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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"

35259 results found.

  1. GRB 250225B: EIRSAT-1 GMOD Detection
  2. GRB 250226A: KAO Optical Upper Limit
  3. GRB 250226A: AbAO AS-32 Optical Upper Limit
  4. EP250223A: Upper limits from Fermi-GBM Observations
  5. GRB 250225B: VLT/HAWKI near-infrared observations
  6. GRB 250226A: Fermi GBM Observation
  7. GRB 250226A / EP250226a: LCO detection of the afterglow
  8. GRB 250225B: VLT/Xshooter imaging
  9. GRB 250205A / EP250205A: further radio observations with the VLA
  10. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  11. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  12. GRB 250225B: INTEGRAL SPI-ACS detection
  13. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  14. EP250226a / GRB 250226A: SVOM/VT optical observations
  15. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  16. EP250226a/GRB 250226A: 1.6m Mephisto observations
  17. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  18. EP250226a/GRB 250226A: Kinder optical follow-up observations
  19. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  20. Fermi GRB 250226B: Global MASTER-Net observations report
  21. GRB 250226B: Fermi GBM Final Real-time Localization
  22. GRB 250225B: Fermi GBM Observation
  23. GRB 250221A: ATCA Detections and Upper Limits
  24. GRB 250225B: REM NIR upper limits
  25. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  26. Konus-Wind detection of GRB 250225B
  27. EP250223a: CrAO ZTSH optical observation
  28. GRB 250225B: VLT optical and near-infrared candidate counterpart
  29. GRB 250225B: VLT/FORS2 candidate optical afterglow
  30. GRB 250225B: SVOM/GRM observation of a long burst
  31. GRB 250226A: GECAM-B detection
  32. GRB 250221A: EP-FXT detection of the X-ray afterglow
  33. GRB 250214A: SVOM/GRM observation
  34. EP250226a/GRB 250226A: GSP detects optical counterpart
  35. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  36. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  37. EP250226a / GRB 250226A: TRT optical counterpart observation
  38. Swift GRB 250225B: Global MASTER-Net observations report
  39. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  40. Fermi GRB 250226A: Global MASTER-Net observations report
  41. GRB 250226A: Fermi GBM Final Real-time Localization
  42. Fermi GRB 250225A: Global MASTER-Net observations report
  43. GRB 250225B: Swift detection of a burst
  44. GRB 250221A: Swift-BAT refined analysis
  45. GRB 250223C: SVOM/GRM observation of a long burst
  46. GRB 250225A: Fermi GBM Final Real-time Localization
  47. GRB 250207a: ATCA Radio Upper Limits
  48. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  49. GRB 250119B: VZLUSAT-2 detection
  50. GRB 250223C: Fermi GBM Final Real-time Localization
  51. GRB 250202B: VZLUSAT-2 detection
  52. GRB 250219A: EP-FXT afterglow detection
  53. GRB 250222A: SVOM/GRM observation of a burst
  54. GRB 250210A: VZLUSAT-2 detection
  55. GRB 250206A: VZLUSAT-2 detection
  56. GRB 250221A: TNOT detection of the optical counterpart
  57. 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
  58. EP250223a: OASDG optical observations
  59. GRB 250223B: Fermi GBM Final Localization
  60. GRB 250221A: VLA radio detection
  61. Fermi GRB 250223A: Global MASTER-Net observations report
  62. GRB 250223A: Fermi GBM Final Real-time Localization
  63. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  64. GRB 250221A: continued Mondy optical observations, brightening afterglow
  65. GRB 250221A: Optical counterpart detection by LCO.
  66. GRB 250221A: Mondy optical observations
  67. Konus-Wind detection of GRB 250221A
  68. GRB 250221A: Assy optical observations
  69. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  70. GRB 250221A: VLT/X-shooter redshift z = 0.768
  71. GRB 250221A: GRANDMA/TAROT Detection
  72. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  73. GRB 250221A: Swift-XRT refined Analysis
  74. GRB 250221A: NOT optical observations
  75. GRB 250221A: 1.6m Mephisto optical detection
  76. GRB 250221A: AKO Optical Upper Limit
  77. GRB 250221A: Swift/UVOT Detection
  78. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  79. GRB 250221A: REM optical/NIR afterglow detection
  80. GRB 250221A: Enhanced Swift-XRT position
  81. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  82. GRB 250221A: Swift detection of a burst with an optical counterpart
  83. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  84. GRB 250220B: Fermi GBM Final Real-time Localization
  85. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  86. GRB 250220A: Fermi GBM Final Real-time Localization
  87. Konus-Wind detection of GRB 250217C (short)
  88. GRB 250219A: Swift/UVOT Upper Limits
  89. GRB 250219A: OHP/T193 optical upper limit
  90. GRB 250219A: NOT optical observations
  91. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  92. GRB 250219A: 1.6m Mephisto optical upper limits
  93. GRB 250219A: SVOM/VT optical counterpart
  94. GRB 250219A: Swift-XRT observations
  95. GRB 250219A: Swift ToO observations
  96. GRB 250219A: SVOM detection of a burst
  97. Konus-Wind detection of GRB 250215A / EP250215a
  98. GRB 250217C: Swift-XRT observations
  99. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  100. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow

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