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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"

26401 results found.

  1. EP250304a: Einstein Probe detection of an X-ray transient
  2. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  3. EP250302a: SAO RAS optical observations
  4. EP250302a : GIT optical follow-up
  5. EP250225a: the candidate optical counterpart is an AGN
  6. EP250302a: Kinder optical follow-up observations
  7. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  8. EP250302a: Swift/UVOT detection
  9. EP250302a: optical observation from the INAF Asiago Observatory
  10. EP250302a: REM NIR upper limits
  11. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  12. EP250302a: Mondy Observations and Optical Light Curve
  13. EP250302a: VLT/MUSE optical redshift z = 1.131
  14. EP250302A: VLT near-infrared observations
  15. EP250302A: VLT/X-shooter tentative redshift
  16. EP250302a: OHP/T193 optical and spectroscopic observations
  17. EP250302a: Swift-XRT observations of a fading X-ray source
  18. EP250302a: Einstein Probe detection of an X-ray transient
  19. EP250302a: SVOM/C-GFT optical observations
  20. GRB 250226A: GRANDMA Optical Observations
  21. EP250302a: Montarrenti Observatory optical detection
  22. EP250302a: Nanshan/HMT optical counterpart detection
  23. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  24. GRB 250225B: VLT near-infrared afterglow confirmation
  25. EP250228a: Optical observations with Kinder and Swift/UVOT
  26. Konus-Wind detection of GRB 250226A
  27. GRB 250225B: EIRSAT-1 GMOD Detection
  28. GRB 250226A: KAO Optical Upper Limit
  29. GRB 250226A: AbAO AS-32 Optical Upper Limit
  30. EP250227a: Global MASTER-Net observations report
  31. EP250223A: Upper limits from Fermi-GBM Observations
  32. EP250227a: TRT optical upper limit
  33. GRB 250225B: VLT/HAWKI near-infrared observations
  34. EP250227a: Optical upper limits with Kinder observations
  35. EP250227a: NOT optical observations
  36. EP250227a: Einstein Probe detected of a fast X-ray transient
  37. EP250228a: updates on the EP observations
  38. GRB 250226A: Fermi GBM Observation
  39. EP250223a: J band upper limit by SYSU 80cm telescope
  40. EP250228a: Swift/XRT localisation
  41. EP250228a: Einstein Probe detection of an X-ray transient
  42. GRB 250226A / EP250226a: LCO detection of the afterglow
  43. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  44. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  45. GRB 250225B: VLT/Xshooter imaging
  46. GRB 250205A / EP250205A: further radio observations with the VLA
  47. EP250225a: NOT optical candidate counterpart
  48. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  49. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  50. EP250225a: TRT optical upper limits
  51. EP250226a/GRB 250226A: 1.6m Mephisto observations
  52. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  53. EP250226a/GRB 250226A: Kinder optical follow-up observations
  54. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  55. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  56. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  57. GRB 250225B: Fermi GBM Observation
  58. GRB 250225B: REM NIR upper limits
  59. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  60. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  61. EP250223a: CrAO ZTSH optical observation
  62. GRB 250225B: VLT optical and near-infrared candidate counterpart
  63. GRB 250225B: SVOM/GRM observation of a long burst
  64. EP250226a/GRB 250226A: GSP detects optical counterpart
  65. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  66. EP250226a / GRB 250226A: TRT optical counterpart observation
  67. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  68. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  69. EP250225a: GSP optical upper limit
  70. EP250223a: GMG Optical Observation
  71. EP250225a: Einstein Probe detected of a fast X-ray transient
  72. GRB 250225B: Swift detection of a burst
  73. EP250223a: GROWTH-India Telescope optical observations
  74. GRB 250221A: Swift-BAT refined analysis
  75. EP250215A: J band upper limit by SYSU 80cm telescope
  76. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  77. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  78. EP250223a: Kinder optical follow-up observations
  79. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  80. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  81. GRB 250119B: VZLUSAT-2 detection
  82. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  83. GRB 250202B: VZLUSAT-2 detection
  84. GRB 250222A: SVOM/GRM observation of a burst
  85. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  86. GRB 250206A: VZLUSAT-2 detection
  87. EP250223a: REM NIR upper limit
  88. EP250223a: TRT optical afterglow observation
  89. EP250223a: refined analysis of the EP-WXT and FXT observations
  90. EP250223a: 1.6m Mephisto and 50cm array observations
  91. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  92. 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
  93. EP250223a: OASDG optical observations
  94. EP250223a: LCO detection of the afterglow
  95. EP250223a: Swift/XRT localization
  96. EP250223a: NOT optical afterglow candidate
  97. EP250223a: Einstein Probe detection of an X-ray transient
  98. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  99. GRB 250221A: Optical counterpart detection by LCO.
  100. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits

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