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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. EP250223a: GMG Optical Observation
  2. EP250225a: Einstein Probe detected of a fast X-ray transient
  3. Fermi GRB 250225A: Global MASTER-Net observations report
  4. GRB 250225B: Swift detection of a burst
  5. EP250223a: GROWTH-India Telescope optical observations
  6. GRB 250221A: Swift-BAT refined analysis
  7. GRB 250223C: SVOM/GRM observation of a long burst
  8. EP250215A: J band upper limit by SYSU 80cm telescope
  9. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  10. GRB 250225A: Fermi GBM Final Real-time Localization
  11. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  12. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  13. EP250223a: Kinder optical follow-up observations
  14. GRB 250207a: ATCA Radio Upper Limits
  15. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  16. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  17. GRB 250119B: VZLUSAT-2 detection
  18. GRB 250223C: Fermi GBM Final Real-time Localization
  19. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  20. GRB 250202B: VZLUSAT-2 detection
  21. GRB 250219A: EP-FXT afterglow detection
  22. EP250223a: GOTO optical afterglow detections
  23. GRB 250222A: SVOM/GRM observation of a burst
  24. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  25. GRB 250210A: VZLUSAT-2 detection
  26. GRB 250206A: VZLUSAT-2 detection
  27. EP250223a: REM NIR upper limit
  28. EP250223a: TRT optical afterglow observation
  29. EP250223a: refined analysis of the EP-WXT and FXT observations
  30. EP250223a: 1.6m Mephisto and 50cm array observations
  31. GRB 250221A: TNOT detection of the optical counterpart
  32. EP250223a: SVOM/VT optical observation
  33. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  34. 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
  35. The EP-WXT trigger 01709131882 is likely a flaring star
  36. EP250223a: OASDG optical observations
  37. EP250223a: LCO detection of the afterglow
  38. EP250223a: early optical detection by BOOTES-4
  39. EP250223a: NOT redshift z = 2.756
  40. EP250223a: Swift/XRT localization
  41. EP250223a: NOT optical afterglow candidate
  42. GRB 250223B: Fermi GBM Final Localization
  43. EP250223a: Global MASTER-Net observations report
  44. GRB 250221A: VLA radio detection
  45. Fermi GRB 250223A: Global MASTER-Net observations report
  46. Fermi trigger No 762020305: Global MASTER-Net observations report
  47. GRB 250223A: Fermi GBM Final Real-time Localization
  48. EP250223a: Einstein Probe detection of an X-ray transient
  49. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  50. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  51. GRB 250221A: continued Mondy optical observations, brightening afterglow
  52. GRB 250221A: Optical counterpart detection by LCO.
  53. GRB 250221A: Mondy optical observations
  54. Konus-Wind detection of GRB 250221A
  55. GRB 250221A: Assy optical observations
  56. EP250220a: FTW optical and NIR observations and upper limits
  57. EP250220a: EP-FXT follow-up observations
  58. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  59. GRB 250221A: VLT/X-shooter redshift z = 0.768
  60. GRB 250221A: GRANDMA/TAROT Detection
  61. Fermi trigger No 761805304: Global MASTER-Net observations report
  62. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  63. GRB 250221A: Swift-XRT refined Analysis
  64. GRB 250221A: NOT optical observations
  65. GRB 250221A: 1.6m Mephisto optical detection
  66. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  67. GRB 250221A: AKO Optical Upper Limit
  68. GRB 250221A: Swift/UVOT Detection
  69. EP250220a: Liverpool Telescope upper limits
  70. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  71. GRB 250221A: REM optical/NIR afterglow detection
  72. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  73. GRB 250221A: Enhanced Swift-XRT position
  74. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  75. EP250220a: 1.6m Mephisto observations
  76. EP250220a: Liverpool Telescope optical upper limits
  77. EP250220a: Optical upper limit with Kinder observations
  78. SVOM trigger sb25022102 is not an astrophysical event
  79. SVOM/sb25022102: SVOM detection of an X-ray transient
  80. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  81. GRB 250221A: Swift detection of a burst with an optical counterpart
  82. Swift GRB250221.15: Global MASTER-Net OT detection
  83. Swift GRB250221.15: Global MASTER-Net observations report
  84. EP250220a: Xinglong optical upper limit
  85. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  86. GRB 250220B: Fermi GBM Final Real-time Localization
  87. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  88. GRB 250220A: Fermi GBM Final Real-time Localization
  89. EP250220a: Global MASTER-Net observations report
  90. EP250220a: EP-WXT detection of a fast X-ray transient
  91. Konus-Wind detection of GRB 250217C (short)
  92. GRB 250219A: Swift/UVOT Upper Limits
  93. GRB 250219A: OHP/T193 optical upper limit
  94. GRB 250219A: NOT optical observations
  95. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  96. GRB 250219A: 1.6m Mephisto optical upper limits
  97. GRB 250219A: SVOM/VT optical counterpart
  98. GRB 250219A: Swift-XRT observations
  99. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  100. GRB 250219A: Swift ToO observations

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