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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"

24604 results found.

  1. EP250304a: TRT optical counterpart detection
  2. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  3. EP250304a: Einstein Probe detection of an X-ray transient
  4. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  5. EP250302a: SAO RAS optical observations
  6. EP250302a : GIT optical follow-up
  7. EP250225a: the candidate optical counterpart is an AGN
  8. EP250302a: Kinder optical follow-up observations
  9. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  10. EP250302a: Swift/UVOT detection
  11. EP250302a: optical observation from the INAF Asiago Observatory
  12. EP250302a: REM NIR upper limits
  13. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  14. EP250302a: Mondy Observations and Optical Light Curve
  15. EP250302a: VLT/MUSE optical redshift z = 1.131
  16. EP250302A: VLT near-infrared observations
  17. EP250302A: VLT/X-shooter tentative redshift
  18. EP250302a: OHP/T193 optical and spectroscopic observations
  19. EP250302a: Swift-XRT observations of a fading X-ray source
  20. EP250302a: Einstein Probe detection of an X-ray transient
  21. EP250302a: SVOM/C-GFT optical observations
  22. GRB 250226A: GRANDMA Optical Observations
  23. EP250302a: Montarrenti Observatory optical detection
  24. EP250302a: Nanshan/HMT optical counterpart detection
  25. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  26. GRB 250225B: VLT near-infrared afterglow confirmation
  27. EP250228a: Optical observations with Kinder and Swift/UVOT
  28. Konus-Wind detection of GRB 250226A
  29. GRB 250225B: EIRSAT-1 GMOD Detection
  30. GRB 250226A: KAO Optical Upper Limit
  31. GRB 250226A: AbAO AS-32 Optical Upper Limit
  32. EP250227a: Global MASTER-Net observations report
  33. EP250223A: Upper limits from Fermi-GBM Observations
  34. EP250227a: TRT optical upper limit
  35. GRB 250225B: VLT/HAWKI near-infrared observations
  36. EP250227a: Optical upper limits with Kinder observations
  37. EP250227a: NOT optical observations
  38. EP250227a: Einstein Probe detected of a fast X-ray transient
  39. EP250228a: updates on the EP observations
  40. GRB 250226A: Fermi GBM Observation
  41. EP250223a: J band upper limit by SYSU 80cm telescope
  42. EP250228a: Swift/XRT localisation
  43. EP250228a: Einstein Probe detection of an X-ray transient
  44. GRB 250226A / EP250226a: LCO detection of the afterglow
  45. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  46. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  47. GRB 250225B: VLT/Xshooter imaging
  48. GRB 250205A / EP250205A: further radio observations with the VLA
  49. EP250225a: NOT optical candidate counterpart
  50. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  51. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  52. EP250225a: TRT optical upper limits
  53. EP250226a/GRB 250226A: 1.6m Mephisto observations
  54. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  55. EP250226a/GRB 250226A: Kinder optical follow-up observations
  56. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  57. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  59. GRB 250225B: Fermi GBM Observation
  60. GRB 250225B: REM NIR upper limits
  61. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  62. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  63. EP250223a: CrAO ZTSH optical observation
  64. GRB 250225B: VLT optical and near-infrared candidate counterpart
  65. GRB 250225B: SVOM/GRM observation of a long burst
  66. EP250226a/GRB 250226A: GSP detects optical counterpart
  67. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  68. EP250226a / GRB 250226A: TRT optical counterpart observation
  69. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  70. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  71. EP250225a: GSP optical upper limit
  72. EP250223a: GMG Optical Observation
  73. EP250225a: Einstein Probe detected of a fast X-ray transient
  74. GRB 250225B: Swift detection of a burst
  75. EP250223a: GROWTH-India Telescope optical observations
  76. GRB 250221A: Swift-BAT refined analysis
  77. EP250215A: J band upper limit by SYSU 80cm telescope
  78. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  79. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  80. EP250223a: Kinder optical follow-up observations
  81. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  82. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  83. GRB 250119B: VZLUSAT-2 detection
  84. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  85. GRB 250202B: VZLUSAT-2 detection
  86. GRB 250222A: SVOM/GRM observation of a burst
  87. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  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. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  94. 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
  95. EP250223a: OASDG optical observations
  96. EP250223a: LCO detection of the afterglow
  97. EP250223a: Swift/XRT localization
  98. EP250223a: NOT optical afterglow candidate
  99. EP250223a: Einstein Probe detection of an X-ray transient
  100. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches

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