroscopic observations of TDEs that can capture the full continuum emission and energetics.

astro-ph.HE↗

arXiv2025

Physical characterization of the FeLoBAL outflow in SDSS J0932+0840: Analysis of VLT/UVES observations

Context: The study of quasar outflows is essential in understanding the connection between active galactic nuclei (AGN) and their host galaxies. We analyze the VLT/UVES spectrum of quasar SDSS J0932+0840 and identify several narrow and broad outflow components in absorption, with multiple ionization species including Fe II, which puts it among a rare class of outflows known as FeLoBALs. Aims: We study one of the outflow components to determine its physical characteristics by determining the total hydrogen column density, ionization parameter and the hydrogen number density. Through these parameters, we aim to obtain the distance of the outflow from the central source, its mass outflow rate and kinetic luminosity, and to constrain the contribution of the outflow to AGN feedback. Methods: We obtain the ionic column densities from the absorption troughs in the spectrum, and use photoionization modeling to extract the physical parameters of the outflow, including the total hydrogen column density and ionization parameter. The relative population of the observed excited states of Fe II is used to model the hydrogen number density of the outflow. Results: We use the Fe II excited states to model the electron number density ($n_e$) and hydrogen number density ($n_H$) independently and obtain $n_e$ $\simeq$ $10^{3.4}$ cm$^{-3}$ and $n_H$ $\simeq$ $10^{4.8}$ cm$^{-3}$. Our analysis of the physical structure of the cloud shows that these two results are consistent with each other. This places the outflow system at a distance of $0.7_{-0.4}^{+0.9}$ kpc from the central source, with mass flow rate ($\dot{M}$) of $43^{+65}_{-26}$ $M_\odot$ yr$^{-1}$ and kinetic luminosity ($\dot{E_k}$) of $0.7^{+1.1}_{-0.4}$ $\times$ $10^{43}$ erg s$^{-1}$.

astro-ph.GA↗

arXiv2024

Cold Quasar Investigation: Comparing Star Formation Rates to Black Hole Growth

Cold quasars are a rare population of luminous, unobscured quasars associated with host galaxies that have a high star formation rate. We aimed to study the host galaxies of sixty four of these cold quasars in order to probe how the supermassive black holes and host galaxies were coevolving. We compiled data from the XXL survey and crossmatched with the VHS, WISE, and HerMES surveys to obtain multiwavelength photometry spanning the Xray to the infrared and including optical spectroscopy. From the data, we calculated the supermassive black hole masses using broad emission from the magnesium II and hydrogen beta lines. We compared this with the stellar mass of the entire galaxy and find that the black holes are significantly more massive than would be predicted by local relations, indicating that the majority of black hole growth precedes the bulk of the the stellar mass formation. In addition to this, we created a spectral energy distribution for each galaxy to calculate the star formation rate. We compared the star formation rate with the black hole accretion rate and find that the stellar mass is rapidly increasing at a relative rate faster than the black hole growth, supporting the picture where the black hole grows first.

astro-ph.GA↗