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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 250225B: VLT/FORS2 candidate optical afterglow
  2. GRB 250225B: SVOM/GRM observation of a long burst
  3. GRB 250226A: GECAM-B detection
  4. GRB 250221A: EP-FXT detection of the X-ray afterglow
  5. GRB 250214A: SVOM/GRM observation
  6. EP250226a/GRB 250226A: GSP detects optical counterpart
  7. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  8. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  9. EP250226a / GRB 250226A: TRT optical counterpart observation
  10. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  11. EP250226a: Global MASTER-Net observations report
  12. Swift GRB 250225B: Global MASTER-Net observations report
  13. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  14. Fermi GRB 250226A: Global MASTER-Net observations report
  15. Fermi trigger No 762205158: Global MASTER-Net observations report
  16. GRB 250226A: Fermi GBM Final Real-time Localization
  17. EP250225a: Global MASTER-Net observations report
  18. EP250225a: GSP optical upper limit
  19. EP250223a: GMG Optical Observation
  20. EP250225a: Einstein Probe detected of a fast X-ray transient
  21. Fermi GRB 250225A: Global MASTER-Net observations report
  22. GRB 250225B: Swift detection of a burst
  23. EP250223a: GROWTH-India Telescope optical observations
  24. GRB 250221A: Swift-BAT refined analysis
  25. GRB 250223C: SVOM/GRM observation of a long burst
  26. EP250215A: J band upper limit by SYSU 80cm telescope
  27. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  28. GRB 250225A: Fermi GBM Final Real-time Localization
  29. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  30. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  31. EP250223a: Kinder optical follow-up observations
  32. GRB 250207a: ATCA Radio Upper Limits
  33. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  34. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  35. GRB 250119B: VZLUSAT-2 detection
  36. GRB 250223C: Fermi GBM Final Real-time Localization
  37. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  38. GRB 250202B: VZLUSAT-2 detection
  39. GRB 250219A: EP-FXT afterglow detection
  40. EP250223a: GOTO optical afterglow detections
  41. GRB 250222A: SVOM/GRM observation of a burst
  42. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  43. GRB 250210A: VZLUSAT-2 detection
  44. GRB 250206A: VZLUSAT-2 detection
  45. EP250223a: REM NIR upper limit
  46. EP250223a: TRT optical afterglow observation
  47. EP250223a: refined analysis of the EP-WXT and FXT observations
  48. EP250223a: 1.6m Mephisto and 50cm array observations
  49. GRB 250221A: TNOT detection of the optical counterpart
  50. EP250223a: SVOM/VT optical observation
  51. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  52. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  53. The EP-WXT trigger 01709131882 is likely a flaring star
  54. EP250223a: OASDG optical observations
  55. EP250223a: LCO detection of the afterglow
  56. EP250223a: early optical detection by BOOTES-4
  57. EP250223a: NOT redshift z = 2.756
  58. EP250223a: Swift/XRT localization
  59. EP250223a: NOT optical afterglow candidate
  60. GRB 250223B: Fermi GBM Final Localization
  61. EP250223a: Global MASTER-Net observations report
  62. GRB 250221A: VLA radio detection
  63. Fermi GRB 250223A: Global MASTER-Net observations report
  64. Fermi trigger No 762020305: Global MASTER-Net observations report
  65. GRB 250223A: Fermi GBM Final Real-time Localization
  66. EP250223a: Einstein Probe detection of an X-ray transient
  67. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  68. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  69. GRB 250221A: continued Mondy optical observations, brightening afterglow
  70. GRB 250221A: Optical counterpart detection by LCO.
  71. GRB 250221A: Mondy optical observations
  72. Konus-Wind detection of GRB 250221A
  73. GRB 250221A: Assy optical observations
  74. EP250220a: FTW optical and NIR observations and upper limits
  75. EP250220a: EP-FXT follow-up observations
  76. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  77. GRB 250221A: VLT/X-shooter redshift z = 0.768
  78. GRB 250221A: GRANDMA/TAROT Detection
  79. Fermi trigger No 761805304: Global MASTER-Net observations report
  80. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  81. GRB 250221A: Swift-XRT refined Analysis
  82. GRB 250221A: NOT optical observations
  83. GRB 250221A: 1.6m Mephisto optical detection
  84. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  85. GRB 250221A: AKO Optical Upper Limit
  86. GRB 250221A: Swift/UVOT Detection
  87. EP250220a: Liverpool Telescope upper limits
  88. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  89. GRB 250221A: REM optical/NIR afterglow detection
  90. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  91. GRB 250221A: Enhanced Swift-XRT position
  92. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  93. EP250220a: 1.6m Mephisto observations
  94. EP250220a: Liverpool Telescope optical upper limits
  95. EP250220a: Optical upper limit with Kinder observations
  96. SVOM trigger sb25022102 is not an astrophysical event
  97. SVOM/sb25022102: SVOM detection of an X-ray transient
  98. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  99. GRB 250221A: Swift detection of a burst with an optical counterpart
  100. Swift GRB250221.15: Global MASTER-Net OT detection

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