arXiv subjects

Vibhavasu Pasumarti

Publications and source records attributed to Vibhavasu Pasumarti.

5 recordsLinked to original sources

arXiv2024

A study of gamma-ray emission from OJ 287 using Fermi-LAT from 2015-2023

We search for gamma-ray emission from OJ287 in the energy range from 0.1-300 GeV during 2015-2023, in coincidence with an extensive observing campaign to monitor the optical flux variability and polarization, as discussed in arXiv:2311.02372. We present results for eight segments in the aforementioned period, with each segment corresponding to an observing season. We report non-zero gamma-ray flux (with $>10σ$ significance) for all the eight segments. The photon and energy flux observed during this period is $\sim 5.2 \times 10^{-8} \rm{ph~cm^{-2}~s^{-1}}$ and $2.75 \times 10^{-5} \rm{MeV~cm^{-2}~s^{-1}}$, respectively, while the SED can be fitted with a power law with a slope of $2.12 \pm 0.02$. The observed luminosity is between $10^{45}-10^{46}$ ergs/sec. Similar to previous works we find a hard cutoff in the gamma-ray spectrum at around 20 GeV. We do not observe any correlations between the peaks in the gamma ray light curves and corresponding optical light cuves in $I$ and $R$ bands, as well as the X-ray light curves from SWIFT between 0.3-10 keV.

astro-ph.HE↗

arXiv2024

Generalized Lomb-Scargle Analysis of 22 years of Super-Kamiokande solar $^8$B neutrino data

We apply the generalized Lomb-Scargle periodogram to 22 years data of solar $^{8}$B neutrino fluxes detected by Super-Kamiokande. The primary motivation of this work was to check if the sinusoidal modulation at a frequency of 9.43/year (with a period of 38 days), which we had found to be marginally significant with the first five years of Super-K data, persists, with the accumulated data. We use four different metrics for the calculation of significance. We do not find any evidence for periodicity at the aforementioned frequency or any other frequency with the updated data. Therefore the marginally detected periodicity at 9.43/year with the first five years of data was only a statistical fluctuation.

hep-ex↗

arXiv2024

A stacked search for spatial coincidences between IceCube neutrinos and radio pulsars

We carry out a stacked search for spatial coincidences between all the known radio pulsars and TeV neutrinos from the IceCube 10 year (2008-2018) muon track data, as a followup to our previous work on searching for spatial coincidences with individual pulsars. We consider three different weighting schemes to stack the contributions from each pulsar. We do not find a statistically significant excess using this method. We report the 95\% c.l. neutrino flux upper limit as a function of the neutrino energy. We have also made our analysis codes publicly available.

astro-ph.HE↗

arXiv2023

Bayesian evidence for spectral lag transition due to Lorentz Invariance Violation for 32 Fermi/GBM Gamma-ray Bursts

We use the spectral lag data of 32 long GRBs detected by Fermi/GBM, which has been recently collated in Liu et al (2022) to quantify the statistical significance of a transition in the spectral lag data based on Lorentz invariance violation (LIV) (for both sub-luminal and super-luminal propagation) using Bayesian model selection. We use two different parametric functions to model the null hypothesis of only intrinsic emission: a smooth broken power law model (SBPL) (proposed in Liu et al) as well as a simple power law model, which has been widely used before in literature. We find that for sub-luminal propagation, when we use the SBPL model as the null hypothesis, five GRBs show ``decisive evidence'' based on Jeffreys' scale for linear LIV and quadratic LIV. When we use the simple power-law model as the null hypothesis, we find that 10 and GRBs show Bayesian ``decisive evidence'' for linear and quadratic LIV, respectively. However these results should not be construed as evidence for LIV, as they would be in conflict with the most stringent upper limits. When we did a test for super-luminal LIV, we find that only four and two GRBs show Bayesian ``decisive evidence'' for linear and quadratic LIV, respectively, assuming a simple power law for the intrinsic emission. When we use the SBPL model, one GRB shows Bayesian ``decisive evidence'' for linear and quadratic LIV. This underscores the importance of adequately modelling the intrinsic emission while obtaining constraints on LIV using spectral lags, since inadequate modelling could masquerade as a signature of LIV.

astro-ph.HE↗

arXiv2022

Search for spatial coincidence between IceCube neutrinos and radio pulsars

We search for a spatial association between radio pulsars and ultra-high energy neutrinos using the publicly available IceCube point source neutrino events catalog. For this purpose we use the unbinned maximum likelihood method to search for a statistically significant excess from each of the pulsars in the ATNF catalog. We do not find any pulsars with detection significance much higher than that expected from a Gaussian distribution, Therefore, we conclude that none of the currently known pulsars contribute to the diffuse neutrino flux detected by IceCube.

astro-ph.HE↗