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ISSN 0236-2457

ASTRONOMICHESKII TSIRKULYAR
Published by the Eurasian Astronomical So ciety and Sternb erg Astronomical Institute No. 1621, 2015 April 20

Conrmation of Pulsed Radio Emission from the Pulsar J1907+0919 (Shitov Radio Pulsar, SGR 1900+14) A.P. Glushak, B.Ya. Losovsky, and D.V. Dumsky
Pushchino Radio Astronomy Observatory, Astro Space Center, P.N. Lebedev Physical Institute, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia E-mail: glushak@prao.ru, blos@prao.ru
Received April 17, 2015

Abstract.

Observations at a frequency of 111 MHz with the Large Phased Array at the

Pushchino Radio Astronomy Observatory of the Astro Space Center of the P.N. Leb edev Physical Institute conrm the pulsed radio emission of the X-ray pulsar J1907+0919 that is a counterpart of the magnetar SGR 1900+14. Its pulsed radio emission was discovered earlier by Shitov (1999). A ux density p erio dogram is built. A new spin p erio d and ux density

P = 5.22756(42)

s

50 + 5

mJy are measured at the Ep o ch 56834.6 MJD. A value of the pulsar

radio emission sp ectral index is estimated as steep est among the sp ectra of known pulsars.

< -4.3.

This radio sp ectrum is one of the

Introduction
The p opulation of magnetars consists of AXP and SGR pulsars, many of which have steep radio sp ectra p eaking at low frequencies [1]. In these cases, we exp ect success in the observations of magnetars at low radio frequencies, just as earlier for AXP 1E 2259+586 and 4U 0142+61 [2]. One more radio PSR J0418+5732, which is a counterpart of SGR 0418+5729, has recently b een discovered at 111 MHz [3]. Long ago another (Shitov) radio PSR J1907+0919, the counterpart of the X-ray pulsar J1907+0919 and SGR 1900+14, was detected at 111 MHz [4, 5]. The request to conrm or refute the 111 MHz detection of PSR J1907+0919 was advanced in [6]. So, the present pap er rep orts the new observations as well as conrms the radio detection of PSR J1907+0919 and measured parameters of its radio emission.

Observations and Results
The observations have b een carried out at a frequency of 111 MHz with the Large Phased Array (LPA) at the Pushchino Radio Astronomy Observatory during the interval of 2014 April 2 - 2014 Octob er 8 (MJD 56749.161556938.6427) for 189.48 days. From this interval, 81 observational sessions were used for pro cessing. Each observational session with the LPA lasted ab out 3 min, and the total exp osure came to 243 min. The eective area was ab out 2.1 Ч 104 m2 , and HPBW was 48.0 Ч 33.5 . The sensitivity of the system came to 50 mJy

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in a frequency band of 1 Hz and at a time constant of 1 s. A digital 512-channel receiver with a bandwidth of 2.560 MHz and sampling time of 2.5 ms was used. Each individual channel had a bandwidth of 5 kHz. The op eration of the system was checked by observing some strong pulsars with well-known ux densities at 111 MHz. Impulsive RFI and bad channels were excluded from the observational data. To pro cess the data, the Fast Folding Algorithm was applied [7], which signicantly diers from the pro cessing metho d used in [4, 5]. During the pro cessing the disp ersion measure was xed to b e the same as in Shitov's measurements, -3 i.e., DM = 281.4 + 0.9 p c cm .

Figure 1: The PSR J1907+0919 average periodogram for 189.5 days at 111 MHz as ux density vs. period with a step of 1.26 ms. Period is given at MJD 56834.6. The signal-to-noise ratio, S/N, is 11 + 0.5 in the maximum, where N is one standard error.
The average p erio dogram of PSR J1907+0919 is shown in Fig. 1. There is broadening of the pulse prole, which is probably due to a quasi-p erio dic character of the radio emission. We detect the p erio d of PSR J1907+0919 to b e 5.22756(42) s at MJD 56834.6, where 56834.6 is the averaged value in the total observational interval 56749.161556938.6427 (MJD), and an error was taken as 1/3 of the p erio dogram step (Fig. 1). The measured radio emission ux density is of the ux densities (<

S

50 + 5 mJy at = 111

at the signal-to-noise ratio of MHz (50 mJy), 430 MHz (

30 ч

Jy) [6] results in sp ectral index

< -4.3

and

11 + 0.5. The comparison < 150 чJy), and 1410 MHz < -2.9, respectively. Here, S . 12.5 + 1.7

This is one of the steep est sp ectra among well-known pulsars, like the one of the Geminga pulsar. kp c (e.g. -3 [8]), meanwhile the NE 2001 free electron distribution mo del [9] at DM = 281.4 p c cm results in 6.7 kp c with an exp ected rough error of 30%. This large discrepancy probably indicates the NE 2001 mo del weakness, which was noted by its authors themselves. Note that at present a distance to SGR 1900+14 is often accepted to b e

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Acknowledgments
This work was supp orted by the Basic Research Program of the Department of Physical Sciences of the Russian Academy of Sciences Active Pro cesses in Galactic and Extragalactic Ob jects. The authors thank L.A. Solovyova for help in preparing this rep ort.

References
1. Malov I.F., ARep

58

, 139 (2014).

2. Malofeev V.M., Teplykh D.A., and Logvinenko, S.V., ARep 4. Shitov Yu.P., IAU Circ. 7110 (1999). 5. Shitov Yu.P., Pugachev, V.D., and Kutuzov, S.M., ASPC 6. Lorimer D.R. and Xilouris K.M., ApJ

56

, 35 (2012).

3. Glushak A.P., Dumsky D.V., and Losovsky B.Ya., ATsir No. 1609 (2014).

545

202

, 685 (2000).

, 385 (2000).

7. Kondratiev V.I., McLaughlin M.A., Lorimer D.R., et al., ApJ 8. Davies B., Figer D.F., Kudritzki R.-P., et al., ApJ

707

702

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Подтверждение импульсного радиоизлучения пульсара J1907+0919 (радиопульсар Шитова, SGR 1900+14) А.П. Глушак, Б.Я. Лосовский и Д.В. Думский
Пущинская радиоастрономическая обсерватория, Астрокосмический центр, Физический институт имени П.Н. Лебедева Российской Академии наук, Пущино, Московская область, 142290, Россия E-mail: glushak@prao.ru, blos@prao.ru
Поступила 17 апреля 2015 года

Резюме.

В наблюдениях на Пущинской радиоастрономической обсерватории с Боль-

шой Синфазной Антенной Астрокосмического центра Физического института имени П.Н. Лебедева на частоте 111 МГц подтверждено обнаруженное ранее Шитовым (1999) импульсное радиоизлучение пульсара J1907+0919, дубликата магнитара SGR 1900+14. Получена периодограмма плотности потока пульсара. Его новый период и плотность потока

P = 5.22756(42)

с

50 + 5

мЯн были измерены на эпоху 56834.6 MJD. Оценена величи-

на спектрального индекса радиоизлучения,

< -4.3.

Этот радиоспектр один из самых

крутых среди спектров известных пульсаров.
Ключевые слова: радиоизлучение, пульсары, магнитары, J1907+0919 (Shitov), SGR

1900+14, SGR 0418+5729.

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