arXiv subjects

B. Cenko

Publications and source records attributed to B. Cenko.

11 recordsLinked to original sources

arXiv2026

The intrinsic luminosity-decay correlation in subsamples of GRB X-ray afterglows

The intrinsic luminosity-decay correlation in gamma-ray burst (GRB) afterglows, between the early-time luminosity and the average rate of decay past this time, has previously been observed in the radio, optical/UV, X-ray and GeV wavebands and quantitatively shows that more luminous afterglows tend to have higher average rates of decay. We have compiled an updated sample of 427 X-ray afterglows with measured redshifts, observed with Swift/XRT over 20 years. For each GRB, we measure the luminosity at 200 seconds in the rest frame, $L_{\mathrm{X,200s}}$, and the average rate of decay from this time, $\alpha_{X,>200s}$. We find these parameters are correlated with a Spearman's rank coefficient ($R_\mathrm{sp}$) of $0.54\pm0.04$ at a significance of $\geq3\sigma$ and a linear regression slope of $0.18\pm0.02$. We separate our sample into subsamples, including 395 long GRBs (LGRBs) and 32 short GRBs (SGRBs) and find evidence of the $L_{\mathrm{X,200s}}$-$\alpha_{X,>200s}$ correlation at a significance of $\geq3\sigma$ in LGRBs but not in SGRBs, consistent with previous studies. In a subsample of 102 LGRBs with well-sampled light curves and late end times, we find that scatter in the correlation is significantly reduced and the strength increases to $R_\mathrm{sp}=0.80\pm0.04$ whilst the slope remains consistent with the full sample. We discuss our results and, briefly, their potential implications on constraining the cause of the correlation. Possible causes include geometric effects due to the angle between the observer and the jet-axis, or some mechanism that regulates the rate at which energy is released by the GRB central engine.

astro-ph.HE↗

arXiv2026

An Afterglow Study of the "New Year's Burst" GRB 220101A

We present a detailed broadband afterglow study of GRB 220101A ($10^4\lesssim\Delta T\lesssim10^7$ s) combining multi-wavelength data from soft X-rays until 6 GHz. The afterglow light curves in both X-ray and optical show distinct steepening around $\sim9$ days, followed by a sharp post-break decay index of $\sim2.99\pm0.10$. We fit the light curves using the afterglow modelling package \texttt{afterglowpy} for both Top-hat and Gaussian jets for different values of the electronic participation fraction $\xi$ from 0.01 to 1.0 and find that, although the radio behavior is well described by the $\xi=1.0$ case, the required circumburst medium (CBM) densities are very low, $<10^{-4}$ cm$^{-3}$. However, the resulting energy requirements are modest, $\sim10^{52}$ erg, with an electron energy distribution (EED) index $p\sim2.05$. Similar results are also obtained from an analytic model fit to the light curve, except the predicted $p$ is higher, $\sim2.40$. The observed post-break decay index of $2.99$ is at least 5$\sigma$ away from $p$, which is one of the steepest observed so far. We also find that when ignoring the radio observations, the CBM density is raised by a few orders of magnitude to $\sim0.01$ cm$^{-3}$ for $\xi=1.0$, still far from the expected ISM density ($>1$ cm$^{-3}$) of GRB environments, which are highly star forming regions. Similarly low ISM densities have been seen in modeling of other LAT GRBs as well, especially ones with reverse-shock features (e.g., GRBs 130427A, 160509A and 160625B), thereby hinting at either an issue with the standard model or possible evacuated cavities where GRBs explode.

