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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"

16202 results found.

  1. GRB 250226A: GRANDMA Optical Observations
  2. EP250302a: Montarrenti Observatory optical detection
  3. EP250302a: Nanshan/HMT optical counterpart detection
  4. The EP-WXT trigger 01709132140 is likely a flaring star
  5. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  6. GRB 250225B: VLT near-infrared afterglow confirmation
  7. EP250228a: Optical observations with Kinder and Swift/UVOT
  8. GRB 250226A: KAO Optical Upper Limit
  9. GRB 250226A: AbAO AS-32 Optical Upper Limit
  10. EP250227a: TRT optical upper limit
  11. GRB 250225B: VLT/HAWKI near-infrared observations
  12. EP250227a: Optical upper limits with Kinder observations
  13. EP250227a: NOT optical observations
  14. EP250227a: Einstein Probe detected of a fast X-ray transient
  15. EP250228a: updates on the EP observations
  16. EP250225a: EP-FXT follow-up observation
  17. EP250223a: J band upper limit by SYSU 80cm telescope
  18. EP250228a: Einstein Probe detection of an X-ray transient
  19. GRB 250225B: VLT/Xshooter imaging
  20. GRB 250205A / EP250205A: further radio observations with the VLA
  21. EP250225a: NOT optical candidate counterpart
  22. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  23. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  24. EP250225a: TRT optical upper limits
  25. EP250226a/GRB 250226A: 1.6m Mephisto observations
  26. EP250226a/GRB 250226A: Kinder optical follow-up observations
  27. GRB 250221A: ATCA Detections and Upper Limits
  28. GRB 250225B: REM NIR upper limits
  29. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  30. EP250223a: CrAO ZTSH optical observation
  31. GRB 250225B: VLT optical and near-infrared candidate counterpart
  32. GRB 250225B: SVOM/GRM observation of a long burst
  33. GRB 250221A: EP-FXT detection of the X-ray afterglow
  34. EP250226a/GRB 250226A: GSP detects optical counterpart
  35. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  36. EP250226a / GRB 250226A: TRT optical counterpart observation
  37. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  38. EP250223a: GMG Optical Observation
  39. EP250225a: Einstein Probe detected of a fast X-ray transient
  40. EP250223a: GROWTH-India Telescope optical observations
  41. EP250215A: J band upper limit by SYSU 80cm telescope
  42. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  43. EP250223a: Kinder optical follow-up observations
  44. GRB 250207a: ATCA Radio Upper Limits
  45. GRB 250219A: EP-FXT afterglow detection
  46. GRB 250222A: SVOM/GRM observation of a burst
  47. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  48. EP250223a: REM NIR upper limit
  49. EP250223a: TRT optical afterglow observation
  50. EP250223a: refined analysis of the EP-WXT and FXT observations
  51. EP250223a: 1.6m Mephisto and 50cm array observations
  52. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  53. 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
  54. The EP-WXT trigger 01709131882 is likely a flaring star
  55. EP250223a: OASDG optical observations
  56. EP250223a: NOT optical afterglow candidate
  57. GRB 250221A: VLA radio detection
  58. EP250223a: Einstein Probe detection of an X-ray transient
  59. GRB 250221A: Optical counterpart detection by LCO.
  60. EP250220a: EP-FXT follow-up observations
  61. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  62. GRB 250221A: GRANDMA/TAROT Detection
  63. GRB 250221A: Swift-XRT refined Analysis
  64. GRB 250221A: 1.6m Mephisto optical detection
  65. GRB 250221A: AKO Optical Upper Limit
  66. GRB 250221A: Swift/UVOT Detection
  67. EP250220a: Liverpool Telescope upper limits
  68. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  69. GRB 250221A: REM optical/NIR afterglow detection
  70. GRB 250221A: Enhanced Swift-XRT position
  71. EP250220a: 1.6m Mephisto observations
  72. EP250220a: Liverpool Telescope optical upper limits
  73. EP250220a: Optical upper limit with Kinder observations
  74. SVOM trigger sb25022102 is not an astrophysical event
  75. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  76. GRB 250221A: Swift detection of a burst with an optical counterpart
  77. EP250220a: Xinglong optical upper limit
  78. EP250220a: EP-WXT detection of a fast X-ray transient
  79. GRB 250219A: Swift/UVOT Upper Limits
  80. GRB 250219A: OHP/T193 optical upper limit
  81. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  82. GRB 250219A: 1.6m Mephisto optical upper limits
  83. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  84. GRB 250217C: Swift-XRT observations
  85. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  86. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  87. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  88. GRB 250217C: SVOM/GRM observation
  89. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  90. GRANDMA/OPD observations of GRB250215A
  91. The EP-WXT trigger 01709131775 is likely a flaring star
  92. GRB 250215A / EP250215a: LCO detection of the afterglow
  93. GRB 250215A: Swift/UVOT Upper Limits
  94. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  95. GRB 250215A: Fermi GBM Observation
  96. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  97. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  98. GRB 250215A: SVOM/GRM observation
  99. EP250215a / GRB 250215A: AstroSat CZTI detection
  100. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart

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