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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"

22111 results found.

  1. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  2. GRB 250311A: Swift-XRT observations
  3. GRB 250309B: 1.3m DFOT Optical observations
  4. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  5. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  6. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  7. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  8. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  9. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  10. GRB 250309B: PRIME near-infrared detection
  11. GRB 250225B: Swift-BAT refined analysis
  12. GRB 250311A/EP250311a: TRT optical upper limit
  13. EP250311a/GRB 250311A: EP-WXT detection
  14. GRB 250309B / AT2025dws: further SAO RAS optical observations
  15. IceCube-250309A: Upper limits from Fermi-GBM Observations
  16. EP250308a: 1.6m Mephisto optical upper limits
  17. IPN triangulation of GRB 250308A (short)
  18. IPN triangulation of GRB 250309B
  19. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  20. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  21. GRB 250309B / IceCube-250309A: GECAM-B observations
  22. GRB 250309B / AT2025dws: SAO RAS optical observations
  23. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  24. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  25. IceCube-250309A: No candidates from the Zwicky Transient Facility
  26. EP250308a: FTW optical and NIR upper limits
  27. EP250308a: Einstein Probe detection of an X-ray transient
  28. EP250308a: NOT optical upper limit
  29. Konus-Wind detection of GRB 250306A
  30. EP250304a: MeerKAT detection of a possible radio counterpart
  31. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  32. EP250302a:Xinglong optical observations
  33. GRB 250306A: AstroSat CZTI detection
  34. GRB 250306A: Swift detection of a burst
  35. GRB250101A: Radio upper limits from VLA observations
  36. GRB 250305A: SVOM/GRM observation of a burst
  37. EP250302a: Optical Observations at CrAO and SAO RAS
  38. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  39. EP 250304A: Optical counterpart detection by LCO
  40. EP250302A: 1.3m DFOT optical afterglow detection
  41. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  42. EP250304a: REM NIR upper limits
  43. IPN triangulation of GRB 250222A
  44. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  45. EP250302a: Mondy Continued Optical Observations
  46. EP250304a: Swift-XRT detection of a fading X-ray source
  47. EP250304a: TRT optical counterpart detection
  48. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  49. EP250304a: Einstein Probe detection of an X-ray transient
  50. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  51. EP250302a: SAO RAS optical observations
  52. EP250302a : GIT optical follow-up
  53. EP250302a: Kinder optical follow-up observations
  54. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  55. EP250302a: Swift/UVOT detection
  56. EP250302a: optical observation from the INAF Asiago Observatory
  57. EP250302a: REM NIR upper limits
  58. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  59. EP250302a: Mondy Observations and Optical Light Curve
  60. EP250302a: VLT/MUSE optical redshift z = 1.131
  61. EP250302A: VLT near-infrared observations
  62. EP250302A: VLT/X-shooter tentative redshift
  63. EP250302a: OHP/T193 optical and spectroscopic observations
  64. EP250302a: Einstein Probe detection of an X-ray transient
  65. EP250302a: SVOM/C-GFT optical observations
  66. GRB 250226A: GRANDMA Optical Observations
  67. EP250302a: Montarrenti Observatory optical detection
  68. EP250302a: Nanshan/HMT optical counterpart detection
  69. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  70. GRB 250225B: VLT near-infrared afterglow confirmation
  71. EP250228a: Optical observations with Kinder and Swift/UVOT
  72. GRB 250226A: KAO Optical Upper Limit
  73. GRB 250226A: AbAO AS-32 Optical Upper Limit
  74. EP250227a: TRT optical upper limit
  75. GRB 250225B: VLT/HAWKI near-infrared observations
  76. EP250227a: Optical upper limits with Kinder observations
  77. EP250227a: NOT optical observations
  78. EP250227a: Einstein Probe detected of a fast X-ray transient
  79. EP250228a: updates on the EP observations
  80. EP250225a: EP-FXT follow-up observation
  81. EP250223a: J band upper limit by SYSU 80cm telescope
  82. EP250228a: Einstein Probe detection of an X-ray transient
  83. GRB 250225B: VLT/Xshooter imaging
  84. GRB 250205A / EP250205A: further radio observations with the VLA
  85. GRB 250225B: INTEGRAL SPI-ACS detection
  86. EP250225a: NOT optical candidate counterpart
  87. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  88. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  89. EP250225a: TRT optical upper limits
  90. EP250226a/GRB 250226A: 1.6m Mephisto observations
  91. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  92. EP250226a/GRB 250226A: Kinder optical follow-up observations
  93. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  95. GRB 250221A: ATCA Detections and Upper Limits
  96. GRB 250225B: REM NIR upper limits
  97. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  98. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  99. EP250223a: CrAO ZTSH optical observation
  100. GRB 250225B: VLT optical and near-infrared candidate counterpart

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