astro-ph.HE↗

arXiv2025

Evidence for an intrinsic luminosity-decay correlation in GRB radio afterglows

We present the discovery of a correlation, in a sample of 16 gamma-ray burst 8.5 GHz radio afterglows, between the intrinsic luminosity measured at 10 days in the rest frame, $L_{\mathrm{Radio,10d}}$, and the average rate of decay past this time, $\alpha_{>10d}$. The correlation has a Spearman's rank coefficient of $-0.70 \pm 0.13$ at a significance of $>3\sigma$ and a linear regression fit of $\alpha_{>10d} = -0.29^{+0.19}_{-0.28} \log \left(L_{\mathrm{Radio,10d}} \right) + 8.12^{+8.86}_{-5.88}$. This finding suggests that more luminous radio afterglows have higher average rates of decay than less luminous ones. We use a Monte Carlo simulation to show the correlation is not produced by chance or selection effects at a confidence level of $>3\sigma$. Previous studies found this relation in optical/UV, X-ray and GeV afterglow light curves, and we have now extended it to radio light curves. The Spearman's rank coefficients and the linear regression slopes for the correlation in each waveband are all consistent within $1\sigma$. We discuss how these new results in the radio band support the effects of observer viewing geometry, and time-varying microphysical parameters, as possible causes of the correlation as suggested in previous works.

astro-ph.HE↗

arXiv2022

The Optical Two and Three-Dimensional Fundamental Plane Correlations for Nearly 180 Gamma-Ray Burst Afterglows with Swift/UVOT, RATIR, and the SUBARU Telescope

Gamma-ray bursts (GRBs) are fascinating events due to their panchromatic nature. We study optical plateaus in GRB afterglows via an extended search into archival data. We comprehensively analyze all published GRBs with known redshifts and optical plateaus observed by many ground-based telescopes (e.g., Subaru Telescope, RATIR) around the world and several space-based observatories such as the Neil Gehrels Swift Observatory. We fit 500 optical light curves (LCs), showing the existence of the plateau in 179 cases. This sample is 75% larger than the previous one (arXiv:2105.10717), and it is the largest compilation so far of optical plateaus. We discover the 3D fundamental plane relation at optical wavelengths using this sample. This correlation is between the rest-frame time at the end of the plateau emission, $T^{*}_{\rm opt}$, its optical luminosity, $L_{\rm opt}$, and the peak in the optical prompt emission, $L_{\rm peak, opt}$, thus resembling the three-dimensional (3D) X-ray fundamental plane relation (arXiv:1604.06840). We correct our sample for redshift evolution and selection effects, discovering that this correlation is indeed intrinsic to GRB physics. We investigate the rest-frame end time distributions in X-rays and optical ($T^{*}_{\rm opt}$, $T^{*}_{\rm X}$), and conclude that the plateau is achromatic only when selection biases are not considered. We also investigate if the 3D optical correlation may be a new discriminant between optical GRB classes and find that there is no significant separation between the classes compared to the Gold sample plane after correcting for evolution.

astro-ph.HE↗

arXiv2021

Towards Equitable, Diverse, and Inclusive Science Collaborations: The Multimessenger Diversity Network

The Multimessenger Diversity Network (MDN), formed in 2018, extends the basic principle of multimessenger astronomy -- that working collaboratively with different approaches enhances understanding and enables previously impossible discoveries -- to equity, diversity, and inclusion (EDI) in science research collaborations. With support from the National Science Foundation INCLUDES program, the MDN focuses on increasing EDI by sharing knowledge, experiences, training, and resources among representatives from multimessenger science collaborations. Representatives to the MDN become engagement leads in their collaboration, extending the reach of the community of practice. An overview of the MDN structure, lessons learned, and how to join are presented.

physics.ed-ph↗

arXiv2020

The Optical Luminosity-Time Correlation for More Than 100 Gamma-Ray Burst Afterglows

Gamma-Ray Bursts (GRBs) are fascinating events due to their panchromatic nature. Their afterglow emission is observed from sub-TeV energies to radio wavelengths. We investigate GRBs that present an optical plateau, leveraging on the resemblance with the X-ray plateau shown in many GRB light curves (LCs). We comprehensively analyze all published GRBs with known redshifts and optical plateau observed mostly by the Neil Gehrels Swift Observatory (Swift). We fit 267 optical LCs and show the existence of the plateau in 102 cases, which is the largest compilation so far of optical plateaus. For 56 Swift GRBs with optical and X-ray plateaus, we compare the rest-frame end time at both wavelengths (T*_opt , T*_X), and conclude that the plateau is achromatic between T*_opt and T*_X. We also confirm the existence of the two-dimensional relations between T*_opt and the optical luminosity at the end of the plateau emission, which resembles the same luminosity-time correlation in X-rays (Dainotti et al. 2013). The existence of this optical correlation has been demonstrated for the largest sample of optical plateaus in the literature to date. The squared scatter in this optical correlation is smallest for the subset of the Gold GRBs with a decrease in the scatter equivalent to 52.4% when compared to the scatter of the entire GRB sample.

