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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"

24889 results found.

  1. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  2. SVOM/MXT upper limit on GRB 250314A
  3. GRB 250314A: SVOM/VT upper limit
  4. GRB 250314A: NOT near-infrared candidate counterpart
  5. GRB 250313A: Fermi GBM Detection
  6. GRB 250312B: Fermi GBM Observation
  7. GRB 250313A: Swift-XRT observations
  8. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  9. GRB 250314A: SVOM detection of a burst
  10. GRB 250313A: AstroSat CZTI detection of a bright long burst
  11. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  12. GRB 250313A: Fermi-LAT detection
  13. EP250304a: Pan-STARRS r and i-band imaging and photometry
  14. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  15. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  16. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  17. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  18. GRB 250312A: Swift-XRT refined Analysis
  19. GRB 250312A: Enhanced Swift-XRT position
  20. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  21. GRB 250226B: Fermi GBM Observation
  22. GRB 250302A: Fermi GBM Observation
  23. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  24. GRB 250312A: Swift detection of a burst
  25. GRB 241213A: VIRT Optical Upper Limit
  26. GRB 241228A: VIRT Optical Upper Limit
  27. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  28. GRB 250311A: Swift-XRT observations
  29. GRB 230509B: 1.3m DFOT Optical observations
  30. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  32. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  33. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  34. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  35. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  36. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  37. GRB 250309B: PRIME near-infrared detection
  38. GRB 250225B: Swift-BAT refined analysis
  39. GRB 250311A/EP250311a: TRT optical upper limit
  40. EP250311a/GRB 250311A: EP-WXT detection
  41. GRB 250311B: SVOM detection of a burst
  42. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  43. GRB 250309B / AT2025dws: further SAO RAS optical observations
  44. EP250308a: 1.6m Mephisto optical upper limits
  45. Konus-Wind detection of GRB 250309B
  46. IPN triangulation of GRB 250308A (short)
  47. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  48. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  49. GRB 250309B: Swift-XRT refined Analysis
  50. GRB 250309B / IceCube-250309A: GECAM-B observations
  51. GRB 250309B / AT2025dws: SAO RAS optical observations
  52. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  53. GRB 250309B: Fermi GBM Observation
  54. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  55. IceCube-250309A: No candidates from the Zwicky Transient Facility
  56. Fermi-LAT gamma-ray observations of IceCube-250309A
  57. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  59. EP250308a: GSP optical upper limit
  60. EP250308a: Einstein Probe detection of an X-ray transient
  61. EP250308a: NOT optical upper limit
  62. GRB 250306A: EIRSAT-1 GMOD detection
  63. GRB 250306A: Swift-BAT refined analysis
  64. GRB 250306A: NuSTAR detection of the prompt emission
  65. EP250304a: MeerKAT detection of a possible radio counterpart
  66. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  67. GRB 250305A: AstroSat CZTI detection
  68. EP250302a:Xinglong optical observations
  69. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  70. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  71. GRB250101A: Radio upper limits from VLA observations
  72. GRB 250305A: SVOM/GRM observation of a burst
  73. The EP-WXT trigger 01709132323 is likely a flaring star
  74. EP250304A: Upper limits from Fermi-GBM Observations
  75. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  76. EP250302a: Optical Observations at CrAO and SAO RAS
  77. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  78. EP 250304A: Optical counterpart detection by LCO
  79. EP250302A: 1.3m DFOT optical afterglow detection
  80. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  81. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  82. EP250304a: REM NIR upper limits
  83. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  84. EP250302a: Mondy Continued Optical Observations
  85. EP250304a: Swift-XRT detection of a fading X-ray source
  86. EP250304a: TRT optical counterpart detection
  87. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  88. EP250304a: Einstein Probe detection of an X-ray transient
  89. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  90. EP250302a: SAO RAS optical observations
  91. EP250302a : GIT optical follow-up
  92. EP250225a: the candidate optical counterpart is an AGN
  93. EP250302a: Kinder optical follow-up observations
  94. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  95. EP250302a: Swift/UVOT detection
  96. EP250302a: optical observation from the INAF Asiago Observatory
  97. EP250302a: REM NIR upper limits
  98. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  99. EP250302a: Mondy Observations and Optical Light Curve
  100. EP250302a: VLT/MUSE optical redshift z = 1.131

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