分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shivani Bhandari
Alexa C. Gordon
Danica R. Scott
Lachlan Marnoch
Navin Sridhar
Pravir Kumar
Clancy W. James
Hao Qiu
Keith W. Bannister
Adam T. Deller
Tarraneh Eftekhari
Wen-fai Fong
Marcin Glowacki
J. Xavier Prochaska
Stuart D. Ryder
Ryan M. Shannon
Sunil Simha
摘要： We present the discovery of as-of-yet non-repeating Fast Radio Burst (FRB) with the Australian Square Kilometer Array Pathfinder (ASKAP) as a part of the Commensal Real-time ASKAP Fast Transients (CRAFT) Survey. FRB 20210117A was detected at the center frequency of 1271.5 MHz with a dispersion measure (DM) of $728.95\pm 0.01$ pc cm$^{-3}$. The sub-arcsecond localization of the burst led to the identification of its host galaxy at a $z=0.214(1)$. Optical observations reveal the host to be a dwarf galaxy with little on-going star formation, very different to the dwarf host galaxies of known repeating FRBs 20121102A, and 20190520B. We find an excess DM contribution from the host and attribute it to the FRB's local environment. We do not find any radio emission from the FRB site or host galaxy. The low magnetized environment and lack of a persistent radio source (PRS) indicate that the FRB source is older than those found in other dwarf host galaxies and establish the diversity of FRB sources in dwarf galaxy environments. We find our observations to be best described by the hypernebula model, where FRB is powered by accretion-jet from a hyper-accreting black hole. Finally, our high-time resolution analysis reveal burst characteristics similar to those seen in repeating FRBs. We encourage follow-up observations of FRB 20210117A to establish any repeating nature.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Alexa C. Gordon
Wen-fai Fong
Charles D. Kilpatrick
Tarraneh Eftekhari
Joel Leja
J. Xavier Prochaska
Anya E. Nugent
Shivani Bhandari
Peter K. Blanchard
Manisha Caleb
Cherie K. Day
Adam T. Deller
Yuxin Dong
Marcin Glowacki
Kelly Gourdji
Alexandra G. Mannings
Elizabeth K. Mahoney
Lachlan Marnoch
Adam A. Miller
Kerry Paterson
摘要： We present a comprehensive catalog of observations and stellar population properties for 23 highly secure host galaxies of fast radio bursts (FRBs). Our sample comprises six repeating FRBs and 17 apparent non-repeaters. We present 82 new photometric and eight new spectroscopic observations of these hosts. Using stellar population synthesis modeling and employing non-parametric star formation histories (SFHs), we find that FRB hosts have a median stellar mass of $\approx 10^{9.8}\,M_{\odot}$, mass-weighted age of $\approx 5.1$~Gyr, and ongoing star formation rate $\approx 1.2\,M_{\odot}$~yr$^{-1}$ but span wide ranges in all properties. Classifying the hosts by degree of star formation, we find that 91\% (21/23 hosts) are star-forming, one is transitioning, and one is quiescent. The majority trace the star-forming main sequence of galaxies, but at least two FRBs originate in less active environments, both of which are apparent non-repeaters. Across all modeled properties, we find no statistically significant distinction between the hosts of repeaters and non-repeaters. However, the hosts of repeating FRBs generally extend to lower stellar masses, and the hosts of non-repeaters arise in more optically luminous galaxies. While four of the galaxies with the most clear and prolonged rises in their SFHs all host repeating FRBs, demonstrating heightened star formation activity in the last $\lesssim 100$~Myr, one non-repeating host shows this SFH. Our results support the young magnetar model for most FRBs in which their progenitors formed through core-collapse supernovae, but the presence of some FRBs in less active environments suggests a fraction form through more delayed channels.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Stuart D. Ryder
Keith W. Bannister
S. Bhandari
A. T. Deller
R. D. Ekers
Marcin Glowacki
Alexa C. Gordon
Kelly Gourdji
C. W. James
Charles D. Kilpatrick
Wenbin Lu
Lachlan Marnoch
V. A. Moss
J. Xavier Prochaska
Hao Qiu
Elaine M. Sadler
Sunil Simha
Mawson W. Sammons
Danica R. Scott
Nicolas Tejos
摘要： Fast radio bursts are millisecond-duration pulses of radio emission that have been found to originate at extragalactic distances. The bursts show dispersion imparted by intervening plasma, with the bulk attributed to the intergalactic medium. Here we report the discovery of a burst, FRB20220610A, in a complex host galaxy system at a redshift of $z=1.016 \pm 0.002$. The relationship between its redshift and dispersion confirm that the bulk of the baryonic matter was ionized and in the intergalactic medium when the universe was almost half its present age. The burst shows evidence for passage through a significant additional column of turbulent and magnetized high-redshift plasma. It extends the maximum observed burst energy by a factor of four, confirming the presence of an energetic burst population at high redshift.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Wen-fai Fong
Yuxin Dong
Joel Leja
Shivani Bhandari
Cherie K. Day
Adam T. Deller
Pravir Kumar
J. Xavier Prochaska
Danica R. Scott
Keith W. Bannister
Tarraneh Eftekhari
Alexa C. Gordon
Kasper E. Heintz
Clancy W. James
Charles D. Kilpatrick
Elizabeth K. Mahony
Alicia Rouco Escorial
Stuart D. Ryder
Ryan M. Shannon
Nicolas Tejos
摘要： We present the Australian Square Kilometre Array Pathfinder (ASKAP) localization and follow-up observations of the host galaxy of the repeating fast radio burst (FRB) source, FRB20201124A, the fifth such extragalactic repeating FRB with an identified host. From spectroscopic observations using the 6.5-m MMT Observatory, we derive a redshift of $z=0.0979 \pm 0.0001$, a star formation rate inferred from H$\alpha$ emission of SFR(H$\alpha$) $\approx 2.1 M_{\odot}$ yr$^{-1}$, and a gas-phase metallicity of 12+log(O/H)$\approx 9.0$. By jointly modeling the 12-filter optical-mid-infrared (MIR) photometry and spectroscopy of the host, we infer a median stellar mass of $\approx 2 \times 10^{10} M_{\odot}$, internal dust extinction of $A_V\approx 1-1.5$ mag, and a mass-weighted stellar population age of $\approx 5-6$ Gyr. Connecting these data to the radio and X-ray observations, we cannot reconcile the broad-band behavior with strong AGN activity and instead attribute the dominant source of persistent radio emission to star formation, likely originating from the circumnuclear region of the host. The modeling also indicates a hot dust component contributing to the MIR luminosity at a level of $\approx 10-30\%$. We model the host galaxy's star formation and mass assembly histories, finding that the host assembled $>90\%$ of its mass by 1 Gyr ago and exhibited a fairly constant SFR for most of its existence, with no clear evidence of past star-burst activity.
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