astro-ph.HE↗

arXiv2020

Hunting distant BL Lacs with the photometric technique using Swift and SARA

BL Lacertae objects (BL Lacs) represent a large fraction (22\%) of gamma-ray sources in the Third Fermi Large Area Telescope catalog (3FGL). Nearly half of the BL Lac population remains without a redshift because of their featureless optical spectra. We aim to increase the number of BL Lacs with a redshift measurement by using the photometric technique. For this work, we have used 6 Swift-UVOT filters and SDSS g,r,i,z optical filters mounted on the 0.65 m SARA-CTIO located in Chile and the 1.0 m SARA-ORM in Canary Islands. A sample of 45 sources was selected from the 3FGL catalog for which photometry was performed in 10 optical and UV filters to obtain redshift measurements. We found 3 sources with z>1.3 while reliable upper limits have been derived for 17 sources. The results presented here bring the total number of high-z (z>1.3) BL Lacs to 29.

astro-ph.HE↗

arXiv2019

Astro2020 APC White Paper: Pursuing diversity, equity, and inclusion in multimessenger astronomy collaborations over the coming decade

A major goal for the astronomy and astrophysics communities is the pursuit of diversity, equity, and inclusion (DEI) in all ranks, from students through professional scientific researchers. Large scientific collaborations - increasingly a primary place for both professional interactions and research opportunities - can play an important role in the DEI effort. Multimessenger astronomy, a new and growing field, is based on the principle that working collaboratively produces synergies, enabling advances that would not be possible without cooperation. The nascent Multimessenger Diversity Network (MDN) is extending this collaborative approach to include DEI initiatives. After we review of the current state of DEI in astronomy and astrophysics, we describe the strategies the MDN is developing and disseminating to support and increase DEI in the fields over the coming decade: provide opportunities (real and virtual) to share DEI knowledge and resources, include DEI in collaboration-level activities, including external reviews, and develop and implement ways to recognize the DEI work of collaboration members.

astro-ph.IM↗

arXiv2017

The THESEUS space mission concept: science case, design and expected performances

THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) follow-up with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift $\sim$10, signatures of Pop III stars, sources and physics of re-ionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the late '20s / early '30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).

astro-ph.IM↗

arXiv2009

A long and homogeneous optical monitoring of the 'naked-eye' burst GRB 080319B with the Palomar-60 telescope

GRB 080319B is one of the brightest and most extensively sampled bursts. It has good coverage at many wavelengths. Here we present the optical observations of the Palomar 60 inch telescope, which spans a long time interval after the burst. We augment the optical dataset with freely available Swift BAT and XRT observations reduced by us. We also compare our conclusions with the published parameters from the rich literature about this burst.

astro-ph.CO↗

arXiv2006

The gamma-ray burst GRB060614 requires a novel explosive process

Over the past decade our physical understanding of gamma-ray bursts (GRBs) has progressed rapidly thanks to the discovery and observation of their long-lived afterglow emission. Long-duration (T < 2 s) GRBs are associated with the explosive deaths of massive stars (``collapsars''), which produce accompanying supernovae, while the short-duration (T > 2 s) GRBs arise from a different origin, which has been argued to be the merger of two compact objects, either neutron stars or black holes. Here we present observations of GRB060614, a 100-s long burst discovered by the Swift satellite, which require the invocation of a new explosive process: either a massive ``collapsar'' that powers a GRB without any associated supernova, or a new type of engine, as long-lived as the collapsar but without any such massive stellar host. We also discuss the properties of this burst's redshift z=0.125 host galaxy, which distinguish it from other long-duration GRBs and suggest that an entirely new type of GRB progenitor may be required.

astro-ph↗