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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"

32546 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. EP250227a: Global MASTER-Net observations report
  5. EP250223A: Upper limits from Fermi-GBM Observations
  6. EP250227a: TRT optical upper limit
  7. GRB 250225B: VLT/HAWKI near-infrared observations
  8. EP250227a: Optical upper limits with Kinder observations
  9. EP250227a: NOT optical observations
  10. EP250228a: updates on the EP observations
  11. GRB 250226A: Fermi GBM Observation
  12. EP250225a: EP-FXT follow-up observation
  13. EP250223a: J band upper limit by SYSU 80cm telescope
  14. EP250228a: Swift/XRT localisation
  15. EP250228a: Global MASTER-Net observations report
  16. GRB 250226A / EP250226a: LCO detection of the afterglow
  17. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  18. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  19. GRB 250225B: VLT/Xshooter imaging
  20. GRB 250205A / EP250205A: further radio observations with the VLA
  21. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  22. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  23. GRB 250225B: INTEGRAL SPI-ACS detection
  24. EP250225a: NOT optical candidate counterpart
  25. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  26. EP250226a / GRB 250226A: SVOM/VT optical observations
  27. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  28. EP250225a: TRT optical upper limits
  29. EP250226a/GRB 250226A: 1.6m Mephisto observations
  30. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  31. EP250226a/GRB 250226A: Kinder optical follow-up observations
  32. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  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 250225B: Fermi GBM Observation
  37. GRB 250221A: ATCA Detections and Upper Limits
  38. GRB 250225B: REM NIR upper limits
  39. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  40. Konus-Wind detection of GRB 250225B
  41. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  42. EP250223a: CrAO ZTSH optical observation
  43. GRB 250225B: VLT optical and near-infrared candidate counterpart
  44. GRB 250225B: VLT/FORS2 candidate optical afterglow
  45. GRB 250225B: SVOM/GRM observation of a long burst
  46. GRB 250226A: GECAM-B detection
  47. GRB 250221A: EP-FXT detection of the X-ray afterglow
  48. GRB 250214A: SVOM/GRM observation
  49. EP250226a/GRB 250226A: GSP detects optical counterpart
  50. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  51. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  52. EP250226a / GRB 250226A: TRT optical counterpart observation
  53. EP250226a: Global MASTER-Net observations report
  54. Swift GRB 250225B: Global MASTER-Net observations report
  55. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  56. Fermi GRB 250226A: Global MASTER-Net observations report
  57. EP250225a: Global MASTER-Net observations report
  58. EP250225a: GSP optical upper limit
  59. EP250223a: GMG Optical Observation
  60. Fermi GRB 250225A: Global MASTER-Net observations report
  61. EP250223a: GROWTH-India Telescope optical observations
  62. GRB 250221A: Swift-BAT refined analysis
  63. GRB 250223C: SVOM/GRM observation of a long burst
  64. EP250215A: J band upper limit by SYSU 80cm telescope
  65. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  66. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  67. EP250223a: Kinder optical follow-up observations
  68. GRB 250207a: ATCA Radio Upper Limits
  69. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  70. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  71. GRB 250119B: VZLUSAT-2 detection
  72. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  73. GRB 250202B: VZLUSAT-2 detection
  74. GRB 250219A: EP-FXT afterglow detection
  75. EP250223a: GOTO optical afterglow detections
  76. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  77. GRB 250210A: VZLUSAT-2 detection
  78. GRB 250206A: VZLUSAT-2 detection
  79. EP250223a: REM NIR upper limit
  80. EP250223a: TRT optical afterglow observation
  81. EP250223a: refined analysis of the EP-WXT and FXT observations
  82. EP250223a: 1.6m Mephisto and 50cm array observations
  83. GRB 250221A: TNOT detection of the optical counterpart
  84. EP250223a: SVOM/VT optical observation
  85. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  86. 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
  87. EP250223a: OASDG optical observations
  88. EP250223a: LCO detection of the afterglow
  89. EP250223a: NOT redshift z = 2.756
  90. EP250223a: Swift/XRT localization
  91. EP250223a: NOT optical afterglow candidate
  92. EP250223a: Global MASTER-Net observations report
  93. GRB 250221A: VLA radio detection
  94. Fermi GRB 250223A: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  96. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  97. GRB 250221A: continued Mondy optical observations, brightening afterglow
  98. GRB 250221A: Optical counterpart detection by LCO.
  99. GRB 250221A: Mondy optical observations
  100. Konus-Wind detection of GRB 250221A

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