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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').
  1. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  3. Fermi GRB 250226B: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  5. GRB 250226B: Fermi GBM Final Real-time Localization
  6. GRB 250225B: Fermi GBM Observation
  7. GRB 250221A: ATCA Detections and Upper Limits
  8. GRB 250225B: REM NIR upper limits
  9. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  10. Konus-Wind detection of GRB 250225B
  11. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  12. EP250223a: CrAO ZTSH optical observation
  13. GRB 250225B: VLT optical and near-infrared candidate counterpart
  14. GRB 250225B: VLT/FORS2 candidate optical afterglow
  15. GRB 250225B: SVOM/GRM observation of a long burst
  16. GRB 250226A: GECAM-B detection
  17. GRB 250221A: EP-FXT detection of the X-ray afterglow
  18. GRB 250214A: SVOM/GRM observation
  19. EP250226a/GRB 250226A: GSP detects optical counterpart
  20. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  21. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  22. EP250226a / GRB 250226A: TRT optical counterpart observation
  23. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  24. EP250226a: Global MASTER-Net observations report
  25. Swift GRB 250225B: Global MASTER-Net observations report
  26. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  27. Fermi GRB 250226A: Global MASTER-Net observations report
  28. Fermi trigger No 762205158: Global MASTER-Net observations report
  29. GRB 250226A: Fermi GBM Final Real-time Localization
  30. EP250225a: Global MASTER-Net observations report
  31. EP250225a: GSP optical upper limit
  32. EP250223a: GMG Optical Observation
  33. EP250225a: Einstein Probe detected of a fast X-ray transient
  34. Fermi GRB 250225A: Global MASTER-Net observations report
  35. GRB 250225B: Swift detection of a burst
  36. EP250223a: GROWTH-India Telescope optical observations
  37. GRB 250221A: Swift-BAT refined analysis
  38. GRB 250223C: SVOM/GRM observation of a long burst
  39. EP250215A: J band upper limit by SYSU 80cm telescope
  40. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  41. GRB 250225A: Fermi GBM Final Real-time Localization
  42. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  43. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  44. EP250223a: Kinder optical follow-up observations
  45. GRB 250207a: ATCA Radio Upper Limits
  46. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  47. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  48. GRB 250119B: VZLUSAT-2 detection
  49. GRB 250223C: Fermi GBM Final Real-time Localization
  50. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  51. GRB 250202B: VZLUSAT-2 detection
  52. GRB 250219A: EP-FXT afterglow detection
  53. EP250223a: GOTO optical afterglow detections
  54. GRB 250222A: SVOM/GRM observation of a burst
  55. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  56. GRB 250210A: VZLUSAT-2 detection
  57. GRB 250206A: VZLUSAT-2 detection
  58. EP250223a: REM NIR upper limit
  59. EP250223a: TRT optical afterglow observation
  60. EP250223a: refined analysis of the EP-WXT and FXT observations
  61. EP250223a: 1.6m Mephisto and 50cm array observations
  62. GRB 250221A: TNOT detection of the optical counterpart
  63. EP250223a: SVOM/VT optical observation
  64. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  65. 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
  66. The EP-WXT trigger 01709131882 is likely a flaring star
  67. EP250223a: OASDG optical observations
  68. EP250223a: LCO detection of the afterglow
  69. EP250223a: early optical detection by BOOTES-4
  70. EP250223a: NOT redshift z = 2.756
  71. EP250223a: Swift/XRT localization
  72. EP250223a: NOT optical afterglow candidate
  73. GRB 250223B: Fermi GBM Final Localization
  74. EP250223a: Global MASTER-Net observations report
  75. GRB 250221A: VLA radio detection
  76. Fermi GRB 250223A: Global MASTER-Net observations report
  77. Fermi trigger No 762020305: Global MASTER-Net observations report
  78. GRB 250223A: Fermi GBM Final Real-time Localization
  79. EP250223a: Einstein Probe detection of an X-ray transient
  80. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  81. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  82. GRB 250221A: continued Mondy optical observations, brightening afterglow
  83. GRB 250221A: Optical counterpart detection by LCO.
  84. GRB 250221A: Mondy optical observations
  85. Konus-Wind detection of GRB 250221A
  86. GRB 250221A: Assy optical observations
  87. EP250220a: FTW optical and NIR observations and upper limits
  88. EP250220a: EP-FXT follow-up observations
  89. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  90. GRB 250221A: VLT/X-shooter redshift z = 0.768
  91. GRB 250221A: GRANDMA/TAROT Detection
  92. Fermi trigger No 761805304: Global MASTER-Net observations report
  93. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  94. GRB 250221A: Swift-XRT refined Analysis
  95. GRB 250221A: NOT optical observations
  96. GRB 250221A: 1.6m Mephisto optical detection
  97. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  98. GRB 250221A: AKO Optical Upper Limit
  99. GRB 250221A: Swift/UVOT Detection
  100. EP250220a: Liverpool Telescope upper limits

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