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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"

35958 results found.

  1. GRB 250226A: KAO Optical Upper Limit
  2. GRB 250226A: AbAO AS-32 Optical Upper Limit
  3. EP250223A: Upper limits from Fermi-GBM Observations
  4. GRB 250225B: VLT/HAWKI near-infrared observations
  5. GRB 250226A: Fermi GBM Observation
  6. GRB 250226A / EP250226a: LCO detection of the afterglow
  7. GRB 250225B: VLT/Xshooter imaging
  8. GRB 250205A / EP250205A: further radio observations with the VLA
  9. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  10. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  11. GRB 250225B: INTEGRAL SPI-ACS detection
  12. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  13. EP250226a / GRB 250226A: SVOM/VT optical observations
  14. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  15. EP250226a/GRB 250226A: 1.6m Mephisto observations
  16. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  17. EP250226a/GRB 250226A: Kinder optical follow-up observations
  18. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  19. Fermi GRB 250226B: Global MASTER-Net observations report
  20. GRB 250226B: Fermi GBM Final Real-time Localization
  21. GRB 250225B: Fermi GBM Observation
  22. GRB 250221A: ATCA Detections and Upper Limits
  23. GRB 250225B: REM NIR upper limits
  24. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  25. Konus-Wind detection of GRB 250225B
  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. Swift GRB 250225B: Global MASTER-Net observations report
  38. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  39. Fermi GRB 250226A: Global MASTER-Net observations report
  40. GRB 250226A: Fermi GBM Final Real-time Localization
  41. Fermi GRB 250225A: Global MASTER-Net observations report
  42. GRB 250225B: Swift detection of a burst
  43. GRB 250221A: Swift-BAT refined analysis
  44. GRB 250223C: SVOM/GRM observation of a long burst
  45. GRB 250225A: Fermi GBM Final Real-time Localization
  46. GRB 250207a: ATCA Radio Upper Limits
  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. GRB 250202B: VZLUSAT-2 detection
  51. GRB 250219A: EP-FXT afterglow detection
  52. GRB 250222A: SVOM/GRM observation of a burst
  53. GRB 250210A: VZLUSAT-2 detection
  54. GRB 250206A: VZLUSAT-2 detection
  55. GRB 250221A: TNOT detection of the optical counterpart
  56. 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
  57. EP250223a: OASDG optical observations
  58. GRB 250223B: Fermi GBM Final Localization
  59. GRB 250221A: VLA radio detection
  60. Fermi GRB 250223A: Global MASTER-Net observations report
  61. GRB 250223A: Fermi GBM Final Real-time Localization
  62. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  63. GRB 250221A: continued Mondy optical observations, brightening afterglow
  64. GRB 250221A: Optical counterpart detection by LCO.
  65. GRB 250221A: Mondy optical observations
  66. Konus-Wind detection of GRB 250221A
  67. GRB 250221A: Assy optical observations
  68. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  69. GRB 250221A: VLT/X-shooter redshift z = 0.768
  70. GRB 250221A: GRANDMA/TAROT Detection
  71. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  72. GRB 250221A: Swift-XRT refined Analysis
  73. GRB 250221A: NOT optical observations
  74. GRB 250221A: 1.6m Mephisto optical detection
  75. GRB 250221A: AKO Optical Upper Limit
  76. GRB 250221A: Swift/UVOT Detection
  77. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  78. GRB 250221A: REM optical/NIR afterglow detection
  79. GRB 250221A: Enhanced Swift-XRT position
  80. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  81. GRB 250221A: Swift detection of a burst with an optical counterpart
  82. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  83. GRB 250220B: Fermi GBM Final Real-time Localization
  84. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  85. GRB 250220A: Fermi GBM Final Real-time Localization
  86. Konus-Wind detection of GRB 250217C (short)
  87. GRB 250219A: Swift/UVOT Upper Limits
  88. GRB 250219A: OHP/T193 optical upper limit
  89. GRB 250219A: NOT optical observations
  90. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  91. GRB 250219A: 1.6m Mephisto optical upper limits
  92. GRB 250219A: SVOM/VT optical counterpart
  93. GRB 250219A: Swift-XRT observations
  94. GRB 250219A: Swift ToO observations
  95. GRB 250219A: SVOM detection of a burst
  96. Konus-Wind detection of GRB 250215A / EP250215a
  97. GRB 250217C: Swift-XRT observations
  98. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  99. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  100. GRB 250217C: SVOM/GRM observation

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