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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"

19043 results found.

  1. GRB 250328A: SVOM/C-GFT optical upper limit
  2. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  3. GRB 250329A: SVOM/VT optical counterpart confirmation
  4. GRB 250329A: SVOM detection of a burst
  5. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  6. GRB 250327B: J-band observations with WINTER
  7. GRB 250327B: LCO optical counterpart detection
  8. GRB 250328A: SVOM detection of a burst
  9. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  10. GRB 250327B: CrAO and SAO RAS Optical Observations
  11. GRB 250327b: Liverpool Telescope optical observations
  12. GRB 250322A: GRANDMA/TNOT optical upper limits
  13. GRB 250327A: SVOM/VT upper limits on the XRT position
  14. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  15. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  16. GRB 250327B: Las Cumbres optical counterpart detection
  17. GRB 250327B: 1.6m Mephisto optical observations
  18. GRB 250327B: SVOM/VT optically bright counterpart
  19. GRB 250327B: SAO RAS optical candidate
  20. GRB 250327B: SVOM detection of a burst
  21. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  22. GRB 250327A: J-band observations with WINTER
  23. GRB 250327A: SVOM/VT optical candidate
  24. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  25. GRB 250327A: DDOTI Optical Observations
  26. GRB 250327A: COLIBRÍ optical upper limit
  27. IPN triangulation of GRB 250322B
  28. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  29. EP250321a: Mondy AZT-33IK Continued Optical Observations
  30. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  31. GRB 250322A: third epoch of NOT optical observations
  32. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  33. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  34. GRB 250322A: further NOT optical observations
  35. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  36. GRB 250322A: Swift/UVOT Upper Limits
  37. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  38. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  39. GRB 250321B: Swift-XRT observations
  40. EP250321a: TNOT Observation of Optical Counterpart
  41. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  42. SVOM/sb25032302: SVOM detection of a long X-ray transient
  43. GRB250322A: STEP/T80S optical limits
  44. GRB 250322A: VLT optical observations
  45. GRB 250322A: VLT near-infrared observations
  46. FRB 250316A: DDOTI Continued Optical Observations
  47. GRB 250322A: NOT optical upper limits
  48. GRB 250322A: Enhanced Swift-XRT position
  49. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  50. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  51. EP250321a: Liverpool Telescope optical follow-up
  52. EP250321a: Mondy AZT-33IK Optical Observations
  53. GRB 250322A: Swift detection of a short burst
  54. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  55. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  56. EP250321A: COLIBRÍ Continuing Optical Observations
  57. GRB 250321B: Swift ToO observations
  58. EP250321a: WFST optical observations
  59. EP250321a: Xinglong 216 decaying optical observations
  60. GRB 250321A: Swift-XRT refined Analysis
  61. GRB 250321B: SVOM detection of a sub-threshold transient event
  62. EP 250321A: Optical counterpart detection by LCO.
  63. EP250321a: Kinder optical follow-up observations
  64. GRB 250321A: Swift/UVOT Upper Limits
  65. GRB 250320B: SVOM/GRM observation of a long burst
  66. EP250321a: LCO optical counterpart detection
  67. EP250321A: COLIBRÍ Optical Observations
  68. EP250321a: REM optical/NIR afterglow detection
  69. EP250321a: TRT optical counterpart detection
  70. EP250321a: Einstein Probe detection of an X-ray transient
  71. GRB 250321A: GOTO optical upper limits
  72. GRB 250314A: Keck/NIRC2 J-band upper limit
  73. EP250226a/GRB 250226A: KAIT optical observations
  74. GRB 250321A: Swift detection of a burst
  75. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  76. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  77. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  78. GRB 250317C: SVOM/GRM observation of a long burst
  79. GRB 250317B: Leavitt Observatory optical upper limit
  80. GRB 250317B: Mondy AZT-33IK Optical Observations
  81. GRB 250317B: NOT optical observations suggest an optical plateau phase
  82. GRB 250317B: OHP/T193 optical observations
  83. GRB250312A: Swift/UVOT Upper Limits
  84. GRB 250317B: REM optical/NIR observations
  85. GRB 250316A: Swift/UVOT Upper Limits
  86. GRB 250314A: REM optical/NIR upper limits
  87. GRB 250316A: AbAO AS-32 Optical Upper Limit
  88. EP 250317B: Fading optical counterpart detection by LCO
  89. GRB 250316A: Swift-XRT afterglow detection
  90. GRB 250317B: LCO detection of the fading optical afterglow
  91. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  92. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  93. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  94. GRB 250317B: SVOM detection of a burst
  95. GRB 250316A: Swift ToO observations
  96. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 250314A: Swift/UVOT Upper Limits
  98. GRB 250314A: Swift XRT Detection
  99. EP250315a: optical counterpart candidate detected by Gemini North
  100. EP250315a: Einstein Probe detection of an X-ray transient

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