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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.

Lucene Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

24575 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. EP250227a: Einstein Probe detected of a fast X-ray transient
  11. EP250228a: updates on the EP observations
  12. GRB 250226A: Fermi GBM Observation
  13. EP250223a: J band upper limit by SYSU 80cm telescope
  14. EP250228a: Swift/XRT localisation
  15. EP250228a: Einstein Probe detection of an X-ray transient
  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. 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. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  27. EP250226a/GRB 250226A: Kinder optical follow-up observations
  28. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  29. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  30. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  31. GRB 250225B: Fermi GBM Observation
  32. GRB 250225B: REM NIR upper limits
  33. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  34. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  35. EP250223a: CrAO ZTSH optical observation
  36. GRB 250225B: VLT optical and near-infrared candidate counterpart
  37. GRB 250225B: SVOM/GRM observation of a long burst
  38. EP250226a/GRB 250226A: GSP detects optical counterpart
  39. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  40. EP250226a / GRB 250226A: TRT optical counterpart observation
  41. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  42. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  43. EP250225a: GSP optical upper limit
  44. EP250223a: GMG Optical Observation
  45. EP250225a: Einstein Probe detected of a fast X-ray transient
  46. GRB 250225B: Swift detection of a burst
  47. EP250223a: GROWTH-India Telescope optical observations
  48. GRB 250221A: Swift-BAT refined analysis
  49. EP250215A: J band upper limit by SYSU 80cm telescope
  50. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  51. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  52. EP250223a: Kinder optical follow-up observations
  53. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  55. GRB 250119B: VZLUSAT-2 detection
  56. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  57. GRB 250202B: VZLUSAT-2 detection
  58. GRB 250222A: SVOM/GRM observation of a burst
  59. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  60. GRB 250206A: VZLUSAT-2 detection
  61. EP250223a: REM NIR upper limit
  62. EP250223a: TRT optical afterglow observation
  63. EP250223a: refined analysis of the EP-WXT and FXT observations
  64. EP250223a: 1.6m Mephisto and 50cm array observations
  65. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  66. 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
  67. EP250223a: OASDG optical observations
  68. EP250223a: LCO detection of the afterglow
  69. EP250223a: Swift/XRT localization
  70. EP250223a: NOT optical afterglow candidate
  71. EP250223a: Einstein Probe detection of an X-ray transient
  72. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  73. GRB 250221A: Optical counterpart detection by LCO.
  74. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  75. GRB 250221A: GRANDMA/TAROT Detection
  76. GRB 250221A: Swift-XRT refined Analysis
  77. GRB 250221A: NOT optical observations
  78. GRB 250221A: 1.6m Mephisto optical detection
  79. GRB 250221A: AKO Optical Upper Limit
  80. GRB 250221A: Swift/UVOT Detection
  81. EP250220a: Liverpool Telescope upper limits
  82. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  83. GRB 250221A: REM optical/NIR afterglow detection
  84. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  85. GRB 250221A: Enhanced Swift-XRT position
  86. EP250220a: 1.6m Mephisto observations
  87. EP250220a: Liverpool Telescope optical upper limits
  88. EP250220a: Optical upper limit with Kinder observations
  89. SVOM trigger sb25022102 is not an astrophysical event
  90. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  91. GRB 250221A: Swift detection of a burst with an optical counterpart
  92. Swift GRB250221.15: Global MASTER-Net OT detection
  93. EP250220a: Xinglong optical upper limit
  94. GRB 250219A: Swift/UVOT Upper Limits
  95. GRB 250219A: OHP/T193 optical upper limit
  96. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  97. GRB 250219A: 1.6m Mephisto optical upper limits
  98. GRB 250219A: Swift-XRT observations
  99. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  100. Konus-Wind detection of GRB 250215A / EP250215a

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