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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"

44399 results found.

  1. EP250227a: Global MASTER-Net observations report
  2. EP250223A: Upper limits from Fermi-GBM Observations
  3. EP250227a: TRT optical upper limit
  4. GRB 250225B: VLT/HAWKI near-infrared observations
  5. EP250227a: Optical upper limits with Kinder observations
  6. EP250227a: NOT optical observations
  7. EP250227a: Einstein Probe detected of a fast X-ray transient
  8. EP250228a: updates on the EP observations
  9. GRB 250226A: Fermi GBM Observation
  10. EP250225a: EP-FXT follow-up observation
  11. EP250223a: J band upper limit by SYSU 80cm telescope
  12. EP250228a: Swift/XRT localisation
  13. EP250228a: Global MASTER-Net observations report
  14. EP250228a: Einstein Probe detection of an X-ray transient
  15. GRB 250226A / EP250226a: LCO detection of the afterglow
  16. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  17. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  18. GRB 250225B: VLT/Xshooter imaging
  19. GRB 250205A / EP250205A: further radio observations with the VLA
  20. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  21. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  22. GRB 250225B: INTEGRAL SPI-ACS detection
  23. EP250225a: NOT optical candidate counterpart
  24. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  25. EP250226a / GRB 250226A: SVOM/VT optical observations
  26. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  27. EP250225a: TRT optical upper limits
  28. EP250226a/GRB 250226A: 1.6m Mephisto observations
  29. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  30. EP250226a/GRB 250226A: Kinder optical follow-up observations
  31. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  32. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  34. Fermi GRB 250226B: Global MASTER-Net observations report
  35. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  36. GRB 250226B: Fermi GBM Final Real-time Localization
  37. GRB 250225B: Fermi GBM Observation
  38. GRB 250221A: ATCA Detections and Upper Limits
  39. GRB 250225B: REM NIR upper limits
  40. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  41. Konus-Wind detection of GRB 250225B
  42. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  43. EP250223a: CrAO ZTSH optical observation
  44. GRB 250225B: VLT optical and near-infrared candidate counterpart
  45. GRB 250225B: VLT/FORS2 candidate optical afterglow
  46. GRB 250225B: SVOM/GRM observation of a long burst
  47. GRB 250226A: GECAM-B detection
  48. GRB 250221A: EP-FXT detection of the X-ray afterglow
  49. GRB 250214A: SVOM/GRM observation
  50. EP250226a/GRB 250226A: GSP detects optical counterpart
  51. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  52. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  53. EP250226a / GRB 250226A: TRT optical counterpart observation
  54. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  55. EP250226a: Global MASTER-Net observations report
  56. Swift GRB 250225B: Global MASTER-Net observations report
  57. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  58. Fermi GRB 250226A: Global MASTER-Net observations report
  59. Fermi trigger No 762205158: Global MASTER-Net observations report
  60. GRB 250226A: Fermi GBM Final Real-time Localization
  61. EP250225a: Global MASTER-Net observations report
  62. EP250225a: GSP optical upper limit
  63. EP250223a: GMG Optical Observation
  64. EP250225a: Einstein Probe detected of a fast X-ray transient
  65. Fermi GRB 250225A: Global MASTER-Net observations report
  66. GRB 250225B: Swift detection of a burst
  67. EP250223a: GROWTH-India Telescope optical observations
  68. GRB 250221A: Swift-BAT refined analysis
  69. GRB 250223C: SVOM/GRM observation of a long burst
  70. EP250215A: J band upper limit by SYSU 80cm telescope
  71. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  72. GRB 250225A: Fermi GBM Final Real-time Localization
  73. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  74. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  75. EP250223a: Kinder optical follow-up observations
  76. GRB 250207a: ATCA Radio Upper Limits
  77. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  78. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  79. GRB 250119B: VZLUSAT-2 detection
  80. GRB 250223C: Fermi GBM Final Real-time Localization
  81. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  82. GRB 250202B: VZLUSAT-2 detection
  83. GRB 250219A: EP-FXT afterglow detection
  84. EP250223a: GOTO optical afterglow detections
  85. GRB 250222A: SVOM/GRM observation of a burst
  86. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  87. GRB 250210A: VZLUSAT-2 detection
  88. GRB 250206A: VZLUSAT-2 detection
  89. EP250223a: REM NIR upper limit
  90. EP250223a: TRT optical afterglow observation
  91. EP250223a: refined analysis of the EP-WXT and FXT observations
  92. EP250223a: 1.6m Mephisto and 50cm array observations
  93. GRB 250221A: TNOT detection of the optical counterpart
  94. EP250223a: SVOM/VT optical observation
  95. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  96. 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
  97. The EP-WXT trigger 01709131882 is likely a flaring star
  98. EP250223a: OASDG optical observations
  99. EP250223a: LCO detection of the afterglow
  100. EP250223a: early optical detection by BOOTES-4

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