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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.

Advanced Search Examples (click to copy):

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

20814 results found.

  1. GRB 250327A: COLIBRÍ optical upper limit
  2. GRB 250327A: Swift detection of a burst
  3. Fermi trigger No 764700395: Global MASTER-Net observations report
  4. Konus-Wind detection of GRB 250322A (short)
  5. IPN triangulation of GRB 250322B
  6. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  7. EP250321a: Mondy AZT-33IK Continued Optical Observations
  8. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  9. GRB 250322A: third epoch of NOT optical observations
  10. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  11. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  12. GRB 250322A: further NOT optical observations
  13. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  14. GRB 250322A: Swift/UVOT Upper Limits
  15. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  16. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  17. GRB 250321B: Swift-XRT observations
  18. EP250321a: TNOT Observation of Optical Counterpart
  19. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  20. GRB 250322B: AstroSat CZTI detection of a bright long burst
  21. GRB250322A: STEP/T80S optical limits
  22. GRB 250322A: Gemini-South optical observations
  23. GRB 250322A: VLT optical observations
  24. GRB 250322A: VLT near-infrared observations
  25. FRB 250316A: DDOTI Continued Optical Observations
  26. GRB 250322A: NOT optical upper limits
  27. GRB 250322A: Enhanced Swift-XRT position
  28. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  29. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  30. EP250321a: Liverpool Telescope optical follow-up
  31. EP250321a: Mondy AZT-33IK Optical Observations
  32. GRB 250322A: Swift detection of a short burst
  33. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  34. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  35. EP250321A: COLIBRÍ Continuing Optical Observations
  36. EP250321a: WFST optical observations
  37. EP250321a: Xinglong 216 decaying optical observations
  38. GRB 250321A: Swift-XRT refined Analysis
  39. EP 250321A: Optical counterpart detection by LCO.
  40. EP250321a: Kinder optical follow-up observations
  41. GRB 250321A: Swift/UVOT Upper Limits
  42. GRB 250320B: SVOM/GRM observation of a long burst
  43. EP250321a: LCO optical counterpart detection
  44. EP250321A: COLIBRÍ Optical Observations
  45. GRB 250320B: AstroSat CZTI detection
  46. EP250321a: REM optical/NIR afterglow detection
  47. EP250321a: TRT optical counterpart detection
  48. EP250321a: Einstein Probe detection of an X-ray transient
  49. GRB 250321A: GOTO optical upper limits
  50. GRB 250314A: Keck/NIRC2 J-band upper limit
  51. EP250226a/GRB 250226A: KAIT optical observations
  52. GRB 250321A: Swift detection of a burst
  53. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  54. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  55. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  56. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  57. GRB 250314A: ATCA radio upper limits
  58. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  59. GRB 250317C: SVOM/GRM observation of a long burst
  60. GRB 250317B: Leavitt Observatory optical upper limit
  61. GRB 250317B: Mondy AZT-33IK Optical Observations
  62. GRB 250317C: AstroSat CZTI detection
  63. GRB 250317B: NOT optical observations suggest an optical plateau phase
  64. GRB 250317B: OHP/T193 optical observations
  65. GRB250312A: Swift/UVOT Upper Limits
  66. GRB 250317B: REM optical/NIR observations
  67. GRB 250317B: Swift-XRT observations
  68. GRB 250316A: Swift/UVOT Upper Limits
  69. GRB 250314A: REM optical/NIR upper limits
  70. GRB 250316A: AbAO AS-32 Optical Upper Limit
  71. EP 250317B: Fading optical counterpart detection by LCO
  72. GRB 250316A: Swift-XRT afterglow detection
  73. GRB 250317B: LCO detection of the fading optical afterglow
  74. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  75. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  76. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  77. GRB 250317B: SVOM detection of a burst
  78. GRB 250316A: Swift-XRT observations
  79. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  80. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  81. GRB 250314A: Swift/UVOT Upper Limits
  82. GRB 250314A: Swift XRT Detection
  83. EP250315a: optical counterpart candidate detected by Gemini North
  84. EP250315a: Einstein Probe detection of an X-ray transient
  85. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  86. SVOM/MXT upper limit on GRB 250314A
  87. GRB 250314A: SVOM/VT upper limit
  88. GRB 250314A: NOT near-infrared candidate counterpart
  89. GRB 250313A: Swift-XRT observations
  90. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  91. GRB 250314A: SVOM detection of a burst
  92. GRB 250313A: AstroSat CZTI detection of a bright long burst
  93. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  94. EP250304a: Pan-STARRS r and i-band imaging and photometry
  95. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  96. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  97. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  98. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  99. GRB 250312A: Enhanced Swift-XRT position
  100. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation

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