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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

22237 results found.

  1. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  2. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  3. GRB 250327A: J-band observations with WINTER
  4. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  5. Fermi GRB 250327A: Global MASTER-Net observations report
  6. Swift GRB 250327A: Global MASTER-Net observations report
  7. GRB 250327A: DDOTI Optical Observations
  8. GRB 250327A: COLIBRÍ optical upper limit
  9. Fermi trigger No 764700395: Global MASTER-Net observations report
  10. EP250321a: Mondy AZT-33IK Continued Optical Observations
  11. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  12. GRB 250322A: third epoch of NOT optical observations
  13. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  14. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  15. GRB 250322A: further NOT optical observations
  16. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  17. GRB 250322A: Swift/UVOT Upper Limits
  18. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  19. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  20. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  21. GRB 250321B: Swift-XRT observations
  22. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  23. GRB 250322A: Gemini-North redshift of candidate host galaxy
  24. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  25. GRB250322A: STEP/T80S optical limits
  26. GRB 250322A: Gemini-South optical observations
  27. GRB 250322A: VLT optical observations
  28. GRB 250322A: VLT near-infrared observations
  29. FRB 250316A: DDOTI Continued Optical Observations
  30. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  31. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  32. GRB 250322A: MASTER optical observation
  33. EP250321a: Liverpool Telescope optical follow-up
  34. EP250321a: Mondy AZT-33IK Optical Observations
  35. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  36. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  37. EP250321a: KAIT optical observations
  38. EP250321A: COLIBRÍ Continuing Optical Observations
  39. GRB 250321B: Swift ToO observations
  40. EP250321a: WFST optical observations
  41. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  42. EP250321a: Xinglong 216 decaying optical observations
  43. EP250321a: SVOM/VT optical observation
  44. EP 250321A: Optical counterpart detection by LCO.
  45. EP250321a: Kinder optical follow-up observations
  46. GRB 250321A: Swift/UVOT Upper Limits
  47. EP250321a: LCO optical counterpart detection
  48. EP250321A: COLIBRÍ Optical Observations
  49. EP250321a: VLT/X-shooter redshift z = 4.368
  50. EP250321a: REM optical/NIR afterglow detection
  51. Fermi GRB 250320B: Global MASTER-Net observations report
  52. EP250321a: Global MASTER-Net observations report
  53. Swift GRB 250321A: Global MASTER-Net observations report
  54. Fermi GRB 250321A: Global MASTER-Net observations report
  55. GRB 250321A: GOTO optical upper limits
  56. GRB 250314A: Keck/NIRC2 J-band upper limit
  57. EP250226a/GRB 250226A: KAIT optical observations
  58. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  59. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  60. Fermi GRB 250319B: Global MASTER-Net observations report
  61. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  62. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  63. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  64. GRB 250314A: ATCA radio upper limits
  65. EP250302a: VLA observations
  66. GRB 250317B: OHP/T193 continued follow-up
  67. GRB 250317B: Leavitt Observatory optical upper limit
  68. GRB 250309B/AT2025dws: further ATCA observations
  69. GRB 250317B: Mondy AZT-33IK Optical Observations
  70. GRB 250317B: NOT optical observations suggest an optical plateau phase
  71. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  72. GRB 250317B: OHP/T193 optical observations
  73. Fermi trigger No 763933627: Global MASTER-Net observations report
  74. GRB250312A: Swift/UVOT Upper Limits
  75. GRB 250317B: REM optical/NIR observations
  76. GRB 250317B: Swift-XRT observations
  77. GRB 250314A: REM optical/NIR upper limits
  78. GRB 250316A: AbAO AS-32 Optical Upper Limit
  79. EP 250317B: Fading optical counterpart detection by LCO
  80. GRB 250316A: Swift-XRT afterglow detection
  81. GRB 250317B: LCO detection of the fading optical afterglow
  82. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  83. GRB 250316A: Swift-XRT observations
  84. Fermi trigger No 763862734: Global MASTER-Net observations report
  85. Fermi GRB 250316A: Global MASTER-Net observations report
  86. GRB 250316A: Swift ToO observations
  87. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  88. GRB 250314A: EP-FXT afterglow detection
  89. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  90. GRB 250314A: Swift/UVOT Upper Limits
  91. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  92. GRB 250314A: Swift XRT Detection
  93. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  94. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  95. GRB 250314A: SVOM/VT upper limit
  96. GRB 250314A: NOT near-infrared candidate counterpart
  97. GRB 250313A: Swift-XRT observations
  98. Konus-Wind detection of GRB 250313A
  99. Fermi trigger No 763581136: Global MASTER-Net observations report
  100. GRB 250313A: Swift ToO observations

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