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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/Xshooter imaging
  2. GRB 250205A / EP250205A: further radio observations with the VLA
  3. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  4. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  5. GRB 250225B: INTEGRAL SPI-ACS detection
  6. EP250225a: NOT optical candidate counterpart
  7. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  8. EP250226a / GRB 250226A: SVOM/VT optical observations
  9. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  10. EP250225a: TRT optical upper limits
  11. EP250226a/GRB 250226A: 1.6m Mephisto observations
  12. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  13. EP250226a/GRB 250226A: Kinder optical follow-up observations
  14. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  15. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  16. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  17. Fermi GRB 250226B: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  19. GRB 250226B: Fermi GBM Final Real-time Localization
  20. GRB 250225B: Fermi GBM Observation
  21. GRB 250221A: ATCA Detections and Upper Limits
  22. GRB 250225B: REM NIR upper limits
  23. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  24. Konus-Wind detection of GRB 250225B
  25. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  26. EP250223a: CrAO ZTSH optical observation
  27. GRB 250225B: VLT optical and near-infrared candidate counterpart
  28. GRB 250225B: VLT/FORS2 candidate optical afterglow
  29. GRB 250225B: SVOM/GRM observation of a long burst
  30. GRB 250226A: GECAM-B detection
  31. GRB 250221A: EP-FXT detection of the X-ray afterglow
  32. GRB 250214A: SVOM/GRM observation
  33. EP250226a/GRB 250226A: GSP detects optical counterpart
  34. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  35. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  36. EP250226a / GRB 250226A: TRT optical counterpart observation
  37. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  38. EP250226a: Global MASTER-Net observations report
  39. Swift GRB 250225B: Global MASTER-Net observations report
  40. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  41. Fermi GRB 250226A: Global MASTER-Net observations report
  42. Fermi trigger No 762205158: Global MASTER-Net observations report
  43. GRB 250226A: Fermi GBM Final Real-time Localization
  44. EP250225a: Global MASTER-Net observations report
  45. EP250225a: GSP optical upper limit
  46. EP250223a: GMG Optical Observation
  47. EP250225a: Einstein Probe detected of a fast X-ray transient
  48. Fermi GRB 250225A: Global MASTER-Net observations report
  49. GRB 250225B: Swift detection of a burst
  50. EP250223a: GROWTH-India Telescope optical observations
  51. GRB 250221A: Swift-BAT refined analysis
  52. GRB 250223C: SVOM/GRM observation of a long burst
  53. EP250215A: J band upper limit by SYSU 80cm telescope
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  55. GRB 250225A: Fermi GBM Final Real-time Localization
  56. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  57. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  58. EP250223a: Kinder optical follow-up observations
  59. GRB 250207a: ATCA Radio Upper Limits
  60. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  61. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  62. GRB 250119B: VZLUSAT-2 detection
  63. GRB 250223C: Fermi GBM Final Real-time Localization
  64. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  65. GRB 250202B: VZLUSAT-2 detection
  66. GRB 250219A: EP-FXT afterglow detection
  67. EP250223a: GOTO optical afterglow detections
  68. GRB 250222A: SVOM/GRM observation of a burst
  69. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  70. GRB 250210A: VZLUSAT-2 detection
  71. GRB 250206A: VZLUSAT-2 detection
  72. EP250223a: REM NIR upper limit
  73. EP250223a: TRT optical afterglow observation
  74. EP250223a: refined analysis of the EP-WXT and FXT observations
  75. EP250223a: 1.6m Mephisto and 50cm array observations
  76. GRB 250221A: TNOT detection of the optical counterpart
  77. EP250223a: SVOM/VT optical observation
  78. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  79. 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
  80. The EP-WXT trigger 01709131882 is likely a flaring star
  81. EP250223a: OASDG optical observations
  82. EP250223a: LCO detection of the afterglow
  83. EP250223a: early optical detection by BOOTES-4
  84. EP250223a: NOT redshift z = 2.756
  85. EP250223a: Swift/XRT localization
  86. EP250223a: NOT optical afterglow candidate
  87. GRB 250223B: Fermi GBM Final Localization
  88. EP250223a: Global MASTER-Net observations report
  89. GRB 250221A: VLA radio detection
  90. Fermi GRB 250223A: Global MASTER-Net observations report
  91. Fermi trigger No 762020305: Global MASTER-Net observations report
  92. GRB 250223A: Fermi GBM Final Real-time Localization
  93. EP250223a: Einstein Probe detection of an X-ray transient
  94. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  95. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  96. GRB 250221A: continued Mondy optical observations, brightening afterglow
  97. GRB 250221A: Optical counterpart detection by LCO.
  98. GRB 250221A: Mondy optical observations
  99. Konus-Wind detection of GRB 250221A
  100. GRB 250221A: Assy optical observations

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