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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

22920 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. GRB 250327A: SVOM/VT optical candidate
  5. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  6. GRB 250327A: DDOTI Optical Observations
  7. GRB 250327A: COLIBRÍ optical upper limit
  8. GRB 250327A: Swift detection of a burst
  9. Fermi trigger No 764700395: Global MASTER-Net observations report
  10. Konus-Wind detection of GRB 250322A (short)
  11. IPN triangulation of GRB 250322B
  12. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  13. EP250321a: Mondy AZT-33IK Continued Optical Observations
  14. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  15. GRB 250322A: third epoch of NOT optical observations
  16. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  17. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  18. GRB 250322A: further NOT optical observations
  19. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  20. GRB 250322A: Swift/UVOT Upper Limits
  21. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  22. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  23. GRB 250321B: Swift-XRT observations
  24. EP250321a: TNOT Observation of Optical Counterpart
  25. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  26. GRB 250322B: AstroSat CZTI detection of a bright long burst
  27. GRB250322A: STEP/T80S optical limits
  28. GRB 250322A: Gemini-South optical observations
  29. GRB 250322A: VLT optical observations
  30. GRB 250322A: VLT near-infrared observations
  31. FRB 250316A: DDOTI Continued Optical Observations
  32. GRB 250322A: NOT optical upper limits
  33. GRB 250322A: Enhanced Swift-XRT position
  34. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  35. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  36. EP250321a: Liverpool Telescope optical follow-up
  37. EP250321a: Mondy AZT-33IK Optical Observations
  38. GRB 250322A: Swift detection of a short burst
  39. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  40. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  41. EP250321A: COLIBRÍ Continuing Optical Observations
  42. EP250321a: WFST optical observations
  43. EP250321a: Xinglong 216 decaying optical observations
  44. GRB 250321A: Swift-XRT refined Analysis
  45. EP 250321A: Optical counterpart detection by LCO.
  46. EP250321a: Kinder optical follow-up observations
  47. GRB 250321A: Swift/UVOT Upper Limits
  48. GRB 250320B: SVOM/GRM observation of a long burst
  49. EP250321a: LCO optical counterpart detection
  50. EP250321A: COLIBRÍ Optical Observations
  51. GRB 250320B: AstroSat CZTI detection
  52. EP250321a: REM optical/NIR afterglow detection
  53. EP250321a: TRT optical counterpart detection
  54. EP250321a: Einstein Probe detection of an X-ray transient
  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 250321A: Swift detection of a burst
  59. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  60. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  61. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  62. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  63. GRB 250314A: ATCA radio upper limits
  64. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  65. GRB 250317C: SVOM/GRM observation of a long burst
  66. GRB 250317B: Leavitt Observatory optical upper limit
  67. GRB 250317B: Mondy AZT-33IK Optical Observations
  68. GRB 250317C: AstroSat CZTI detection
  69. GRB 250317B: NOT optical observations suggest an optical plateau phase
  70. GRB 250317B: OHP/T193 optical observations
  71. GRB250312A: Swift/UVOT Upper Limits
  72. GRB 250317B: REM optical/NIR observations
  73. GRB 250317B: Swift-XRT observations
  74. GRB 250316A: Swift/UVOT Upper Limits
  75. GRB 250314A: REM optical/NIR upper limits
  76. GRB 250316A: AbAO AS-32 Optical Upper Limit
  77. EP 250317B: Fading optical counterpart detection by LCO
  78. GRB 250316A: Swift-XRT afterglow detection
  79. GRB 250317B: LCO detection of the fading optical afterglow
  80. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  81. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  82. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  83. GRB 250317B: SVOM detection of a burst
  84. GRB 250316A: Swift-XRT observations
  85. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  86. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  87. GRB 250314A: Swift/UVOT Upper Limits
  88. GRB 250314A: Swift XRT Detection
  89. EP250315a: optical counterpart candidate detected by Gemini North
  90. EP250315a: Einstein Probe detection of an X-ray transient
  91. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  92. SVOM/MXT upper limit on GRB 250314A
  93. GRB 250314A: SVOM/VT upper limit
  94. GRB 250314A: NOT near-infrared candidate counterpart
  95. GRB 250313A: Swift-XRT observations
  96. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  97. GRB 250314A: SVOM detection of a burst
  98. GRB 250313A: AstroSat CZTI detection of a bright long burst
  99. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  100. EP250304a: Pan-STARRS r and i-band imaging and photometry

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