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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"

24758 results found.

  1. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  2. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  3. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  4. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  5. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  6. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  7. GRB 250309B: PRIME near-infrared detection
  8. GRB 250225B: Swift-BAT refined analysis
  9. GRB 250311A/EP250311a: TRT optical upper limit
  10. EP250311a/GRB 250311A: EP-WXT detection
  11. GRB 250311B: SVOM detection of a burst
  12. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  13. GRB 250309B / AT2025dws: further SAO RAS optical observations
  14. EP250308a: 1.6m Mephisto optical upper limits
  15. Konus-Wind detection of GRB 250309B
  16. IPN triangulation of GRB 250308A (short)
  17. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  18. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  19. GRB 250309B: Swift-XRT refined Analysis
  20. GRB 250309B / IceCube-250309A: GECAM-B observations
  21. GRB 250309B / AT2025dws: SAO RAS optical observations
  22. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  23. GRB 250309B: Fermi GBM Observation
  24. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  25. IceCube-250309A: No candidates from the Zwicky Transient Facility
  26. Fermi-LAT gamma-ray observations of IceCube-250309A
  27. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  29. EP250308a: GSP optical upper limit
  30. EP250308a: Einstein Probe detection of an X-ray transient
  31. EP250308a: NOT optical upper limit
  32. GRB 250306A: EIRSAT-1 GMOD detection
  33. GRB 250306A: Swift-BAT refined analysis
  34. GRB 250306A: NuSTAR detection of the prompt emission
  35. EP250304a: MeerKAT detection of a possible radio counterpart
  36. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  37. GRB 250305A: AstroSat CZTI detection
  38. EP250302a:Xinglong optical observations
  39. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  40. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  41. GRB250101A: Radio upper limits from VLA observations
  42. GRB 250305A: SVOM/GRM observation of a burst
  43. The EP-WXT trigger 01709132323 is likely a flaring star
  44. EP250304A: Upper limits from Fermi-GBM Observations
  45. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  46. EP250302a: Optical Observations at CrAO and SAO RAS
  47. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  48. EP 250304A: Optical counterpart detection by LCO
  49. EP250302A: 1.3m DFOT optical afterglow detection
  50. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  51. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  52. EP250304a: REM NIR upper limits
  53. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  54. EP250302a: Mondy Continued Optical Observations
  55. EP250304a: Swift-XRT detection of a fading X-ray source
  56. EP250304a: TRT optical counterpart detection
  57. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  58. EP250304a: Einstein Probe detection of an X-ray transient
  59. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  60. EP250302a: SAO RAS optical observations
  61. EP250302a : GIT optical follow-up
  62. EP250225a: the candidate optical counterpart is an AGN
  63. EP250302a: Kinder optical follow-up observations
  64. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  65. EP250302a: Swift/UVOT detection
  66. EP250302a: optical observation from the INAF Asiago Observatory
  67. EP250302a: REM NIR upper limits
  68. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  69. EP250302a: Mondy Observations and Optical Light Curve
  70. EP250302a: VLT/MUSE optical redshift z = 1.131
  71. EP250302A: VLT near-infrared observations
  72. EP250302A: VLT/X-shooter tentative redshift
  73. EP250302a: OHP/T193 optical and spectroscopic observations
  74. EP250302a: Swift-XRT observations of a fading X-ray source
  75. EP250302a: Einstein Probe detection of an X-ray transient
  76. EP250302a: SVOM/C-GFT optical observations
  77. GRB 250226A: GRANDMA Optical Observations
  78. EP250302a: Montarrenti Observatory optical detection
  79. EP250302a: Nanshan/HMT optical counterpart detection
  80. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  81. GRB 250225B: VLT near-infrared afterglow confirmation
  82. EP250228a: Optical observations with Kinder and Swift/UVOT
  83. Konus-Wind detection of GRB 250226A
  84. GRB 250225B: EIRSAT-1 GMOD Detection
  85. GRB 250226A: KAO Optical Upper Limit
  86. GRB 250226A: AbAO AS-32 Optical Upper Limit
  87. EP250227a: Global MASTER-Net observations report
  88. EP250223A: Upper limits from Fermi-GBM Observations
  89. EP250227a: TRT optical upper limit
  90. GRB 250225B: VLT/HAWKI near-infrared observations
  91. EP250227a: Optical upper limits with Kinder observations
  92. EP250227a: NOT optical observations
  93. EP250227a: Einstein Probe detected of a fast X-ray transient
  94. EP250228a: updates on the EP observations
  95. GRB 250226A: Fermi GBM Observation
  96. EP250223a: J band upper limit by SYSU 80cm telescope
  97. EP250228a: Swift/XRT localisation
  98. EP250228a: Einstein Probe detection of an X-ray transient
  99. GRB 250226A / EP250226a: LCO detection of the afterglow
  100. LIGO/Virgo/KAGRA S250227e: Updated Sky localization

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